Crf450r stroker tuning

[mattmoto441]

Ok I am working on a 06 crf450r that just was rebuilt with a cylinder works stroker crank and vertex high comp piston. Before the rebuild the bike had a fmf full exhaust and a boysen acc pump and ran perfectly. Now the bike is super hard to start when hot or cold and when running if ublet it idle it will just seem to flame out or die after 2-3sec and it a ***** to start back up again . When running and on the track the bike makes great power and runs smooth but if u kill it or it dies its a ***** to get going again . I dunno of its weak spark or a jetting issue.

So if anyone can point me in the right direction of whats up with this thing I would appreciate it.

NOTE I did check the valves and they are all within spec also .

How would you check to c if the coild has a bad ground ? I have had a tingle come through the clutch lever and wasn't sure if that was because the coil was grounding over ??

[Shawn_Mc]

Big bore and a high compression piston? How high?

 

Its probably jetting. could be a cam timing thing too. It might be retarded one tooth.

 

Check the timing using the link at the top of the forum using the stator side, not the crank gear side. Its amazing how well they'll run with the timing retarded that far.

[mattmoto441]

Well I think I fixed the hard starting problem with the coil wire wasnt into the coil cap well now it starts up much easier. Onlybthing now is that when youngo wot in 3/4 and chop the throttle off the bike will idle down and die unless you blip the throttle and then the idle comes back . Also taking off slo at low rpm the bike will just go puh and die/flameout sometimes

I put the carb back to stock jetting settings

Also if anything if feels as if the timing is advanced but the marks are all dead on .

Its not a big bore its just a stroker and a vertex 13-1 piston. Its 470cc

[tonkaman]

I have big bore and stroked motor with a 13.5:1 piston. I sent the carb to Tokyo mods to modify and tune to those specs. They got it perfectly dialed in for me, I would highly recommend sending it to them

[calco88]

Too rich on the idle end/pilot circuit. With big bores, you actually have to jet them slightly leaner due to the increased vacuum. Turn in the fuel screw while idling, it should start to idle stronger, if you get all the way in, go down a size on the pilot jet and repeat.