YZF750R runability problem
Hello everyone. I am working on a friend's 97 750. The problem is that it really hesitates in low rpm. Just falls on it's face as soon as the clutch grabs. Runs quite well without a load.
Originally it didn't run. Fuel was stale. I cleaned the carbs although they did not look like they needed it. Took them apart, soaked them, put them back together and synced. Seemed to be lean at idle, I put 40 size pilot jets. It's better, but not good. Seems too rich. No matter what adjustments I make, it just isn't right. For fuel mixture screw adjustment, I ended up with (turns out, from cyl 1 to 4) - 4, 4.5, 1.5, 4. Plugs show rich condition.
I decided to check the valve clearances.
From cyl 1 to cyl 4, left to right, exhaust clearances are
.229 .229 | .203 .229 | .229 .203 | .229 .203
Intake valves are
.152 .076 .052 | .152 .051 .102 | .102 .102 .102 | .127 .127 .127
Do you think those clearances are enough to cause the problem?
A stretched timing chain can compound this problem? How does one test a timing chain wear?
The bike runs very well once the engine is up past 4k RPM.