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Discussion Starter #1 (Edited)
HI THERE

i have tried to post this 2 times now and something goes wrong each time…got the shits with it now so short version coming up…..

i have a problem with oil coming from the breather pipe…thought compression, new rings but 30 mins later same thing…baffled to what it is, can hear the engine bubbling sometime after turning it over on start button…not right!!!

finally got free time to strip it…took off clutch side casing and removed gasket (copy) and noticed this (picture 2)…i then compared to a japanese branded gasket and saw this difference (picture 3)!!

can someone tell me it that hole is part of the breathing system of the engine, i poked a wire in and it went in 7"+ so into the crank case for sure.

i really hope someone knows the awnser and its YES so i don't have to strip the engine any further!!

thanks in advance

superchip

P.S. i haven't been able to use this bike more than ½ an hour since building it 10 months ago!!!
 

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When I look up the gasket on bike bandit it shows a gasket like the one in lower photo. I do believe the hole is part of the breather vent system. Hopefully someone can chime in here and confirm this.
 

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What does the cover look like. Is there a corresponding hole or "place" air or oil would go if the hole is uncovered? I vote for leaving it un-covered if the gasket is from a reputable supplier. OEM Yamaha by any chance?
 

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Just a guess but this might be an air passage to allow clutch side to act as additional air plenum volume to help lessen windage losses in crankcase from piston cycling up and down. With the air passage sealed up the reduced "surge tank" volume results in increased crankcase peak pressure pulses thus likely accounting for the observed breather tube discharge.
Huh? Just leave air passage unblocked as in picture #3, reassemble, reinstall, retest and report would be my recommendation if you cannot get more knowledgable advice. I know this represents a bit of work. Hopefully someone else will green-light idea that gasket is your only problem.
 

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the corresponding hole idea should be the determining factor of your question. If there is one, I'd put it back together after cutting away the gasket.
 

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Discussion Starter #6
thank for the replies….neither gaskets are OME, the 1 blocking the hole was cut here in thailand and the other is an aftermarket set from japan. i have used the japanese ones a couple of times now without any issues…so i am hoping that the blocked section on the other gasket is just a cutting error, and the cause of my problems.

this is the case side, i have put the gaskets on top of each other so you can see the difference, in the picture where they are removed you can see that the section in question is not fully closed there is a slight gap, which would tell me that it should be open.
 

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What I do know is all crankcases need to be able to relieve crankcase pressure. if not ive heard of cases like this happening and causing people headaches like you have gone through yourself. relieving crankcase pressure also helps the motor run more free. less pressure less stress.
 

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Discussion Starter #8
Whoo hoo

…the gasket was the cause of my problem!!!!….this issue was doing my head in as i was baffled as to what the problem was, i even installed new rings days before my compression tester arrived because i was sure it was that..turns out i wasted a set of rings n gaskets now…..so after nearly 12 months of the bike abandoned just sitting gathering dust i can finally use it…although i have acquired 5 more TW200's and 2 TW225's since building this one.
it was originally black but as this bike has been off the road i did a bit of swapping and painting and re-worked a few things.



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Looks good. Glad to hear you got it figured out. Now go ride it
 

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