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Old 05-25-2008, 10:48 AM
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cityevader cityevader is offline
Motorized Bicycle Elite Member
Join Date: May 2008
Location: Santa Cruiz, CA
Posts: 170
Default Suddenly running better

I've been battling engine performance for awhile now on my PK-80 with 44T, 25:1 synthetic oil and 91 octane, my weight 180 lbs. It just didn't want to come up into 2 stroke rpm range unless it was going downhill. On the flats and particularly on a slight grade, it would surge between 2 and 4 stroke running. Steeper grade had less surging. Clearly a mixture issue, but without an RC engine-like mixture screw, it simply sucks! (hmmm, a Saito 4 stroke radial engine in-frame? Nice!)
Resealing manifold and carb, checking float, needle, and seat for debris, moving mixture needle clip into all four slots, matching intake/exhaust manifold ports didn't help. Scouring this site came up with nothing else to really go for.
So I took it on it's maiden voyage to work (20 miles one way) with an estimate 75 miles of break in roadtesting, and a few miles into the way back it just suddenly, miraculously, started to run consistently! No more surging, just smooth operation...nice!
I still wish it had more power on the hills, as even a very modest incline loses a lot of speed, but overall, much happier now. Wish I knew what changed!
I guess it is true, the firt 100 miles or so should be just ridden through without worrying too much about performance.
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