B or C piston

C

coachtech

New member
Hi all, I have a '11 ec300 with 100+ hours on it and a 'B' cylinder and found 'A' and 'C' wossner top end kits. Should I get The 'C' or keep looking for a 'B'.

I searched on here some people use the larger piston in a used cylinder that was not replated. Any suggestions would be greatly appreciated.

jz
 
coachtech said:
Hi all, I have a '11 ec300 with 100+ hours on it and a 'B' cylinder and found 'A' and 'C' wossner top end kits. Should I get The 'C' or keep looking for a 'B'.

I searched on here some people use the larger piston in a used cylinder that was not replated. Any suggestions would be greatly appreciated.

jz
Click to expand...

Depends if you can accurately measure the cylinder, or have someone do it you may be able to get a C to work. I replaced my A with another at 70hours. Wossner kit. There felt to be less play between the piston and cylinder when dropping them both through the jug without the rings on.

Have you contacted anyone to see if they can order you a B?
 
You will be fine with the C, I do a size up on all rebuilds. I have a B in my A cyl now with 100 hrs on it and will replace with the same soon. You will not be able to measure the cyl accurately enough without some expensive tools and proper technique. Your talking about .01mm or .00039" between sizes, technique and temperature will introduce more error than what you are trying to measure.
 
Jakobi said:
Depends if you can accurately measure the cylinder, or have someone do it you may be able to get a C to work. I replaced my A with another at 70hours. Wossner kit. There felt to be less play between the piston and cylinder when dropping them both through the jug without the rings on.

Have you contacted anyone to see if they can order you a B?
Click to expand...

Accurate tooling for this operation I do not currently possess. I just serched the internet, mostly ebay as I found other forum users here found good deals on kits.

GMP said:
You will be fine with the C, I do a size up on all rebuilds. I have a B in my A cyl now with 100 hrs on it and will replace with the same soon. You will not be able to measure the cyl accurately enough without some expensive tools and proper technique. Your talking about .01mm or .00039" between sizes, technique and temperature will introduce more error than what you are trying to measure.
Click to expand...



Thank you, I thought that was the case. I just wanted to verify the results I found.

http://www.ebay.com/itm/TOP-END-WOS...Parts_Accessories&vxp=mtr&hash=item53eb490211

^^good deal?

jz
 
Looks good to me :)

Thanks for the info Glenn. Would there ever be much chance that going up a size would result in not enough clearance? Or more likely that ring end gap would be a cause for issue?

Coachtech, good to see they give you the full stack of base gaskets to work with too. Are you planning on doing any work to the port timing/squish?
 
the chance of going up a size being too tight, is miniscule. my borematic has difficulty getting repeatable .0005" - the difference is so small that temperature has more effect... there's plenty of clearance. you'd need some pretty high end gauges to measure the difference between bore sizes.
 
;) Cool, good info. Thank you GasGas Guru's!

Jakobi, yes I was going to measure squish and use a gasket to maximize squish w/out effecting port timing much. My bike runs great for my riding style and feel no need to make any major modification. Let's call it "fine-tuning" if necessary.

jz
 
coachtech said:
;) Cool, good info. Thank you GasGas Guru's!

Jakobi, yes I was going to measure squish and use a gasket to maximize squish w/out effecting port timing much. My bike runs great for my riding style and feel no need to make any major modification. Let's call it "fine-tuning" if necessary.

jz
Click to expand...

If you're happy with the delivery of the engine now I would keep the port timing the same. If your squish is still too big for comfort spend the coin and get the head turned down a little. This approach will give you a little more everywhere (not crazy power, just a bit stronger - and better fuel economy - more stable jetting). If you drop a gasket you will change the port timing and sacrifice top end but gain some bottom. No other pro's really except its cheap and easy.

There was a thread which showed some graphs and the effects of head/gasket works on the engine. I'll try and dig it up.
 
Just buy the C...the difference between the A to B to C is so small that even in a brand new engine you should be able to put a C in an A bore and still not have any seizing issues. I just put a C wossner in my A cylinder and have no issues. I read that back when 2 strokes were the most common MXer that race engine builders put C pistons in A cylinders right off the bat in a brand new motor just to tighten on the tolerences a bit..you would never have an issue unless you started the bike cold and held it wide open causing a cold seize
 
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