Air sucking gaskets yamaha

[Daacuso]

After cleaning my carbs from my 1999 Yamaha 30 3 cilinder i have a gasket problem. I have this problem with the carb gasket but also with the other gasket mounted at the thing that is behind the carbs (dont know the exact word in English). I have already smoothen the carbs etc. so that the surface is completly straight. I also replaced all the gaskets so that should be fine too. After rebuilding the engine runs smooth on all three cilinders. But after a short run (about half an hour) the gaskets start leaking. Causing air coming through. So the engine doesn't run fine anymore. Spraying with breakcleaner on the gaskets while engine is running has immediate effect, engine rpm increases. So it's defintly a gasket problem. The screws have been mounted at 8 nm. What can be the problem? Must I tighten the screws more or is it just a not completly staight surface? (which i doubt). It's the fifth time i dismounted everything (first time with new gaskets), but the problem keeps coming back.<br /><br />Hope somebody can help me.<br /><br />(sorry for the early reply, touched the wrong button so the whole story wasn't posted yet

 

[jim dozier]

Re: Air sucking gaskets yamaha

OK describe your problem. Also tell us what motor, what year, prior history, and what you did to it and what leads you to believe you have a problem.

 

[JB]

Re: Air sucking gaskets yamaha

Say, Jim.<br /><br />I find all of the answers to your questions in the first post. Did Daacuso edit it after you posted?

 

[jim dozier]

Re: Air sucking gaskets yamaha

Yes JB, he's making me look bad.<br /><br />The only reason I can think of that the carb mount is leaking is that the mating surfaces are <br /><br />1. not clean<br />2. not flat<br />3. wrong gasket<br />4. not tight enough<br /><br />Are you sure they are flat, check with a machinist straight edge.

 

[Daacuso]

Re: Air sucking gaskets yamaha

Thx for the reply and jimd sorry for making you look bad But the weird thing about all this is that it also happened with old gaskets and a not prepared surface. Engine runs fine after rebuilding but starts leaking after some time. Now with a prepared surface and new gaskets still the same problem. I have a friend which is a mechanic, and he gave me his approval. Measured the surface and checked everything. New gaskets and a flat clean surface and still leaking. Problem is that I don't know exactly how tighten screws has to be. I don't want to ruin my engine by tighten the screws too much. I let my friend look at it once, and we will measure everything again. And maybe i try it with liquid gasket. For the record; gaskets are the right ones. More tips are very welcome.