Topic: vfr 750 pistons into sohc 750

[dusterdude]

ive been told that vfr 750 pistons will work in our sohc`s to give about 900 cc`s.can anyone confirm or deny this?if so,what years?thanks

[bwaller]

Mark,

You might want to check the VFR pin diameter, the VF500F pin is 16mm so I expect the 750 is larger also.

[dusterdude]

thanks,ill keep that in the back of my brain.pj told me to use gs1000 pistons which are 70mm.so thats another route too.

[turboguzzi]

they are also a 4 valve design, rather flat and 750 sohc's need quite a bit of dome for a decent CR but who knows....

maybe tell us who told you?

:-)

TG

PS Bwaller, think I found you 60mm pistons


 

[bwaller]

Oh really TG, I may have to kiss you on the lips 

[moham]

wow.

[turboguzzi]

let's not get carried away

try these

Honda VTR250 1988-1990

60mm bore

[bwaller]

Don't worry, I don't give it up that easy!

I'll look into those, thanks.

[bwaller]

For those that give a rats ass the VTR 60mm piston also uses a 16mm wrist pin...... crap!

[754]

So how do they look otherwise?? i have bored  out lots of small ends for a few reasons..

[turboguzzi]

And I have the opposite problem

turns out that Kitaco has some really cool 57mm pistons for little honda's big bore kits but they all have 14mm pins....

sounds easier to enlarge the piston hole, the bugger is doing the spring ring groove!

TG

[billybobobrain]

For those that give a rats ass the VTR 60mm piston also uses a 16mm wrist pin...... crap!

60mm? = 900, on a 750? Sorry to bust a bubble 836 kits are 65mm.

[bwaller]

bobobrain, we completely derailed dusterdudes first post. He was talking about VFR750 pistons making 900cc's.

The 60mm's are for the CB550.

So bubble burster....no harm done.

[billybobobrain]

Wow I must have missed something!

Sorry to be so ignorant.

[754]

smaller is easy.. bronze bush in the small end....easy...

[turboguzzi]

Yes, bushing is an idea, just have some doubts about the strength of a bushing that is 0.5mm/0.02" thick.

Reaming the piston gudgeon pin boss to +1mm with an adjustable reamer doesn't sound too hard.

TG

[754]

Tho I have not had a chance to measure, the bushes used appear quite thin..

I have this theory I use often, if a pice is fitted right, ie wont be loose, and made of tough material, (bronze is), then it has nowhere it can go and should work!

 Re making bigger bore in pistons, lots of chance to screwup..&
unless you use buttons, there is a large amount extra work on redoing the circlip grooves.

Have you ever removed .040 from anything with an expandable hand reamer? you would be lucky to do it in an hour per piston, and it can get exhausting.

I do a bit of work for engines shops, on changing size of small ends.. usualy it involves me boring out all but the last .003thou on a mill, then the rod is finished on a hone..

My thought is, bushing the small ends, there is no way to screwup the actual expensive parts, wurst is you loose a few bushings..FWIW...

[fang]

Check out this discussion:
http://forums.sohc4.net/index.php?topic=45040.msg472779#msg472779

EDIT:
check out this one over at Satanic Mechanic too.

peace and grease
-fang