Carb fuel passage clog?!? Lost power.. ideas

[theswedishthing]

Cruising home on the highway last night on my '86 GS400E (canadian model), running like a dream as usual. Get out from behind a truck in a single lane construction area at the start of an uphill onto a big bridge, throttle up a bit, shift up into 5th... nothing there.

Make it over the bridge, then down shift, down shift etc and stall out on the steeper uphill after the bridge. Check for leaks, obvious things wrong etc.. Get it going again and limp home another 15km with a real feeling of underpower and starvation of something.

It will start on choke fine, but not rev up, and will not idle (have to turn the throttle a quarter. The throttle stop is in its usual place; the cable slides well. I haven't taken the carbs apart yet, but am thinking there's something in a fuel passageway or blocking the intake. Any ideas, thoughts?

Cheers

[tkent02]

Could be the gas tank vent isn't venting. Could also be a chunk of something blocking some carburetor passage someplace, but that would only take out one cylinder. Could be a petcock issue.

[MisterCinders]

If it runs/revs on 1/4 throttle but won't idle without choke, what does it sound like when it dies?

Have you tried starting and idling just on PRI?

Can you coax it into idling with the idle screw turned in more (i.e., similar to 1/4 throttle)?

You haven't changed the carbs, but do you have a fuel filter inline? Maybe the filter or other part of the line is clogged and refusing to let in enough fuel to keep the bowls filled. Start with the tank and follow the fuel path like tkent says - tank vent -> petcock -> fuel line and filter (if you have one) -> fuel T connection and pilot fuel jet (though it seems odd that all the pilot jets would crap out at once).

[theswedishthing]

I don't have a fuel filter in my lines. I will start with the tank & petcock, I guess. Although it bums me out to take the cock off as you never know what it'll do to the gaskets! Always better to keep things together - unless you have no choice like in this case.
Thanks for the suggestions. I'll get back to you with a progress report come Monday-Tuesday.

[tkent02]

You can check the petcock without ever removing it.
But usually the O ring or gasket is fine to re use.

[tom203]

You can check the petcock without ever removing it.
But usually the O ring or gasket is fine to re use.

Yes, but the only way to tell if petcock filter is in good shape,is to remove petcock ; you probably will have to get new two special "sealing washers"- try your hradware store.

[hjfisk]

Have you tried running it in the prime position?