'90 xr600 trouble can you help

KTM's I know like the back of my hand so I though no problem when a friend wanted his xr600 checked out. I mean how hard could it be right? I was wrong. I've spent about 8 hours on this and have gotten nowhere. :D

A friend brought his '90 xr600 over because it had been sitting in the garage for 6-8 months (I told him he was abusing his bike). The bike ran great the last time he rode it. We can start it no problem and she idles fine but at anything past an idle the bike spits and sputters, blows black smoke and wont clean out. It's kind of like he's running with the choke on only worse.

We've put fresh gas in, set the valves, cleaned the carb, set/checked the float hight, and ohmed the coil (primary,secondary and cap), pulse coil, and changed the plug. Compression feels good, and I've even checked all the engine grounds. Carb is stock: stock needle middle clip position, 50 pilot, and a 155 main jet with a supper trap exhaust.

I'm at a loss for what to do next anyone have any ideas :D:):D

Thanks in advance,

Travis

Oh yeah the plug is BLACK.

You said you checked the float hight. Did you check to see if the valve shuts off when the float is full. I've had a piece of rubber from the pet cock stuck in mine. I found it when I pulled the float needle out.

Pulled the needle and blew through the lines but I'll check again to see if something is wedged in there. Thanks for the reply.

Hey man. Does the old XR have a tiny little hole at the bottom of the float bowl which vents back up to the top? If so, clean it out, it's so tiny it's probably clogged and will give the exact symptoms you're describing.

I don't know if the XR carb has that, but my old DR did, and it sat for a few months, and I spent tons of time cleaning everything, checking the coil, and so on, only to have a friend of mine ask about that tiny little hole at the bottom of the bowl. And yep, it was clogged.

Maybe that's a possibility? I don't know but I hope you get it running!

L.L.

I figured it out :) There is a venturi at the intake of the carb that aerates the fuel as it comes up the needle jet- it was clogged. I cleaned it out and she runs great. Thanks for the replies.

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