86 -DT40 compression differance

[dogscoop]

Well.. with another summer upon us here in the cold north I just took my old 86 model DT40 out of hibernation. It doesn't have a huge amount of hours on it but I think it's dying of old age anyway. It starts ok but blows a lot of smoke when cold and it idles a bit rough with the occasion cough. I did a compression test on it and got 92 psi and 115 psi. I can't find my factory manual to check what it should be but my question is.

Is the 23 psi difference between the 2 cylinders way over the normal limit?

What risk am I taking by running the engine with the above compression?

Cheers... and have a great summer!


Bill Carr
Norway

 

[shortcut]

Re: 86 -DT40 compression difference

Re: 86 -DT40 compression difference

That is a rather large difference, over time it will cause excess wear, being out of balance. Perhaps the rings on the low cylinder are stuck and not seating well, with a little run time it may improve. I would think 5lbs between would be safe.

Jeff

 

[JUSTINTIME]

Re: 86 -DT40 compression difference

Re: 86 -DT40 compression difference

do a de-carb

 

[dogscoop]

Re: 86 -DT40 compression difference

Re: 86 -DT40 compression difference

do a de-carb

Thanks.. I never thought of that. Is a decarb likely to just even out the compression differences or actually boost the cylinder that's low? (almost, but not he same thing)

Cheers

Bill

 

[JUSTINTIME]

Re: 86 -DT40 compression difference

Re: 86 -DT40 compression difference

Thanks.. I never thought of that. Is a decarb likely to just even out the compression differences or actually boost the cylinder that's low? (almost, but not he same thing)

Cheers

Bill

it could, you never know

 

[deejaycee_2000]

Re: 86 -DT40 compression difference

Re: 86 -DT40 compression difference

.... it might even them out, but don't expect the compression to be more ..... a carb build up adds to the compression .......