engine tuning help

[Trikeaholic]

ok, have a 70 motor, brand new china motor. (i know, i know) anyway, it started right up and ran good. Started to break up on the top end and idle like chit. sits a few minutes and starts right up and idles fine again, but still, breaks up on the top end and once it does that, it idles like chit and hard as heck to start again. WTF??? is it lean? its not smoking like its too fat. Im no tuner so give me some ideas!

[mdunn]

Does it only do it after the engine gets hot? Might be the ignition breaking down. I could undderstand the being lean up top and breaking up, but it shouldn't be that lean at idle unless something is wrong with the carb.

[Trikeaholic]

seems to be when the motor gets hot, why would the ignition be breaking up? I thought of that too, but then I figured thats "impossible". I guess anything is possible. I will tear into the carb, prolly some crap in it (tears from a child laborer or something)

[Jason Hall]

Are the valves to tight? Might want to check Em out.

[Trikeaholic]

why would it have those symptoms if that is the problem Jason?

[Trikeaholic]

ok, just started it and rode it around, seemed to run fine, let it heat up pretty good too. sounds like it has a little clatter somewhere in the motor like in the cam chain area, nothing too severe but I better check that out. have to run it alot today and see whats up. any more hints??

[Jason Hall]

The reason It would do that If the valves were to tight Is because the valve clearance is usually set cold. When the engine warms up all the metal moving parts expand. If the valves are set to tight, when everything swells from the heat, the valves will hang open slightly. That could cause your problem. Especially the hard starting when hot.

[Trikeaholic]

well, we just rode it and yes, once it got hot it ran like crap. do I take off those little chrome caps and set the clearance? how much??

[Jason Hall]

Yes you take off the little round caps. Valve clearance on a 4 stroke Honda Is usually .004 Intake & .008 exhaust. You might want to call around to find a definate clearance. Make sure the engine Is at TDC compression stroke. Both valves should be closed, that will be compression stroke. There Is a T on the flywheel that lines up with an arrow or line In the side cover. Not real sure exactly what engine you have, so I don't know where the timing marks are. Don't forget, set the clearance with the engine cold.

[MTS]

Make sure to go though that carb with a fine tooth comb, lately seen alot of the knockoff carbs with casting flaw's in the Circuts, not letting enough fuel in ect,,

[Freakshow]

Check the plug as well ..if it's the stock one from china I'd throw it out and put in an NGK. I have a few of those motors and had a plug that sparked good outside the case, but wouldnt under compression??!!??

took awhile to figure that one out

[ceaserthethird]

Do a search i have the correct settings for the ATC 70 motor -

Search for - Guy's i hope i did this right - Valve's / Feeler gauge

[Trikeaholic]

well, it seems to be running in just fine, the more we run it, the better it seems to run, even when hot. It turns out it is a 110 (supposed to be a 70, go figure.) Anyways, the lil holic wanted a dirt bike so I agreed that if he got good grades for 2nd grade, he would get a dirt bike. he passed with all A's and B's with one C which wasn't bad considering he had been failing that subject. Anyways, I could NOT bring myself to buy an 8 year old kid an $1800 mini bike that in my opinion, looked cheesy. I found a really neat looking china 70 that actually had the proportions of a full size MX bike. Since I had really good luck with my daughters Kazuma quad, I figured WTF? $569 shipped. After we broke it in for a while, it runs super. When I was a kid, you either bought a "name brand" if you wanted a "real" motorcycle or you only had one other option-a lawnmower engine mini bike. I had a Honda mini trail 50 back then and this china bike is 10 times cooler than that was and for half the money. No brainer there. I will put up some pics and reviews in the proper forum if anyone is interested. Thanks for all the input.

[Trouble]