jawa 05 scooter lacks power.
so i picked up this mid 60's jawa 05 50cc scooter (i couldn't pass - looks like a mini cezeta to me) it had sat a long time, motor was very mildly stuck - i pulled head - tapped on piston mildly, and it was unstuck.
it starts easy, idles good, pulls nice in first gear. but that's it. riding along and shift to second and it loses power, revs drop and eventually stalls. i can downshift to first and it'll recover and rev/run like it should. it's only 3hp or so - and i weigh 190lbs - so i don't know if i'm being optimistic as it should pull me up a slight hill in 2nd/3rd (it doesn't now)...
so i set the points (didn't adjust timing), made sure the exhaust wasn't plugged, cleaned carb, new plug. no love. same issues.
i'm guessing either the rings are stuck in the lands, the rings are wore, bore is outta spec, or timing is off. there's no air leaks, and compression is so-so......
it also could be - wet side crank seal (that's grasping at straws..)..it does not smoke excessively, jetting, but i doubt it - i tried moving the needle around, and thoroughly cleaned jets, - it's a jikov carb, so the adjustability is almost nil..... could be worn slide/needle maybe? but it seems like it's not carb related, in 1st gear it pulls fine at all throttle positions. in 2nd gear no throttle position pulls at all. could be sprocket ratio (there are 5 different front sprockets available - maybe dpo geared it so high it wouldn't pull anything but first?)
i'm gonna check the timing and give it a try - otherwise it's a tear down and wait forever for parts - all the motor parts are available for it, it's just a long slow shipping process from eastern european countries..
anybody have any other ideas?
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stainlesscycle screwed with this post 12-07-2012 at 05:50 AM