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compression test
Posted: Thu Oct 23, 2008 7:46 pm
by steve speed
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
Re: compression test
Posted: Thu Oct 23, 2008 8:21 pm
by lars
The numbers look good to me, how many miles?
Re: compression test
Posted: Thu Oct 23, 2008 8:45 pm
by steve speed
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
Re: compression test
Posted: Sun Oct 26, 2008 2:48 pm
by lars
Does the bike smoke a lot at start up?
Re: compression test
Posted: Sun Oct 26, 2008 11:08 pm
by steve speed
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
Re: compression test
Posted: Mon Oct 27, 2008 6:32 pm
by steve speed
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
Re: compression test
Posted: Mon Oct 27, 2008 7:03 pm
by Killerwhale
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 it´s going to bang. Those Arias pistons used by Over where 12,5:1 and whe know that bike flew!
Re: compression test
Posted: Mon Oct 27, 2008 8:35 pm
by steve speed
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
Re: compression test
Posted: Tue Oct 28, 2008 12:21 am
by Killerwhale
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 don´t you think JE would recommend a balanced crank?? .....and wouldn´t they´ve done lighter pistons to start with??....they´re not wankers over there....