Smoke from Intake side

Kamran Abolhasani /

I am trying to help a friend of mine with an older honda, I think its an Express. Well when trying to start it a small amount of exhaust comes out of the intake of the carb and it will not start or 'put'. It is getting gas and spark. Im thinking its a matter of compression, what do you guys think?

-Kamran

Re: Smoke from Intake side

Under the intake manifold, you'll find a plate that contains what are called reed valves.

On intake they open and the compression of the crank case gases, closes them.

If they are shot, this would happen.

I cant think of any other thing that would cause this. Break it down and clean everything.

Handle the reed valves with care and just make sure they are clean and seating.

Mike

Re: Smoke from Intake side

Steamboat Aka J. R. Stevens /

Is the bike a 2-stroke or 4-stroke? Jim.

Re: Smoke from Intake side

Kamran Abolhasani /

Its a 2 stroke...

Ill check the reeds, that does sound like a probable cause, thanks.

Kamran

Re: Smoke from Intake side

It would be a good reason it wouldn't start.

When the piston goes up to compress, the fuel/air are pulled into the crank by the lower pressure under the piston.

When the piston powers and is forced down, it compresses the gas/air that was drawn in. (this is where your reeds may be failing to close)

When the piston gets down to the bottom of its stroke, the compresses gas.air are forced into the cylinder above the piston.

No compression of this gas/air then no "scavage". Scavage is the term for getting the gas/air into the cylinder.

Good Luck and worse comes to worse, I see these reeds on ebay all the time.

Mike

Re: Smoke from Intake side

Does it smell like exhaust or just a whitish vapor cloud?

A small bit of vapor at the carb is pretty normal for a two stroke. Air has mass. On the inlet stroke the air is accelerated towards the inlet port. When the inlet port is closed by the piston (or when the reeds are forced shut by the pressure in the crankcase) the air will bounce back thru the carb. You normally do not see this as it is captured in the air filter and drawn back in on the next inlet stroke.

Re: Smoke from Intake side

Leon Swarmer /

I am wondering if timing could be the issue

Re: Smoke from Intake side

Steamboat Aka J. R. Stevens /

Hey 50plus, If the engine was piston ported, I could see the timing causing problems but someone posted this engine has reed valves. Jim.

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