Vf1000R Cyllinders On A Vfr800Fi?

[CornerCarver]

I would say CSS would be a great budget way to reinforce the factory cylinders of up to 74mm, because it is only about $250, minimal machining and not risking the sleeves sinking or shifting.

On overbores over 74mm , you are right, Darton resleeving would be the way to go. With Darton sleeves and oringing, you could insure a bullet proof 75mm or 76mm block.

Need as much as possible on the overbore to keep the costs of stroking the crank down...want a 12-15% increase in displacement over the superb work of Phil (HighSideNZ)!

It is not achievable with off the shelf CBR slugs in the VFR block so we will see what sleeving options can be had.

[CandyRedRC46]

How many mm are you thinking on the final bore? 76, 77, 78mm??

[Mohawk]

I would say CSS would be a great budget way to reinforce the factory cylinders of up to 74mm, because it is only about $250, minimal machining and not risking the sleeves sinking or shifting.

On overbores over 74mm , you are right, Darton resleeving would be the way to go. With Darton sleeves and oringing, you could insure a bullet proof 75mm or 76mm block.

Need as much as possible on the overbore to keep the costs of stroking the crank down...want a 12-15% increase in displacement over the superb work of Phil (HighSideNZ)!

It is not achievable with off the shelf CBR slugs in the VFR block so we will see what sleeving options can be had.

So you can go to 74mm in the existiong liners if you are lucky like HighsideNZ, if they are cast a bit off centre then they could fail as the MMC would be less than 1mm thick ! The MMC outer diameter is 77mm +/- 0.5mm depending on how central they are to the bore.

So 78mm would be the next overbore size unless you fit a liner of some description. I found a company on Austria that were willing to plasma spray coat a lining on the alloy of a 78mm bore but it was approx $3000 just for the sparay job. a 78mm bore could use CRF250 2 ring pistons for a race bike or CBR250 or 1000RR for a road bike. But as HighsideNZ has said water sealing could be an issue.

A cheap ish option is some Kawasaki ZX9R 75mm iron wet liners modified to use as press fit liners & bored to 76mm, leaving 2.5mm wall for a total OD of 81mm, thus leaving 3.5mm of the existing alloy wall, giving 870cc using CBR250/1000RR pistons. It's the machining that cost money.

Alternately with the CSS deck support, you could removed the whole alloy cylinder & use a stepped iron liner with O-ring seals to the crank case a bit like the VF1000R had. But you stillhave the head waterways issue that HighsideNZ mentioned.

[CornerCarver]

I would say CSS would be a great budget way to reinforce the factory cylinders of up to 74mm, because it is only about $250, minimal machining and not risking the sleeves sinking or shifting.

On overbores over 74mm , you are right, Darton resleeving would be the way to go. With Darton sleeves and oringing, you could insure a bullet proof 75mm or 76mm block.

Need as much as possible on the overbore to keep the costs of stroking the crank down...want a 12-15% increase in displacement over the superb work of Phil (HighSideNZ)!

It is not achievable with off the shelf CBR slugs in the VFR block so we will see what sleeving options can be had.

So you can go to 74mm in the existiong liners if you are lucky like HighsideNZ, if they are cast a bit off centre then they could fail as the MMC would be less than 1mm thick ! The MMC outer diameter is 77mm +/- 0.5mm depending on how central they are to the bore.

So 78mm would be the next overbore size unless you fit a liner of some description. I found a company on Austria that were willing to plasma spray coat a lining on the alloy of a 78mm bore but it was approx $3000 just for the sparay job. a 78mm bore could use CRF250 2 ring pistons for a race bike or CBR250 or 1000RR for a road bike. But as HighsideNZ has said water sealing could be an issue.

A cheap ish option is some Kawasaki ZX9R 75mm iron wet liners modified to use as press fit liners & bored to 76mm, leaving 2.5mm wall for a total OD of 81mm, thus leaving 3.5mm of the existing alloy wall, giving 870cc using CBR250/1000RR pistons. It's the machining that cost money.

Alternately with the CSS deck support, you could removed the whole alloy cylinder & use a stepped iron liner with O-ring seals to the crank case a bit like the VF1000R had. But you stillhave the head waterways issue that HighsideNZ mentioned.

This is what I am looking at first http://www.darton-international.com/rd_svcs.html and the engineering is willing to reverse engineer sleeves for the RC46 block.

Not really concerned about the CSS deck support until I find out how close to 82 mm we can get on the bore. All the big brains in my rolodex will then devour the water jacket in the head problem like it was a petit dejeuner.

The CSS deck support may be needed but none of this may be possible so I wont even contact them until I find out what the sleeve solution is.

Wont know until the

[HighSideNZ]

Those Darton sleeves are centrifugal cast iron same as what I made my sleeves for the VF750/880 back in 1984.

Any good machine shop should be able to make them from a good drawing.

[CandyRedRC46]

The thing is, there are darton MID sleeves, dry sleeves and wet sleeves. They all serve a different purpose. But the MID Sleeves basically combine the principals of a resleeve and a cylinder support system. Darton MID Sleeves are basically a resleeve that converts the deck from an open deck to a close deck, which greatly reinforces and strengthens the cylinders.

Sent from my A0001 using Tapatalk

[BiKenG]

Whilst I applaud the effort and ingenuity being applied here, I have to ask the question, why? I am not trying to dismiss the discussion as worthless or in any way criticise, but I am simply intrigued.

The idea of more power is appealing, but part of the joy of the VFR800 is not being involved in the modern bike power race and I am veering away from modern machinery as such high power outputs generally come with low speed ride-ability problems, for which they have to include fancy electronics with multiple ride modes etc.

If you just want a powerful V4, what about Aprilia as that route will provide what you seek, albeit with horrendous fuel consumption? What about in a year or so when Honda release a new RVF1000, with more power than you'll ever need, better handling and lighter than we'll ever be able to achieve with a VFR?

Personally, I do like the idea of achieving a power output equivalent to the RC45 as drivability could be maintained, but I wouldn't really be looking for any more than that.

Like I said, I'm not trying to knock the idea of pushing the boundaries of the VFR, but how do your desires fit with the alternatives I mention above?

[CornerCarver]

Whilst I applaud the effort and ingenuity being applied here, I have to ask the question, why? I am not trying to dismiss the discussion as worthless or in any way criticise, but I am simply intrigued.

The idea of more power is appealing, but part of the joy of the VFR800 is not being involved in the modern bike power race and I am veering away from modern machinery as such high power outputs generally come with low speed ride-ability problems, for which they have to include fancy electronics with multiple ride modes etc.

If you just want a powerful V4, what about Aprilia as that route will provide what you seek, albeit with horrendous fuel consumption? What about in a year or so when Honda release a new RVF1000, with more power than you'll ever need, better handling and lighter than we'll ever be able to achieve with a VFR?

Personally, I do like the idea of achieving a power output equivalent to the RC45 as drivability could be maintained, but I wouldn't really be looking for any more than that.

Like I said, I'm not trying to knock the idea of pushing the boundaries of the VFR, but how do your desires fit with the alternatives I mention above?

All good and sane questions to be sure, like many questions asked by those gazing skyward at the party about to summit the peak. I appreciate the non-judgemental phrasing of the questions so let's see how many I can answer.

1. "The idea of more power is appealing, but part of the joy of the VFR800 is not being involved in the modern bike power race and I am veering away from modern machinery as such high power outputs generally come with low speed ride-ability problems, for which they have to include fancy electronics with multiple ride modes etc."

Not really involved in the modern bike power race but looking for a slight upgrade in torque (and therefore power) so maybe taking the output per/cc from 1986 levels to say 2006 levels. If you use the GSXR750 as the 3/4 liter benchmark for how the modern power race has developed then if I recall correctly the GSXR circa 2006-07 was approximately 150 hp at the crank / 125 at the wheel. I love the V4 power curve as the torque down low is similar to a V2 but the lighter rotational mass allows it to spin up more quickly and rev out past the typical V2. That love of the V4 brings us to your next observation.

2. "If you just want a powerful V4, what about Aprilia as that route will provide what you seek, albeit with horrendous fuel consumption? What about in a year or so when Honda release a new RVF1000, with more power than you'll ever need, better handling and lighter than we'll ever be able to achieve with a VFR?"

I have had to talk myself off the Aprilia RSV4 so many times. I actually rode the first one that was brought to the US to train the service techs. It had no serial number plate and was listed with the DOT/Feds as not ridable so I was limited to a parking lot but it was sublime. I love the Aprilia solution to the unreliable cam chain tensioners which is to drive on bank of cams with a chain (no triangle so no tensioner needed) and the other bank with a gear from the chain driven cam. You get just a hint of gear whine if you know what to listen for . I don't have one because early ones had fuel tank issues and by the time they corrected that I was back to holding my breathe waiting for the 1000cc Honda V4. This engine exercise is primarily for a dedicated track V4 but depending on the cost and complexity of the evolution I may build an additional item and pop it in a late model 6G or 8G used VFR. None of this will preclude me from putting my name on the list for a 1000cc successor to the RC45 if that ever appears from the vapors of my dreams.

3. "Personally, I do like the idea of achieving a power output equivalent to the RC45 as drivability could be maintained, but I wouldn't really be looking for any more than that."

This is the neighborhood that I am looking at but with torque output in the next postal code, closer to 75 ft-lbs. and not the upper rev range of an RC45. To have a realistic shot at achieving that level of grunt I will need displacement so I want to know what the boundaries are for displacement within the RC46 block. A dream scenario would be to have a set of RC45 cams made and when stroking the crank change the firing order to 360 degree. Too much work really but one can dream, no?

4. "Like I said, I'm not trying to knock the idea of pushing the boundaries of the VFR, but how do your desires fit with the alternatives I mention above?"

Want a Honda V4 for the track (and possibly for the street) that has +- 75 ft-lbs of torque and 150 hp. Like the RSV4 but it is very small for a 34" inseam pilot my age and doesn't have Honda service network and reliability but more than makes up for it with 185 hp that guzzles fuel like a sailor on liberty. Don't want a CBR and if I did choose an inline 4 repli-racer it would either be an R1 (flat plane virtual V4) or I would stick with a 3/4 liter GSXR.

[BiKenG]

Yes, the Aprilia comparison is skewed by the (no doubt accurate) perception that Aprilia's product and service is not up to Honda's standards. Let's face it, a manufacturing and service company that simply closes down for a month during the height of the season during which every owner wants to be using their product, just so they can all go on holiday at the same time, doesn't deserve the consideration they do get.

And then there's the horrific fuel consumption. I developed my FireFighter as a bike to use on my annual European tours and very good it is too, as Mohawk will testify. I had been considering a new Tuono V4R which is a terrific bike, but even getting off an SP-2 the Tuono felt like sitting on a plank. Great looking seat, but what a plank. You may not consider a CBR interesting but a FireBlade is a very consummate machine. More performance than you'd ever need or could possibly use on the road and thankfully devoid of electronic gizmos. Just a bloody good bike and quite frugal. A 2008 model I had returned 53.4 mpg on several of my Euro trips, carefully recording all fuel used and the mileage at each stop and overall, so not just a quick tankful calculation. A Tuono rider had recently returned from a very similar trip (France, Alps etc) of similar mileage (about 2,500 mls) and he had also measured his fuel usage and achieved between 33 and 34 mpg.

It makes me laugh when riders say "I didn't buy a sports bike to worry about fuel consumption" which is a ridiculous statement. Just how much fuel can be consumed before it is considered unacceptable. In the end, forearmed with the knowledge of a FireBlade's consumption, I calculated the difference between the fuel costs for the 2 bikes would more than pay for a new pair of tyres for each trip which kinda put it into perspective. Needless to say, i bought another FireBlade and turned it into my FireFighter.

My problem with in-line 4 performance bikes is they are buzzy feeling (not vibes) and frenetic. It's not a relaxing ride and you're always looking for an extra top gear. V twins are the opposite but have their own foibles. For me the V4 is the best of both worlds. But I digress.

The big issue I see looming for VFR800 performance enhancements will be the RVF1000. I am very sure we will be seeing a production, although probably homologation special as per RC45, V4 1000 that will be the intended bike for WSB and performance-wise this will blow any VFR800 based machine into the weeds. Again, note, I'm not knocking the VFR800, just thinking ahead. But, it will be a full on race track refugee with all the 'features' expected. Undoubtedly with a LOT more electronics than we've previously seen from Honda and definitely race styling which certainly does not appeal to me.

I love the idea of a 1000cc Honda V4, but with the power it will undoubtedly have and all the electronics, I'm not sure I'd even want it if they made a decent naked version to suit my preference. Nah, who am I kidding, of course I would.

But I actually think that a VFR800, in a naked style that I like would be a better road bike. Still fast enough and with better low speed manners. 120hp, at the rear wheel, that would be nice. But it HAS to maintain perfect low speed drivability, at least as good as a std. VFR. Hmmm, will RC45 cams fit straight in?

[BiKenG]

CornerCarver, one more thing, you said the Aprilia has no cam chain tensioner due to just driving a single cam with the chain, but why would that eliminate the need for a tensioner and as far as I can see, the Aprilia V4 uses a tensioner just like every other bike with a cam chain.

Are Honda's tensioners still so much of a problem? I know they've had their issues in the past (I was there during the CX500 debacle), but I'm not aware of any undue tensioner problems these days, or are there still issues not being experienced by other manufacturers?

[BiKenG]

The RSV4 has a cam chain drive on both sides of the engine and both seem to have the same tensioning arrangement - except when they re-interpreted WSB rules and replaced with gear driven cams for racing. But I think the authorities put a stop to that.

One thing about Honda is, they never give in. For example, the CX500 was trouble right from the start. Everything. Cam chains, tensioners, generators, CDI, big ends, mains. Absolute nightmare. Japan even shipped short blocks to be put into bikes whose engine had badly failed, just to keep customers on the road and they have NEVER done that, before or since.

There were 2 of us performing the new model training on the CX500 and knowing the problems Honda had had in the past with bikes like the G5 (remember those), we proudly displayed the wonderfully short cam chain and tensioner of the CX and proclaimed, "well we won't have any trouble with this will we". Talk about having to eat ones words. The worst disaster of a bike Honda ever produced, as I said, almost everything went wrong. Honda felt so bad they took all the Service staff out for dinner (who said bun fight) just to say Sorry.

But they kept on working at it and as each revision of the cam chain tensioner was introduced and quickly failed, they designed a new one, until they didn't fail. All the other problems also similarly worked on and re-worked and eventually it became probably the longest lived bike on the roads that you've ever seen, with really old ones still going strong so many years later. Never liked it myself but it was actually very popular and became a very good and extremely reliable bike. But what a turnaround.

That debacle, closely followed by problems with the first VFs was instrumental in Honda designing that first VFR with gear driven cams. It was crucial that Honda regain 'face' and the new VFR just HAD to work right with no chance of old problems like that re-surfacing. All of which was our gain as we got a brilliant bike that is still going strong, even though it has now reverted to chain driven cams. So I'd hate to think cam chain problems had returned.

[gll429]

blah blah blah.. apila , blah duc blah blah blah blah..

we all know there are more powerful bikes out there..

the point is getting the most out of a honda vfr even if its modded in insane ways..

[CornerCarver]

CornerCarver, one more thing, you said the Aprilia has no cam chain tensioner due to just driving a single cam with the chain, but why would that eliminate the need for a tensioner and as far as I can see, the Aprilia V4 uses a tensioner just like every other bike with a cam chain.

Are Honda's tensioners still so much of a problem? I know they've had their issues in the past (I was there during the CX500 debacle), but I'm not aware of any undue tensioner problems these days, or are there still issues not being experienced by other manufacturers?

I should have clarified my statement regarding the cam chain tensioners.

Without a pair of cams and drive sprocket the chain does not have to make an isosceles triangle but just a mostly parallel loop around the drive and driven sprockets. This arrangement requires less pressure from the cam chain tensioner because there is much less slack to be taken up when compared to a triangular configuration of drive and driven sprockets.

I don't know if Honda has improved their CCT design or not or if the VFR's use CBR style CCT's still and maybe the only difference between all the CBR guys who complain of CCT wear and purchase aftermarket CCTs is just a result of CBR's being consistently rev'ed higher and harder than VFRs.

[CornerCarver]

Yes, the Aprilia comparison is skewed by the (no doubt accurate) perception that Aprilia's product and service is not up to Honda's standards. Let's face it, a manufacturing and service company that simply closes down for a month during the height of the season during which every owner wants to be using their product, just so they can all go on holiday at the same time, doesn't deserve the consideration they do get.

And then there's the horrific fuel consumption. I developed my FireFighter as a bike to use on my annual European tours and very good it is too, as Mohawk will testify. I had been considering a new Tuono V4R which is a terrific bike, but even getting off an SP-2 the Tuono felt like sitting on a plank. Great looking seat, but what a plank. You may not consider a CBR interesting but a FireBlade is a very consummate machine. More performance than you'd ever need or could possibly use on the road and thankfully devoid of electronic gizmos. Just a bloody good bike and quite frugal. A 2008 model I had returned 53.4 mpg on several of my Euro trips, carefully recording all fuel used and the mileage at each stop and overall, so not just a quick tankful calculation. A Tuono rider had recently returned from a very similar trip (France, Alps etc) of similar mileage (about 2,500 mls) and he had also measured his fuel usage and achieved between 33 and 34 mpg.

It makes me laugh when riders say "I didn't buy a sports bike to worry about fuel consumption" which is a ridiculous statement. Just how much fuel can be consumed before it is considered unacceptable. In the end, forearmed with the knowledge of a FireBlade's consumption, I calculated the difference between the fuel costs for the 2 bikes would more than pay for a new pair of tyres for each trip which kinda put it into perspective. Needless to say, i bought another FireBlade and turned it into my FireFighter.

My problem with in-line 4 performance bikes is they are buzzy feeling (not vibes) and frenetic. It's not a relaxing ride and you're always looking for an extra top gear. V twins are the opposite but have their own foibles. For me the V4 is the best of both worlds. But I digress.

The big issue I see looming for VFR800 performance enhancements will be the RVF1000. I am very sure we will be seeing a production, although probably homologation special as per RC45, V4 1000 that will be the intended bike for WSB and performance-wise this will blow any VFR800 based machine into the weeds. Again, note, I'm not knocking the VFR800, just thinking ahead. But, it will be a full on race track refugee with all the 'features' expected. Undoubtedly with a LOT more electronics than we've previously seen from Honda and definitely race styling which certainly does not appeal to me.

I love the idea of a 1000cc Honda V4, but with the power it will undoubtedly have and all the electronics, I'm not sure I'd even want it if they made a decent naked version to suit my preference. Nah, who am I kidding, of course I would.

But I actually think that a VFR800, in a naked style that I like would be a better road bike. Still fast enough and with better low speed manners. 120hp, at the rear wheel, that would be nice. But it HAS to maintain perfect low speed drivability, at least as good as a std. VFR. Hmmm, will RC45 cams fit straight in?

Responding to your points that I bolded in order:

Americans who travel have long ago given up trying to figure out how some nations get by with a 30 hour work week and a month off during the summer. The service network here in North America should, if properly managed, be able to figure how to minimize this impact on serving their customer base. If Aprilia would place a large stock of service/repair in NA that was factory owned then they could mitigate the long lead times for these parts often quoted to Aprilia customers.

Sargent to the rescue!

Knowing that you use Imperial gallons I have about this same spread from a VFR depending on how I choose to ride it. Many 6G owners who have dropped a tooth on the front sprocket would love to see 38-40 mpg when exercising the VTEC range.

I agree obviously or I wouldn't be tilting at windmills and looking for property near Sancho.

Obviously even without the RVF1000 looming the market for performance enhancements to the VFR will never amount to much and as a basis for a WSBK platform it damn well better blow away anything from a production based 3/4 liter machine that a nobody like me can finagle.

An RVF1000 full on track refugee does appeal to me. Not sure that I have the proper size attachments to ever flog it on the track in the same manner that I have/do my VFR.

Easy for you to say when your sidebar notes that you already have an RC45 in the stable.

To each his own.

No, the RC45 cams have the wrong firing order for the VFR due to the 360 vs 180 crank layout and firing order.

[BiKenG]

Of course the RC45 cams wouldn't fit. Silly me. Have to copy the profile, like Mohawk has.

Yes I do still have the RC45, but I will be selling it. I just don't want to ride a race track replica on the road any more, too uncomfortable and too frustrating. I always thought about making a naked bike out of it, but I wanted a bit bigger and more power and for my European trips a shaft is very nice - so I turned my attention to the VFR1200 and wonderful that has turned out. But I still hanker for what I could do with an RC45 and then it hit me. Find a pre V-Tec 800 and start with that. Even if I never increase its power, I will enjoy riding it more than I ever would contorting myself around the RC45. If I want an adrenaline fuelled blast (if such a thing is possible still in the UK) I hop on the FireFighter which is stupendous - and comfortable. But I'm rambling.

I understand about wanting to do things for ones self, but I suffer from self doubt when there's a ready made off the shelf answer to what I'm trying to achieve. However I'm in no way criticising anyone who wanted to press on ahead on their own. I just think it's an interesting discussion, although veering off topic I guess from the original technical banter.

[GearWhyne]

Has anyone had cams redone at the standard timing, but with a bit of extra lift?

It was a neat and cheap mod on a 4 cyl car I had years ago and gave a nice bit of extra shove everywhere.

I also searched a lot a couple of years back for anything done with playing with the ignition advance (on the 4th Gen), but didn't find much at all. On decent fuel I can imagine there being some easy gain there if there's a part or method to do it that isn't costly or a hassle. I probably didn't look at Power Commander type stuff that people use on the 5th Gen and up, so maybe that's already catered for in some way, but I remember back around '97 that a guy I knew had changed a part with something aftermarket on his GSX-R750 that moved the spark enough to help make his Suzuki howl more like a World Supers ZX-7R.

[BiKenG]

Seems to me the first thing to establish is the difference between the 5th Gen and the RC45. Mohawk is possibly the best source on this as I think he copied the cams, but whether that was profile and timing I cannot remember. What I can remember is that the RC45 goes very well. What has to be done to a 5th Gen to achieve that, without resorting to overboring (or ruining the tractability etc). Surely it must be possible?

Cams can of course be copied, fuelling and ignition should all be controllable by a Power Commander or equivalent. What else?

Are the RC45 throttle bodies larger? I know they're not huge and making them larger doesn't work as Larry (Busylittleshop) found out. How do they compare to the VFR? There's probably info on this somewhere, but anyone know offhand the sizes?

There's 2 levels of mods I think. Those that I'm talking about here that are relatively simple and then there's the overboring which is a whole different level of commitment - and cost.

Does anyone manufacture suitable cams, i.e. so you don't need Honda OEM ones to start with? Or is that actually a more expensive option?

Sorry if these are old questions. I guess I'm a bit late to the VFR800 modding party.

[BiKenG]

OK, searching further reveals the RC45 throttle bodies are 46mm while the VFR uses 36. Quite a difference it would appear, but as they both use 40mm velocity stacks and Mohawk has shown, not a serious restriction in real terms. Get to keep a good midrange too and that's important for the road.

So the crucial upgrade is cams. Would it not be worth finding a suitable 'supplier' and organising a 'group buy'?

[CandyRedRC46]

OK, searching further reveals the RC45 throttle bodies are 46mm while the VFR uses 36. Quite a difference it would appear, but as they both use 40mm velocity stacks and Mohawk has shown, not a serious restriction in real terms. Get to keep a good midrange too and that's important for the road.

So the crucial upgrade is cams. Would it not be worth finding a suitable 'supplier' and organising a 'group buy'?

The factory throttle bodies can be slightly overbored from factory 40mm at Entrance> 36mm at butter fly > 35x32mm at the exit; to overbore 40mm at entrance > 38mm at butterfly and exit. I have had that for over a year now and it works very well.

As far as modifying the ignition timing, this can not be done with power commander or bazzaz. It can be done with an ECU reflash by Guhl on the 2006 and newer VFR800s or with a Rapid Bike Racing module.

I have had the Rapid Bike Racing module and it has been working great since October 2014. The sixth gen models seem to respond extremely well to about 5 degrees advance in the low to midrange RPMs and 1 degree of retard on the top end, while the fifth gens seem to only like about 2 degrees of ignition advance. I have a feeling this has to do with the vtec models only having one intake valve open in the low to midrange.

http://www.vfrdiscussion.com/forum/index.php/topic/79208-throttle-body-overbore-teaser/page-1

[HighSideNZ]

I agree with you CRRC46 re the advance.

With my Gen 5 engine in a Gen 6 frame, and running the Gen 6 electronics, I've had to retard the ignition at the top by about 1 deg and the midrange back by about 3 deg with the RB Racing.

Phil

[Rush2112]

You guys are AWESOME!!!

I love this stuff!

BKG... pull your crank and cams out of your RC45 and stuff them in a 5th gen engine, figure out the FI and ignition and you have a dream bike... all day comfort and power. I am being silly...

I'm working on mildly stroking a 5th gen crank to achieve an actual old MotoGP spec 800cc, increased compression with RC45 profiled cams... why??? I don't really know.... It is just friggin' fun!!!

...now, if I could only get a proper exhaust header...

[The Phantom]

Has anyone had cams redone at the standard timing, but with a bit of extra lift?

It was a neat and cheap mod on a 4 cyl car I had years ago and gave a nice bit of extra shove everywhere.

An Australian company did some cam work for early V4s (VF750). An old VFRD topic that touches on this (I never did look into it any further):

http://www.vfrdiscussion.com/forum/index.php/topic/63059-camshaft-specs/

Here's the spec from the VF750 page.

[GearWhyne]

There were aftermarket cam reworkings for the 1st Gen that at least a couple of guys I knew put in at the time, but I never knew the name of the company. I rode one and there was a nice extra surge as the revs climbed. An unscientific performance evaluation over a quarter-mile had the VFR just hanging close behind a VF1000F by the end of the run, before The Plod showed up and enquired what the VFR went like.

Given the stock header and carb/intake layout, especially the downsizing on the 4G and mild tune, I've wondered if a sensible bit of extra lift could be an ideal mod, and easy enough for most companies, even if not ones that are bike-inclined.

I'm sure there are threads I found here a couple of years back about some owners sending away sets to get redone. With an aftermarket slip-on, possibly even just the inlet cams would do.

But the ignition advance on the 4G seems like something no one really found a mod for, as far a hunt around online some time back could find.

A bit of advance and a bit of extra lift sound like about all that would be worth doing unless you want to get a fair bit more serious and spendy. Aside from gearing, of course.

[CandyRedRC46]

On a 3rd/4th gen vfr750, I think a timing plate would be easy enough to fab up. The problem would be, being a fixed adjustment, you would more than likely be increasing power at the topend at the expense of low end or vice versa.

How awesome would it be if we could buy off the shelf stage 1, 2, and 3 aftermarket bolt on cams for the vfr800? Just buy cams, slap them in and retune, without having to experiment with profiles and degreeing and worrying about possible negligent companies etc...

[GearWhyne]

Evidently this German mob still still over a "Stage 1" cam reprofile for 3rd and 4th Gen, but nothing for earlier or later models.

A bit of a change from the usual story of later models getting most of the goodies these days.

http://www.gw-racing-parts.de/index2.php?view=nocken&HID=15&lan=en

Almost at the bottom of the list.

250 degrees and 9mm lift quoted for both inlet and exhaust with no specific mention of needing different springs than stock. Possibly a fair indication of a safe amout of extra lift for otherwise stock harware. 5th Gen was enough of a redesign that what might be doable along similar lines might be more of a guess, but the above numbers might be something to take onboard.

I'm more interested in just some extra lift without otherwise altering overlap any more than necessary, though the increased duration might just be maintaining the same lobe profile with that greater lift. I wouldn't want to move the curve to higher RPM with the smaller inlets/header diameters on the 4G compared to the 3G, although it's for both models. It does say more top end, but whether the extra lift gives any net gain down low is the question.

Unless I'm missing something else, more charge/higher pressure making for faster flame propogation might mean leaving the ignition advance stock would be the way to go for a daily road rider.

585 (Euro, I'll assume) doesn't sound bad, depending on freight and how it exhanges with one's own currency at any given time.

I wonder why they don't do the 5th Gen?

*Edited to add link for pricier tuning packages, like headwork and such - http://www.gw-racing-parts.de/index2.php?view=tuning&HID=15&type=VFR%20750%20RC36&von=1990&bis=1997&lan=en