ATC 125m rich condition possible float level issue?

[Lrequa92]

I have a 1985 ATC 125m that has had a rich idle issue since I bought it. After it has been idling for a minute or two, when you give it like an 1/8th to 1/4 throttle, it will sputter and blow a little bit of black smoke from the exhaust eventually cleaning itself out and running smooth throughout the rpm range. I see the black smoke to be excess fuel. Am I correct in thinking this? It has the OEM carburetor and all the stock kehin jets and the carb has been cleaned multiple times. It does this with the fuel petcock in the ON position. When I put it to the OFF position, at first it will sputter a little bit. It seems that once it lowers the fuel level in the carb a little bit, I can give it the 1/8th to 1/4 throttle and it will not sputter. I turn the fuel petcock back to ON, and let it idle for 30 seconds and give it a little gas and it will sputter again with some black smoke. Has anyone ran into this issue before and does it sound like the float is allowing the bowl to fill too much causing a rich condition? Thanks

[Lrequa92]

Anyone have any thoughts?

[Shawn Powell]

Floats are there to keep the carb from over flowing. So my answer would be no, I don’t think this is your issue. Have you tried adjusting your air mixture screw? Sounds like it’s too far out. I’d turn it on half a turn and see what happens. Also make sure your choke is all the way closed.


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[knappyfeet]

When I put it to the OFF position, at first it will sputter a little bit. It seems that once it lowers the fuel level in the carb a little bit, I can give it the 1/8th to 1/4 throttle and it will not sputter. I turn the fuel petcock back to ON, and let it idle for 30 seconds and give it a little gas and it will sputter again with some black smoke. Has anyone ran into this issue before and does it sound like the float is allowing the bowl to fill too much causing a rich condition? Thanks

My little 90 exhibited the same running condition. My float needle was not seating properly for a couple reasons but what I did was replace the entire float assembly and float needle and make sure the seating area is not damaged/pitted/scar/etc. Once adjusted no more flooding..ie....no more rich condition.

Also make sure the air screw assembly is correct with spring, washer, oring. Sometimes when cleaning things get blown out and lost. I would just replace the entire screw assembly and turn out whatever the manual recommends. Maybe no more than 2 turns out??..

Good luck

[ironchop]

Incorrect float level will absolutely cause a rich or lean condition. It's not just a shut off valve.

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[Shawn Powell]

I had no idea , I’ve only had float issues when they stick and the carb overflows. Learn something every day.


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[Lrequa92]

The needle and float are both new and the level is not adjustable on these carburetors. The fuel/air mixture screw has the spring but they never came with an o-ring from the factory based on the diagrams I have looked at. I have adjusted it all over the place and it doesn't seem to ever make a real difference. The only real difference I notice is when I shut the fuel petcock from ON to OFF. That's why I am thinking it may be an issue with the seat. The seat on these carbs is part of the housing of the carb so it may wear out over time.

[Lrequa92]

My buddy has another 125m that idles perfect and does not have that rich idle condition so I am going to try swapping his carb on to mine and see if it cures the issue.

[Lrequa92]

So I swapped my buddies carb, coil, and cdi and it did the same thing. I ohmed the pulse generator and am getting 94 ohms. The manual says 90 ohms is the spec. Is 94 high enough to worry about it?

[Rob Canadian]

How is the air filter? I would not worry about the ohms at this time.

What filter are you running? Maybe choked up at low RPS and loading up the engine. Resticted air filer on a carb engine is like a choke.

[Lrequa92]

Im running the OEM Honda air filter. Its not that old so it is clean. I already tried it with the lid off and also with the filter completely out and it still loads up at idle. I have also made sure the choke cable has enough slack so it is not sticking on.

[ironchop]

You change the sparkpug?

I've been coming across brand new plugs that didn't have a fat enough spark. I ordered a whole box of NGK plugs off eBay once that were apparently Chinese knockoffs or fake NGK as three of them were junk with tiny or no spark at all. I threw the whole box away

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[Lrequa92]

Yeah I have changed the plug multiple times. I always get them from advance auto parts. I run an NGK D8EA plug. Does anyone think 94 ohms is high for the pulse generator? I wouldn't think 4 ohms over the spec would matter but I don't know for sure.

[ironchop]

Yeah I have changed the plug multiple times. I always get them from advance auto parts. I run an NGK D8EA plug. Does anyone think 94 ohms is high for the pulse generator? I wouldn't think 4 ohms over the spec would matter but I don't know for sure.94 sounds like too much resistance if the spec is 90. Measure the resistance on your buddies running trike and see what his is.

In your other thread you asked if the spec was the same for 110/125 and I'm pretty sure they are supposed to use the same specs and equipment. I believe they are nearly the same motor with just different displacements

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[Lrequa92]

Alright Ill check it on my buddies.

[86125m]

typically I would say 94 ohms would be close enough for navy work as my electronics professor says. But have you actually physically inspected the pulse generator as I have had bikes in the past that the generator has ohmed out but the actual generator was broken.

[86125m]

and have you considered that it might just be time for an engine overhaul.

[Lrequa92]

Yes I have visually inspected the generator and it looked normal to me. I did not notice anything broken. I also have considered an engine overhaul. I actually have already had the head and cylinder off already to inspect everything. I was thinking maybe the intake valve was leaking by but I tested it and it didn't leak at all. Both valves were in good shape. The cylinder and piston and rings looked mint also. Back when I did a compression test, I had around 165-170psi. The manual says the spec is 177.8 plus or minus 21.3, so I fall right within that spec. The service limit is 128 according to the manual also.

[knappyfeet]

OK.......... I'm getting confused with all the other stuff. Black smoke and a sputtering/flooding condition exist right? It clears up after some normal throttle operation right? More importantly........it stops doing it after the fuel valve is off right? When you inspect the plugs are they black like a running rich condition? The exact same condition happens with your friends carb right? and not on his right?

Remove the gas cap on your tank and see if it does the same thing....or if it acts in any way different.


edit...... better yet, if you can bypass the tank all together...try that.

[86125m]

Do you happen to have trash in your fuel tank cause that can also cause problems. Try an in-line fuel filter.

[Lrequa92]

I tried removing the gas cap and I even put my buddies fuel tank on and it still has the rich condition lol. Its a weird issue... My tank is spotless on the inside. Im probably going to have to go through all of the wiring.