Stumped on atc 90 not running

[81ATC185S]

Ok, now I am really lost. My 77 ATC 90 has fuel, in the carb, intake and cylinder, it has good spark and the ignition is timed good, the valves are timed DEAD ON and it has good compression and it WONT RUN! Even with either and gas down the cylinder!

[sweetip2000]

Did you or someone else paint or powder coat the frame ? Check the ground wire on the frame. Make sure its clean no corrosion.
Try starting it with the gas cap off. The rest will be trial and error. Good luck man.

[effort=results]

Is the timing 180 degrees out

[Hgibson]

Has it sat for a long period of time?

[Hgibson]

My 200x sat for 4 years and it had the same exact symptoms as yours and some a couple days ago it fired up. I just kept kicking and kicking. Try starting fluid into the back of the carb.

[81ATC185S]

It was running, and yes I tried either

[81ATC185S]

Still not understanding the problem

[shortline10]

Replace the points ! Even if their showing a nice big spark they go bad .

[81ATC185S]

Is there a way to tell they are bad? They look straight and clean. Ill try a new plug soon, and then coil ground, and then new points if all else fails.

[coolpool]

I'm not sure how much this will affect this motor, but I'm wondering if your flywheel keyway has partially sheared throwing the ignition off slightly? I have a new set of points I can sell to you for a very good price.

[350for350]

Another thing you could try. Check your valve clearance. If there's too much clearance, your valves may not be opening far enough or not at all.

[81ATC185S]

valve clearance is good, and the flywheel key is in good shape. It was running, stalled and now wont run..

[jerkin]

What do you call "good" compression?

[81ATC185S]

I can't hold my thumb over the spark plug hole and make an air tight seal. It ran really good now it wont run again.

[barnett468]

.
put the bike in the shade and lay the plug on the engine head with the plug wire connected and carefully kick it over fairly fast and look at the spark.

if it is pale blue it is very ood . . i it is yellow it is weak but should still run . . if you can hardly see it, it may not have as much current as you need.

check the plug gap, it should be around .024 inches.

look at the plug color, if it is black, you should clean it.

plug color

dry black = too rich

moist black = oil and maybe too rich

white = way too lean

lite tan = good

if the gas is old and loos pale yellow, it is getting bad . . if it is fairly dark yellow it is junk.

pull the hose off the carb and let gas run into the container or around 30 seconds, if it starts to slow dramatically, your gas cap s not venting in which case you can loosen it just to test how long it will run.

if it is getting gas from the gas tank, try to start with 1/3 rd throttle and no choke . . kick t several times, if it does not run or at least pop at at all, quickly remove the plug and look at it, if it is dry, it is not getting gas thru the carb so put the plug back in and open the throttle and spray starting fluid in for 2 seconds then try it again.

if it is wet, your timing may be off.

k at

obalybgsjlay the

[81ATC185S]

Its a bright blue spark. I ordered a new plug for it as this one has gone sort of "Yellow".

[barnett468]

Its a bright blue spark. I ordered a new plug for it as this one has gone sort of "Yellow".

ok, xlnt spark and your plug is NOT the problem . . it is just fine.


this plug looks very good

https://i.ytimg.com/vi/saCDmyiBmb0/hqdefault.jpg

[barnett468]

.
if your plug looked like this it might misfire and dies et.

http://www.mustangcollective.com/imagehosting/74649f9dbf218e7b.jpg

[jerkin]

I can't hold my thumb over the spark plug hole and make an air tight seal. It ran really good now it wont run again.

That doesn't mean anything, you need to get a compression gauge and do a real test to rule out a compression issue.

[81ATC185S]

But it ran well for 5 minutes. It obviously had good enough compression.

[jerkin]

But it ran well for 5 minutes. It obviously had good enough compression.

The key word there is "had", it doesn't matter what it did then, it matters what it's doing now. There are probably a half dozen things that could have happened in that 5 minutes that could have caused it to lose compression, cracked ring, timing chain jumped, valve stuck/bent, burnt a hole in the piston, etc. You start with the basics and the easy stuff and move on from there. A compression test doesn't take 5 minutes. If you don't have or can't borrow a compression tester you can get one at harbor freight for $10.

[81ATC185S]

Borrowed a compression tester from a bud, tested out at 30psi. It turns out it has stuck compression rings. I swapped a jug and piston off a parts engine and she fired up first pull. Thanks for all the help guys!

[barnett468]

.
ok but it your gas is yellow from jurassic goo, it will run for a little while until the rings or valves stick.

[81ATC185S]

No the gas is clean. I had it out for a 10 minute run yesterday.

[ATC_Bros]

i had something like this happen to me after riding abit but what happen was the shut off switch on the handle bars malfunctioned and stuck in off, YES it moved back and forth but was Rusted stuck inside and once i fixed and cleaned that up it fired up FIRST PULL and EVERYONE since then, this is one bike #1 for me (1980 ATC 185 with 1982 ATC 185s engine with Wiseco top end kit), try it and see also check the connections coming from the Stator which is right by the recoil start theres 3 wires....2 with a cheap white connection(lights) and then the single wire which on mine is Primary on the Stator which is your Sending wire for ignition, like i said on all my bike it is anyways, hope it helps