Will bad reed alone, lower compression?

[Rhodester]

70 Johnson suddenly runs like crap.<br />Fuel blowing out center carb at idle.<br />Bad reed, right?<br />Did a compression test just for drill.<br />85 on the cyl. blowing fuel, 110 on the other two.<br />Question: Wouldn't a broken reed cause lower compression on it's own, or should I pull the head and check for possible ingestion damage?<br /><br />Thanks,<br />Dave

 

[Joe Reeves]

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.

 

[Rhodester]

Re: Will bad reed alone, lower compression?

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

 

[G DANE]

Re: 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.

 

[Forktail]

Re: Will bad reed alone, lower compression?

Rhodester, a broken reed won't affect compression unless, as the others have said, it damaged your piston/cylinder when it broke. There are other things that could cause fuel to blow out the carb, like a bad crank seal.<br /><br />First I would verify whether or not you really do have a broken reed. Then maybe de-carb and check compression again. If it's still low, put some oil in the cylinder and check compression again. If it comes up you most likely have ring/cylinder wall damage. Then I would pull the head, etc. Good luck.