performane difference between 700 and 750 2nd gen

'Facts' and 'Proof' ...

Sheesh ...

Are you suggesting that the perceived difference in performance is due to something other than the increase in displacement?

Seems to me that's really unlikely. So unlikely that the suggestion is ludicrous.

 

Yeah, I read post #17. Just read it again to make sure I understood it the first time. What post #17 suggests is that his carbs were screwed up before he changed the displacement (a wild ass guess), and are now somehow better after the displacement increased (another WAG). The only 'facts' I see in this thread are the claimed horsepower numbers which show an 11hp difference between the two displacements.

My question remains the same, and so does my conclusion.

 

Actually the carbs on my bike were stock. The 700 started and ran fine. The 750 starts and runs fine. I doubt if there is a significant difference in the carburation required. I threw this out in case you need a motor and have a choice between the 700 and 750.

Apparently some think that 700=750.

 

... and I disagree. Based on (again) the only 'facts' presented here, the difference is 11 horsepower. Got any facts to debate against that?

I didn't think so.

 

Respect all your opinions

There is a noticeable difference between between the 700 and 750. When honda set the 24 hour endurance record that was held by suzuki ,both the 700 and 750 set records,both bikes were tuned by honda.the 750 was faster,but the 700 was no slouch. I started this thread because of what i read as the respective hp of both units,I found it hard to believe a 20+ difference.
After a lot of fact finding I found my answer,11 hp is more realistic,
In 86 I bought a 750 from the dealer for whom I was the service mgr.At that time I rode both ,and yes, You could feel the difference.I pulled the cams out and sent them to kaz yoshima and had them reground,It Was a blast to ride.
Now,About the dyno,it is a great tuning tool but not an absolute.You may dyno your bike one day and with a 10-15 degree change your information is not relative,as was stated temp change effects jetting.
Thank all of you for your input.
Gary

 

dyno numbers

I would like to see the numbers too.reality is that the 750 will walk away from the 700.just like to know how much it takes to do that.

Gary

 

Anyone know off the top of their heads what the oversize bore ring changes on a 750 creates volume wise?
Did they make hot cams for these bikes to buy off the shelf? Yosh made some or would you have to get them custom made?

I bet the 750 could be a real screamer if you ported and polished the head, hot cam and overbore.
Is it possible to bore these out to 1000cc?

 

Hi duki The stock bore is 70 mm, 1 mm oversize is 21 ccs of displacement. Wiseco doesnt show any 86 VFR pistons

 

cams

The 750 cams are different than the 700,,You would have to send your cams out to have them redone,they would weld them and then grind a new profile,In 86 when i sent mine to Ontario mt,i believe they sent them to cam motion.You have to send them yours because off the gear drive,but i do not know if they do them anymore
I read on a different form that someone would custom make a bore kit with a 2 set minimum.kit was over 800 cc.

p.s.
good head work always helps

gary

 

I know some guys are experimenting with CBR929 pistons. They are 4mm larger than the 750's yielding 836cc's if I remember correctly. Their only concern is the distance from the top of the wrist pin to the dome. If it works, then you only need a cheap set of used 929 pistons and a GOOD shop that can bore it. You can follow it here...

96 vfr750 cbr929 pistons???/ - VFR Discussion

 

If the Honda Service Manual is correct, the camshafts on the 700 and 750 both share the same Cam Lobe Height profiles for intake and exhaust.

The difference seems to be in the valve opening position specs. Looks like a 10 degree difference for Intake Valve opening, and 10 degree difference for Exhaust Valve closing.

 

I have a set of 1mm over Cosworth high compression forged pistons for an 86 750 sitting in my barn. Did several other motor upgrades back when they were in. I'll post a more complete reply later. but oversize pistons were available one day.

 

Rustedroot: Do they talk about where the lobe centers are on both engines?