Another hard to start when hot thread..

I want to get some honest opinions before I start tearing down a great running bike for a hot start problem im having. The bike is an 02 crf450, I just shimmed the valves end of last season and have about 15hr on them, it was the first thing I checked and am still at .006 an.007 intake and .011 and .012 exhaust and .014 de compressor, also when I shimmed it was never more than .001 off and in my hotcams kit I was about in the middle of the shim kit in size used.. Jetting is at 170 main 45 pilot 1 1/8 turn for 3000ft. Brand new plug looks nice and coffee brown. Clean air filter and fresh oil every other ride.. The thing runs amazing, no decel pop or backfire ever, nice crisp pop when you blip the throttle, plenty of power, idles fine at a stand still but occasionally dies if im going slow and using the clutch a lot (I ride trails). It starts fine cold but will not KICKSTART hot, if you coast start it it fires right up first pop every time.. And yes Im kicking it properly , quick, hard single kicks, no throttle.. Hotstart seems to help, actually when it does fire hot its only with hot start.


Anyone have any ideas??


Im thinking possibly the top end could be worn and the compression is low? I bought the bike last year and it looks like it was well taken care of but did some decent riding.


Ive read a lot about people running .004 -.009 valve clearances, im not sure of the benefits of this but would it help my hot starting issue? 


Using the hot start when hot is totally normal.

...and quick, hard, single kicks are not really best. Follow through but don't kick your hardest.


Check you plug wire/cap/plug and grounds.

The Honda plug caps are junk, replace it.


A perfectly clean virgin pilot jet and fresh non-ovalized needle jet will also make a big difference in starting.


Without knowing the condition of your main air jet, hot start plunger, choke plunger, slide plate seal, pilot jet, needle jet, and jetting, it's impossible to say if it's jetting related, but it usually is.

The slide plate, slide plate seal, and needle jet are supposed to be replaced at 150 hours, and almost nobody does this.

I had the same issue with my 06, it would even stall on down hills with the clutch in.


I would rebuild / clean the carb with auto brake cleaner, and replace all the jets, its cheap insurance while you have the carb out.

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