compression test

steve speed · Post by **steve speed** » Thu Oct 23, 2008 7:46 pm

i did one today i am trying to find out if i need a rebore or just hone and rings this was my findings with a cold engine

left cylinder 172 psi,,,, with a bit of oil 178 psi
right cylinder 168 psi,,,,, and with oil 180 psi
which is near what yamaha say it should be ,,,what do you think ?
yamaha say
175std
182 max
145 min
max differance between cylinders 14.5 psi

lars · Post by **lars** » Thu Oct 23, 2008 8:21 pm

The numbers look good to me, how many miles?

steve speed · Post by **steve speed** » Thu Oct 23, 2008 8:45 pm

i think its done about 20,000 miles but before i got the bike the emulsion tubes needed doing , and who knows for how long , i just feel that my oil problems are valve stem seals but i will hone the bores and fit new rings while its in bits

lars · Post by **lars** » Sun Oct 26, 2008 2:48 pm

Does the bike smoke a lot at start up?

steve speed · Post by **steve speed** » Sun Oct 26, 2008 11:08 pm

no smoke on start up or when running , my mates tell me that on the over run it smokes a bit ,( no leaks ), but it uses 1lt of oil per 1000 miles

steve speed · Post by **steve speed** » Mon Oct 27, 2008 6:32 pm

striped it down today ,, and its not good

ring gap 0.4 which is just in ,,but piston to bore i can get a 0.3 feeler gauge between piston and bore ,,not good ,,so its a rebore ,, also the valve stem seals are really hard

now do i go je or not

Killerwhale · Post by **Killerwhale** » Mon Oct 27, 2008 7:03 pm

steve speed wrote:striped it down today ,, and its not good ring gap 0.4 which is just in ,,but piston to bore i can get a 0.3 feeler gauge between piston and bore ,,not good ,,so its a rebore ,, also the valve stem seals are really hard now do i go je or not

Go JE for sure, if doing bores why not have more cc with high comp!
I would skim the head while at it, maybe 12,5-13:1....then itÂ´s going to bang. Those Arias pistons used by Over where 12,5:1 and whe know that bike flew!

steve speed · Post by **steve speed** » Mon Oct 27, 2008 8:35 pm

i would go je but i am a bit concerned as the je pistons are heavier and i really don't want to have re balance the crank

Killerwhale · Post by **Killerwhale** » Tue Oct 28, 2008 12:21 am

steve speed wrote:i would go je but i am a bit concerned as the je pistons are heavier and i really don't want to have re balance the crank

IF this was critical donÂ´t you think JE would recommend a balanced crank?? .....and wouldnÂ´t theyÂ´ve done lighter pistons to start with??....theyÂ´re not wankers over there....

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compression test

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