VFR700 Cam timings

Hi,

I live in the UK and own a 1988 VFR750FJ - a fantastic bike and one I never intend to part with. It's had a fair number of mods done to the wheels and rolling chassis; RC30 forks, VFR400 front wheel, CBR600 F3 rear wheel, RC30 kit carriers and rotors, Brembo Goldline calipers, Ohlins shock, but now I want to turn my attention to the engine.

I've read in a number of places that the VFR700 US market bikes had hotter cams to compensate for the lack of capacity (displacement in US-speak). Does anyone have solid proof of this; for instance would anyone have a Honda workshop manual that would give the degrees before and after TDC that the inlet and exhaust valves open and close?

If so, I'd very much like to compare that with the specifications for my '88 750. If there are worthwhile differences, I may be sniffing around breakers yards in the US...

Oh yes - and hello everybody!

Graham

 

Degrees won't tell you what you need to know: lift and duration at lift.

One cam can be specified with different opening/closing angles, and two different cams can have the same specs for opening/ closing.

My ignorant guess is that there's no difference in the cams you're wondering about, but a check of part #s might be illuminating but not definite info.

 

The manual does list a service limIt on the lobes of 31.37 for the intake and 31.43 for the exhaust. Intake opens at 10 BTDC and closes at 40 ABDC. Exhaust opens at 40 BBDC and closes at 10 ATDC. Hope that helps.

 

Hi TC, thanks for that. You probably won't be surprised to know that the figures you have given for the VFR700 are exactly the same as those in my Honda VFR750 workshop manual.

So this story of the hotter VFR700 cams is sounding more like an urban myth every second. I will do some checking on part numbers, but I'm not optimistic...

 

Just checked on the fiches at cmsnl.com, and there are different part numbers for the US and Euro camshafts. These are what I found:

VFR700F2 (1987)

Front Exhaust - 14130MK8770
Front Inlet - 14110MK8770
Rear Inlet - 14120MK8770
Rear Exhaust - 14140MK8770

VFR750 FH (1987)

Front Exhaust - 14130ML7690
Front Inlet - 14110ML7690
Rear Inlet - 14120ML7690
Rear Exhaust - 14140ML7690

ML7 is a commonly-seen component of RC24 part numbers, and is seen in many places on both US and Euro-spec RC24s. RK8 appears to apply only to US-spec VFR700s. So it certainly looks as if the US-spec cams were different to the Euro ones. Other parts of the cam assembly (valves, rocker arms, valve springs, gear train etc.) all have ML7 in the part number and are the same as Euro spec machines.

But are they actually 'hotter' cams? Unless someone has hard data on cam lift and duration at lift, we're still none the wiser...

 

I have some laying around that I can measure the lift on but you are SOL on the duration specs.

 

http://www.megacyclecams.com/catalog/pages/page 36.pdf

click me!!! you should be able to get all specs at megacycle cams

 

Wrong model

I think you'll find the info on that page is chiefly for the VF (chain driven cam) models, not the VFR (gear driven cam) models. Certainly Megacycle cams for the RC24 and onwards are listed as no longer available (and unfortunately neither is the cam timing information).

 

opps my bad, I would bet if you called or e mailed them they could give you the information