'88 Yamaha XV500 Special fuel problem

[Mal1975]

Hi all. Bit of a strange problem here that I'd like some help with. While idling my bike seems fine, while cruising at highway speeds it also runs fine, HOWEVER, at 50kph around town it chokes up it only takes a km or so. I have to give it a Cpl of good revs before stopping at intersections or it will stall. It doesn't matter if I travel in a lower gear and keep the RPM higher it still does it. I have thought there might be a bit of crap in carb, but if that was the case it would do it at all speeds and would run lean rather than rich if at all. The fuel tap is in the on position not the prime position (should that make any difference at all) it was running fine a Cpl of weeks ago, this has just started I have made no changes to mixture at all. any help would be much appreciated as its rapidly becoming a pain in the ass!!!! lol

[F5 Dave]

Pull both plugs and see how black they are esp against each other. Im thinking worn emulsion tubes or leaky float needle. Good carb clean on the cards too.

[Grumph]

Drain and clean the float bowls first. These aren't noted for carb wear probs but do suffer from the emissions crap fitted. The tank breathes through a canister which is prone to blocking as an example. I'm suspecting your prob is simply water in the bowls.

[Tazz]

That the one from Blenheim?

[awayatc]

Sounds like it is slowly flooding....?
when floats rise they may not shut the fuel of properly...

[Mal1975]

That the one from Blenheim?

Nah Feilding, bought it from a guy in Ashhurst about 3 months ago :)

[Bender]

Pull both plugs and see how black they are esp against each other. Im thinking worn emulsion tubes or leaky float needle. Good carb clean on the cards too.

This.

Emulsion tubes worn right where they sit at 50kph. New tubes AND needles are in your future.

[xcalibur]

That the one from Blenheim?
I managed to snap up the one from Blenheim (if we are thinking about the same bike) I had a similar problem except it was only the front cylinder. Turned out to be that the vacuum line going to the fuel petcock was sucking fuel down into the front cylinder causing it to run horrendously rich. I plugged it and now use it on the PRI setting when running and ON or RES when not running.

[Tazz]

I managed to snap up the one from Blenheim (if we are thinking about the same bike) I had a similar problem except it was only the front cylinder. Turned out to be that the vacuum line going to the fuel petcock was sucking fuel down into the front cylinder causing it to run horrendously rich. I plugged it and now use it on the PRI setting when running and ON or RES when not running.

I forgot when the auction was closing on that damnit. Wanted the motor and knew it was something simple.

Hope you're enjoying it!