no power with new 80cc kit

[jbcoasty]

:s:doh:I just got done rebuilding my 50cc qmb139 had a crankshaft issue replaced crank put on a 80cc kit I got from scrappy dogs. All adjustments right on (timing,valves,compression,sparkplug gap) have stock carb with a #88 jet with uni round filter max speed 30mph and only 4,000rpm, with stock airbox on 25mph and 4,000 rpm max. got 4.5 gram weights in variator and new clutch with big spring this thing just bogs down and will not get out of its own way. before the crank went out I was running the uni filter and the #88 jet on the 50cc and would run 40-45mph at 6,000 rpm this thing got me stumped

[Firehawk989]

Probably need a bigger jet. You went from 50cc to 80cc with no jet change.

[qwertydude]

50cc to 80cc with an open air filter requires a jetting change. Usually in the 95 range or so but be sure to buy an assortment to fine tune. 92, 95, 98, 100 ought to cover you.

[jbcoasty]

Talked with the fine folks at Scrappy dogs and I do have to small of a jet getting a #95 sent and will go from there

[skuttadawg]

I used a 95 MJ with a 50mm BBK with stock airbox and exhaust . Since you have a Uni you would need larger than a 95 MJ perhaps . Here is a jet kit with many sizes http://www.partsforscooters.com/114-49-QMB139-Main-Jet-Kit?sc=34&category=133078

Remove the spark plug and compare the firing end with this chart to see how the jetting is http://www.4secondsflat.com/plug_chart.html