81 650 CSR intermittent idle problems

Last week, on the way home from work (approx 6 miles), I pulled in the clutch to coast down a long hill, and after a short time, the engine died. I let out the clutch to comp start it, and it ran just fine the rest of the way home. I figured I must have fat fingered the kill switch just enough to kill it, but not enough to engage the "off" position.

The next day, I took the highway home and again, when I pulled in the clutch to coast up the off ramp (uphill this time), it died. Again I let the clutch out to start it, and got two lights down the road, when it died again. I used the same restart method and blipped the throttle a couple of times, and it ran just fine the rest of the way home. I called my friend, who has done a lot of vintage bike riding and trading, and he said that sometimes old carbureted bikes will do that when it gets warmer out (temp had broken 80 degrees both days). Seemed to make some small sense since it ran just fine both mornings (at about 70 degrees).

So, today the bike ran great up until I hit the driveway (basically level). It sputtered and died when I came to a stop. I restarted it with the starter and it didn't want to idle on its own. I could make it idle (roughly) by cracking the throttle a little (approx 1800 rpm).

I have not had any trouble in the cooler weather. It seems to have started since the weather got warmer.

Now I am hoping the collective wisdom of the forum can help me make her run right, since the weather is only going to get warmer here. I've given all the info I can think of, but may have left something out.

Would assure valve clearances are within specs.

May need further tune-up items such as new correct spark plugs, carb sync and pilot screw adjustments, and possible cleaning of pilot circuit.

Would also assure battery is good, properly serviced and freshly charged.

Good Fortune!

It's possible the carbs are a little dirty inside. You may want to add some Seafoam to the next tank of gas to see if that will clean out any mild buildup. Be sure to follow the instructions regarding how much per gallon; don't dump the whole can in. Ed

I have actually run a couple of tanks of seafoam treated gas through her, just because I was unsure of the PO's maintenance habits. I have slowly realized that they amounted to putting gas in the tank. Luckily he claimed to only have had it for a year.

I will take Patton's advice, as soon as I can.

Does anyone carry a carb rebuild kit, or do I just have to buy individual parts? I figure if I'm taking the carbs apart, I should put new seals in, at minimum...

Slade74 wrote: Does anyone carry a carb rebuild kit, or do I just have to buy individual parts? I figure if I'm taking the carbs apart, I should put new seals in, at minimum...

There's a fair chance that the carbs may be cleaned and returned to serviceable condition without needing any new parts or gaskets. Sometimes, even the float bowl gaskets may be re-used if they aren't torn during removal before cleaning the float bowl.

Would clean the passages, jets, and orifices, inspect the float needle and pilot screws, reassemble, and assure fuel levels are within specs by performing the clear tube tests.




Good Fortune!

Thanks.

I am always impressed by the knowledge of the people on this forum. I am also frequently amazed by the resources many have, example: the diagram Patton provided above. Thank you very much sir. I think it will be a help.