See full version: Will bad reed alone, lower compression
Hi Rhodester<br /><br />Sorry to hear about this. I lost an entire leaf and chipped one on one of my cylinders, it didnt change compression at all. JB helped me find the error. Luckily it was stuck behind the intake bypass cover. Maybee you got cylinder scoring, if you had bad luck. Some shops have a scope to look at cylinderwalls without pulling head. [links]
Re: Will bad reed alone, lower compression?
Rhodester. Having low compression on the same cylinder that you suspect has a broken leaf valve (reed) would indicate that a leaf valve flap has broken off and was drawn into the piston/cylinder area, damaging the piston and cylinder wall.<br /><br />The difference in compression of 25 psi is a strong indication of major problems. Remove the cylinder head and inspect the engine.
Thank you Joe.<br />I was afraid that with that much loss of compression that might be the case.<br />What should I be looking for, once the head is off?<br /><br />Thanks again,<br />Dave
Re: Will bad reed alone, lower compression?
Re: Will bad reed alone, lower compression? more
After you’ve gone through the steps above, you will most likely have found the culprit of the two-stroke engine’s lack of compression. However, if the steps above did not solve your issue, it is probably time to call a professional.
A cracked piston ring will allow air to escape from the cylinder and won’t let your engine create the pressure required to run. If your engine will start, but won’t hold compression or sputters and dies when you accelerate, there’s probably an issue with your piston rings. more
Next, take a look at your reed valve. The reed valve is positioned in the air/fuel/oil intake pipe that leads from the carburetor into the crankcase, where the compression happens. The reed valve’s main function is only to allow the air and liquid coming from the carburetor to travel in one direction (source). [links]
If your reed valve is broken or cracked, it could allow the air/fuel/oil mixture to escape back through the intake. The piston’s movement would then not create the pressure it was supposed to, and you’d be left with a lack of compression.
Since the head gasket faces such a large amount of pressure from the engine, it’s possible for it to spring a leak. This is harder to determine than a blown gasket, and you may need to replace the head gasket just to rule this out as a possibility.
To check your piston rings, you’ll need to disassemble the cylinder head. This includes removing the piston from the cylinder to check the piston rings. When you do this, be sure to cover the open cylinder to stop any debris from falling into the chamber. more
1995 Squarenose - 701 61x Blue/Jetmaniac ported motor, ADA Head, B-Pipe, BlackJack 44, X-Metal Pole, Hazard Bracket [links]
I had a motor with a bad reed from sinking. Still tested a solid 170 / 170 compression. [links]
My motor had several broken / cracked / missing reeds. They were bad enough that my carb wouldn't pull fuel through the lines, pulse line was almost non existent.
1992 X2 - Westcoast Head, Factory Pipe, SBN 44, Cut SXR Prop , JetTrim Seat / Dash Covers
1995 Squarenose - 701 61x Blue/Jetmaniac ported motor, ADA Head, B-Pipe, BlackJack 44, X-Metal Pole, Hazard Bracket here
No, a reed valve won't show up in compression.here
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