NGC - small engine carb seat repair?

[brider]

I figured someone here would have as much or more knowledge as some random post I'd find on the 'net:

I have a Yamaha tracked snowblower with a carb that gushes fuel from the top vent when it's running. It's a carb I bought new 5-6 seasons ago, but I don't take special pains to store it in the summer, just maybe run the float bowl dry. Starts every winter.

But I was "told" that the carb needle-seat does not "like" ethanol gas, and can somehow be degraded by contact with gas thru storage. ??  Don't know how this happens with the float bowl drained, but in any event the seat is a non-replaceable item, but the needle is. The entire carb might be replaceable for a high cost, but I'd rather see if the seat (part of the carb body?) can be polished or re-worked first (hey-there's the Guzzi content), assuming the needle isn't stepped.

Is there any other reason, besides a needle/seat that isn't shutting off the gas, that would cause gas to gush out the top vent?

[Antietam Classic Cycle]

I've polished the (non-removable) seats in Dellorto VHB carbs by cutting a Q-Tip in half, chucking the half into my drill, applying a bit of fine valve grinding compound, inserting it into the seat and running the drill for a few seconds. B&S carbs used to have a replaceable Teflon(?) seat insert and metal needle - I'm not sure if something like that could be retrofitted to other carbs or not. 

[cliffrod]

We've had fits with ethanol gas over the past several years. it could be a needle and seat issue but if your carb hasn't been apart yet, you may find there's simply chunks of corrosion or ?? obstructing the float and preventing free movement. Not uncommon to find the bowl literally packed full of corrosion like a mold around the float.  And cleaning it as needed sometimes opens pinholes through bowl.  Not cool..

I don't like to advocate for made in china parts, just sharing what we learned a few months ago in case you eventually go the same route. 

We worked on a Norton 750 to change his dual carbs to a single made-in-china-mikuni-copy.  It was approx $23 including shipping, which was all that mattered to him compared to a name brand replacement $$. Wouldn't run right as received.  After 2-3 hrs of fiddling (not proper machining work, but close) we had installed a real Mikuni jet and main needle and it runs great.  No idea how long it will last, but he's happy and knows what he has.  If you do go that route with a cheap copy and your carb body is deteriorated, you may be able to hybrid parts like Charlie mentions into a new body.

Good luck.

[brider]

I've polished the (non-removable) seats in Dellorto VHB carbs by cutting a Q-Tip in half, chucking the half into my drill, applying a bit of fine valve grinding compound, inserting it into the seat and running the drill for a few seconds.

THIS is along the lines of what I was thinking would be the only way to polish the seat. Thanks for filling in the details, Charlie. Not gonna try to retro-fit a needle/seat, I'll pay the $$ for a getting-rarer carb first.

[Chuck in Indiana]

THIS is along the lines of what I was thinking would be the only way to polish the seat. Thanks for filling in the details, Charlie. Not gonna try to retro-fit a needle/seat, I'll pay the $$ for a getting-rarer carb first.

I've done the same to good (and bad) effect. If the seat is just crudded up (technical term) it'll work. If it's corroded, you are whizzin in the wind. 

[larrys]

The actual seat for the needle may not be the metal of the carb body but a rubbery/plastic insert. I know that carbs on Tecumsehs and some other small engines have this. If it does have the insert, maybe the ethanol has degraded it. You can buy Chinese carbs real cheap $12-14 on the innanet for many small engines. I've bought a few and they work! A carb from Yamaha is likely to be $70-80. YMMV.
Larry

[BRG-BIRD]

The actual seat for the needle may not be the metal of the carb body but a rubbery/plastic insert. I know that carbs on Tecumsehs and some other small engines have this. If it does have the insert, maybe the ethanol has degraded it. You can buy Chinese carbs real cheap $12-14 on the innanet for many small engines. I've bought a few and they work! A carb from Yamaha is likely to be $70-80. YMMV.
Larry

I agree with this and you may be able to buy the needle and seat for just a few dollars like a Tecumseh. That’s what I did a few years ago the day before Christmas when the snow blower would not start. There was a pile of snow on the driveway with more coming that night. After a complete epic meltdown (by me) I realized the gas tank was empty from a leaking needle and seat.

[Chuck in Indiana]

I agree with this and you may be able to buy the needle and seat for just a few dollars like a Tecumseh. That’s what I did a few years ago the day before Christmas when the snow blower would not start. There was a pile of snow on the driveway with more coming that night. After a complete epic meltdown (by me) I realized the gas tank was empty from a leaking needle and seat.

That's the problem. The seat is cast into the carb body on some small engines, so there is no replacing it.

[larrys]

That's the problem. The seat is cast into the carb body on some small engines, so there is no replacing it.

Right. Need to take it apart and have a looksee.
Larry

[Mike Tashjian]

 Yes, first rule of any repair is identify the problem.  Take the carb off and remove the bowl to see what is going on in there.  The float can be bad, or stuck and it's possible the needle and seat have damage or just a piece of crud on them.  I like to put small length of tubing on the fuel inlet with the carb upside down and blow air in(by mouth) to see how well the floats weight can seal the needle.  Yamaha usually has pretty reliable products.  Find your problem first, then assess the parts and problem solving becomes much easier.   Mike

[brider]

...the day before Christmas when the snow blower would not start. There was a pile of snow on the driveway with more coming that night. After a complete epic meltdown (by me)...

This sounds like me! I had this problem with this snowblower/carb last winter and it was so bad I pulled the carb off and inspected it, outside, with huge snow coming down in big flakes on top of me. The thing ran fine but gushed gas, and I wouldn't have cared except it splashed all over the muffler as the engine was shaking on it's rubber mounts. So not finding anything visibly wrong, I put it back together with the fuel-pump vacuum manifold installed in the wrong order, after the carb went on the studs, instead of first, against the cyl head. No vacuum to the fuel pump. Didn't realize it until at least 6" more snow fell.

I believe at that point I just drove the thing to the shed and used the tractor plow for the rest of the winter. Naturally, I did ZERO to try to fix it all spring/summer/fall. I figured I'd just use the tractor again (which I like better anyway) all winter, but that POS went thru 2 ignition coils while mowing, so I parked it in disgust, figuring I'd just use the snowblower all winter. Wait a minute.....

So I turned to my 2nd tractor, which does NOT have a plow, but DOES have a massive snowblower that I've never used that came with it when I bought it. Yes! But just last week as I disconnected the mower deck to get ready to mount the snowblower, all the bearing balls for the rear bearing for the front PTO shaft fell out onto the ground when I pulled off the deck driveshaft. I have no idea how long that thing ran with no useable bearing support. I will assume the front bearings for that shaft are toast, too.

My wife LOVES all this, BTW...

Regarding Chinese carbs: I put in an order for the Yamaha carb from a Japanese parts supplier, but the carb came back "out of production - no stock". But I DO have a part #, but internet searches for that P/N don't pull up Chinese knock-offs.

This weekend I will pull the carb again and eyeball the needle and seat to assess their condition. The needle assy IS available if it's stepped.

I'll also put in a plug for the tracked-snowblower configuration. It rocks! This is the only one I've owned, a used Yamaha YS828T, and I can blow paths all around the house on the hilly yard for the dogs and to the woodpile.

[BRG-BIRD]

Good luck, hope you get it sorted!