[HighColorado+9k]

My Rincon was running good. It had a slight bog/stumble from idle when whacking the throttle in neutral that I decided to ignore. The bog/stumble was less noticeable when in gear riding it. So it seemed the bog/stumble was getting worse. I tried adjusting the Pilot, idle screw. It made it worse. Way worse. Bad bog/stumble when whacking the throttle in neutral. Bad bog/stumble in 1st gear when nailing the throttle. After it reaches a higher rpm it recovers. When I shift to 2nd gear it stumbles again until the rpms come up and it recovers. Cruising in 3rd gear at a lower rpm if I give it throttle to gain speed it bogs. My guess is to low of rpms.
I don't understand what changed to make it start running bad in the first place. Changed the fuel in the tank to eliminate bad fuel. Check fuel line, spark plug, etc. Found nothing. Removed carb and checked it out. Found nothing.
This was bought used and currently has over 3 k miles on it. I think it was treated poorly by previous owner/owners. I did a carb rebuild when I got it. There was a hole in the diaphragm. The carb is stock except for a 134 main jet. The plug color: at the electrode, nice brownish/tan color. From the tip of the electrode down into the plug the color gradually gets darker. The edge, end of the threads where the ground electrode is attached has a slight amount of black soot.

I'm at a loss as to what changed. I'm very careful with fuel refills to keep junk out of the fuel tank. I don't think changing any jets will help because it ran good until now. So do I rebuild it again or buy a new Honda carb? Should I put the 134 main in the new one? Or put a 148 main jet in because according to the service manual that is the jet recommended for up to 8 K feet. Close enough I guess.
I ride above 9 K feet.
Opinions welcome. I'm lost as to what changed that started this bog/stumble.

 

[Oilcan]

I suspect a vacuum leak, or a clogged passageway in the carb

For the vacuum leak.

If you have a propane torch, turn it on and allow the propane gas to flow around the outside of the carb while running (remember the propane will sink), so hold it above and closely around the sides of the carb and the hose from the air filter area, and the tube into the head (no wind or it may not work)... if there is a vacuum leak, your motor rpm will increase as the propane gas is sucked into the combustion chamber.... There might be another torn diaphragm

Carb service

The stock jets are 152 main and 50 Slow. To go from sea level 0-3000' adjust the pilot screw (2 3/8 initial setting) when you reach altitude of 8000' turn the pilot screw in 1/2 turn.

If you go inside the carb, make sure the float and needle are not "sticking " and the float is not full of gas. Set the float level (use the base of the carb as reference. Sounds like a good night on the bench

 

[HighColorado+9k]

Thanks Oilcan for taking the time to post all the info.
I do have a service manual.
I got it fixed.
I fixed it by putting the air box cover on it. Before this happened it ran the best with the air box cover removed. It lost some performance with the cover on. Thinking of installing TPI air valves on the air box cover. I believe it needs a little more air.
I still don't know what happened. I'm no stranger to carbs. Used to race 1/4 mile back in the 70's when carbs were the norm.
Thanks again.

 

[Harley Dog]

I have had TPI valves on my air box cover for years now. They did make a difference for the better. They can be adjusted which I find useful when changing for altitude. I also have one air box cover that is screened on top. It works great when I go up over 8000 feet. Just don't do any swimming with the Rincon with the TPI valves.

 

[HighColorado+9k]

Thanks Harley Dog. I have looked at TPI valves more than once in the past. It was running good with the air box cover off so I never purchased them. Now I believe it's necessary. Will order them.

 

[HighColorado+9k]

I got the TPI air valves installed in the air box cover. Installed 2 valves and run them opened all the way. Helped improve performance.
Putting some on my friends Foreman.
A bit pricey with shipping IMO.

 

[HighColorado+9k]

Well I got tired of the hard starts to plow snow. It was requiring starting fluid every time.
Put a new OEM carb on it. Changed the main jet to a 148. Starts better than it ever has and idles better to. No more slight bog.
Waiting for the weather to warm up to trail ride it so I can check it out thoroughly.
I should have done this along time ago.

 

[BLKRinnyrdr]

A new oem carb is one of the best improvements to an old machine IMO, especially if it has any fuel issues!

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