Just wondering if it would work.. the F2 compression ratio 11:5.1 and the F3 was 12:1 and if I remember correctly honda achieved this by increasing the dome on F3 pistons from the F2..

 

I've been reading some general engine building articles. It says in one of those articles you get roughly 4% increase in power by bumping up the compression 1 point. So judging from my calculations if you already had 90hp, you would get a gain of 1.9 hp for a total of almost 92hp. Why bother unless the engine is already torn down, then why not.

 

Now my F2 had only 86 hp (dynoed twice with 2 different pipes) so I would get an increase of 1.75. Not worth the trouble if you ask me. But I sure would like to build a hopped up F2 or F3 engine, just because. 13.5 compression 637cc kit, lightened & knife edged crank, a set of good carbs, and some cams. Total loss electrical system to free up some more horse, now that would fun. Now something like that would probably get 105 to 110 horsepower.

 

if your concern is numbers only then yea but my focus is the whole power curve.. with that bumb In compression you should get a gain through out the curve.. I was looking in to a 637 kit 13.1 compression

 

You don't think that almost 2 hp increase from changing pipes is worth it?I would think you would and especially sence your F2 is a track bike

 

I didnt mean I got a 2 hp increase from changing pipes. I meant according to my calculations by increasing compression a 1/2 point I would gain 1.75 hp based on my 85.9 hp with D&D pipe, and 86.5 with the Freddie Spencer/Mike Velesco pipe. Yes, I do think gaining 2hp by switching pipes would be worth it (if the pipe was cheap $ enough). But thats not what I got. You misunderstood my comment Pat. But I dont think its worth the trouble, price wise, to increase compression for only 2hp. Also from what I understand by increasing compression and/or displacement, you gain hp pretty much across the whole curve.

 

Sorry frank I guess I miss understood. . I have a spare Lower end out of a 91 I may just build that.. how's the racing going?

 

No racing, no track days, no job. I was laid off last Nov 13, Friday the 13th. Imagine that.

 

From what I've heard, a cheap 637cc upgrade for F2's & F3's, is F4I pistons. They are 67mm compared to F2 & F3 pistons which are 65mm. As long as you could find someone you trust to bore the cylinders properly. Way less expensive then buying new JE or Wiseco 637 kit. Now heres a question, how far could you bore a F2 and still be safe? If you could go more the 2mm, why not get 1mm over Wiseco or JE F4I pistons for a F2 or F3 then you would have almost a 660cc engine. I wonder what the compression would be on that. "koko TL1000" put F4I pistons in his F2, Its been a while, but its here on this forum somewhere.

 

Ohhh man i'm sorry frank about your job. . I'm out of work myself because of a torn acl... ) I'm pretty sure that 2mm is the most you can go with an F2 and be safe.. the problem with doing any build is we always want more... what I mean is I'll set off to do a big bore kit then to complement the build I'll start saying to myself that I need to do cams and then a port job... you know how it goes... I wouldn't mind if money was not an issue. .