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Old 04-30-2015, 01:25 PM
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MASTERBATES MASTERBATES is offline
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Default 83 Suzuki Lt125 studdering Q&A

So im having a long and drawn out issue with an 83 suzuki LT125 4X6 ATV.
The issues have been going on for quite some time, with multiple attempted remidies it still hasnt resolved the issue. I will describe the best i can, and follow up with the actions i have taken.
Upon a cold start first pull fires right up. It idles about a 1/4-1/2 throttle. After a couple minuite warm up it will idle down and remain there.

Running down the road and at an idle, it makes a hollow(bub.bub bub bub.bub) sound. Like its a flat spot in the fuel circuit. Holding a steady speed down the road does the same thing... coming to a stop it slowly idles down, unless it is hot, (ex. Woods riding) then i wont idle and will die.
Yes. This atv is 32 yrs old, i know, but it was what i grew up riding. I can live with this ,but would be much happier with a smooth running machine.

Onto the attempted remidies....
I have replaced 3 carburators, jetting each time to what it likes best. Plug has a brown tint on the porcelin.
2 cams last one purchased new. Topend rebuild new gaskets piston,rings, timing chain.
Muliple checks on timing and compression (which checks out good, with no bleed off) lapped the valves also.

Any other suggestions? It does run from a fuel pump which is also new.
Leak tests around the carb assure me it is air tight
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TM 150 XRX-P&P head,A13cam,opened exhaust,140 main,38 pilot,adj cdi, perf coil,115mm variaitor,12 gm rollers,NCYpulley,2000 rpm springs,racing clutch,taller rear tires,and etc.
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Old 04-30-2015, 03:46 PM
liduno liduno is offline
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If it has good compression, good carb, and the valves are seating correctly then it sounds electrical.

Other than the miscellaneous options, like a bad ground, bad connection, or a bad wire somewhere, there really is only a few things it could be.

Ignition coil, pickup coil, cdi, and some stators have an exciter coil?
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Old 04-30-2015, 10:11 PM
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x-bird x-bird is offline
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does it have the manual compression release pull for easy starting? I was goingg to suggest worn cam lobes, but you covered that. any chance the compression release mech is hanging up and keep the exhaust valve from closing?

Tossing out ideas
float height?
float needle and seat mismatch to the fuel pump pressure?
plugged up exhasut/muffler?
crankcase pressure not venting?
fuel tank vent clear?-- matter of fact, that was the cause of very similar symptoms with one of my 18hp kohler mower engines. Start fine, run awhile but n opt full power, get hot, stall and not want to restart.

Last edited by x-bird; 04-30-2015 at 10:13 PM.
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Old 03-29-2016, 10:00 PM
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Mine has been this way for years!
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TM 150 XRX-P&P head,A13cam,opened exhaust,140 main,38 pilot,adj cdi, perf coil,115mm variaitor,12 gm rollers,NCYpulley,2000 rpm springs,racing clutch,taller rear tires,and etc.
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Old 06-03-2016, 01:55 PM
hgibson hgibson is offline
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Exhaust leak?
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