bengo Posted May 31, 2011 Share Posted May 31, 2011 Ive restored a 1981 yz125h and cant get it to run properly. It runs fine flat out at full throttle however it has no power and runs rough in the midrange and will not idle no matter how I ajust the idle and air screws. I have fully rebuilt the motor. Also can anyone tell me the slide and needle sizes thanks in advance bengo new member. PS its an Australian model with a 32mm mikuni carb. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 31, 2011 Moderator Share Posted May 31, 2011 sounds to me like a blocked pilot jet 'bengo' take it out and can you see that it is not blocked, blow through it, hold it up to the light, use a magnifying glass to inspect it...whatever is required Greetings and Link to comment Share on other sites More sharing options...
bengo Posted June 1, 2011 Author Share Posted June 1, 2011 Thanks for the welcome and rapid reply oldgitonabike. I should have been more descriptive,I have cleaned out the jets and all passageways ect the slide does raise when the Idle screw is wound in and will idle if you open the throttle slightly. Under no load it revs cleanly to full revs,however when riding it has no power from 1/4 to 3/4 throttle run rough (splutters and surges) but it clears up at full throttle and then it really flies. It is also consuming a slight amount of gearbox oil,I have replaced the crank seals however had to reuse the sleeve the seal runs on as they are no longer available from yamaha anymore. It has new bore piston and rings and starts easily it has got me stumped. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 1, 2011 Moderator Share Posted June 1, 2011 if its burning gearbox oil thats a problem, did you remember to fit the O ring under the sleeve you mentioned? Link to comment Share on other sites More sharing options...
bengo Posted June 1, 2011 Author Share Posted June 1, 2011 No there was none fitted on disassembly and the crappy clymer manual does not show one. It was burning heaps of oil before so I pulled the sleeve back out and smeared silastic between inside of sleeve and crank this slowed usage of oil somewhat but not completly. where does "o"ring go crank side or gear side and would burning the oil be the cause of the rough running and poor performance? Link to comment Share on other sites More sharing options...
Moderator Airhead Posted June 2, 2011 Moderator Share Posted June 2, 2011 No there was none fitted on disassembly and the crappy clymer manual does not show one. It was burning heaps of oil before so I pulled the sleeve back out and smeared silastic between inside of sleeve and crank this slowed usage of oil somewhat but not completly. where does "o"ring go crank side or gear side and would burning the oil be the cause of the rough running and poor performance? I wrongly assumed it would be the same as my DT175...that has an 'o' ring. Seems odd that the little yz doesnt have one. Link to comment Share on other sites More sharing options...
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