Help!

I'm haveing trouble with my "new to me" 1975 XS650. When I bought it the right cylinder would not idle. It would kick in arould 2500 rpms and run ok, but when just cruising at 50 mph or less the right side would just kind of gurgle. Under power it ran good. Me and a very experienced mechanic went through everything for about 6 hours today. Timing, valves, points, carbs... The previous owner had rebuilt the carbs a while ago and told me the right cylinder ran rich, Boy does it! When it idles for a short time the right side smokes like crazy and when I pull the plug it's soaked with gas.
We took both carbs down a dozen times. The previous owner had saved all the factory carb parts when he rebuilt them so we put them back to stock. The needles in the rebuitd kit that he had used were about 1/8" shorter then the stock ones. After we put them back together the left ran GREAT, better then with the rebuild kit parts but the right side ran the same.
I'm at my wits end. Anybody ran into this before?
I'm begining to think the right carb has a cracked passage somewhere. That being said, I guess I'm looking for a right carb body for a '75 XS if anybody's got one laying around.

Thanks...

Get with your mechanic friend and see what he thinks about this:

Check if the bowl base is perfectly flat, and check that the mating carb body surface is flat, not warped.

Some carbs that have been ham-handed in the past have the screw hole/mounting corners bent up, by tightening screws before full seating, preventing a good flat fit in the critical center area.

Check the four corners where the bowl screws are. I've run into several cases where a PO torqued the bowl screws before fully seating the bowl, warping it, allowing leakage around the needle jet area.

Take-off the carb gasket, put a tiny dollip (use toothpick) of grease on the float bowl in that little flat spot between the mainjet hole and the brass idle hole. Then carefully place the bowl fully on the body, then remove. If the body and bowl are flat, that little grease dot will be flattened. You can adjust how big a dot to use to determine just how far out of flat they are. Real tiny dot undisturbed means out-of-flat is at least the height on the dot. Do both carbs, interchange float bowls to confirm. You get the idea...

Looks like you were right , bad float bowl!
I can switch bowls from side to side and the problem follows the bowl.

Now to find a "H" bowl

Thanks!

TwoManyXS1Bs said:

Get with your mechanic friend and see what he thinks about this:

Check if the bowl base is perfectly flat, and check that the mating carb body surface is flat, not warped.

Some carbs that have been ham-handed in the past have the screw hole/mounting corners bent up, by tightening screws before full seating, preventing a good flat fit in the critical center area.

Check the four corners where the bowl screws are. I've run into several cases where a PO torqued the bowl screws before fully seating the bowl, warping it, allowing leakage around the needle jet area.

Take-off the carb gasket, put a tiny dollip (use toothpick) of grease on the float bowl in that little flat spot between the mainjet hole and the brass idle hole. Then carefully place the bowl fully on the body, then remove. If the body and bowl are flat, that little grease dot will be flattened. You can adjust how big a dot to use to determine just how far out of flat they are. Real tiny dot undisturbed means out-of-flat is at least the height on the dot. Do both carbs, interchange float bowls to confirm. You get the idea...

Click to expand...

You might be able to sand that one flat again.

We'll give it a shot!

5twins said:

You might be able to sand that one flat again.

Click to expand...

Okay, so the problem follows the bowl. Good work, problem isolation. Just to be sure, you'd like to confirm that you have the proper bowl and idle jet combo, since it's easy to improperly intermix these.

The earlier bowls had the idle bleed air passage going down to the side of the pilot jet, meeting with the jet's aerator holes. The idle jet must have its fuel orifice at the bottom of the jet.

The later bowls have the idle bleed air passage as a channel, that meets-up with the idle jet above the idle jet. The idle jet must have its fuel orifice at the top of the jet.

Closely study the carb guide (found in the tech:carburation section) for pics and particulars...

I bow in respect to the problem solving that just happened in this thread.

Hey, Sparky, welcome to the party. Yeah, Katmol is 'getting it'. Carb problems are rampant in this forum. The carb variations and questionable 'rebuild kits' present quite a challenge to the newcomer.

This thread may help. Pay close attention to 5Twins posts:

http://www.xs650.com/forum/showthread.php?t=7569