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1983 RM80 questions

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Greetings forum members,

    I was on craigslist a few weeks ago and decided, "screw it Im gonna buy a little 80 2 stroke to rip around on for friends to ride". So low and behold 340$ later, here I am with a 1983 RM80. Didn't run when I picked her up but fresh premix and cleaned the gunk and varnish of 30 years out of the carb and she fired 3 kick. Original seat, faded plastics but other than that original. So I think it was a good buy. Chain snapped on third day so got a new one and its working great. Leaks tranny fluid and coolant out of the right side water pump and clutch gaskets but only a few drips every day so I really dont mind topping off the rad and tranny before every ride. Its pretty much what I expected for a 31 year old bike. Anyways heres the only issue, sometimes when Im flying in 6th or 5th it will just cut out full throttle just wuuwuwuwu then after a sec BRAAP it comes back to life. It also will cut out and oscillate in revs on and off when full throttle in neutral. Im 99%sure its running a bit rich because Im at higher elevation but Id rather have that than lean since I am riding it very hard to carry my weight. Because of this if you're not on the gas or lugging it it will foul. It would not start one time, So I pushed it in gear and eventually it started. Idk if that is a common way to "unfoul" the plug but every time it has fouled I have been able to get it restarted by pushing it. I replaced the plug and it ran fantastic for a few minutes and did not cut out or do the weird neutral rev thing but after a bit of riding it started doing it again, not as bad as the fouled plug but not as good as when it was fresh fresh. I did a plug check and it looks pretty good. Im running lucas oil semi synthetic at 32:1 and 91 pump gas with some generic octane boost (add it to all my gas) and atf in the tranny. My friends old 96 RM80 did a similar 'pulse rev' when full throttle but this one seems to cut rather than just 'pulse'. Anyways sorry to ramble but if theres anything contributing to these issue or anything else that is common with these bikes let me know. thanks! 

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i dont know what it could be, maybe i would run a plug hotter? what plug are you running now? in both of my 85's i run br9es and they dont do taht

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Could be the coil or stator getting bad. Usually when they heat up that's when you lose spark. I've seen it where the spark was so weak it wouldn't kick start but a push start would work. Once it cools down a bit it'll fire right back up. Also I would check the compression it may just need a fresh top end. Good luck!

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Yes, if there isn't any or it's not a good blue strong spark than there's a faulty ignition component. Check the spark when cold first so if there is a change when hot you'll notice it.

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i dont know what it could be, maybe i would run a plug hotter? what plug are you running now? in both of my 85's i run br9es and they dont do taht

Its a B8ES

Definitely sounds like a spark issue to me. Does it get worse when it gets warmed up?

yes it runs great when its cold only when its warm is it shitty

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Could be the coil or stator getting bad. Usually when they heat up that's when you lose spark. I've seen it where the spark was so weak it wouldn't kick start but a push start would work. Once it cools down a bit it'll fire right back up. Also I would check the compression it may just need a fresh top end. Good luck!

im replacing the coil and topend soon. thanks this sounds exactly like the issue it sometimes doesnt start hot then the push start works

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Yeah to diagnose whether it's the coil or stator, I would check fire on the plug when cold to get a baseline as well as the power wire running up from the stator. To check stator I usually just get a buddy to kick the engine over with the plug out and arc the power wire across the engine. Then when it's nice and warm do the same thing. Then you can pinpoint which is causing the weak spark. It should be a noticeable difference

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Yeah to diagnose whether it's the coil or stator, I would check fire on the plug when cold to get a baseline as well as the power wire running up from the stator. To check stator I usually just get a buddy to kick the engine over with the plug out and arc the power wire across the engine. Then when it's nice and warm do the same thing. Then you can pinpoint which is causing the weak spark. It should be a noticeable difference

Alright im hoping its not the stator because i dont feel like pulling the cover and flywheel just more hassle and bullshit I already ordered a new coil and top end so hopefully those combined willl clear it up. Another quick question. As i stated before she leaks tranny fluid but i cant pinpoint the drip (runs along the cases/frame) it appears that its leaking from the stator side cover but to my knowledge theres no oil in there is there? Ive seen bikes with oil surrounded stators but ive never seen it on a 2 stroke or a bike of this age and design. 

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Not sure about the 2stroke, but I would assume it would be. It's either the side cover gasket or the output shaft seal. Either way pretty easy to replace. Even the stator isn't hard to change if need be.

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To be honest if it's only a small leak having to add a little oil between oil changes isn't bad for the engine as long as you never run it low. At least there's always fresh oil in the motor.

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To be honest if it's only a small leak having to add a little oil between oil changes isn't bad for the engine as long as you never run it low. At least there's always fresh oil in the motor.

exactly that has been my thinking the entire time, barely leaks any and besides two strokes being simple motors the tranny is the least of my concern i need to get the ignition figured out

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ya you guys got it on point , if i were you i would run br9es or br10es, br10es is the plug they run when the bike is new. also im sorry to hi-jack your post but i have an rm 85 and it smokes ALOT, i pulled of the head and the o-rings were shot, i put new ones in and its still running like it is burning coolant, could this be a jetting issue or not, i have the air fuel mixture screw two and a half turns out.

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10 outa 10 times bikes that have running issues and prefer to be bump started need top ends.

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