# Throttle Shaft Leaks



## LSE (Apr 4, 2012)

Don't matter what brand engine, I usually will replace the carb when a Throttle Shaft leak is detected. However, I'd like to get a discussion going on any successes techs have had fixing these throttle shaft leaks. It would be great to be able to get some of these carbs working properly instead of replacing. Any suggestions on fixing these leaks that cause Hunting and Surging (assuming the governor has been static set its not a governor or intake manifold leak)?


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## paulr44 (Oct 14, 2008)

Unless you can re-bush the carb. body and replace the shaft, there is no fixing a worn throttle shaft. Kohler used to sell a bushing/shaft kit for the K/Magnum series, as far as I know they're all NLA. As air filter systems have improved, we've seen less of shaft leaks as an issue - very rare in fact. Better carbs. these days also have lip seals on the shafts, and are included in shaft replacement kits.


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## 30yearTech (Sep 14, 2006)

Most surging or hunting issues i run across are usually due to a plugged or dirty pilot or idle circuit jet. I don't run across a lot of units with worn throttle shafts, and those that are usually will have wear in the carburetor body, so as Paul indicated you have to replace the shaft and put a bushing in the carburetor. Prices on many newer carburetors has dropped enough that replacement is not as expensive an option as it used to be.


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## light mechanic (Jul 18, 2008)

LSE I am luck enough to have a lathe so I can make bushings out of Bronze,in years past I used to use felt dipped in oil or an O ring that would help but 30 year Tech said most of the time if is the idle side jets and passages that need to be cleaned.


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## paulr44 (Oct 14, 2008)

All of us I assume (you know what that means) accept you've diagnosed a worn shaft. As 30yr points out, usually a cycling (surge/hunting) issue is due to jet restriction, be it pilot (idle) circuit or high-speed. However, on rare occasions it can be caused by a governor problem be it worn, sticky, or spring issue. Just my 2cents...


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## LSE (Apr 4, 2012)

Thanks for replying guys.
It's been pretty common in my shop over the past few years for techs to clean a carb and still have some engines hunting or surging. I've re-visited Carb cleaning techniques with the techs to make sure we are opening up ports and jets and worked with them on static governor adjusting so they could work with overcoming hunting and surging. Don't get me wrong, we have successes in most cases, however it seems to come up more often than I like.
What we find most of the time we can spray brake cleaner at the throttle shaft at idle and we get RPM increase.
At that point I usually go back over "Did we clean the carb by hand good and wire out jets/ports" and then drop in an ultrasonic cleaner, and if we did a static governor adjust as well as check for binding linkages or problems with springs with the throttle. I also ask them to check carb and intake manifold gaskets for leakage.
We usually opt to see if a customer will approve a carb replacement.


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## paulr44 (Oct 14, 2008)

Hmm, I can't agree with the spray test. I'd submit that any butterfly type carburetor with some hours on it will allow brake cleaner past it, unless it has a seal. All too often the inexpensive type or aftermarket carbs will allow engine surge despite having been thoroughly cleaned.

On the other hand, going back in time Tecumseh snow engine carbs often surged after rebuild so I started ordering main jets which helped the problem. Scraping out the jet orifice can work, but as you surely know it's easy to go too far and you can't put that metal back. A slight surge can be excused (and explained to the customer) if it smooths out under load, as it's still functional. Snow engines sometimes surged when new. And, they need to be jetted for and tested at 32 deg. or so as the mixture needs to be richer than fair-weather engines.

Agreed: carb. replacement today is often cost-effective, has guaranteed results and if you use an OEM carb. any problems can be addressed under warranty, so is often the best solution. After all, who is it in the end that pays for a failed carb. rebuild?


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## LSE (Apr 4, 2012)

Paul, I guess what's dumbfounding to me is let's say we're working with a Briggs Intek single cylinder that has either a Walbro or Nikki carb and it's surging. If the governor has been static adjusted and the linkage is not an issue from governor to the throttle we then look to the carb and hand clean it, wire out all small holes, drop it in an ultra-sonic cleaner and put new intake and carb gaskets on, only to have it surge. This type of problem is common where we are at and we generally opt to replace the carb at this point. I'm rather shocked that this isn't more common in other regions from the response I'm getting on this topic. I will be re-visiting with my techs tomorrow what feedback I've received regarding clogged jets, but I find it hard to believe we are that bad at cleaning carbs (I've personally had techs give me the carbs and cleaned them myself to make sure it's done correctly). There's a piece of the puzzle I'm missing, but I appreciate your feedback as well as everyone else's.
I do understand that there's some cases the surge/hunt stops when under a load, however we can't let a customer's unit go back without addressing the issue and suggesting ultimately what the correct fix would be. Nobody wants a poor running engine unless their budget dictates they will just deal with it.
You know how it goes ....... Unit comes in for a Tune Up (because a Tune Up fixes everything....right?) Tech diags unit and it comes down to the engine surges. We do the Tune Up, clean carb if the customer approves, unit still surges then the end result in the customers opinion is we didn't fix it correctly.
Spring is near and I want to beat this issue before the shop has 200 units and no time to waste. LOL


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## 30yearTech (Sep 14, 2006)

LSE said:


> Paul, I guess what's dumbfounding to me is let's say we're working with a Briggs Intek single cylinder that has either a Walbro or Nikki carb and it's surging. If the governor has been static adjusted and the linkage is not an issue from governor to the throttle we then look to the carb and hand clean it, wire out all small holes, drop it in an ultra-sonic cleaner and put new intake and carb gaskets on, only to have it surge. This type of problem is common where we are at and we generally opt to replace the carb at this point. I'm rather shocked that this isn't more common in other regions from the response I'm getting on this topic. I will be re-visiting with my techs tomorrow what feedback I've received regarding clogged jets, but I find it hard to believe we are that bad at cleaning carbs (I've personally had techs give me the carbs and cleaned them myself to make sure it's done correctly). There's a piece of the puzzle I'm missing, but I appreciate your feedback as well as everyone else's.
> I do understand that there's some cases the surge/hunt stops when under a load, however we can't let a customer's unit go back without addressing the issue and suggesting ultimately what the correct fix would be. Nobody wants a poor running engine unless their budget dictates they will just deal with it.
> You know how it goes ....... Unit comes in for a Tune Up (because a Tune Up fixes everything....right?) Tech diags unit and it comes down to the engine surges. We do the Tune Up, clean carb if the customer approves, unit still surges then the end result in the customers opinion is we didn't fix it correctly.
> Spring is near and I want to beat this issue before the shop has 200 units and no time to waste. LOL


I find (particularly on the Nikki Carburetors), that the passage way from the air intake in front of the carburetor to the pick up port in the carburetor body gets plugged and no fuel can be drawn up and fed to the idle circuit. I have cleaned many a carburetor, put it back on and have it surge. Upon rechecking only to find I don't have good flow through this jet. I use an orifice drill kit to clean out any restriction until I get a good flow of spray through the passage way, this usually takes care of any surging. Make sure the passage is open in the plastic fuel transfer tube. If this is the primary cause of the surging, it generally will occur when there is little to no load on the engine, if the surging clears up by applying a load, such as engaging the mower blades, then a restricted idle circuit is usually the cause of this issue. If it continues no matter the load, then it's probably a governor problem.


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## LSE (Apr 4, 2012)

30yearTech said:


> I find (particularly on the Nikki Carburetors), that the passage way from the air intake in front of the carburetor to the pick up port in the carburetor body gets plugged and no fuel can be drawn up and fed to the idle circuit. I have cleaned many a carburetor, put it back on and have it surge. Upon rechecking only to find I don't have good flow through this jet. I use an orifice drill kit to clean out any restriction until I get a good flow of spray through the passage way, this usually takes care of any surging. Make sure the passage is open in the plastic fuel transfer tube. If this is the primary cause of the surging, it generally will occur when there is little to no load on the engine, if the surging clears up by applying a load, such as engaging the mower blades, then a restricted idle circuit is usually the cause of this issue. If it continues no matter the load, then it's probably a governor problem.


Thank you 30 year, I've received some great feedback and instruction from everyone here. I've meet with my techs already and will show them your message above as well. Many thanks for everyone taking the time to share and respond!
You've helped me several times over the past 10 yrs (I've changed screen names here). Your screen name should be 40 year tech by now LOL.


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## paulr44 (Oct 14, 2008)

And one other thing, a little secret harkening back to Snow King engine days that somtimes helps: on a problem engine, when you do the static gov. adj. back off a small amount on the arm so you actually have a touch of play vs. zero play.


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