Can't fix vacuum leak

Tristan Gillett

New Member
Jan 31, 2019
13
7
3
Magna, UT
Hello. Recently, I switched out the cylinder on my two stroke, and after doing so, I have a really bad vacuum leak. The RPMs pretty high, as if i'm holding the throttle half way, and in neutral, it skyrockets. As of right now, I have sealed the carb mounting spot with heat resistant caulk, made a new head gasket out of silicone gasket maker, as well as made the carb level. I have also made a gasket for inbetween the intake manifold and the intake hole on the cylinder. Anyone know what else I should do? Will gasket maker be strong enough for a head? I can add pictures if anyone requests any. Thank you for any help.
 

Greg58

Well-Known Member
May 1, 2011
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Did you replace the base gasket when you changed the cylinder? That is a problem leak area, the head gasket is re-useable, I would go back to it.
 

Tristan Gillett

New Member
Jan 31, 2019
13
7
3
Magna, UT
I didn't replace the base gasket. Didn't even think to check there. Is the head gasket the metal piece that sits inbetween the head and the cylinder?
 

bairdco

a guy who makes cool bikes
Aug 18, 2009
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living the dream in southern california
Before you do anything else, put the metal head gasket back in. It's designed to seal as the temperature heats up and cools down. Thermal expansion and contraction, basically.

Silicon gasket sealer is not gonna work.
 
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Larry Trotter

Active Member
Nov 26, 2017
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It must be getting fuel also some place, are you sure the throttle slide went in properly when you replaced the carburetor?
 

Tristan Gillett

New Member
Jan 31, 2019
13
7
3
Magna, UT
Before you do anything else, put the metal head gasket back in. It's designed to seal as the temperature heats up and cools down. Thermal expansion and contraction, basically.

Silicon gasket sealer is not gonna work.
I put the metal head gasket back.

It must be getting fuel also some place, are you sure the throttle slide went in properly when you replaced the carburetor?
Yes.

For the most part, it's fixed.