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Thread: ignition control module

  1. #1

    ignition control module

    Do these go out often. Say every 26 years! The ol bike won't rev. It was doing this and i rebuilt the carbs. No luck. First instinct is it isn't getting gas. Starting to think its ignition. Idles great but won't rev up. Gets to about 3500 and just won't rev any higher. Oh wait. Let me go see if a mouse or something got in the airbreather.

    Nice fat blue sparks. Dunno. Any ideas

  2. #2
    Registered User Guenther's Avatar
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    Either ignition advance or gasoline flow

    Did you check the ignition advance? You need a stroboscope to check this.

    All gas lines/filters clean? Make sure the exhaust has cooled down (just in case to prevent a disaster). Get some clean can (old coffee can) and unplug the gasoline hose from the carburetor and let it trip into the can. How does the gasoline stream look?

    Type/year is always good to tell ohers type and year.

    /Guenther

  3. #3
    Liaison 20774's Avatar
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    Torn diaphragms?
    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!

  4. #4
    Registered User
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    Fuel starvation is the first place to look. Unplug a fuel line and make sure you get at LEAST 250 ml (8 fluid ounces) per minute, though I would expect at least twice that amount from a healthy petcock. A torn diaphram can behave with the exact symptoms you have. A stuck float needle also has the same symptom. After rebuilding the carbs you should have noticed a torn diaphram or stuck needle.The ignition module can crap out exactly as you describe, though the usual method is intermittantly turning off altogether and then working again when it cools off. The ignition timing is hard to change without the idle speed being affected, but it is worth checking the high speed timing mark to be sure the ignition didn't stick in the idle position. That would be a very abnormal condition because the usual problem is for the the ignition to get stuck in the high speed-full advance position and the bike will idle fast. Bad gas is another remote possibility, you could drain the tank and put in new gas. That would be a good time to pull the petcock and clean it. Also, how is your gas tank vented? There has to be a way for air to get into the tank as the fuel goes out.

  5. #5
    Nutfarm
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    I rescued a guy off the freeway just alittle while ago, he had a older BMW twin that would run for a while then quit, or it would run fine at low engine speeds. His probblem was in fact a nearly pluged gas cap vent, so by the time he stoped took off his gear the carbs would be full again so it would run fine. We were on an old bike ride, and I was on a Norton, and I always carry a few things when I ride one of my British bikes, alittle tie wire is one of them, whitch I used to cleen out the vent hole, once under way I kept my eye on him for a few miles and all was well. I know it dos'nt look good when a guy on a Norton rescues a guy on a BMW, but when we ride around on the old relics things can and do happen.

    Ken G.

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