bore and sleeve

has anyone bored a 5gen out if so how far is the limit with sleeving?

 

honda lists pistons at .25 and .5 oversize. so half MM max overbore. aftermarket (like wiseco) can cut anything you want, and honda is usually conservative. with some maths the possibility of 1mm OS pistons is, well, possible. sleeving doesn't gain you oversize bores unless someone makes a big bore sleeve. sleeving returns a block to the original stock bore size, making a worn out overbore block usable again.

 

If you really want to know how far you can go thickness wise, get the cylinders sonic tested for thickness. Some automotive race type machine shops should be able to help. Though just because you have the thickness doesn't mean you can bore big. Depends on strength of whats left and possible cylinder distortion, if any, when running. That's a hard one to figure out though. Mostly by experience or trial and error.

 

sonic testing is like getting dyno results. go to 10 shops, you will get 10 different answers. can always look into stroking it too.

 

.030-.050 over bore should be fine. Where you gonna get the crank and or rods or pistons for the stroker kit? Are they out there?

 

send the crank out to be modified and have wiseco cut custom pistons. really its not that expensive. crank mods can run from 300-1300 depending on what you want. custom cut 4 banger pistons from wiseco run about 500$ i almost always opt for custom cut pistons, they are usually only a little bit more costly then what they consider standard order pistons and the tolereances can be WAY tighter.

 

just curious as stroking would have high piston velocity issues. slightly bigger bore would help get more out of it.

 

goal is overall to update my 98 with modern tech. ceramic lined sleeves etc. bring power up to modern levels.

 

lack of hp is the only reason anyone would sell their vfr. it'll be interesting to see what can be achieved with improved tech.

 

Ha Ha, you need to do some reasearch the VFR800 already has aluminium/ceramic cylinders, there is NO sleeve & NO steel liner. The cylinders are cast into the upper crankcase, so boring them out to replace with steel may be a problem. I was looking at this for another upgrade to my bike & have a spare engine to play with. I was considering a 2mm overbore in the standard liner & using a 1mm stainless steel band heat expanded & slipped over the outside of the cylinders if I don't think they are strong enough ! I would then use CBR929 74mm pistons, assuming when I measure them that everything would fit with the correct clearances.

Heres a couple of pics with the rear cylinder head removed.





Cylinder walls are 8mm thick as standard, id=72mm, od=88mm. A 2mm overbore would boost capacity to 825cc & compression to approx 12.6/1, whilst reducing the cylinder wall thickness to 7mm.

Have fun.

 

different ceramic to the carbon impregnated one they use. much lower friction coefficient.

 

Hogg

thanks

 

Just remember that the VFR800 engine is identical to the RC45 in all basic dimensions, so if you had the money & engineering ability 190rwhp is possible. You would have to do a lot to it though.

New rods. New pistons. New head gaskets. Welded crank. New cams. HRC equivalent valves & springs. New throttle bodies. RC45 race exhaust. New ECU & ignition control system. Give me 20,000 pounds & I get you an RC45 power output. But remember that it would be either useless or mad on the roads

I don't have the dish for that !