Found my backfire problem, maybe

[Gbannish]

Hi,

This summer I added a Mark's 4-2 exhaust and Morley Muscle jet carb kit overhauling the carbs. Immediate increase in power was observed, along with some very minor popping at 3-4k in 1st, 2nd. Being an expert in denial, I ignored the symptom. Weeks later the popping became worse, occuring in all gears at around that rpm. Then one morning, after after riding through a rainstorm, the bike felt like it would "catch", running great, then cut out on 1 or 2 cylinders. It would do this on and off for about 20 minutes, then would turn on and run great for the rest of my 1.5 hour commute. L

First I assumed an electrical problem or water in the gas. I added SeaFoam and pretended that fixed it for a day, but it came back. Last Tuesday, it cut out on the 1 or two cylinders permanently.

I pulled the plugs and noticed the #3 cylinder plug was a little dark, but my denial was in effect and wrote it off as nothing. Then I pulled the air filter and looked at the slides, and found that on the 3 cylinder the brass tube that the needle slides into was loose. Apparently I must have forgotten to tighten the bolt inside the carb or it came loose.

So now I'm thinking that's my only problem. But my history in problem solving skills is near zero, slightly worse than my carb rebuilding skills!

Thoughts?

Greg

 

[sdt354]

You are better than you give yourself credit for. The loose tube was dripping gas causing a rich condition. Plus the needle wasn't positioned where it was meant to be, making the rich condition worse.
Some problems are cheap to fix. Frustating for sure though, but nice to figure out and be able to help someone else down the line with the same issue you had.
Steve-o

 

[Rusty McNeil]

Good find I'd say.

That screw your talking about is hollow, basically like a jet without a hole all the way through the top.

Being hollow its very easy to slightly over tighten and have it break later.

I learned this the hard way two days ago when I got that "oh shit" give on the screw when I was tightening down.
Good luck finding that one in the misc. bolt bin.

I got one on order but in the meantime took a jet, soldered the hole shut in it and stuck it in there.

 

[Rhoy Carter]

Rusty, I have some extra tubes.
Rhoy

 

[95spfldmax]

Hi,

This summer I added a Mark's 4-2 exhaust and Morley Muscle jet carb kit overhauling the carbs. Immediate increase in power was observed, along with some very minor popping at 3-4k in 1st, 2nd. Being an expert in denial, I ignored the symptom. Weeks later the popping became worse, occuring in all gears at around that rpm. Then one morning, after after riding through a rainstorm, the bike felt like it would "catch", running great, then cut out on 1 or 2 cylinders. It would do this on and off for about 20 minutes, then would turn on and run great for the rest of my 1.5 hour commute. L

First I assumed an electrical problem or water in the gas. I added SeaFoam and pretended that fixed it for a day, but it came back. Last Tuesday, it cut out on the 1 or two cylinders permanently.

I pulled the plugs and noticed the #3 cylinder plug was a little dark, but my denial was in effect and wrote it off as nothing. Then I pulled the air filter and looked at the slides, and found that on the 3 cylinder the brass tube that the needle slides into was loose. Apparently I must have forgotten to tighten the bolt inside the carb or it came loose.

So now I'm thinking that's my only problem. But my history in problem solving skills is near zero, slightly worse than my carb rebuilding skills!

Thoughts?

Greg

It's always nice to figure something out....and for no dollars....priceless.........now switch the #3 plug with a different cyl and put some miles on her....recheck in 50-100 miles or something and hopefully alls been running fine and all of the sparkplugs agree........enjoy the rest of the riding season....swweeeetttt...unk:

 

[Rusty McNeil]

Rusty, I have some extra tubes.
Rhoy

My tube was ok. The screw failed w/o damaging it.

 

[dannymax]

Too little too late but I'm sure I got some of those hanging around Rusty. :worthy:

 

[06VMAXIMUS]

Just read this as well. Doesn't the needle tube he is refering to have an o-ring under it, and is held in place by the jet block? If the tube is loose, maybe the o-ring is missing or broken?

 

[[email protected]]

Guess I'm not the only one to snap one of those hollow screws.

 

[Rusty McNeil]

Just read this as well. Doesn't the needle tube he is refering to have an o-ring under it, and is held in place by the jet block? If the tube is loose, maybe the o-ring is missing or broken?

It's does have an o ring, but the screw that was broken is what holds the tube from drifting into the carb throat, possibly being dragged by the moving needle.
Even if it doesn't move the missing screw leaves an unregulated giant hole between the fuel bowl and the carb throat.

 

[dannymax]

It's does have an o ring, but the screw that was broken is what holds the tube from drifting into the carb throat, possibly being dragged by the moving needle.
Even if it doesn't move the missing screw leaves an unregulated giant hole between the fuel bowl and the carb throat.

If there's one thing I can't stand it's an unregulated giant hole!! :rofl_200::rofl_200::rofl_200: