Planet Minis

nola_fiddy

Hello all,
I have a 1978 XR75 that is in very good shape. It starts on first kick but runs rough throughout the range and doesn't produce the power it should. It is definitly missfiring. I have replaced the coil, carbuerator, spark plug, plug cap and replaced the points/condenser with a CDI. After each part swap, I tested the bike and it ran the same as before. The only thing left is the stator. The stator looks like it is new (but it's 30 years old) and I hate to rewind the thing if it is not the culprit.

I've replaced the rings and checked the valves and timing chain position etc. All are looking good. But the bike still runs rough and gets hot quick. Could the stator be causing the misfire?

thanks,
nola_fiddy

darkrider001

Did you disconnect the kill switch yet? try that, make sure you cover the open terminals.

nola_fiddy

I did not try that yet. I did notice that the switch seems a little worn. I will try this tonight. Thanks for the input. I want to try as many things a possible before I mess with the stator.

Pat Farsole

The engines made after 1976 that had no oil slinger on the crank and had the cam running half on the actual head ....... wore the cam journals and crank out IF the oil wasn't religiously changed on a regular basis ........

Due to slop in the journals , the cam and crank jump around causing sputtering and misfiring ......... To check ...... grab a hold of the flywheel to see if you can move it from side to side or WORSE still ... up and down and front to rear .... Also check to see if you can move the cam around the same ways while the rockers are on the base circle ... IF there is movement you can try fine tuning it until the cows come home and never get the thing running right .....

The slingerless models also wear the big end of the rod out if the oil isn't changed regularly whereas the earlier models lasted for stacks longer .....

I've checked HUNDREDS of the later model engines out (used) and they're ALL worn out the same way ... especially XR100 motors .....

Yet you can find PLENTY of the earlier engines that are still in good condition and reusable ........ some even have good stock bores !!!!!!!

nola_fiddy

Pat,
Thanks for the good info in your post. I printed this one out and put it in my xr75 manual for future reference. I had heard that the older model motors were designed better and had better potential for performance. This was the first time I hear a reason why it was so. Thanks!

I checked out my flywheel and cam shaft play and everything was nice and tight. I am the original owner of the bike and it has low hours. I plan on checking out the entire wireing system this weekend and see if I can find something before I start on my stator. I will post back the results.

later,
nola_fiddy