Ive got a strange situation with my 2021 KTM SX250 2 stroke that im soon to investigate, but would be interested if anyone has any advice first.
The bike starts easy in 1 or 2 kicks from cold with choke, and warms up great. Its a little more smokey than ideal but once warm there is no smoke at all.
Starts 1st kick when hot.
Plug looks great, maybe a tiny bit rich.
The problem is that when revving the bike it takes a while for the revs to drop back down to idle, but once there it idles fine. On track it runs great, loads of power, but when braking hard and off the throttle the revs will take so long to come down that im usually back on the gas before it does.
I can only explain it like a hanging idle but it runs great, starts great, and plug looks good.
Im going to strip the carb and inspect, also the air boot and reeds.
Any ideas?
Thanks
You have an air leak forming probably around the reed block. It won't effect performance until it leans out the jetting enough to cause a seizure.
Other common source of an air leak left side main seal behind the flywheel stator. Fix it now not later.
Is this a new sensation? As in, it just started doing this and did not do it before? Did you recently change something?
What jetting, fuel, oil, and ratio are you running?
If this is not an air leak, then a hanging idle is typically caused by being too lean on the pilot or needle straight section.
Thanks.
Did a few bits this morning -
Checked for leaks whilst running with carb cleaner around the carb, boots, intake, reed block, and igntion cover. No change detected.
Took carb off and cleaned. Jetting is stock, 450 main 35 pilot. Air screw was about 3 turns out so have adjusted to 1.5.
Took the Vforce 4R reed block out and found a damaged petal. The corner is chipped off and the cage it sits on is damaged causing a gap. This may be the issue? Ive ordered a Boyesen Rad Valve to replace it.
Top end has done 29hrs now, do you think it needs replacing yet? The skirt looks perfect condition through the reed port
Forget the last sentence, ive just removed the cylinder as the bike is stripped down anyway, and the piston looks pretty done so I'll put a new one in
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Yeah.. def fix the reeds and piston.. and then get on AJ's jetting from the thread. It's a big improvement to the 250.
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