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1973 dt1 won't go over 4000rpm
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Posted by: THREADLOCK
I rebuit a 1973 yammaha 250. Swapped a crank from another bike and used original magnito. The bike starts on 2nd kick, idels fine but, when I rev the motor to 4000rpm it looses power and shuts down. I checked for broken wires repaired one but still have the same problem.
I tore the bike down because the motor siezed. It ran fine at that time (except for the oil pump). The only difference between then and now is the crank. Could this be a timing problem, or would worn points cause this??
Posted by: rugrat
im thinkin new points if you installed old ones,, was crank exactly same, check for worn woodruff key on mag
Posted by: THREADLOCK
Crank was the same. Actually, the orginial had a slight groove starting to wear into the shaft. The new one has no wear marks. Also, when I hit 4000 the motor doesn't totally cu out. If I let fall back down to about 1000 rpm I can feather the throttle and keep the engine running. Would bad points kill the engine??
Posted by: TWRT
It kinda sounds like a fuel problem. When the engine revs, it uses more fuel and may drain the carb. Make sure you have good fuel flow. The points/timing could play a part, but I'm not sure. It has been many years since I worked on one. Also, check all passages in the carb for blockage.
Posted by: THREADLOCK
Thanks everyone!!! This is a little embaressing but....I retro fitted a quad air cleaner
foam to my air cleaner cage and tucked the excess material into the cage. Once I cut out the excess material the bike took off!!! Wheelies in three gears.
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