1991 150 TXRP runs rough at slow speeds

[jeffm]

I have a 1991 Yamaha 150 TXRP, motor was just rebuilt. Motor idles smooth in neutral and runs fine over 2000 RPM. At low speeds (800 - 2000 RPM) motor runs rough when in gear. Have not experienced any stalling. Spark plugs are all dry and ****en brown (checked after high RPM run). Any suggestions on possible causes appreciated!

[99yam40]

Pilot jet/passages have trash in them would be my thoughts

[jeffm]

pilot jet

Thanks 99. Just so I am clear is the pilot jet/jets located on the bottom of the carb bowl?

Thanks

[99yam40]

I am not sure on that motor's carbs, but you should be able to check a parts break down of your carbs to see.
Why did you rebuild the motor and what all did you do during the rebuild?

If you had piston problems, did you find what caused that and fixed it so it will not happen to the rebuild. carbs running lean cylinders will eat pistons

[jeffm]

I changed all of the bearing, seals,gaskets and hoses newfuel pumps, heads, piston rings (honed cylinders) etc. Reset all linkages to factory specs. Basically did the rebuild as a winter project. The pistons were in good shape. One thing I failed to mention is after the engine was rebuuilt I had a bad fuel issue and had to drain the gas from tank and system. The gas was really bad so I am thinking you are right on about a clogged passage. I looked at the parts break down and it does show the low speed jets in the bottom of the bowl. Just wanted to make sure we were talking about the same jets (low speed vs pilot).

[99yam40]

may not hurt to do all the carbs completly to make sure if you had bad stuf in there