NEWS PARTS JEEP & 4x4 ATV & UTV

250 SX Problems

1142 Views 4 Replies 0 Participants Last post by cleartoy, Apr 2, 2000

Discussion Starter · Apr 1, 2000

I have a 1985 Honda 250 SX, with about 20 total hours on it (I haven't gotten out much with it). After not riding it for several years, I tried riding it today. It starts & runs okay, but starts to sputter at higher RPM's. Almost acts as if it's running out of fuel (kind of like vapor lock on a car). The fuel filter screen (in the shutoff valve) is clean. The spark plug is clean & appears to be gapped appropriately. I'm not sure if this tells anything, but I tried hooking up an automotive timing light (to see if it was the ignition system faltering), and it seems to quit at higher RPM's; however, after it quits flashing, it won't flash even at lower RPM's until I bring it back down to idle (even though the engine seems to be running fine at mid-RPM's). This makes me suspect that the timing light can't keep up with the flash rate of a 1-cylinder engine at high RPM's.

Does anyone have any suggestions on what to try?

Thanks and regards,
Michael

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Discussion Starter · #2 · Apr 2, 2000

What elevation are you riding at? What main jet are you running? Are you using the lid for the air filter?

Sputtering at high rpms is a sign of a too lean(small) main jet.

-cleartoy

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Discussion Starter · #3 · Apr 2, 2000

Everything is stock, exactly as the thing rolled off the showroom floor. Riding it at sea level, though the humidity is usually pretty high (coastal plains of North Carolina). Not sure if the climate or humidity have been that drastic of a change, but all of my previous riding was at sea level in Oregon (lower humidity, usually cooler temperatures).

I've only had it out a handful of times since it was new, and always drained the gas after a ride. However, I didn't drain it after riding it once last September (just remembered I did that); the sputtering was present then, but not quite as severe as now.

Thanks and regards,
Michael

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Discussion Starter · #4 · Apr 2, 2000

sounds like the pilot jet is clogged up. i would take the carb off and clean everything out REALLY good with carb cleaner and compressed air. good luck

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Discussion Starter · #5 · Apr 2, 2000

Pilot jet controls mixture from 0- a little over 1/8 throttle.

Main jet is starts around half throttle, but really chimes in around 3/4-full throttle.

For humid conditions, the bike will run richer, so you would jet LEANER.

However, i agree with Pete, thouroughly clean out that carb and try it again.

-cleartoy

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