1986 Honda VFR750F

Discussion in 'Specifications' started by michael, Jan 29, 2006.

  1. Fastdruid

    Fastdruid New Member

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    The 86 has an analogue ignition system with a cam sensor, the 87 has a digital ignition system without a cam sensor, the 88-89 is different again with difference advance settings...Maybe. The HBoL says FG-FJ 15-37deg BTDC with the FK being 12-35 BTDC. Except the 88 'FJ' had two ECU's, the later one was identical to the 89 'FK'. I think the HBoL is wrong here in that the early FJ was the same as the FG-FH but the later one was the same as the FK.

    The 86 drives the tacho off the ECU (same wire also triggers the fuel pump relay) while the 87 drives the tacho off the #1 ignition coil (and triggers the fuel pump relay off the #3 coil.) The 88-89 then goes back to a (dedicated) wire from the ECU for the tacho with the fuel relay now off coil #4.

    Not to mention also that the 86 cams themselves are different from the 87 both in carrying the aforementioned cam sensor pickup but also being "sprung".

    In addition to all that the pulse generator and pickups are all different between the 86 and 87 and then the starter, idler and pulse generator again are different to the 88/89. Also the crankcase covers differ, there are 3 different right types and two left. The alternator swaps direction between the early and later bikes and the crank, flywheel etc all change to match.
     
  2. Fastdruid

    Fastdruid New Member

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    From memory the VF1000 was based on the VF750, the "R" being based on the "F" but with gear-driven cams. I believe that the VF is wider than the VFR but I read somewhere that the engine mounts all line up.

    So maybe...but it might be too wide.

    If you're in the UK and have a spare VF1000 engine I've got a scrap frame you can test it with.

    Although as the VF1000R only makes 122PS I personally think you'd be better off boring the VFR750F out to 840cc which would give you as much power but with far less hassle.
     
  3. BiKenG

    BiKenG New Member

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    Ah, so the '86 RC24 engine uniquely had a cam sensor. Hmm, could be handy when adding fuel injection.

    I believe a VF1000 engine will fit into a VF750 frame, and the first VF1000R heads were narrower than later ones which might be crucial. But how close are the engine mounts between the VF750 and the VFR750 RC24. Indeed how close are they between the RC24 and the RC36?

    How easy is it bore an RC24 engine? Seems like all of them, up to the 800 are rather limited in that respect due to the lack of thickness of the liners.
     
  4. Fastdruid

    Fastdruid New Member

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    It's also got smaller valves than the 88/89 bikes, along with redesigned cam gear train.

    Worth of mention also is that the gearboxes are different also. 88/89 (and RC36) have the same gearbox mechanism as the RC30 (only ratios differ), 86/87 are totally different, even the lever where it exits the cases is different.

    Allegedly a VFR750F will fit into a VF750, no idea on the other way round. https://vfrworld.com/threads/thinking-of-fitting-honda-vfr-750-engine-to-old-vf750f.36671/


    RC36 not very close. Mostly because the RC24 bolts into the rear of the rear head while the RC36 bolts into the side. So for a RC24 into RC36 of the 4 bolt locations (per side) I think two might line up. Potentially 3. While the other way round of the 5 only 3 (maybe 4) line up.

    Then you have the exhaust ports are angled wrong, the thermostat is in the wrong place and the output shaft is too short. Although if you were to run it with a 360 degree crank engine you could do it RCV style and run two exhausts under the seat, two underneath.

    Relatively easy. TTS offered one to +4mm and will still do one although no longer listed. Archive page is here:
    http://web.archive.org/web/20070826...71&PHPSESSID=04f2f2a19a8741a9fa7141453b52bc00

    The big issue is reboring it to size as being a V4 it's somewhat tricky and easy to get it wrong. Gives ~120hp at the wheel though.
     
  5. BiKenG

    BiKenG New Member

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    All good info thanks. I have a couple of potential projects rattling around in my head. :)

    RC24 engine into RC36 frame
    RC46 engine into RC24 frame
    VF1000R engine into Al. beam frame (24 or 36)

    BTW, is your RC24 frame usable?
     
    Last edited: Aug 1, 2019
  6. Fastdruid

    Fastdruid New Member

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    RC24 into RC36 is ideally going to need the RC36 output shaft (you could maybe use an RC30 front sprocket though) and exhausts are going to be a pain, the rear ports both point to the right while the RC24 point to the middle. Plus the heads are quite a bit bigger due to the follower design and I think you'd run into front wheel clearance problems.

    RC46 into RC24... not sure there, ignoring the engine mounts the pivot for the swingarm is going to be awkward and the engine arguably is no better than the 750. The only real advantage is that it revs higher (in part due to being shorter stroke) but makes no more power than a well sorted late RC24 or RC36

    [​IMG]

    A 750 bored out to 72mm would probably make more power and be easier.

    The RC24 (89/FK) frame I have spare is I'm afraid junk, snapped footpeg mount and I'd been having a bit of a hack round with it to see what could be made to fit. Only of use for experiments. Although I do have a V5 for it!
    [​IMG]
     
  7. BiKenG

    BiKenG New Member

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    I realise there would be a lot to match up in either case, but these projects are not imagined as simple engine swaps, but as replicas to mimic an original as closely as possible. Exhaust fabrication is a given and frame modification (cutting, welding etc) not out of the question.

    Regarding the 800 engine, they are basically the RC45 motor and that was the pinnacle of Honda's V4 development (apart from current MotoGP exotica) so ideal for what I have in mind. Someone has put an 800/RC46 SwingArm into the RC24 and there is also an RC45 engined RC24 floating around Japan, so it's doable, although requiring either the rear S/A mount cut off the back of the RC46 engine, or cutting away part of the frame in that area and I think the latter is probably the best approach.

    Is there a simple way to determine the age of an RC24 engine from its engine number? Since there are so many differences, is there any easily accessible list of what engine numbers were produced which year?
     
  8. squirrelman#1

    squirrelman#1 New Member

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    you have a road bike to ride while you're toying with your fantasies searching for a couple more hp ?

    from experience i know that a gen3 engine fits into a gen2 frame but only 3 of 5 mounting points line up, and the shifter interferes with the side stand mount. (not my experiment; i bought it this way.)

    12-1-17 042.JPG

    8--1--17 030.JPG
     
    Last edited: Aug 2, 2019
  9. NorcalBoy

    NorcalBoy Member

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    This person lost me when they tried to say the VFR800 engine was the pinnacle of V4 development.
     
  10. BiKenG

    BiKenG New Member

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    That's interesting, thanks. Can you confirm what you mean by Gen3. By Gen2 you clearly mean RC24, so is that an RC36 engine? I'm amazed it's that close.

    Regarding other bikes, yes I have a few and several with far more horsepower so you misunderstand if you think this is purely chasing horsepower. In fact power has NOTHING whatsoever to do with it. I have bikes I can ride and I have many projects that I devise, for fun, to achieve something that cannot be otherwise achieved. Not exactly fantasy. I have the raw materials and I'm currently at the stage of figuring what will work best together to suit these particular aims.

    I appreciate that some simply buy a bike and ride it, but whilst I do have bikes to ride, I also enjoy re-imagining and re-purposing older machinery. Been doing it for over 50 years and will continue to do so until I am unable to wield a spanner.
     
  11. BiKenG

    BiKenG New Member

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    I'll probably regret answering this, but I will anyway.

    I said that the VFR800 engines "are basically the RC45 motor and that was the pinnacle of Honda's V4 development (apart from current MotoGP exotica)". So not really what you stated I said at all. I guess the question then is what other Honda V4 (road going, not MotoGP) exceeds the RC45's capabilities and that you would thereby claim is the actual pinnacle of Honda's V4 development.

    I will qualify the above to mean pre VTEC VFR800. Although a development from the Gen5, the Gen6 takes the engine further from the RC45 design. I guess I should have made that clear in my original comment. My apologies for that omission.
     
  12. Fastdruid

    Fastdruid New Member

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    The HBoL has them.
    [​IMG]

    Note however this does not cover RC35 or RC37 engines/frames which may be mistaken for RC24. I would avoid such things unless you have a VFR750P or VFR750K and need spares!
     
  13. Fastdruid

    Fastdruid New Member

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    Yes...and no. The trouble is that while the RC46 uses "technology" from the RC45 it is a very much detuned version. The RC24 was the pinnacle at the time (until the RC30), the RC46 isn't even close to being the pinnacle when it came out. Far from it. Maybe if it had been released in 1994 but by 1998 it was old tech.

    Anything is possible with enough effort and it doesn't have to make any sense apart from what "you" want to do (I wouldn't bother with a SSSA in an RC24 for example, there are no advantages apart from looks).

    The RC24 uses the engine as a stressed member though which may affect things. Saying that, while the design of the RC24 frame uses quite a substantial construction to the rear, if you managed to line up the swingarm pivot in the engine with the pivot points in the frame you could potentially bolt though the entire thing.
     
  14. BiKenG

    BiKenG New Member

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    There is more similarity between the RC45 and RC46 engines than you might imagine. Of course the RC45 was in a higher (though not extreme) state of tune, but apparently some RC46 parts were manufactured in modified RC45 moulds. RC46 crankcases can and have been used in RC45 engines (for which there are no longer any moulds available to make more spare parts). Also the valve angle and head design is essentially the same although the RC45 made more use of magnesium and titanium and was hence more than twice the cost, but the fact remains that the RC46 engine is essentially an RC45 engine in a lower state of tune (and with a lump out the back to which the SSSA attached).

    I stand by what I said. Since then Honda have not produced a better V4 road going bike and hence the RC45 remains the pinnacle of their V4 development.

    In truth, when the MotoGP rules dropped max capacity to 800cc (and I think max of 4 cylinders at that same time) Honda's 800cc V4 engine was a direct descendent of the RC45. There's nothing necessarily 'old tech' about the RC45 engine and when planning a mid sized Honda V4 roadster but without the cost of basing it on an RC45, using an RC46 Gen5 engine is the next best thing.

    Will there ever be a V4 FireBlade? Well not with that name, but they ARE working on a V4 1000cc superbike. Whether it ever sees the light of day is another matter, but hopefully we will get to see it. It's just sad that it's taken Honda so long.

    In any case, I am not chasing horsepower. I simply enjoy planning and constructing bikes that are different from what is available in the showrooms. I have several VFR based projects on the go, as well as others based on the CX, CBX, NX, CRF, Gold Wing and Valkyrie - just for the hell of it. Having worked for Honda, I tend to base my special projects on Honda products as I know and trust their engineering expertise. However it's always good to find out if someone has already done certain aspects of what I am planning as it can be a great time saver.

    So many projects, so little time. :)
     
  15. Fastdruid

    Fastdruid New Member

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    You misunderstand my meaning. The RC24, the RC30 and the RC45 were at the pinnacle of Honda tech when introduced. All the rest of the VFR's weren't.

    The RC46 was 4 years after the RC45 and didn't improve on the RC45. The RC45 was the pinnacle of V4 technology in 1994. The RC46 was no more advanced, it was old hat. So even when it was introduced it wasn't at the pinnacle of Honda tech. The only advantage it has over the 750 in stock form is that it's slightly smaller and lighter.

    The RC24 however was a brand new engine with everything improved over the VF750. Smaller, lighter, massively more powerful. The racing experience of the F1 class (basically using VF750 cases) was carried over to the road engines . It was the pinnacle of (roadgoing) Honda V4 tech until the RC30 (which was basically an updated RC24 engine). It was raced (and won) and again the racing experience of the RC24 was carried over to the RC30.
     
  16. BiKenG

    BiKenG New Member

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    Thanks for that, exactly the information I needed.
     
  17. BiKenG

    BiKenG New Member

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    I think there is some misunderstanding and some agreement. I never said the RC46 was the pinnacle or any improvement over the RC45. I said the RC46 was basically an RC45 engine and THAT was the pinnacle of Honda's V4 development. Obviously the 46 is in a lower state of tune etc, but it was the same basic design and although you qualify that by saying 'then', my point is that they've not improved on it since. The RC45 engine was the last and the best road going V4 engine Honda have produced, then and have not bettered since. Ergo, it remains the pinnacle of Honda's V4 development.

    Hence, the best Honda V4 engine (avoiding cost of the RC45) is the RC46. Unless anyone can suggest otherwise.

    Having said all that, I think the VFR1200 motor is superb, but it's not mid sized, is shaft drive, a lot bigger and heavier and I wouldn't say it surpasses the RC45. It was just designed for a different job. Whilst I have produced one VFR1200 special (see my avatar) my interest in RC24/36/45/46 etc is for different projects and pinnacle or not, an RC46 Gen5 engine will be going in one of them (RC24 frame), probably an RC24 in another (RC36.2 frame) and hopefully an SC16 in the other (RC24 or 36 frame, whichever fits best), with specific reasons for choosing each. However, those reasons are immaterial. I'm just trying to find out as much as I can about possible fitments, hoping to avoid having to buy something just to see if it fits and then finding it does not. Once I have ascertained something is possible, then I can go ahead and I'll figure out the how. But I don't want to waste money buying an engine that actually will never fit the desired frame. I cannot afford to keep doing that. Hence I research it all first and that inevitably means asking questions and I'm always grateful for helpful answers as indeed I try to give when asked about any of my previously completed projects.

    Aren't forums great. :)
     
  18. Fastdruid

    Fastdruid New Member

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    *cough* RC213V-S

    [​IMG]

    May be a tiny bit more expensive than even an RC45 though. ;)
     
  19. BiKenG

    BiKenG New Member

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    Ha, yes of course, but as basically the MotoGP engine (and such an exorbitant price) I was not including that.

    Interesting that you mention it though as one of my projects is to build an RCV replica. The visually closest frame would be the RC36.2 and ideally I'd like it to be 1000cc. Hence my enquiry into squeezing an SC16 motor into an RC36 frame. It's just for fun and visual appeal, not for track use or anything like that and indeed not much interest in riding it at all as I'm no longer prepared (or able) to wrap myself around the tank, lean on my wrists and scrunch my legs up to get my feet on the absurdly high footpegs. They look nice though and coloured plastics are available.

    Haven't figured out the Swing-Arm yet though. :(

    Anyway, I might as well wait to see if there is a new V4 SuperBike and then look for a crashed bike to utilise the engine. Not like I haven't got enough other projects to be getting on with. :)
     
  20. Fastdruid

    Fastdruid New Member

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    CBR600RR? :)

    [​IMG]
     
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