please help!

As far as I can tell, I have the three ingredients in combustion (spark, compression, and a properly atomized mixture), but it still won't fire. My manual says that if the above elements are OK, check the valve lash. I can't find any other reference to valve lash in it, so I don't even know what I am looking for.

Any ideas would be GREATLY appreciated, because I need all the horsepower I can get to turn my tiller. I don't want to take the head off the engine if I can avoid it.

Again, thanks.

I would say that if in fact you have 140# of compression in that cylinder, and that in fact you have a good hot spark, it should then be firing. I would be interested in knowing why you think it is that #1 doesn't work and the other 3 do. How have you determined this?

Thanks for the quick reply. The reason I think it is not firing is because it makes no difference in the sound of the engine or the RPM if I use an insulated pliers to pull the wire off the plug while the tractor is running, then replace it. If I pull the wire off any other plug, the drop in RPM and increment in roughness is immediately apparent. Hope this helps.

On a related note, in my manual, the desired compression is listed as 130 psi on each cylinder, and there is a note that readings greater than 10 psi over that are evidence of carbon buildup. As I noted (or should have) in my first post, I have 145 on one of the other cylinders, and 130 on the remaining two. Is there any product (fuel additive, intake spray, or other) you know of that can be used to dislodge the carbon (assuming that is the problem) without taking the thing apart? The tractor is generally in excellent working order, with the exception of this problem.

Thanks to all for your help.

Bill

Here's an idea. Do you have an inductive timing light, you know, one of those types that you clamp over the plug wire? If so, take it out there and clamp it onto the plug wires one at a time and see if you can get your light to flash consistently with each cylinder. If #1 gives trouble with this test, maybe you can swap around such things as plugs and/or wires to see if the problem goes to a different hole. Maybe you could also consider re-doing your compression test to verify your last readings. Possibly you have an occassional sticking valve that was behaving during your last compression test.

I wouldn't be too worried about the differences in compression readings, that really is not that much difference. The best way to get rid of carbon buildup is to take that tractor and work the snot out of it for about half an hour. I do this on a dyno if a customer asks me to do it. Looks really cool in the dark. Freaked me out the first time I saw all that fire works coming out the stack though!