Ok there should be no issue between it being from the buyou 300, they have same exact motor and tranny. The output shaft is the only difference. Did you get a new spark plug? Dumb question but have to ask. It may be bad and cause this issue. If so did you set the gap? If all is good on that end then, Sounds like the stator is your culprit. It worked fine when you pull started it because there was no load on the stator. When you use the starter there is a slight load that will make a slightly weaker spark when used. If you had the motor apart it could have gotten out of gap or there may be rust built up on the pickup. Simple fix just clean it with really fine sand paper or reset the gap.
04 KFX400,Crasko 450bbk, Crasko P&P,DRZ flywheel,Web cams,custom Yosh header w/FMF PC4,FCR39,ESR intake,Leager A arms,ESW modded 450r shocks,GTT rear link,Tag stem and bars,JBcustoms frame gussets,LSR axel,YFZ450 front calipers.
99 Lakota, DG excellerator,400ex carb,CWR 335 kit,CWR .390 cam,JB custom intake,Crasko P&P head,400ex rear hubs, Modified KFX400 front suspension.
88 Tecate 4 mostly stock Bills pipe and works shocks.
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