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Thread: High Idle

  1. #1

    High Idle

    I recently converted my R90s to electronic ignition (Alpha from Motorrad Elektrik), and after going for a long ride yesterday, I'm having an issue with the idle creeping up.

    e.g. I'll be riding and come to a stop sign and the idle is perfect at about 1000 rpm. Then the next stop it might be closer to 1800 rpm.

    Since the issue can't be with sticky advance weights, I'm wondering if the engine is sucking air through the manifolds or carburetor's (stock Dellorto's)

    Everything appear tight and tidy. What's the best way to troubleshoot?



  2. #2
    Liaison 20774's Avatar
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    Sep 2005
    San Antonio, TX
    Couldn't hurt to spray some brake cleaner around the carb connections to the heads. Also, giving a call to Rick would be good, too!
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3

    High Idle

    Found the problem last night. The left side Dellorto appears to have a vacuum leak between the carb insulator (the plastic part that inserts into the carb, and where it slides over the intake manifold.

    I sprayed some carb cleaner around that area, engine running, and engine speed changed each time (lowered RPM). This same test did not reveal a problem on the right side.

    The fit between the insulator and manifold's on both sides could be a tad tighter IMHO, but is there a good way to seal the insulator against the manifold? I was thinking some fuel resistant gasket material, applied to the outside of the intake manifold, but maybe there's something better.



  4. #4

    Towards a solution

    Talked with Randy Long he agreed that "sealing" the carb insulator to the intake manifold could be accomplished with some Permatex gray fuel resistant gasket maker. I installed last night so I'll check after work to see if it resolved the issue.

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