broken timing chain?

[rubiconrider]

so my friend has an 85(i think) honda atc200m big red and her ex-boyfriend rode it a few months ago and now it wont run. she has no idea what he did to it so she brought it to me. you can pull it over and it basically freewheels. i put my thumb over the plug hole and it doesn't even attempt to blow my finger off. i have yet to take the cover off to see whats going on in there but when i flip the decompressor on and crank it over it doesn't kick it off so im assuming the cam is not rotating. are these common for breaking timing chains? also are they interference engines? if so does anyone ever get lucky and not bend valves? i just wanted to know cuz she doesn't want to spend a pile of money on it. if its more than the timing chain ill likely just buy it from her and have to fix it anyways. any help will be greatly appreciated.

[atc007]

You're on the right track! Tear into it and see what's wrong. Sounds like it broke and or derailed. Post back w any more questions.

[rubiconrider]

interference engine?

[RubberSalt]

Yup. heads for these can be a little difficult to find it seems. I'd ask around and see if other 200 heads will fit, Honda was nice and made most parts fit every bike.

If it has bent valve guides and what not... There is always this. Looks to be what it MIGHT need.

[rubiconrider]

alrighty. ill have to pull it apart and assess the damage

[honda4h]

the timing chain is cheap its the time involved and whats it worth.

[ctbale]

thats a good question on if these are interference engines, I have never heard one way or another.

[atc007]

Being a mechanic,never really understood when they started calling import engines,"interference" Yes,when an engine gets far enough out of time, Mr,valve is gonna say hello to Mr. Piston,And they do not get along.I got a 96 Geo Metro,brand new off the lot in a flood car buyout,it was a Suzuki 3 cylinder. It was in a bad Sandy flood. I drained,cleaned,the usual . Wouldn't try to run,tore in deeper,the timing cover and belt were FULL of sand. The belt had spun,cleaned it out a 100%,retimed it,put a new TBI on her,and the guy I sold it to put over 100,000 on it before he sold it. It was all SORTS of out of time,,but I got lucky,,the 2nd time in my life,I might add! If it's jumped more than a cpl teeth,it will bend a valve,seldom do you get the guides. Replace the bent valve,valves,and lap them in w new seals ,good for another 20.

[rubiconrider]

well being a fellow mechanic i have always referred to an "interference" engine as one that the valves will hit the piston when the timing belt/chain BREAKS. obviously if the engine is so badly out of time that the valve is way open when the piston reaches TDC its gonna hit. but when the chain/belt breaks the cam is gonna stop in a certain position because of the pressure of the valve springs acting on the cam lobes, and if its a non interference engine there is enough clearance between the piston at TDC and the valve to not bend the valves. but thats just my understanding

[mohadib]

yeah, freewheeling engines valve train does not interfere with the piston travel. Not all import engines are interference, maybe thats your source of confusion. For instance, Toyota makes a bunch of engines that are non interference.

[ctbale]

yup, non interference engines pistons will not bend valves. interference engines might. http://www.gates.com/brochure.cfm?br...cation_id=3487 But I think even if the timing chain breaks on one of these, and it is a interference engine, its highly unlikely the cam will stop at the top of the lobe, even a few degrees on either side, the roker will slide off closing the valve,