Generac/ Dixie Chopper carburetor bleed air jet O-rings.

[Auto Doc's]

Hello folks,

I have a 2005 Generac 15KW 992CC model OE 6221 engine with a bit of a hunting surge at high RPM. The same engine was used on the larger Dixie Chopper mowers.

It has an OE carburetor that has been cleaned well, and the bleed air (pilot) jets were resized just a little to resolve the rapid low idle surging, but I still have a very slow throttle "hunting" of the RPM when running at top speed. (3600 RPM/ 61 Hertz) This engine is servo throttle controlled and there are no intake or carburetor mounting gasket leaks. Applying a load when powering my house makes no difference.

Applying the choke slightly does not help the condition, so it is not a main jet "over lean" issue.

The tiny O-rings on the bleed air (pilot) jets did appear slightly deformed and felt rigid when I was putting it back together, so I think that is where my problem is.

I already know these O-rings have to be a specific size, and others look similar from the aftermarket carburetors, but they are slightly fatter and do not let the bleed air jets slip into place like they should.

Also, I am not a fan of the aftermarket carburetors for this application (Been there already and it was worse)

An OE carburetor is exceedingly high $$$ and I question if they are still genuine or just re-boxed clones.

Any help is appreciated (A rebuild kit would be nice if they can be found)

 

[Tiger Small Engine]

Hello folks,

I have a 2005 Generac 15KW 992CC model OE 6221 engine with a bit of a hunting surge at high RPM. The same engine was used on the larger Dixie Chopper mowers.
It has an OE carburetor that has been cleaned well, and the bleed air jets were resized just a little to resolve the rapid low idle surging, but I still have a very slow throttle "hunting" of the RPM when running at top speed. (3600 RPM/ 61 Hertz) This engine is servo throttle controlled and there are no intake or carburetor mounting gasket leaks. Applying a load when powering my house makes no difference.

Applying the choke slightly does not help the condition, so it is not a main jet "over lean" issue.

The tiny O-rings on the bleed air jets did appear slightly deformed and felt rigid when I was putting it back together, so I think that is where my problem is.

I already know these O-rings have to be a specific size, and others look similar from the aftermarket carburetors, but they are slightly fatter and do not let the bleed air jets slip into place like they should.

Also, I am not a fan of the aftermarket carburetors for this application (Been there already and it was worse)

An OE carburetor is exceedingly high $$$ and I question if they are still genuine or just re-boxed clones.

Any help is appreciated (A rebuild kit would be nice if they can be found)

Try installing a spring onto the throttle connection to stop the slight surging at WOT.

 

[Auto Doc's]

Hello M.,

The servo motor to throttle arm link has pop on nylon ball sockets and there is absolutely no free play between them. I have checked. Thanks for the idea. The throttle shaft housing fitment also had no excessive play when I checked

This carburetor design is quite tedious to get on and off the machine, but I have learned to double nut the air box mounting studs and take them out and that allows enough room to lift the carburetor up and out without removing the intake. The mounting gaskets will stay in place with a little 3M spray adhesive.

The Generac built big V-twin engine are well built, but their designs are not very repair tech friendly when it comes to the carburetor access.

EDIT:

While searching around and watching some You Tube videos, I did find one where James Condon mentioned that the Honda carburetor pilot jet O-rings would likely work, so I may take a chance and order some of those to see if they will work. He was working on a 10KW Generac with a V-twin on it and similar carburetor.

I am doing my winter power outage emergency preparedness and don't want to have this baby down over some tiny carburetor O-rings.

 

[StarTech]

GeeWiz I have been removing the mounting studs for years. It not only a Generac problem. Many equipment OEMs don't design repair friendly just what is easiest to assemble in a factory setting.

As for the o-rings they are very hard to source. Most suppliers don't even carry o-rings that small. They are out there but finding where to get them is the nightmare part.

Generac also tends not provide carb kits just replacement carbs. We must be too stupid to rebuild a carb or is it a crab...

 

[Rivets]

This may sound stupid, but the one thing i’ve done to solve this problem is to drop the Hertz down-to 59-60. Do this by droppingthe RPM’s to 3450-3500. This is still in normal operating range and doesn’t affect output. Works about 50% of the time.

 

[Auto Doc's]

Hello R.,

Fortunately, the 15KW Generac portable I have is the earlier version that has a Hertz adjustment on the main processor behind the outlet panel. I have it adjusted to 60 Hz (Back when it was tested while running at a steady high speed with no load.

Late last night I did locate some Honda pilot jet O-rings on eBay, and I will see if they will be correct when they come in. (I have an old spare Generac carburetor that I can test fit them in to see if they slip in properly)

Hopefully, I don't have to resort to a new Generac carburetor or an aftermarket clone carburetor.

Life would be better if they had just drilled calibrated pilot air bleed passages like they do on many of the Kohler and B&S style carburetors.

If the weather turns bad in the next week or so, I may just leave well enough alone until the Springtime because the surge is very slight as it is right now.

 

[Auto Doc's]

GeeWiz I have been removing the mounting studs for years. It not only a Generac problem. Many equipment OEMs don't design repair friendly just what is easiest to assemble in a factory setting.

As for the o-rings they are very hard to source. Most suppliers don't even carry o-rings that small. They are out there but finding where to get them is the nightmare part.

Generac also tends not provide carb kits just replacement carbs. We must be too stupid to rebuild a carb or is it a crab...

Hi Star Tech,

As stupid has people have gotten, fewer and fewer can even explain in detail how a carburetor even works. I have read all the books about theory and understand them well, but they can still be a "crab" once in a while.

Engineers have picked up on this industry trend, so whole OEM carburetors and clone carburetors have become the resolution because why sell kits if no one knows how to install them correctly?

Carburetor kits are quickly fading away has carburetors are also fading away and losing ground to newer, more complicated fuel injection systems.

 

[StarTech]

This may sound stupid, but the one thing i’ve done to solve this problem is to drop the Hertz down-to 59-60. Do this by dropping the RPM’s to 3450-3500. This is still in normal operating range and doesn’t affect output. Works about 50% of the time.

That RPM range drops the Hz down to 57.5-58.34 Hz and not 59-60 Hz which would be 3540-3600 rpm for a two pole alternator.

Formula is RPM / 60 for Hz. The formula changes to RPM / 30 for 4 pole alternators but of these are on diesel generators.

 

[ILENGINE]

Hi Star Tech,

As stupid has people have gotten, fewer and fewer can even explain in detail how a carburetor even works. I have read all the books about theory and understand them well, but they can still be a "crab" once in a while.

Engineers have picked up on this industry trend, so whole OEM carburetors and clone carburetors have become the resolution because why sell kits if no one knows how to install them correctly?

Carburetor kits are quickly fading away has carburetors are also fading away and losing ground to newer, more complicated fuel injection systems.

When you deal with OEM carb kits that are 70-110% of the cost of a new OEM carb, Carbs get replaced instead of repairs. Also then you have the sealed cross drilled passages that are on the edge of too lean and a 1/4 micron of corrosion makes what should be a smooth running engine into a surging fit. And the only option is replacement carb.

And in some cases I am starting to wonder if EFI might be the simpler system. Has anybody tried to read the codes on a Briggs, Kohler, other EFI engines with a OBD2 scanner with an adapter cable. Looks like all use the battery positive, ground and either K-Line or CAN+/CAN-

 

[Auto Doc's]

Hello ILENGINE,

Even though we are straying off the current subject a little, this is an interesting question you pose.

Most I have seen require a dedicated scanner/ code reader platform, but I have seen OBD adapters offered for various UTV's and other equipment, not sure if the communications protocol is the same Baud rate for an automotive scanner to communicate. (Maybe Generic ODB might work on these because all network systems are approved/ developed to meet SAE standards?)

The biggest problem is manufacturers are withholding code a repair information and treating has exclusive to only their dealer networks. Sad problem with that is that no one is training the dealer tech or the technology is too advanced for many of them to even understand. Dealer tech training is a joke. Aside from that, the employee turnover rate is very fast.

I have not had the pleasure of dealing with very many fuel injection systems on riders, but I have been dealing with these on-board diagnostic systems in the automotive and UTV vehicles since they came out. (I'm formerly a master ASE automotive technician)

On the UTV side practically everything has switched to fuel injection, and they can be tricky to work with if a person does not understand how a BMAP, TMAP and TPS sensor work. A person cannot just start adjusting the idle stop screw without making things worse.

I mostly deal with 5 to 20-year-old fuel injected Polaris Rangers, John Deere Gators and Kawasaki mules around my area. The main problems I see are usually temp sensors, water in the fuel and failing fuel pumps. Of course, these get even more neglect and abuse than most other equipment.