Fastdruid

So, I was reading this VFR world thread and it got me thinking. The common denominator between the old and new engines (which both had the same behaviour) was the clutch hydraulic system. However when I came to returning it to the road the clutch master cylinder was in need of new seals but while replacing them, on inspection the bore was corroded so I replaced it with an newer "recon" second hand one which was claimed already rebuilt with new seals. It's possible though that some muck was dislodged and pushed back up which has caused an issue. I'll think I'll have a mess with the hydraulic system tonight, double check the return port is clear and flush/bleed it through with more fresh fluid. I've got to see if I've got any more spare slaves (the one I've found is seized so will probably need new piston as well as seal) but I'm sure I've got at least one more somewhere! Maybe later a justification for an oberon slave!

Nothing added. Only ever used "bike specific" oil.

Thing is though.... while the bike has 72k on it the current engine has ~31k (26k when I fitted it) and it had the same "odd" clutch slip in that it would slip when cold but as soon as it warmed up it was fine. I swapped the clutch at that point and that clutch now has only 5k on it. I kept all the plates because they were all on the upper limits for thickness. The brand new clutch did exactly the same as the previous one *AND* the previous engine. It was never a massive concern however because outside of the depths of winter it was already warm enough by the time I'd got to suitable roads! There are two constants. 1) The slave cylinder (and the master cylinder etc). 2) The oil. Now I did find a suggestion somewhere that the gasket thickness was somewhat critical to the clutch so I refitted the gasket between engine and sprocket cover that was previously missing. Somewhat foolishly I didn't test things *before* replacing it but now it slips all the time even when hot. It is however about 11 years since I've ridden it "in anger" and it hence my suspicion that it's the springs that have relaxed over time. Now I have no idea what rate the springs are but if for example they are 20N/mm then for each mm they've lost in length the clutch has lost 100N of clamping pressure. The "spare" springs are ~1.5mm shorter than they should be, I suspect the ones in there have lost more.

Right now I'll settle for it not slipping! I can cross the bridge of it being too heavy later as I have a hard limit of a trackday next week! Either way though I need to check it out, there is no point in taking it apart without the parts to fix it and EBC springs are both cheaper and quicker to arrive.

Well, to put it another way, I wouldn't do a trackday with it as it stands as it would be massively frustrating but there is a VFR/RVF400 meet up at the weekend that we might go to (with my wife on her RVF400) which is a ~50mile round trip ride. I'd happily do that on it with the current level of clutch slip.

This issue "went away". When I went back to look at things again it just worked as it should. On looking at the wiring diagram however it was clear that the warning light and the cut out circuit are two entirely separate things (which is how I could have the warning light on but it didn't cut the ignition). My suspicion therefore is a dodgy switch. Although I guess I can't entirely rule out a short in the wiring harness. It may be one of those things that clears up with use, the stand has after all barely been used in 11 years!

So I can't remember exactly what I had in it before. I know it was Motul but which one? I do know that I stuck Motul 5000 in there this time. Thinking about things though, the springs that I've got spare haven't been in an engine for 16 years but had lost a chunk of length. I can't remember but I suspect I swapped the springs for new ones (on the basis that the DSS Clutch kit includes them), if I did then they're still 16 years old now. If I didn't then they're 34 years old. On that basis I ordered some new EBC springs. I've already ordered a gasket so I'll swap them out when they turn up and inspect the plates and frictions at the same time. In the mean while I'll bleed the clutch and see if the oil change has helped. It's still ridable... just can't give it full throttle!

I'm suspecting oil or something really odd going on with the slave. Someone did suggest air in the line and I guess maybe it might prevent it returning as much as it should. I didn't *actually* bleed it after taking the slave piston out and cleaning things up but rather just operated it until it felt right and the bubbles stopped. Odd thing is that this is the second engine with the *same* issue, we wont go into the sordid details right now but on the original engine...the clutch slipped when *cold* but only once...and then was fine. So swapped in a new engine, lower mileage from an FK (mine being an FJ should have been the same). The good news here is that the new engine was *MUCH* healthier than mine had ever been. The only part swapped over from the original bike was the clutch slave...and I used the same oil. Still did the same, slipped when *cold* for the first full throttle then was fine. I swapped in a brand new clutch. Still did it. Roll forward to now and it's worse. Not just slipping when cold but when hot too. Now I did, purposely put in an oil I expected to swap in not very many miles[1] (and I can't even remember if that was the same oil I used to use) so I've just changed that (to Putoline Sport 4R (this stuff https://www.putoline.com/en/catalogue/product/3249/sport-4r-10w-40/6851/ ). I'll test it out tomorrow. I have also spent some time measuring the old plates I took out from it. They're all *WELL* within tolerance. Standard is 2.92mm-3.08mm and the very worst of them is 3.03mm. Between those and my "for spares" RC35 engine I have a stack that measures 27.7mm (and 9*3.08mm should me 27.72mm). I have a full set of spare steels, all as far as I can tell flat and ~2mm thick (there is size or wear limit given for the steel plates). What doesn't measure up however are the springs I've got two spare sets. They're both in spec but should be 44.4mm and they measure ~43mm. Well within the service limit (41.2mm) but not great. [1] Mostly because I swapped the oil without changing the filter and because while the oil was unopened it was old. I figured ideal to use to flush the engine and then refill with fresh and change the filter.

Another short (17miles) ride out today, more successful. No explosions of coolant. Slightly odd behaviour at one point from the sidestand warning light but apart from that the only issue is that the clutch is slipping under full throttle. Suspect maybe oil so I'm going to change to another brand and see if that helps. If not then its new clutch time.

*EXACTLY*! No fuel gauge, no clock, no little sidestand warning light...but look at it! 😍 Sure mine is more practical but at what cost?! 🤣

It's not a bad dash! Just my least favourite of the VFR750 dashes. My fav is the round dash '86 but equally it's has the least features and is the least practical.

I've owned it since 2004, done about 45k on it but mostly due to having children haven't ridden it in the last 11 years. Not through any kind of "giving up riding", just didn't have the time, then the MOT lapsed and then it needed things doing and whole inertia thing meant it sat. Anyway, for reasons I decided that I would sort it for an up and coming trackday, even if I only do one session on it (I'm taking my normal track bike as well) it was motivation with a firm goal to get it sorted. Even if I don't now take it, it's now running, MOTd, insured and fully road legal so (as it stopped raining here for longer than 10 minutes) I took it out for its first shakedown ride yesterday. Wasn't *entirely* successful as I got home just as steam started rising and a massive gush of water from the lower hose...It's properly burst. Thankfully I have a spare so swapped that over (plus ordered a new silicone set) and fixed a couple of other niggles too, I plan another short ride out tomorrow then assuming that is fine I'll venture further afield.

I'm not sure where you'd put it though. The temp gauge is pretty big on the "round" clock version. Ideally you'd want something akin to the later RC36 bikes, although I'm equally not a fan of the "massive dash" look and my preference from a looks perspective is "round" clock RC24 > "square" clock RC24 == RC36/1 > RC36/2. If you had the "square" clocks you could fit in the later right side clocks with a new overlay to replace the fuel gauge with a volt meter...but then if you're fitting that bit you might as well swap out the fuel sensor for the later one and have a working fuel gauge!

I've probably cursed myself too. Particularly as I've fitted an LED headlight bulb (for more light, not less power). It has also reminded me that I have one of these battery monitors to fit to mine.

Honestly? Yes. FWIW mine is still (at least *I've* not changed it in 20 years and 46k) on the original reg/rec at 72k. I agree with both there. Don't forget just in front of the lower yoke is the oil cooler too so while I'm not sure how much heat comes off it things won't be cool there either. This is not mine and personally I don't like it but equally I think he's gone too far the other way! FWIW I mounted my track bike reg/rec to an aluminium plate that sits inside the tail as far as any heat sources as possible. Which is pretty much where the ECU used to live (and that I moved to hang off the front subframe). Not really practical on the VFR though.

IMO while a neat solution that is not the best place to put it. The frame gets *HOT* and there is significant hot air from the rad blowing straight over those fins and out the side vents. You want it to be as cool as possible and that is going to heat it not cool it. Now the problem is I don't have a better solution, I've got (what looks like anyway) the same one to try and fit to mine and there are no great places for it, doesn't fit in the original location. I'm thinking can go in the space under the seat over the toolkit "pocket" location but given it gets hot enough to feel warmth *THROUGH* the seat I'm not entirely sure that's great either...but then again where is actually cool on these bikes?

FWIW the HBoL gives different ignition timing for the 86, 87, 88-89 and 90 etc. The various Official Honda Manuals however say 15° BTDC for the 86 and 15° BTDC for the 88-89 and 15° BTDC for the 90-96! I would therefor suspect that the timing "change" between the two different triggers is less an actual change and more the mechanics of how its triggered. Don't forget that the pickups also change between 86,87,88-89 and 90+. I would leave well alone, if you want to mess with timing it would be better to just fit the later trigger wheel, an aftermarket ECU and move the ignition advance in "software".

If you have the Honda manual it gives some detail about how it works. 1 and 3 are rear, 2 and 4 are front cylinders. Essentially the pulse generator tells it to fire, the cam sensor tells it *which* one to fire. The manual says it's a microcomputer... I think that's somewhat over-egging it!

Ignore the drawings on the 'fiche as anything other than a "suggestion" of location! Never, *EVER* take them as any idea of what the part looks like! I've noticed on a *lot* of parts they've totally changed the part but re-used the earlier drawing. The only times it's vaguely accurate is when they've added a totally new part (as different to changed) and hence drawn something new. Quick example. https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/VFR/1989/VFR750FK/Frame/FRAME/13ML7G41/F__3100/2/10183 Yeah, the 88-89 subframe looks *NOTHING* like that! Note it also goes the other way too with the earlier 'fiches updated to add in later options to allow one image to serve multiple bikes, again as an example. https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/VFR/1986/VFR750FG/Frame/REAR-FENDER/13ML7G41/F__2600/2/10147 '86 'Fiche, yet shows the 88+ sub-subframe as well as parts for the VFR750P!

Totally get you, I was just giving you (and of course anyone else reading this later) the information on what needs doing. Personally, if the electronics are otherwise good[1], although a pain in the **** because of the limited number of parts left I would try and get a good s/h '86 clutch because it is such a pain to have to get and swap so many parts. Personally I'm going going down the swap everything route with my '86 engine....but I have all the parts I need already and more importantly, I *don't* have an '86 ECU! [1] ie if the ECU itself is fine (which isn't guaranteed with the age of them), simple test of course being you can bump start it and it runs fine!

86 is an analogue ignitor system utilising a simple trigger along with a cam sensor. The 87+ uses (IIRC) 12-1, ie 11 regularly spaced teeth and one missing and hence calculates the crank position. 87 uses its own ignition system which is different to the 88-89 which is different again to the 90-97. You can retrofit the newer parts to the 86 however you need quite a few more than you'd expect, you will need. 1) Pickups 2) Starter motor (one off an RC30 will do [not even joking]). 3) Idler gear. 4) The actual sprag/starter ring *AND* the gear. 5) ECU 6) Tacho 7) Fuel cut relay (off 87+) Plus some re-wiring. The additional parts are required because Honda changed the starter motor number of teeth, the idler gear and the starter gear etc. So because you need to change the starter gear you then need to change the idler and because you need to change the idler you need to change the starter! Tacho changed 86, 87 and 88+ 86 runs a dedicated tacho (and fuel relay) connection. 87 (US 700 as well) runs the tacho off the #1 coil. Fuel cut from #3 coil. You could use the 87 tacho on any year if you use a feed from a coil. 88-89 RC24 and 90+ RC36 Runs a dedicated tacho connection that is different to the 86. Fuel cut from #4 coil. 87 is even more of an odd-ball as it's kind of half way between the 86 and the later models. If you're going to bother to upgrade parts then I'd avoid it, might as well go all as then you have 8 years (US) or 10 years (rest of world) worth of s/h parts to pick from rather than one years worth! The RC36 is identical to the 88-89 RC24 for all the relevant engine internal parts except for the pickups. Unsure what the difference is between the pickups (HBoL does give a different resistance value for the "L" model) but it does mean if you were to pick up all the relevant engine internal parts from an RC36 they should fit the earlier RC24/26. Easiest ECU to retrofit would be the 88-89, you can pick the connector shells up and just repin the old connectors to new ones and it fits exactly in the same space. RC36 uses a totally different connector and would be a pain. Only question is though...is the 700's timing different to the 750 and is that enough to matter?

Stock '86 270mm Stock '87+ (uses different linkage and a harder shock) 280mm Recommendation generally is to use the '86 linkage with up to a 295mm shock (ideally an adjustable one).... but that is really needed if you're also fitting CBR600F2 or CBR600F3 wheels with more modern tyres as a 160/60 R17 is 41.4mm smaller diameter (1.63") which lowers the back ~20mm (~4/5"). They can afford to go up quite some way before it gets anything other than stable, you can lower the front instead but then you start to lose ground clearance. Not a problem on the road but is if it goes to the track (as found out with the footpegs!) Also if you've already stiffened the front then effectively it's raised it quite a bit. Fork springs are almightily soft as stock, I measured mine (stock) as 40mm (~1.5") unloaded/static sag while it should be about 30-35mm (for the road). That said, I'm genuinely unsure about wtf is going on with the Honda claimed rake/trail on these, having drawn it out based on measurements from mine ('88) the claimed 27°40' and 108mm (4.3") is physically impossible. Either the '86 runs a different offset and they didn't update the specs or they're measuring rake and trail individually under different conditions! I figure though using a 120/70R17 front can take it to about 26° while keeping trail at a nice 100mm (4in), or a tiny bit more for the original tyres (as they're larger diameter which all things being equal increases trail).

I must admit I wondered why the earlier RC24/26 had one while the later RC24 didn't. The 88-89 RC24 however has a sidestand switch with both a warning light and a cut-out! Unsure if the later one would just fit though (and you'd have to import from Europe etc), Honda moved the position of the gear change shaft so things are a bit different in that area. https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/VFR/1986/VFR750FG/Frame/STAND-1-/13ML7G41/F__2300/2/10147 vs https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/VFR/1988/VFR750FJ/Frame/STAND-2-/13ML7G41/F__2301/2/10171

Thanks for sharing, love to see the differences between the various RCs, particularly the ultra rare versions. Shame you feel you need to sell but totally understandable. It's hard enough for parts for the "common" older VFR's without the problem of rare "unobtainium" parts. The low down mounts though, more likely carried over from the RC24. The RC30 being essentially a production version of the RC24 '6X' engine with new/better heads and a *much* better more advanced production version of the chassis from the (endurance/prototype race bike) RVF750. But the RC24 also used those mounts so it wouldn't have been a massive leap for Moriwaki to experiment with (re)using them and then of course Honda then did the same with the RC45 (and similar with the baby NC30->NC35). "Bubba Shobert's VFR750" Moriwaki RC30 Chassis

A few more "Fairing" sources to add. https://www.skidmarx.co.uk/road-replacement-bodywork#/model-vfr750_fg_h https://www.skidmarx.co.uk/road-replacement-bodywork#/model-vfr750_fj_k Race fairings https://www.raggededgeracing.com/fairings/honda/ Also Robert Wittey from PDQ Motorcycle Developments does race fairings (UK Only).