ATC hard start when warm

[spacerust]

One of my 70’s start first or second pull every since I got it. The problem is after I’ve ran it for ten minutes or so (approx...may be less) it will either stop or if I turn it off, then it becomes hard to start. I’m thinking it may be a fuel problem. It has new fuel lines, tank is clean, carb is clean. I’m going to change fuel filter and open to suggestions.


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[Rob Canadian]

I am kinda thinking maybe the gas cap is not venting properly.

[spacerust]

Interesting. I’ll swap out the cap and try that.


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[fabiodriven]

Very likely the valves need to be adjusted.

[DAM shop]

I am kinda thinking maybe the gas cap is not venting properly.

We've had this happen. How's your plug look after those 10 minutes?

[spacerust]

I haven’t checked the plug, I’m out of town right now, but what should I look for? What happened to yours?


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[coolpool]

Ding, ding, ding for Fabio! Valves are probably set too tight making you lose compression as the metal expands.

[DAM shop]

I haven’t checked the plug, I’m out of town right now, but what should I look for? What happened to yours?


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A vapor lock on your gas cap won't allow fuel to flow, usually happens after a short time of riding and she'll just stall out..
Your plug should be light tan, you don't want white or black and oily or sooty, light tan in color is a good burning plug. But you should also check your valves like the others said.

[spacerust]

I’m heading back home later this afternoon. If the plug is black or other, what should I check?


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[fabiodriven]

Honestly I'd skip the plug and just adjust the valves. It's very easy to do and your most likely problem. It would be the first logical step.

[spacerust]

Okay. I don’t have my manual on me, but just to keep my mind busy on the drive, it’s .005 on the intake and outtake right? If I remember correctly.


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[DAM shop]

Okay. I don’t have my manual on me, but just to keep my mind busy on the drive, it’s .005 on the intake and outtake right? If I remember correctly.


Sent from my iPhone using Tapatalk05mm or .002in on the valve tappet clearance.

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[fieldy]

Do you have a factory air filter on this trike? Do these 70's use traditional points and condenser? I suspect some overheating, valves do seem probable. Did it ever restart good? We want some plug pictures too!

[fabiodriven]

Do you have a factory air filter on this trike? Do these 70's use traditional points and condenser? I suspect some overheating, valves do seem probable. Did it ever restart good? We want some plug pictures too!

He didn't say anything about overheating, I don't know why you would suggest that. Every laydown engine I've had has done this at one time or another. It's a routine adjustment to account for normal wear and tear.

[fieldy]

I have had trouble restarting 4 stroke motors that i know were slightly overheated. Thats why i said that.

[spacerust]

So i adjusted the valves, changed out to another gas cap and it started right up as usual. I let it idle for about five minutes because I was closing the garage tp try it out and then my son asked me to adjust his bike seat. I started to do that and told him to go and turn it off since I would be longer than I thought. All the while it idled fine. Once he turned it off and I did what I had to do, I tried to restart it and it wont start again. Here is a pic of the spark plug. https://uploads.tapatalk-cdn.com/20180225/6bb1f05fb8b96c4f995432e45efdc829.jpg


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[fabiodriven]

OK, sounds good. What year is your 70? I'm going to assume it doesn't have points in the ignition but a condenser could possibly cause this if you do have points. If not, my next guess would be stator or CDI, assuming it has a CDI box. Both can be tested with a meter, but I don't know how to do it. I've seen ignition coils fail, but not that often. It's not impossible though.

[spacerust]

Its an 83.


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[fabiodriven]

Alright I don't know if that has points or not. If it does have points, I'd suspect the condenser. If you're going to replace the condenser, you might as well change the points or update to a solid state ignition. That would be your choice and we don't know that that's your problem yet.

If it were mine I'd run it until it's warm enough to where you know it's not going to restart. Then I'd pull the spark plug and see if you have spark or not when the engine is warm.

[spacerust]

Okay. Ill try that tomorrow and let you know.


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[geyerman89]

fabiodriven advise is good. When it wont start,take plug out, ground it, crank it over. this will tell you if its electrical or not.

[DLK]

I have a Yamaha 200 1985 and had the same problem... After cleaning messing with the carb/plug/gas. I finally got to the point where I could start it when warm but it still hates to idle after about 5 min of running. Runs great as long as I give it gas but releasing the throttle a little bit and it dies. My plug looks the same as your black.

Did you try completely replacing the plug?