QuestionI have a Honda xr100r 1987 model, that I can't hardly ever start, I usually have to pop the clutch while rolling down a hill to start it. It sometimes studders and backfires when started and will cut off if I let off the throddle. I took it to the mechanic and he said the carbuerator was clogged but another thought it was the timing chain. It still did not run after he cleaned the carbuerator. What do you think.
AnswerJosh, get a compression check done to determine what is going on inside the cylinder. If the readings are very low, the cam timing could be off and/or the engine is worn inside. Have the valves adjusted to .002" COLD on the compression stroke. The compression may come up some, if the valves are tight and not closing fully.
A blocked carb idle jet will certainly make it almost impossible to start and idle, but apparently the carb has been cleaned and checked for blocked passages and jets.
That leaves either tight valves, low compression, ignition timing inaccurately set or camtiming incorrect.
When the valve clearances are checked, the motor can be turned over one more turn, to get the valves to overlap. At this point, both valves should be slightly opened. IF they are not doing that function, then the camtiming is off a tooth, one way or the other, most likely.
Bill Silver
