Blazerdman Posted July 5, 2016 Share Posted July 5, 2016 Hi guys, I recently bought an 02 VFR and have fallen in love. I am certain I will keep this bike for as longs as it lives, so with that in mind and 54,000km on the clock I've started thinking ahead to engine rebuilds and the such and figured if I'm gonna have it long enough for that to happen I should look into getting it overbored and possibly stroked as well. I've done a fair amount of research on the overbore so far and have come to the conclusion that 74mm maybe even a 75mm will work, albeit with a lot of work I'd have to do. My main question I guess would be is it possible to have the stroke increased as well? I'm new to V4 engines so I'm just not educated in such things and have come up with nothing via normally reliable google. Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted July 5, 2016 Member Contributer Share Posted July 5, 2016 Someone with specific knowledge will be along soon, but if I'm not mistaken the RC46 engine (VFR800Fi and VTEC), (72 x 48mm, 781 and 782cc), was a stroked version of the RC45 engine (72 x 46mm. 749cc), so there may be no physical space to increase the stroke any further. Overbore is possible, both using the (obsolete) Dynamo Humm big bore kits as well as using CBR 929 pistons as detailed elsewhere on the forum. The other (obsolete) option was a supercharger from A&A Performance. There aren't a lot of VFR hot rodders...but you will probably find them on VFRD! Ciao, Link to comment Share on other sites More sharing options...
Blazerdman Posted July 6, 2016 Author Share Posted July 6, 2016 Yeah I read Mohawk & HighSide's threads on the overbore's and am certain I can do them, but I'd like to make what we all wanted Honda to do with these and make a litre bike. Or at least I'd like to make something as close to that as possible whilst still being a reliable daily commuter kind of bike. Link to comment Share on other sites More sharing options...
Member Contributer Marvelicious Posted July 6, 2016 Member Contributer Share Posted July 6, 2016 What? Are you too cheap to buy a RC213V-S? Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted July 6, 2016 Member Contributer Share Posted July 6, 2016 I think you'll find because of the design the engine block, and bore materials the 840cc 5th Gen and the 870cc 4th gen overbores that Dynamo Humm chose (with a LOT of know-how, experience/testing and thought) with improved cams are the quickest/best combination of achieving what you said you wanted: A 1000cc litre bike we all wanted " I'd like to make something as close to that as possible whilst still being a reliable daily commuter kind of bike " ...Messing with larger exhaust or intake valving is futile--the sizes (not materials) were designed with Superbike/GP 800cc racing in mind..so thats a bust. You could mess with the crank, go for extremely light pistons and Ti fractured con-rods...but again, it buys you a few rev's but not necessarily worth the price/performance increase ration... There is no such thing as a free lunch. But there is a difference between a loaded 5 Guys hamburger (VERY good) and a setting at a three star Michelin Resturaunt (RC213V)...the overbore is limited and with good cams still get you near 140hp (HighSideNZ 136hp)...not Litre bike power (of today) but darn tasty! Link to comment Share on other sites More sharing options...
CandyRedRC46 Posted July 6, 2016 Share Posted July 6, 2016 I believe Mohawk already confirmed that 5th gens cannot be stroked, due to interference with the cam gear drive, but still no word on if 6th gens can be stroked out a few mm's. The VFR800 has a ridiculous rod:stroke ratio of over 2.1 (101mm or 102mm rod and 48mm stroke), so a 2mm stroke would still have a rod ratio of at least 2.0 which is still great and capable of very high revs, but this is all dependent on whether there is adequate clearance in the 6th gen block. Link to comment Share on other sites More sharing options...
Member Contributer Mohawk Posted July 7, 2016 Member Contributer Share Posted July 7, 2016 The problem with stroking a combined case/block engine is it has to be done on the crank using shorter Pistons or rods. On a separate block engine, you just add a spacer under the block, then adjust the crank throw to suit & use normal Pistons. The thing is you would be hard pressed to find a piston with a low enough deck height to make it worth the effort. You may be able to get RC45 rods which are Ti &/or get custom ones made, but again a lot of expense for very little return. The same goes for the 6th gen. Remember the 800 is already a stroked RC45 engine ! I have 120hp without taking the engine apart & HighsideNZ has implemented my 2mm over bore in the standard engine for 825cc & copied most of my other mods for approx 140hp. Dynomo Hums big bore for the 800 was 870cc, using JE pistons & Iron liners, this only made 120hp but with more torque in the low end/mid-range. If you really want to throw money at this, then you could take it to a maximum 916cc with a big bore alone, but you will have a bill of 6-10k dollars, your choice ;) Link to comment Share on other sites More sharing options...
Member Contributer JZH Posted July 7, 2016 Member Contributer Share Posted July 7, 2016 "Speed costs money. How fast you wanna go?" Ciao, Link to comment Share on other sites More sharing options...
Blazerdman Posted July 8, 2016 Author Share Posted July 8, 2016 6-10k, damn might as well create my own frame at the same time and new electronics at that rate. Cheers for the info though, given a lot of food for thought. Link to comment Share on other sites More sharing options...
Member Contributer zupatun Posted July 8, 2016 Member Contributer Share Posted July 8, 2016 If your bike's your second or you're single and like to tinker then I think getting it bored out, doing the head right and pistons and cams like HisideNZ or Mohawk would be TONS of fun and you'd love the outcome. If you're into learning about how to work on engines, FI to create a sleeper or a show bike then this route is up your alley. But it is time consuming, a long term process (not a couple months obviously) and looks like patience pays off. However, if you want to send it off to people and have it done right the first time by handing over a check...then you're just plain out of luck. When Dynamo Humm went out of business, getting a turn-key solution went out the door. My friend has an 840cc 4th gen and he loves the extra 10+hp...and another (NYC guy) still has his 870cc 5th gen...but it rarely gets ridden until he retires in Arizona in a year or two--it is a marked differnce over my 5th gen...just roll the throttle and the front end comes up. I don't know if HisideNZ or Mohawk totaled up the cost to do what they did individually from a $ for parts perspective...obviously if you total up their labor/time it will be much more. I haven't scoured past posts to find that or not... Matt Link to comment Share on other sites More sharing options...
Member Contributer HighSideNZ Posted September 7, 2016 Member Contributer Share Posted September 7, 2016 Just to chime in on this thread. Yep, it can be done but the cost is the main constraint. As Mohawk has alluded to, He came up with the initial idea as to using the 74mm pistons from the CBR but even with those you need to deck the pistons and deepen/relocate the valve pockets etc. So if you don't have the tools then it is going to be an up hill battle. It took me quite some time to find a company capable of, and will to, bore the MMC liners and they did a great job. All the rest of the work was manual by me and you do need to balance pistons, rods etc as the masses are quite different from stock. There are even simple things like opening up the stock head gaskets to suit the new bore, that is not a trivial task if you don't have the equipment. I feel it was well worth it, and now with 30,000 km on the engine it is still going strong. But you have to be prepared for the long hours of manual fettling. One last thing. The biggest improvement from a single items is the exhaust. I could not find a TwoBrothers header system so bought an RC45 Shark system and cut it up and made it fit. The difference on the first run after that I feel was 20 hp. Phil Link to comment Share on other sites More sharing options...
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