Makita 6400 fresh 7910 rebuild, ran fine all day then suddenly rich

[DPSElias]

Like the title says, I ran almost a tank through my fresh rebuild and ran great and strong, but it in the bucket of my tractor hit a bump and boom wouldn’t start and flooded, carb intake is visibly wet and when I did get it started it wouldn’t idle and bogged down at WOT. Any guess on what would be wrong? I’ll readjust the carb tomorrow but fear that won’t solve the issue. Thanks.


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[Thommo]

The needle in the carby is leaking. It could have a bit of dirt jammed under the seat

 

[DPSElias]

The needle in the carby is leaking. It could have a bit of dirt jammed under the seat

Thanks, so recommend pulling carb and blasting it with some cleaner or rebuild?


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[Thommo]

I would just pull the carb apart and clean it. Check the tip of the needle while you have it apart. I have seen needles where the viton tip has completely come off and others have been torn where they contact the seat or have a groove worn in them

 

[DPSElias]

I would just pull the carb apart and clean it. Check the tip of the needle while you have it apart. I have seen needles where the viton tip has completely come off and others have been torn where they contact the seat or have a groove worn in them

I took it apart and found a piece of metal that seemed to get dislodged from where it’s suppose to be, put it back still having issues, I’ll remove again and pull the need out and look deeper. Guess this serves me right helping out neighbors [emoji853]


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[Thommo]

What did the dislodged piece of metal look like? If it was the welsh plug your saw will flood because the fuel will bypass the low speed mixture screw.

 

[Deleted member 117362]

I took it apart and found a piece of metal that seemed to get dislodged from where it’s suppose to be, put it back still having issues, I’ll remove again and pull the need out and look deeper. Guess this serves me right helping out neighbors [emoji853]


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No shame in helping your neighbor, I would give them a saw. Mechanical things break, write it off and help will come your way. Good person to have helped them.

 

[DPSElias]

What did the dislodged piece of metal look like? If it was the welsh plug your saw will flood because the fuel will bypass the low speed mixture screw.

Yes it was this welsh plug, finally was able find the part name last night [emoji846]. I put it back seems to be holding but it is still flooding, I'm hoping there is just some dirt in the needle as that's the only thing I didn't take out as it seemed to be functioning fine and the welsh plug was floating around and looked like the obvious culprit [emoji846] will check it this afternoon when I get out of work.


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[DPSElias]

No shame in helping your neighbor, I would give them a saw. Mechanical things break, write it off and help will come your way. Good person to have helped them.

Thanks, this won't deter me from continuing to help, plus it was my own fault I had the saw in the loader and didn't see the bump, still wouldn't have thought it would of hurt the saw any but guess I was wrong. Lesson learned don't transport saw in bucket, frustrating lesson but a lesson [emoji846] but never took this carb apart so it nice getting acquainted with it [emoji846]


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[Thommo]

The welsh plug will be a dome shape when new and has to be put in place and then flattened out with a pin punch to expand it so that it seals in the carb body. If it is not a tight fit then fuel will leak past it and cause your saw to run rich. You can seal them with nail polish if they are leaking too

 

[DPSElias]

The welsh plug will be a dome shape when new and has to be put in place and then flattened out with a pin punch to expand it so that it seals in the carb body. If it is not a tight fit then fuel will leak past it and cause your saw to run rich. You can seal them with nail polish if they are leaking too

The fuel won't break down the nail polish?


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[smokey7]

Nail polish will eventually break down. Im sure there is a solvent resistant sealer available but with a new welch plug they seal very tight and rarely need anything on them to seal. That is what i would recommend you to do is just buy a rebuild kit islnstall all of it except reuse your needle lever/arm and spring. And be sure its set to the proper lever. One last thing test your popoff pressure before and after rebuild record the numbers with a wet needel (mix or wd40) i suapect is should pop right about 10-15psi. Too low it will flood too easy and too high it will starve for fuel.

 

[DPSElias]

Nail polish will eventually break down. Im sure there is a solvent resistant sealer available but with a new welch plug they seal very tight and rarely need anything on them to seal. That is what i would recommend you to do is just buy a rebuild kit islnstall all of it except reuse your needle lever/arm and spring. And be sure its set to the proper lever. One last thing test your popoff pressure before and after rebuild record the numbers with a wet needel (mix or wd40) i suapect is should pop right about 10-15psi. Too low it will flood too easy and too high it will starve for fuel.

Thanks Smokey! I use the pre-mixed ethanol free gas you get at Home Depot and Lowe’s so I should be good for a bit. But I have a rebuild kit on the way and a new backup carb, but I used some nail polish to seal the last bit and glad to say the saw is back up and running well. I’m still shocked that the plug just fell out in the first place and how much a pain it was to seal.

Thanks to the girlfriend my sealant matches my saw

This was a last resort, the Welch plug still had a dome to it so I put it in and flattened it out but still leaked.

Thanks everyone for the help, learned a lot about these little carbs.


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