SOURCE: 2005 yamaha yzf 250-unstable idle
I had the same problem, Turns out that my shims were finished, replace the chims and check clearences.
SOURCE: Cleaning Carb Jets
not to a trained ear also go by rpm and spark plug color
NOTE: use copper wire to clean jets, sync is just thottles are same position as all carb's just leave them adjustments alone will be fine if are out use a 1/8 drill an place in between piston/butterfly to carb bore to sync/calibrate
better use a manometer for adjusting screws
depends on condition of org parts
worn = richer running
new = lean an clean
also if changed the exhaust system need to
re-calibrate carbs for max performance
SOURCE: 350 raptor only runs with full choke on ,
Hi Mike,
You will find that there is a problem with the carbie. It runs with the choke on because the choke engages the "enricher" circuit. The idle circuit is different a different circuit inside the carb. When just crack the throttle on, you use the pilot circuit, and then main jet with more twist of the grip. You will need to completely strip the carb, remove all jets, spray carbie cleaner throughout, and blow out all capillary tubes and holes inside the carb with compressed air. Pay particular attention to the fine holes inside the venturi near the butterfly valve. You may need to use a fine piece of wire, like a guitar string to open up any that are clogged.
There is not much else that will cause the symptoms you have. Check for air leaks about the inlet manifold also, spray some carbie cleaner about the manifold connections boots, the revs will change when it sucks up the cleaner through the leak.
Happy to talk to you more about it.
regards
robotek
SOURCE: what would cause a 2003 yamaha raptor 350 to
Either way too lean, or air intake leak, or the cam timing is out.
Does it help with the choke on?
Not certain of the timing on that model, but at top dead centre there should be some marks on the cam sprockets that will line up with the rocker gasket surface. The previous owner may have changed the timing by a tooth or two to try for more performance .
SOURCE: fzr 600 got killer spark pulls fuel valves in
This is not the news you probably want to hear but backfiring thru the carbs when you have good spark can be one of 2 things... either the valves are sticking / not closing properly due to carbon or the cam timing has shifted from the original position.
It would be best to do a compression test. You should have a minimum of 100 PSIG for an engine with major problems and up to 150 for a healthy engine. If you can not get 100 PSIG then it will be time for some serious engine service.
There is a possibility of the kill switch wire in the handle bar grip grounding under the grip to the handlebar but, since you said you have killer spark I doubt this is your problem.
Thanks for using FixYa.
Kelly
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