Top Speed Troubles

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ZRTMWA

New Member
Feb 23, 2010
142
0
0
Baltimore, Maryland
I have a slant head PK-80 (66cc) from LEB with an NGK iridium spark plug running Opti 2 at 1:100. I had a normal exhaust, carb and 44T sprocket and my bike got 30mph at WOT (it did bog a little).

Now I got a 36T sprocket, a SBP expansion chamber, and a "speed" carb. I was having trouble with the carb at first but I fixed those problems. However now I get 32mph (it still bogs at WOT). Is there anything I can do to increase my speed. Should it have only gone up 2mph? Possible causes for bogging at WOT?

Also, for anyone who has the SBP expansion chamber: how much did you cut off of the tunable copper pipe, to max out top speed? So far i've only cut off .25"
 
timboellner

timboellner

Member
Apr 1, 2009
435
0
16
Towson Maryland
Post some pics of your sparkplug.
Do a plug chop. Run that baby at WOT and pull in the clutch and shut
it down. Let it cool, pull the plug and see what the plug looks like.
Bogging is a loosely used term around here.
Is it 4 stroking at WOT or screaming in 2 stroke mode ?
Bogging is usually associated with a lean condition.
Usually under acceleration when you goose it.
You might just be at your engines limit, after all it's just a little
turd of an engine, not a Hyabusa.
 
B

Black_Moons

New Member
Oct 25, 2010
205
2
0
Canada, Bc
Did you port match the intake and exhaust? that makes a pertty big diffrence in power.

also intake leaks can cause the mixture to go lean and some loss in power. make sure it is sealed WELL.
 
Z

zaviii

New Member
Oct 17, 2008
65
0
0
Chico, Ca
Sounds like its not getting enough fuel and or throttle on the top end. I'm in California and mine lost its top end because it got colder. Colder air means more oxygen, more oxygen to the engine needs more fuel to mix with. Try moving you needle e-clip one spot down. Also try turning the cable tension on the top of the carburetor CCW a half turn or so. If this it too low you won't get full throttle.

Good luck

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