2sTrokeLove Posted July 6, 2012 Report Share Posted July 6, 2012 i just built this 421 cub, new everything, got it all together, it kicks and fires right up for a split second, ive tried evry advice ive gotten from members on here idk wats wrong idk if its the harness or this dynatech cdi box, i know its not the carbs or the gaps ive cheked all those...ive tried alot of stuff. fresh gas evrything... its so close to wanting to run but just dies so fast...any help would be great. ty. 421 cub 19cc domes stock carbs for now stock timing t5s for now ....could it be something with the harness. it seems like timing but....its all stock. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted July 6, 2012 Report Share Posted July 6, 2012 Did you change your jetting? Quote Link to comment Share on other sites More sharing options...
2sTrokeLove Posted July 6, 2012 Author Report Share Posted July 6, 2012 Did you change your jetting? not yet but was told it still should fire up with horrible jetting.. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted July 6, 2012 Report Share Posted July 6, 2012 not yet but was told it still should fire up with horrible jetting.. I don't think so. The cubs move a lot of air, what did you upgrade from? Quote Link to comment Share on other sites More sharing options...
2sTrokeLove Posted July 6, 2012 Author Report Share Posted July 6, 2012 I don't think so. The cubs move a lot of air, what did you upgrade from? stock to 421 4mil just slowly upgrading everything.. Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted July 6, 2012 Report Share Posted July 6, 2012 I'm not the best but I would really look into that. Did you check your squish or compression? What jetting are you at now? Quote Link to comment Share on other sites More sharing options...
2sTrokeLove Posted July 6, 2012 Author Report Share Posted July 6, 2012 plenty of compression, 19cc domes with 13...or 30 degree squish angle is that too much or? have to check jetting still, could these domes be setup for alky only? Quote Link to comment Share on other sites More sharing options...
sheerider11 Posted July 7, 2012 Report Share Posted July 7, 2012 Hmm, I'm the last to be giving out advice. I'll let someone else chime in that has a idea on what there talking about. Quote Link to comment Share on other sites More sharing options...
Rotax Raptor Posted July 7, 2012 Report Share Posted July 7, 2012 I'm thinking carbs. If I'm not mistaking, stock carbs are 26mm and you need to be running 35s on that 421. Just a thought. Quote Link to comment Share on other sites More sharing options...
Finch Posted July 7, 2012 Report Share Posted July 7, 2012 what jets ya have in there now? should run just lack alot of potential Quote Link to comment Share on other sites More sharing options...
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