'84 ATC 200m idle, popping sound

[cal200m]

Hey y'all,
I just bought a 200m and now I'm noticing some issues, the idle drops down and will eventually die but if I bump the throttle it will idle way up for a minute before dropping back down, I got a complete rebuild kit for the carb but have not done it yet. This is all new to me but would like to do my own work. Also it makes a popping sound during idle and when I release the throttle. I checked the spark plug and it had fresh oil on it, what does that mean? I could use some advice if you guys don't mind helping a newbie. Thanks

[kb0nly]

As for the idle and popping, get the carb rebuilt first and start from there, no sense of trouble shooting anything with a dirty carb.

If you got oil on the plug its one of two things, leaking valve stem seals or oil blowing past the rings. Does it smoke while its running or just a short amount of smoke when it first starts? If the valve stem seals are leaking you usually get a little oil burning off when you first start it then it doesn't smoke after that. If its rings/bore you get smoking whenever its running.

With the valve stem seals after it sits a while the oil leaks down past them and drips onto the back of the valves, if the valve was open while it was sitting it would just leak into the cylinder, if it was closed it just pools on the back until you go to start it and then it gets pulled in/runs into the cylinder. I have seen some where they pool up oil on the back of the intake valve and when you go to start it you get a nice huge cloud of smoke.. LOL

[cal200m]

Thanks for the feed back, It doesn't smoke at all. When I start it you get a little but it's cold out and the smoke is a very light color like your car does when you first start it. No blue or black smoke so I feel good about that. I just don't want to tear it up since I just got it. I have downloaded the pdf repair manual so I know how to fix it when I know what's wrong with it. It fires right up I use the electric start but it seems to only kick over once or twice and it's running I just don't like how it sounds.

[tri again]

200?
Look under the cover that says 'cdi'.
That model may have an advance plate that likes to
cry for attention.
It should rotate a little to advace the spark AND return. 2 tiny springs too.
can you click on:
service manual
?
Plus the other suggestions.
Search key is working like a dream too.

[cal200m]

I did some valve adjustments and I did check the mechanical advance it did seem to return. Maybe not as strong as it should. I just got a compression checker I'll check that this weekend. Also is there supposed to be any slop in the rear? It seems everytime I look at this thing there is something else wrong. Are rear axle bearings difficult to change? Should be a great ride when I can get it all together. Thanks for any and all input you guys are awesome.

[kb0nly]

You can remove the advancer and clean it and lubricate it, it might just be sticking.

Is it side to side movement in the rear axle or up and down? If its side to side check and adjust the axle nuts on the right side, takes a 40mm wrench. The bearing are not that terrible to change, lots of teardown and wrenching but not a terrible job on the chain drive rears.

[cal200m]

Well I got the carb rebuilt but bot able to run yet. The gas line cracked and started leaking so I will replace that in the next day or so. As far as the slop in the rear it is up and down. I hope to have it running and update status by tomorrow night.

[kb0nly]

If its up and down slop then you need new bearings. Pretty common.

[cal200m]

Well I got the carb kit in and adjusted (sort of) it holds idle now but makes like a snapping popping sound I'm going to try amd tweak it this weekend when I check the compression. I gave it ride the other day and as soon as I hit the throttle the front end came right off the ground. It's very responsive. Up next will be rear axel bearings and brakes. Noticed I need a front tire as well. It seems to be never-ending right now. Thanks for all the advice and input.

[barnett468]

Under EXACTLY what conditions does it pop ie., at idle or under acceleration or all the time?


I would check the timing at idle, then rev it and see if it returns to the proper mark. If it is ok, and the valves have clearance, then the valves might be burnt and leaking.

You can put the piston on tdc fire position, then remove the intake and exhaust and spray brake cleaner in the ports one at a time. If it disappears fast your valve is leaking.

[shortline10]

The factory size small jet is to small , install a # 40 small jet , very common issue on the 185/200cc honda utility bikes .

[cal200m]

It has popping at idle and when I release the throttle. I've reset the valves close to the .002 clearence range. It was way more than that and it helped some but still same issues. I will do a leak down test as soon as I get a hold of the tester to check for the leaks past valves. I'm not sure what size jet came with the rebuild kit it was an aftermarket from moose.

[shortline10]

Stock jet is usually a 35 or 38 and the little hiccup your referring to is very common , sometimes lowering the slide clip which raises the needle helps .
Also did you replaced the needle seat in the carb when you did the kit ?


It has popping at idle and when I release the throttle. I've reset the valves close to the .002 clearence range. It was way more than that and it helped some but still same issues. I will do a leak down test as soon as I get a hold of the tester to check for the leaks past valves. I'm not sure what size jet came with the rebuild kit it was an aftermarket from moose.

[cal200m]

I just replaced the jets and springs and throttle needle. It's running ok when it warms up but if I turn the idle speed up to keep it running when it warms up I have to turn it back down so it doesn't jump when I put it in gear. How far do I drop the clip? Just one notch?