How do you detect air leaks?

Cr9ck · #1 10-28-2008, 02:53 PM

HI I don't know much at all about engines or anything. My question is how do you detect air leaks? Is it dangerous to have an exhaust air leak? Im using exhaust paper for a few days because my pad fell apart and Im nearly broke.

Spunout · #2 10-28-2008, 03:20 PM

with a warm, idling engine, flip the choke all the way up to ON. if it doesnt die right away, you probably have one.

where is it coming from? there's lots of places....carb/intake, intake/jug, head/jug, jug/base.

set your idle a little faster than normal. spray some brake wash or carb cleaner around those parts. if the idle goes up or down when you hit a certain spot, thats where the leak might be.

Cr9ck · #3 10-28-2008, 03:39 PM

yeah somewhere seems to be leaking as it is running really hot. i wonder if it is just my exhaust? I flipped the choke up and it didn't die so yeah. Is there any way to run the engine without moving the bicycle? I don't have a stand.

How long does it take to kill it if it has leaks?

Thanks

Bikeguy Joe · #4 10-28-2008, 03:47 PM

If it has an air leak and you run it too much, you will kill it.

If you mean when spraying, sometimes you'll barely hear it speed up or slow down.

Just fire it up, have a helper hold the clutch in and spray around the places like the carb to manifold joint, manifold to cylinder gasket. It's easier to just take off the manifold where the two bolts hold it on, smear a thin film of RTV or any other silicone on BOTH sides of the gasket, and re-install.

You may want to check the top of the carb too. sometimes they are loose and suck air in there too.

Cr9ck · #5 10-28-2008, 04:03 PM

Is the manifold where the carb goes into the engine? How can I fix the top of the carb if is that? Would the exhaust gasket be an issue?

Bikeguy Joe · #6 10-28-2008, 04:10 PM

The exhaust gasket isn't a major issue, but should be fixed if it is leaking.
The manifold is the "neck" between the carb and the cylinder.

As for the top of the carb, just make sure it is tight.

Cr9ck · #7 10-28-2008, 04:13 PM

How do I start the bike without a stand then? Do I just hold the seat and rotate the pedals?

Bikeguy Joe · #8 10-28-2008, 04:18 PM

Quote:

Originally Posted by Cr9ck

How do I start the bike without a stand then? Do I just hold the seat and rotate the pedals?

Get on, pedal, release the clutch, and when it's running, ride back to the workshop and pull in the clutch and lock it, or hold it and have a helper spray the goods.

Cr9ck · #9 10-28-2008, 04:51 PM

Yeah I figured it out. it only runs if i really choke it. I sprayed wd-40 around where the carb connects to the intake manifold and it revved up the first time. I tried it again and this time when I hit it with wd40 it revved down each time I did until it cut out... The intake manifod itself seems fine and the part where the carb connects to it is tight.

I have also detected that around the primer pin near the screw gas is leaking. Perhaps it is leaking out the side of the carb. I tightened the screw but I think it is still leaking.

Any help would be greatly appreciated.

Thanks

old motorbike · #10 10-28-2008, 09:05 PM

Loosen the carb retaining bolt and slide off the carb. Clean the manifold neck and inside the carb where it slides on with carb cleaner, brake cleaner, even alcohol. It just needs to be dry and clean. Smear on a coat of RTV silicone to the manifold neck and slide carb back on over it and tighten bolt. Let it cure for a while and see if it still has an air leak.

The primer will always leak some.