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XR100 misfiring - ignition question

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Hi all,

This forum has been very helpful in repairing and restoring my son's 1985 (1991 engine) XR100R. We bought a new piston .040 over, got the cylinder bored, lapped the valves ourselves, and replaced the cam chain and cam sprocket (the crank sprocket appears to be pressed on and not easily replaced). We rebuilt the carb, including thoroughly cleaning the body in an ultrasonic cleaner and blowing out all passages. We got a nice used frame from acguy on TT and sanded and painted it candy apple red (looks real sharp!).

So last night I installed the carb and put on the muffler and wouldn't you know it started right up on the second kick!! I was psyched! Until I rode it around the yard and found it still has the same problem as before the rebuild, which is that it misfires seriously as you raise the RPM. It idles fine but won't develop power as you open the throttle. I replaced the points during the overhaul and carefully adjusted static timing. I don't have a decent timing light, but I suspect either the magneto or coil/capacitor are flaky.

My question is how often do magnetos fail, compared to coil or condensor? I can't think of how to diagnose this without equipment that I don't have. The coil and condensor would be the cheaper items to replace in order to rule them out first. BTW, the spark plug is also new so I rule that out already.

Before the overhaul the bike was ridden perhaps a total of a couple of hours (maybe one tank of gas total). The misfiring got steadily worse over that time, but it never had much power beyond first and second gear. It has always blown a lot of black smoke which to me means unburnt gas. The carb has a new needle and jet, carefully adjusted float level, and no gas coming out of the overflow hose.

Any ideas?

Regards,

Peter

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Same thing happened with my buddies 85 with a 120 kit... Easiest thing to do is to buy a cdi system from a newer bike(one on Ebay right now)... or if you have the cash... the Kitaco inner rotor ignition(about $365) is a kick butt piece... good luck.

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I cannot stress this enough: Points Suck!!! My friends and I spent many years with the same problem. Having it work perfect while tuning it, only to have it crap out on the track. My only fix is a CDI. I have only had 1 issue over 10 years with a CDI. (XR100 not XR200) The main problem (my opinion, which means nothing) is all points ignitions are close to 20 years old (more or less). So I imagine they tend to degrade a bit. When I finally shelled out the big bucks for the CDI and my bike started up and reved bottom to the top without missing a beat, I was never happier. It was the best $350 I spent.

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OK solcalxr, you've convinced me. But I can't afford to spend another $350 on this old beater bike. I'll wait for a used CDI setup on ebay... Mostly I see the boxes alone, never the entire setup. I'll keep looking.

Regards,

Peter

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True, but points are repairable. You can replace the entire points system for under 20, new. A new CDI at the Honda dealer is $150 bucks, and I think mine went out. I got a used one on Ebay for $50. My CDI Migfht be bad from being submerged though, and other than that, they are very reliable. At this point I'm 49% for points and 51% for CDI.

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A new CDI for $150????? Remember to swap points to CDI to need these things: backing plate $25, o ring and seal $7, stator $85, Loom $40, flywheel $125, black box $75, coil $40, cap $15, holders $10. I think that's everything.

The price on replacing the parts on a points igntion are somewhat the same. Unless you mean the points themselves are $20, But I thought they were about 6 bucks. But the stator, flywheels, etc. are more or the same.

Ebay is definately the way to go. I've bought a few ignitions for pretty cheap. (about 1/5 the price of new)

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Someone picked up a brand new XR200 oil pump assembly for $2.50 on Ebay. I kick myself every 10 minutes for not catching that. I put my crappy scratched gears back in the engine dammit. Yeah, I mean replacing just the points and condensor as opposed to replacing the CDI unit.

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There's a ton of points ignition stuff on ebay ending today with not that many bids. Even some XL stuff, if you want lights. :thumbsup:

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Not nearly as good of a deal as the $75 I paid for that same setup a few months ago off ebay... hehe :thumbsup:

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Hi, I was wondering if there is a kit out there that would allow me to put a small block in my XR200? How much is the kit, and is it easy to do?

Thanks!

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Your points motor Tip of the Day; get an old flywheel, remove the points cam. Remove the flywheel from the good engine, slide the cam over the crankshaft, point the lobe at the timing mark, adjust the points. Perfect every time.

My bet on your misfire problem is a worn main needle and seat. Replace them!

Robert :cry:

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Robert,

Thanks for the tip.

As to the carb, I did already replace the main needle and jet; no joy.

Regards,

Peter

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