Qd 20 poor compression (update)

[CritterBob]

Well I borrowed a friends compression tester( Crafstman) and tested my old qd 20. Top cylinder I got about 48 pounds per pull. The bottom cylinder I got 50 pounds. I did give it a shot of gas in each cylinder and it did pop once. I suspected the coil needs replacing but now I wonder if rings and cylinders are a problem too. Worth replacing? Any thoughts, suggestions would be most welcome.

 

[4.0l sahara]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

put a little oil in each cylinder and if it goes up a good amount that leads to worn rings/cylinders. Could also be alot of carbon build up.

 

[CritterBob]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

There was a good deal of carbon in the motor above the water impellar. Will try some oil too. Thanks so much for the reply!

 

[F_R]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

"Per Pull???" That's not how you do it. Keep pulling till the gauge won't go any higher. That's your compression reading.

 

[reeldutch]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

does it have compression releave feature to make ropestarting easy?

 

[4.0l sahara]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

ya the oil will temporarily seal up old worn rings. You could hone and re ring it for less than 100$

 

[CritterBob]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

Guess I messed up. I just took a reading after one pull. I am a newby if ya all haven't figured it out. Yes there is a pressure release button on the tester. Going to try again right now! Thanks again fellas!!!!!!!!!!!!

 

[4.0l sahara]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

missed that. Thats your prob.

 

[CritterBob]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

O.K here is what I came up with. Retested the top cylinder dry and it topped out around 70. Gave both cylinders a good squirt of oil and both cranked up to 135 t0 140. Now what?

 

[wbeaton]

Re: Qd 20 poor compression

Re: Qd 20 poor compression

Well, the numbers are crazy, but the main thing is they are about even. That motor will run on 70 psi so I'd say you are fine compression wise.

Now check those coils. If they are original they have to come out.