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View Full Version : ATC 90 Engine HELP!!



kcordova56
01-01-2021, 06:18 AM
Hey I just recently bought a go kart and it had a ATC 90 Engine and I know it isn't a 3 wheeler but it's the same engine from one and its an engine problem. (I can even take a wheel off to make it a 3 wheeler).

But I just bought a spark plug because the one it came with was a little old. It came with 2 new carburetors and the old one. I put one of them on and it didn't work great so I put the other one on.


I had it tuned right and it rode but the shifts were a little rough. (I don't know if that's normal with these but its something that happens. So when I went to ride I have to almost look for the gears. (Also don't know if that's normal). So it shifts into all gears good but they feel WAYYYYY too short and don't know if that's right/Normal. It's literally like 1~2 seconds till I have to shift since it doesn't accelerate anymore.


I think somethings wrong because I hear they have a top speed of like 35 and that's the normal 3 wheeler with huge tires. I Have like 11" tires so I think it should be faster. I think somethings wrong with it because top speed feels like 15 mph AT MOST.


So my problem is that its way too slow.(I think it also may be running too rich and need to fine tune it). BUT don't think it effects performance that much.

There's more problems but this is one I'm clueless about. I'm willing to tear it apart to see if there's something broken inside but have no idea what to look for since I'm still really new to all this.



Also F Carburetors

Jim mac
01-01-2021, 11:18 AM
is the low/high range lever in the high range position? I bet if you post the tooth count both engine side and axle side with the diameter of the tire someone here could tell you if you need to change the sprockets. going from a 22 inch tire like on a atc90 down to a 11 inch tire will cut the speed in half, without changing to a smaller rear sprocket. jim

kcordova56
01-01-2021, 05:13 PM
Its an 89cc engine from a 1976 ATC90

The sprocket has 49 Teeth

And the wheel size is about 12"

And its a 1 wheel peel (only drives 1 wheel)

kcordova56
01-01-2021, 06:57 PM
its in high but It could also be stuck in low maybe???

When I got it running once i put it from low to high while it was on and heard a little scrape could I have broken it?

DAM shop
01-01-2021, 07:35 PM
Try engaging the hi/low selector while it’s in gear, do it at a low speed and see if you can get it to engage in both ranges.