Crying in the rain.

Well I just tryed to run a compression test on my 82 xj750 seca. After going threw parts list for compleatly rebuilding the brakes front and rear. And also total carb rebuild, valve adjustment and shocks, and tire. I decided to run a compression test to see if motor worth spending that much on. Now keep in mind the bike dont run, when it did it poured gas on floor, and into oil. So long story short I could not run motor to warm up. I followed the manuals instructions as much as possible. (no carbs on bike @ test time, unplugged Ic) I did test one time , and results are as follows #1 145psi #2 90psi #3 120 psi #4 150 psi. I added 1tsp oil into all cylinder and results are better but still all over.
#1 190psi #2 135psi #3 140psi #4 180psi. so from those reading i dont know what to make of them. should I finish carb rebuild? (valves barly in spec) and get bike running then retest? or should i just plan on total rebuild? and if so are these bikes worth the large amount of money spent for a casual rider? Ill end up spending about what a new low end bike cost 3-4k range.

 

Adding the oil helped the rings seal and give better compression results. Since this motor has not run for a long time I say the rings are stuck in the groves. The numbers say there is no problem with the valves. If it was mine I would get the carbs on the bike and run the engine through a couple of heat cycles(run engine for 10 to 15 minutes and let cool, repeat) then recheck the compression. Get everything is spec first, valves , carbs, fresh oil and filter before you do.

 

Thank you, that was pretty much my plan, but needed assistance on the compression problem. but ill run it again after i get the bike running again. for the third time. Ive had it running but poorly weekend or so ago, but when i went to start it this weekend it didnt. Id imagine that the plugs are fowled again from running rich. ill clean those too. thank you again.

 

With those comp figures the bike should run and be rideable, once everything else is sorted.
After a run the figures 'may' improve.

 

XJs tend to "saturate" plugs rather than foul them. Once that happens, they generally will NOT make spark anymore, despite attempts to clean them. This often causes a lot of unecessary ignition diagnosis; just replace the plugs if they got "wet."

 

Get the bike running and run a can of Seafoam through the tank.

This should clear the fuelsystem and the rings.

remember to take it easy on the engine for the first runs...