86 750 engine rebuild

So I picked up a 750 engine for my 86 VFR700F. I plan on rebuilding it before I put it in. In this rebuild I would like to add some performance. My goal is to be about as fast as a modern 600cc sport bike, I think 120hp at the wheel would be a good number.

I have a 4 into 1 yosh exhaust as a start.

I have not had a chance to tear into the 750 yet but, the person I bought it from said that the bike had lots of safety wire on it and it may have been used for racing, so there may be some hidden goodies on the inside.

So what I would like is some advice as what I could to to get more performance out of this engine, some tips and tricks for the rebuild, and the name of any place that still sells some power adders for these engines. Also if anyone on here has some parts they have been holding on to and want to get rid of them let me know. I would would be looking for all the internal performance parts, valves, valve springs, retainers, pistons, cam, etc... I also plan on documenting the rebuild here so stay tuned, and thanks for the help

 

I'd never trust an ex-race engine on a streetbike considering the extreme use they've been put to. If the PO was playing by the rules, don't expect any exotic parts inside, and if you can't obtain new rod and crank bearings, no real rebuild is possible.

You'll never get that bike as fast as a modern 600 because of weight, engine, and tire limitations. Your money would be better spent improving the suspension and converting to F2 wheels.

Naturally aspirated, 120 rear wheel hp is totally unrealistic because the performance parts you'd need are not available or astronomically priced from HRC.

Switching from a 700 to a 750 will only net you about 4 hp or so, no big improvement.

 

One of these guys claims he's around 125hp at the wheel. He mentions an 840 kit, which is ~$3k investment by itself.

Here is the thread: Turning an old VFR750 into a race bike. [Archive] - Honda VFR Club

 

I do not trust an ex-race engine in a street bike thats why I am rebuilding it.

I do not expect any exotic parts inside nor did a pay enough for the engine to believe that there would be any in there, I was just saying that there is a slight possibility.

I an not at all interested in get rid of the white 3 spoke wheels. I sold my F3 to get an 86 VFR so if handling and speed were all that was important to me I would have just kept the F3. I do how ever miss the power (I do not really notice a big difference in handling between the two).

I do understand that it may be a difficult to reach 120 wheel hp, that is just a number I put out there. I am not too concerned with numbers because that is all they are.

I have read many threads debating what gains you actually get from switching from a 700 to 750, and that is now why I started this one.

Thank you for your input I will take you suggestions into consideration

 

Thanks for the link McViffer

 

Any possible gains above stock would need radical improvements in cc's, larger valves, head porting, HRC cams and carbs, valve springs, air box, intake trumpets, CDI, totally new custom exhaust and lots of dyno tuning, cam timing, things i know nothing about and with an expert to make it run best, whatever secret Factory setup Fred Merkel and Bubba wuz runnin'
in AMA when the VFR wuz #1 in class back then. Factory archives in Japan would be the first place to search., but t6hat ibnfo may STILL be classified !

Such a bike would not be well-suited to street riding in any metropolitan community with laws and cops that can't be bribed so you don't have to go to court because it's way too fast, lacks low-end power, and contradicts adult good sense.:crazy:

Who expects that a large percentage increase in power wouldn't eat transmissions, bearings, cooling systems, and clutches that were never designed for it and wants to trade power for reliability and longevity ? Anyone who wants a faster, more powerful VFR should get a CBR 1000R and find out how much technonogy has progressed and stop fantisizing that you, not anyone you know could EVER put that power to sensible use on the roads of a civilized society.

Motorcycle riders mostly want to ride the newest bike they can afford because the newest is the bestest as far as i know.**



** Only one rider's drunkin' opinion......I love old bikes, but want something newer to RIDE !

Improved tires, suspension, brakes, you need it !!