125 Tri moto hard start

[youngbuck]

Hi guys,
I have a yamaha 125 tri moto. It always started well and ran well. Out of no-where it just began to start hard. It used to be a 1-4 pull machine. Now I can pull till my hand falls off and a combination of choking and pushing the throttle while pulling the rope will eventually get it started. Once started it runs and idles just fine. I can drive in all gears and different speeds and run fine. It seems to have good spark when I checked it. Though I have nothing similar to compare it to. The other thing is the rope kicks back out of my hand a lot and it backfires too while trying to start it. I have taken the carb apart multiple times a have found nothing obvious. I have cleaned it multiple times with no improvement. I checked the reeds and they don't seem drastically warped or anything. One reed is just a smidge from touching. I use this little machine a lot during the maple syrup season and need to get it to start better. Is there anything I can do? I really appreciate all of your help

[El Camexican]

- Have you checked to see that your choke is working properly? When you get the thing running and warm put the choke on and it should stall. If not it isn’t working or your jetting is way off.
- How many turns out is your air screw at now and did you move it before the problems started?
- Do you notice if your idles speed is a little lower that before you started having issues?
- If everything above checks out and your air filter is decent and you have put that carb together properly my next step would be to pull the pipe off and take a look to see if it is obstructed at all and if the top of the piston isn’t heavily caked with deposits. While you’re in there look and see (take a photo if you can) if there are dark brown, or black stains below the piston rings.

[youngbuck]

My air screw is 1 1/2 turns out. When I had the reed assembly out I did notice some brown below the rings when the piston was at the bottom of it's stroke. I couldn't see much and there wasn't much brown. I will take the pipe off and check the piston. Are you thinking that the piston is carboned up? If so can I clean it with out taking the engine apart? I will also double check the choke too. The idle speed is about the same as it was. I haven't changed the the air screw I just put it back the way it was each time I take the carb apart.

[El Camexican]

If your only problem was that it was just taking a bunch of pulls to start and that it ran fine after that I would say 100% choke issue. However you mentioned that it is back firing and harder to pull too. That shouldn’t happen from a choke issue. I wonder if perhaps fuel is leaking into your engine when it is parked. Do you close the petcock when you park it? Does it finally fire up with the throttle partially open? A crankcase full of fuel could cause the hard pulling and backfiring.

Don’t worry too much about the brown stains below your rings. It means the rings are worn, but you aren’t racing it, so it might run another 20 years like that. To clean the piston you need to remove the head. Don't worry about that for now either. Tell me about the petcock and what all seems to get it started these days.

[Bren_downe]

Have you replaced the spark plug? What color was the plug?

[youngbuck]

Hi guys,
My spark plug is a tan color. Last night I got it started and pulled the choke and it killed it dead. Is that the only way to check if it is a choke problem. The weird part is if I can get it started it will run great for any amount of time. I can run for a half hour around the yard and as soon as I shut it off and try to pull start it right away. It won't start. Do you think it is possibly the coil?

[El Camexican]

Hi guys,
My spark plug is a tan color. Last night I got it started and pulled the choke and it killed it dead. Is that the only way to check if it is a choke problem. The weird part is if I can get it started it will run great for any amount of time. I can run for a half hour around the yard and as soon as I shut it off and try to pull start it right away. It won't start. Do you think it is possibly the coil?

Sounds like the choke is good. Electrical problems usualy get worse with heat, not better, so I doubt it. Tan plug is good. I'd tell you to check your compression, but you said it is getting harder to pull. Did you do anything to your float when you had the carb apart?