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oneclick
10-14-2008, 05:41 PM
I tore apart the engine and replaced the timing chain on my z50 engine (for my atc70), i bought a complete gasket kit, new points and condenser, etc... got it all put back together, and it still won't start...

after bolting the engine up to the trike i let it sit overnight, the next day i came out to put the carb, exhaust, and wire it up... i noticed a tiny puddle of oil under the trike, i took a look and i found it was coming from the exhaust port, what would cause this? and how to fix? it doesn't leak alot, maybe 1 drop every 2-3 hours.

here is a list of things i done to it...

removed engine and set it up on my workbench.
removed the whole top-end.
removed the stator plate itself.
removed old timing/cam chain.
released pressure on the cam chain adjuster.
put on the new cam chain.
scraped all the old gaskets off the top-end parts.
put new gaskets between trans case and cylinder.
slid the cylinder on and inserted the piston.
inserted the cam guide roller and bolt.
then new gaskets between cylinder and head.
slid on the head itself.
tightened the head bolts/acorn nuts.
bolted cam chain to cam (making sure 0 lined up, and the T lined up).
put new gaskets on the head cover, cam cover, head bearing cover and valve cover seals.
then with the stator - i removed the old points and condenser.
installed the new points/condenser onto the stator.
then reinstalled the stator plate itself with a new gasket.
then put the flywheel on and set the points with a feeler guage (set to .012).
after setting with the feeler guage i also hooked up a light and battery and the light dims right on the F like it should.

engine completed.

i didn't touch anything inside the head itself, it didn't leak oil in the exhaust before,
and it still won't start! it's getting really frustrating. :( i can get it to backfire though... i stopped messing with the trike for a few days and then last night i tried starting it again, still just a backfire every now and then, i also checked and adjusted the valves last night but nothing.

it's a 1981 z50 engine, using the stock 70 carb, the carb has been cleaned inside and out and totally rebuilt (new gaskets, jets, needle, slide, float needle, etc...).

it's getting plenty of gas, air and has really good spark (bright blue). i'm stumped!

Any suggestions?


Jason

Erics350x
10-14-2008, 06:48 PM
Back firing means the timing is wrong. Did you over fill it with oil or use too much oil when putting the top end on? Did you stagger the rig gaps?

oneclick
10-14-2008, 06:56 PM
Back firing means the timing is wrong. Did you over fill it with oil or use too much oil when putting the top end on? Did you stagger the rig gaps?

cam chain is positioned correct at both the cam and the flywheel, points are set correct, i set them at .012 and then i also used the light setup as shown in the manual, it dims right on the F... is there anything i'm missing on the timing of it?

and the oil level is in the middle of the dipstick, and for the rings i did not check the staggering, i didn't move them from the original positions, this was my first thought for the oil problem.

I'm about to give up on it - LOL...


Jason

oneclick
10-14-2008, 08:17 PM
i have another question...

if i tore this down again to check the piston rings, or to put a new piston and rings on it... would i need another new gasket kit? or could the new ones i just put on it, be reuseable?


Jason

fabiodriven
10-14-2008, 08:21 PM
i have another question...

if i tore this down again to check the piston rings, or to put a new piston and rings on it... would i need another new gasket kit? or could the new ones i just put on it, be reuseable?


Jason

I would re-use any of 'em but the head gasket. But if you're getting another head gasket, you'll probably end up with a whole top-end gasket kit so at that point it's like "Well I might as well replace them all." You could save the old ones for spares-

Erics350x
10-14-2008, 11:28 PM
If you havent ran it then you can re-use all the gaskets. Try rotating the cam 180 degrees and reinstalling the chain. Or just check and make sure the valves are closed when the engine is at TDC

threewheelin-feelin
10-15-2008, 10:29 PM
i agree on the timeing...i ran into almost the exact same problem a week ago when i put my 200s back together...does that have a cdi? i set my cam right but i put the cdi on 180 degrees out they can go in two ways...just my 2 cent

oneclick
10-15-2008, 11:54 PM
i figured out the problem.. but it still won't run. :(

the problem was i didn't have the piston at tdc when i put the cam chain on, and i was trying to be carefull too - LOL, my mistake... but the engine still won't run.

I'm thinking it could possibly be a bent valve? since it is leaking a drop or 2 of oil out of the exhaust every hour or two it sits... it's still doing that. When i had it apart today the valves overall they looked fine, but the exhaust valve didn't look to be seated fully... The whole reason for tearing down the engine was to replace the cam chain... the old one was stretched out and the tensioner maxed out too... with the chain that far stretched - could that of bent the valve?

if so... i do have the original 70 engine, the head on it looks EXACTLY like the one on the z50 engine, would the 70 head work with the z50 cylinder? if so, i might swap them out tomorrow and see what happens... they look exactly alike! i just don't know if the valves and cam are different sizes and if that would be an issue or not?...


Jason

oneclick
11-14-2008, 02:28 PM
IT RUNS - lol...

I gave up on the trike a couple weeks ago, but yesterday i finally started working on it again, and today i finally got to ride it!

Here is what i ended up doing...

it was a z50 engine, 3 speed.
I bought an 88cc cylinder and piston and used the 70 head off of the extra OG motor, got it all put back together and got it running yesterday, BUT... i couldn't get it to idle down at all... so i called my brother, he came over today and got it to idle down and idle right (after ALOT of adjusting), then the fun started... i put the seat/fenders on it and rode it up and down the street a few times (it's 44 out and raining too!), then my brother got on it, after a few minutes he tried to pop a wheelie and over guessed it and stood it up on the rear, he was on the ground still hanging onto the handle bars - LOL... i had to run over and shut it off cause he couldn't reach the switch... after that he took it easier on it, just thought that was kinda funny, he should of gotten used to the bike and it's power before trying something like that.

but in the end, it runs and runs well... just sucks that it has all this power now and only 3 gears, now i'll be taking the tranny gearing out of the OG 70 case and put in this one to make it a 4 sp... but that'll be later on, for now i'll ride it as it is. :)

Jason