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Discussion Starter · #1 ·
Hi all,

First off, you guys have never failed me yet. Thanks to all the help I got on here last summer, I've been enjoying some great rides on my revived 1970 CL-350. When I bought it I did the usual complete carb tear-down/timing adjust/oil filter clean, new plugs, and it ran pretty well. Then it died last fall, but with a new battery (old one was badly sulfonated) and new plugs (again) it fired right up this spring!

It's often a hard starter, although it has periods where it'll go on the 2nd kick. Once running, it's great at first - pulls hard all the way to the red-line and shifts smoothly. However, when I get about 15-20 miles from home it'll start stumbling when I give it throttle (losing power and then suddenly getting it back). It will continue to do this off-and-on for the rest of the ride (no backfiring though). Once it cools down it seems ok again for a while. I also noticed this last year on "longer" (>20 mile) rides (although there were few of those because of fueling issues I had at the time).

I check the (static) timing regularly and it's dead on. I think the advance seems to be working ok in that it doesn't bog down (the loss of power I get doesn't seem to be like what you get with a stuck advance). The charging system appears to be working too (it does have the original rectifier but it checks out, and on longer rides at higher rpm it will top up the new battery back to 12.5v).

I suspect it's the coils. I have not changed the points/condenser or the coils, and plug caps look original (they do get loose, so maybe that's it perhaps?). I'm planning to go the electronic ignition route at some point so I've been ignoring these components until now.

I can't find the thread, but I remember others reporting this problem. Could the coils be overheating and causing a spark problem? Bad condenser? Some kind of issue with the plug caps when they're hot? If so, I'll probably spring for some new parts.

[In the interest of full disclosure (and in case it helps) it does have another issue. It fouls the left-side plug after a while (it's oil fouling sadly), so I suspect the rings might be starting to go. Compression is still ok at 160-170 on both sides. It's not burning any oil that I can see, but it must be burning some obviously. It also drips 5-10 drops of dark oil after a hard ride (perhaps coming from the breather?). When this gets worse, I'll probably do a re-bore and tackle the tensioner issue at the same time, but for now I want to keep riding it.]
 

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Sounds like you may have the same problem that I had with my 450, increasing resistance in the ignition switch as it gets hotter causing low voltage to the coils.
I posted here.
viewtopic.php?f=5&t=378&st=0&sk=t&sd=a&start=110

When the bike is hot you can back probe the black/white wire at the coils with a voltmeter and the engine running. You should see full battery voltage or around 13.5 volts. On my bike there was only 8.5 volts here when the bike was hot. About 4 to 5 volts being dropped across the ignition switch. Your plug oiling issue may just be the head gasket leaking from the cam chain tunnel into on of the cylinders.
 

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Discussion Starter · #3 ·
johnnyc14 said:
Sounds like you may have the same problem that I had with my 450, increasing resistance in the ignition switch as it gets hotter causing low voltage to the coils.
I posted here.
viewtopic.php?f=5&t=378&st=0&sk=t&sd=a&start=110

When the bike is hot you can back probe the black/white wire at the coils with a voltmeter and the engine running. You should see full battery voltage or around 13.5 volts. On my bike there was only 8.5 volts here when the bike was hot. About 4 to 5 bolts being dropped across the ignition switch. Your plug oiling issue may just be the head gasket leaking from the cam chain tunnel into on of the cylinders.
Thanks! I'll try that out (good excuse for a ride too). Your thread is fantastic too. Beautiful bike!
 
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