The guy that sold me the mini bike stated that the engine was a replacement and had low hours. The label on the engine agrees with the first part as the DOM indicates the year 2000. It already runs pretty good with the new adjustable carb but I like to clean out the carbon and check the valve/tappet clearance when starting with a used engine. The engine is pretty clean on the outside. All of the bolts still have nice plating on them. The frame provides enough clearance to tear into the engine without removing it from the frame. I took this opportunity to do some porting to the intake manifold since the stock port is not round where it attaches to the engine. Close inspection of the carburetor revealed that the throttle would not open all the way. I tweaked the little tab on the throttle plate to allow this. The choke was the same way, it would not open all the way so I tweaked the as well. It would have been nice to pull the valves out and clean up the bowl area of the intake port since that has some restrictions. I wanted to complete the job in one evening but available time did not permit fiddling with the valves. Full porting will have to wait for another day.
There is still visible crosshatch in the cylinder. The valves seem to fit their guides without excess slop and I measured tappet clearance 0.006" on the exhaust valve and 0.005" on the intake valve. Everything cleaned up nicely and went back together perfectly. Of course it was almost 11:00PM on a week night so I just started it up and let it run for 30 seconds. To following evening I ran it some more and readjusted the carb slightly and was able to lean out the idle and high speed. Upon riding the bike I immediately noticed more low end grunt. This probably has more to do with the cleaning and carb adjustment rather then the porting of the intake manifold.
Finally, here is a pile of pics for your viewing pleasure. Please forgive my horrible LG phone camera. I just couldn't bring myself to handle the Canon camera with greasy hands.
-Ray
There is still visible crosshatch in the cylinder. The valves seem to fit their guides without excess slop and I measured tappet clearance 0.006" on the exhaust valve and 0.005" on the intake valve. Everything cleaned up nicely and went back together perfectly. Of course it was almost 11:00PM on a week night so I just started it up and let it run for 30 seconds. To following evening I ran it some more and readjusted the carb slightly and was able to lean out the idle and high speed. Upon riding the bike I immediately noticed more low end grunt. This probably has more to do with the cleaning and carb adjustment rather then the porting of the intake manifold.
Finally, here is a pile of pics for your viewing pleasure. Please forgive my horrible LG phone camera. I just couldn't bring myself to handle the Canon camera with greasy hands.
-Ray