idle surging, running high

[j2]

Posted this in the tech section as well. My BW 150 has been solid for over 4 years and 14K miles. Did a belt change on it and really screwed that up (special tool needed to hold variator), but that's another story. It runs great now, but it is idling at about 4K I made sure the mixture screw is factory spec and fooled around with the idle speed (linkage) screw until I got it to idle about 2K. Noticed it was surging. Started it cold a week later, and it started instantly, but it was back to the 4K idle again. I suspect vacuum leak or maybe a steeenkin bistarter problem (hate those ... Oh, for a manual choke). Anyone experience the same? Suggest a solution?

[j2]

Don't have a lot of time to wrench around, but I have now checked the resistance across the bistarter. Found it measures about 7 ohms on a cheap meter. Spec is 10 ohms. Not sure if the slightly low resistance means the bistarter is bad (switch not closing). I will probably just order one online and replace it.

Since the idle is surging, I am concerned about a vacuum leak, but when I looked down at that engine from the inspection hatch under the seat .... Oh crap! There are hoses running all over that engine. Some look like vacuum hoses but seem to lead to wiring harnesses. I expect that some are fuel delivery and pollution control. One comes off the vacuum chamber and terminates in thin air ... goes nowhere. If I had to replace a vacuum hose, which of those hoses would I replace? Looks like replacing all would be a big job. Any help with hose identification?

[art]

  I don't have your model but surging is most likly a fuel delivery problem(not enouph fuel or too much air?) A carb clean may help. Try some seafoam and make sure the carb boot is tight.
 As for an air leak try to follow the hoses back from the fuel intake side of the carb. Just got to inspect close one at a time. Another thought is pull and check your spark plug. Here's a scale to give you an idia whats going on in the mix.    http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html  .

[j2]

Thanks for the suggestions. I put in a new plug ... one of the first things I did. I set up the idle mixture and speed screw. These actions made it idle fairly well, but I still noticed surging. Started it a week later, and it was back to idling at 4K again. I have ordered a new bistarter. These things only cost 20 bucks. Actually, I could get a whole new carb for about 60 bucks. If the scoot continues to exhibit this wierdness, I may just replace the carb and get one with a manual choke (Huzzah!). I will try the Seafoam, as per your suggestion. Funny thing is, the scooter runs better now than it did brand new ... when traveling at regular traffic speeds, up to about 60 mph. I would think that, if there were some blockage in the carb, the scoot would not run so well down the road. The issue is only the idle. If it goes any higher than 4K, it is going to engage the centrifugal clutch and start burning that, if it is not already making some contact. I am going to replace that bistarter ... or to be truthful, I will bribe a friend to help me with that. I am very limited when it comes to wrenching skills.

[axy]

Don't have a lot of time to wrench around, but I have now checked the resistance across the bistarter. Found it measures about 7 ohms on a cheap meter. Spec is 10 ohms. Not sure if the slightly low resistance means the bistarter is bad (switch not closing). I will probably just order one online and replace it.

16 Ohm on my gf`s A125, should be also 10 Ohm...