Need help atc 70 knocking sound?

[Erock86]

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never heard motor run before i got it. put new rings and new cylinder and head on it. It starts first pull but i hear this knocking. Sounds like to me its coming from the crankshaft area. I have the timing chain pretty tight. And next weekend ill recheck the valves adjustment to make sure its not that.

So im thinking it maybe the con rod to crankshaft bearing. But id like to hear what others think before i got tearing it completely down.Never tore down the lower part of a motor before so pretty nervous. Any information or opinions i can get will be appreciated.

[Scootertrash]

Hard to tell in the vid. Valve noise is usually a ticking sound not a knock.

Adjust the chain to the repair manual specs and get your idle set to the proper speed.

Take a long handled screwdriver or a wooden dowel and place one end against the crankcase and the other end up to your ear (with the screwdriver, place the handle to your ear). You should be able to get an idea of the location of the knock by placing the dowel/screwdriver in various spots on the crankcase. If it's the rod bearing or crank bearings the knock will get louder the closer you get to the crankshaft on the case. If it's the rod or crank the rhythm of the knock will increase and decrease with the RPM of the motor.

Did you have the cylinder bored/honed to fit the piston or did you just buy the parts and throw it together?

[Erock86]

thanks for the tips scootertrash. Im gonna get back at it this weekend. i bought a hole new top end kit online. (head cylinder piston and rings) it suppose to be a bolt on and go deal. yea i didn't run it very long at all so i didn't get to mess with it much to adjust the carb yet. ill try the screwdriver method this weekend also. I plan on making sure i have the valves adjusted properly also.

[Scootertrash]

Got a link to the kit?

[Erock86]

http://www.ebay.com/itm/310871537352...%3AMEBIDX%3AIT

[SteveCZ28]

id be leary of that top end kit. i myself have a 79 atc 70 that i was thinking of just doing that top end to. i emailed the guy, and he said its more or less a univeral kit for the 70's. and to expect lower than normal compression ratios with it, being as its not an exact oem replacement. sure itll work, but wont be perfect

[Erock86]

im gonna tear it back all down when i get some more time i have the orginal cylinder and head and they actually look pretty good i kinda bought the kit prematurely before tearing it down just to give the bike a quick fresh top end. The knocking im getting may be something else im just gonna have to tear it back down and see if i can find anything.

i wasn't worried about a little loss of power since its for my soon to be 6 year old. I should have saved myself a lot of headache and just bought the lifan motor swap for him. but then one that came with carb and all was clutch and didn't want him to be learning that just yet. I seen other auto motors on ebay but i wasn't sure if they would be bolt on ready and if the orginal atc 70 carb and coil ignition would would work for them.

[Scootertrash]

Did you try the screwdriver/wooden dowel test?

[Erock86]

nope its my youngest sons b day this weekend so idk how much ill get to work on it this weekend . When i get time ill defiantly try that out first and reset valves first as well.

[Scootertrash]

Make sure you update the thread

[oscarmayer]

could be piston to valve contact. if the timing is off 1 tooth that can happen.

[Erock86]

Little update will have more info tonight. I rechecked the valves and they seemed good. i tried using the screwdriver to pinpoint to noise. But i couldn't pinpoint it and was worried about running it to long with the noise. But i do have some information. I idiotically had the piston in with the intake and exhaust notches on the piston switched. Idk if that would have caused the knocking but does explain the little bit of smoke i was getting im sure. I also forgot to mention i bought that whole top end kit but i decided to use the original Honda piston with new rings instead of the piston the kit came with because i thought the piston it came with looked cheap. But i started comparing the two and the original Honda piston has more on the top end of the piston(from the wrist pin hole to the top of the piston) then the one the kit came with. This may be what was causing the knock? So im going to put the other piston in with new rings and see if that is what causing it.

also these rings that i bought have no marks on them i looked on youtube to find out where they go but i don't want to install them upside down.

[Erock86]

also checked the conrod and i do not think that is the problem it only moves a hair side to side and no movement back and fourth.

[Erock86]

update for the night: Knocking is gone = ]. But its still not 100% the cheap carb i ordered for it off ebay sucks so i put the original carb back on it and it runs alot better but it leakes gas so i gotta fix that. But this thing still smokes the cylinder is brand new when i tore it back down tonight it still looked brand new. I put new piston and rings in it and it still smokes. Im almost postive i didn't line up all 3 rings so im not sure what is goin on.