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Discussion Starter · #1 ·
i have been having a ton of engine problems with my '78 CM 185 T. I know that running it out of gas was a big mistake, and led to a lot of crap in my carb. i have cleaner in it but i dont think it's helping that well. Aside from that, my engine is only running on one cylinder. My dad is an engineer, and it's still puzzling him. we tried putting new spark plugs and sort of helped for about 30 miles. the next day my left cylinder still wont want to cycle. we tried switching the coils of the spark plug but that didn't work either. i had to replace my mufflers to shorties, but still ran fine. i dont have enough time to completely troubleshoot it and am about to take it to the shop, which i don't want to do. i would love as much help as possible.
thank you.
 

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carb cleaner won't eat rust. You will have to get old guitar strings, compressed air or something to clear the passages.
 

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And be prepared to do a bit of work on the bike yourself. These old bikes do require quite a bit of maintenance so unless you're willing to do the work yourself you will have to find a decent mechanic to work on it.
It's not hard to work on the bike, but you have to be willing to do the work and learn. We can help along the way as needed.

First thing first, you're going to need to to go down the list

1. Check cam chain tension
2. Check valve clearance
3. Check ignition timing
4. Check and make sure you are getting good sparks from both spark plugs and coils.
5. Once all the above checked out, take the carbs off the bike and clean it up really good with carb cleaner. Take out all the jets and clean them as well as any passage ways on the carbs.
 

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Since the bike only has one carb, you can rule that out. And it only has one set of points, so that can be ruled out. This leads to the spark plugs, plug cap, coil wire, coil, or an internal engine problem relating to that cylinder. I have seen brand new spark plugs be bad. Just worked on a bike last week that the owner put brand new plugs in and could not get it to run, turned out one was bad. What does the plug look like, Is it black? The 6volt coils on these early twinstars have been known to go bad. You can check them along with the wires and caps with an Ohm/volt meter. If it is not any of these, and the plug is black/sooty it might be oil fouling.
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Has compression been checked on that engine?
 

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Discussion Starter · #8 ·
Number 4 that you pointed out I think is our main problem, but my dad and I have already replaced the spark plugs three times, and the same plug has fouled, we cleaned it, and then fouls again after about 20 miles.
 

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if the plugs are fouling that quick then I suspect your air fuel mixture is way too rich. When you look at the fouled plugs are they sooty black or greasy or wet with fuel?
 

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Since the one plug is fouling, you must have a problem with the coil, plug wire, or spark plug cap. Have you tried switching the plug wires to see if the problem moves to the other cylinder?
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the same plug has fouled, we cleaned it, and then fouls again after about 20 miles.
Wait... Fuel-fouled - or oil-fouled? Have you done a compression test yet?

Regards,
 
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