problem with txt300 engine

[ronenzz]

Hi everyone,

I really hope someone will have a good idea here because Im frustrated....

I have just overhauld the engine.
replace everything but except the piston and the rings which were changed
10 hours ago and were checked for clearance and wear.

the engine run fine and starts fine.
but it takes out small bubbles of air through the excess hose (in the attached picture) and the oil is dripping our.
I have reoverhauled the engine twice!!! and still cant find the reason for this thing.
have gone over each and every part in the microfiche and nothing seems to be wrong.
please advice!!!

[Leo]

Can be pressure from motor going to gearbox? Is the middle gasket leaking?

[JSE]

[the engine run fine and starts fine.
but it takes out small bubbles of air through the excess hose (in the attached picture) and the oil is dripping our.
I have reoverhauled the engine twice!!! and still cant find the reason for this thing.
have gone over each and every part in the microfiche and nothing seems to be wrong.
please advice!!!

That breather hose connects to a hollow shaft in the transmission (the spigot hole where that elbow goes into is in the center of the transmission bearing). There should be a stepped washer and special capscrew holding the clutch hub on. The special capscrew is gun drilled and has the head shaved down a few millimeters to clear the clutch servo cylinder. You might want to take some pliars and move the outer spigot so it faces straight up and then tap it lightly to retain it in that position. The breather hose goes up and curves over the top of the cylinder brace. A little drip now and then is normal.

The unusual transmission breather system on this bike is designed to avoid the transmission sucking water in when in deep water (not unusual for a Trials bike). A "normal" hose off the back of the case system will suck in water when doused in a creek as the sudden cooling of the case will create a vacuum and this will draw creek water back into the transmission breather hose.

Your transmission might be over-filled. You should have about 400/425cc's of transmission fluid in the case (this looks like a post-2002 Pro, which took only 350cc's), not the 500/550cc's as stated in the GasGas manual spec.'s. The tranny fluid should show about 3/4ths of the way up the sidecover sight glass with the bike held straight up on level ground.

If you want to keep this engine in good shape, you'll want to change the tranny fluid every 15-20 hours depending on conditions. The main bearings in the Pro are lubricated by the tranny fluid, not by pre-mix in the "normal" two-stroke.

Jon

[Fred1956]

Thanks Jon-- FYI to those of you that have GG trials bikes as well as enduro models JSE (Jon) is a very knowledgable tuner & tech writer who has a high level passion for all things mechanical (especially trials) I sent him the link to ronenzz's question because I knew he could answer it. He also writes tech articles & tips on http://www.gasgas.com/tech.htm He is one of the nicest guys you could ever meet and always eager to help with mechanical questions/problems. He has a long list of engine type experiences from plonking along at trials speed to blasting away at road race or Top Fuel pace

[JSE]

Originally Posted by Fred1956

Thanks Jon-- FYI to those of you that have GG trials bikes as well as enduro models JSE (Jon) is a very knowledgable tuner & tech writer who has a high level passion for all things mechanical (especially trials) I sent him the link to ronenzz's question because I knew he could answer it. He also writes tech articles & tips on http://www.gasgas.com/tech.htm He is one of the nicest guys you could ever meet and always eager to help with mechanical questions/problems. He has a long list of engine type experiences from plonking along at trials speed to blasting away at road race or Top Fuel pace

Don't believe Fred, he lies a lot...........

Jon

ps. Just so you know, I was kidding. Fred is a good friend......

[ronenzz]

no comment from jon?

[Fred1956]

Originally Posted by ronenzz

no comment from jon?

About?? He did answer your question from the original post.....on the same day you posted the question...