# Enlarging jets



## Rentahusband (Aug 25, 2008)

Working on a 5hp Tecumseh, LEV115. Unit was brought to me as it would not run right. Someone had tinkered with it prior and damaged the bowl gasket. As long as I had it apart I replaced the needle/seat along with cleaning the bowl nut. With the air filter on or off the unit would still not run smoothly unless I restricted the air flow with the filter off. It did not take much for it to even out. What I wound up doing is enlarging the main jet in the bowl nut. I have a drill bit set #s 60-80. I startrd with the bit that fit the hole and went two more sizes larger. Unit now purrs like a kitten. 
Wondering if any of you have done this. 
Dean


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## chuck_thehammer (Oct 24, 2007)

I have done this for years on motorcycles, as they are always setup from the factory lean.
I think anything today with a carb is setup lean to make the EPA happy.

Chuck


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## cleverlever (May 13, 2009)

I took this one step further and adapted and older adjustable jet to replace the fixed orfice jet.

Made a post on the subject but couldn't find any one else that had done it.

I did the idle also but that didn't work as well and the adjustable high speed jet impacts the idle so i have to figure out the passage between the high speed and low speed jet


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## Bob DiGiacomo (Jan 15, 2009)

In the bowl nut which hole are you enlarging with the drill bit. The 2 bigger horizontal holes on the bottom by the nut head, or the tiny vertical hole that runs through the center of the bowl nut. I am working on a 6.5 tecumseh and think this method might work. I cleaned everything and replaced all gaskets, but the engine has a slight hesitation.


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## 30yearTech (Sep 14, 2006)

It would be the center hole. FYI it is a violation of federal law to make any modifications that would affect emissions on any C.A.R.B OR E.P.A. engine.


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## cleverlever (May 13, 2009)

The EPA information you post is correct but I really thing the government has larger problems than chasing a guy that removed a couple thousanths of an inch from a carb jet in his lawnmower

To me the irony is that they lean up the carbs to save fuel reduce emissions and they load up the mower with so many safety controls its almost worthless as a lawn mower but they remove the throttle so you can't bring the engine to an idle.

In my opinion the ability to reduce engine speed would save gas and reduce danger of spitting out rocks etc when you cross driveways.


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## 30yearTech (Sep 14, 2006)

cleverlever said:


> The EPA information you post is correct but I really thing the government has larger problems than chasing a guy that removed a couple thousanths of an inch from a carb jet in his lawnmower
> 
> To me the irony is that they lean up the carbs to save fuel reduce emissions and they load up the mower with so many safety controls its almost worthless as a lawn mower but they remove the throttle so you can't bring the engine to an idle.
> 
> In my opinion the ability to reduce engine speed would save gas and reduce danger of spitting out rocks etc when you cross driveways.


Government regulations have nothing to do with the omission of an adjustable throttle. This is more of a cost cutting issue with the equipment manufacturer.


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## cleverlever (May 13, 2009)

Thank you for reinforcing the point I am making.

The government overlooks the issues that could really make a diffrerence while nit picking the little stuff.

You tell me ,is a lawnmower with a throttle more fuel efficient and safer than a mower with a fixed speed engine?


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## 30yearTech (Sep 14, 2006)

cleverlever said:


> Thank you for reinforcing the point I am making.
> 
> The government overlooks the issues that could really make a diffrerence while nit picking the little stuff.
> 
> You tell me ,is a lawnmower with a throttle more fuel efficient and safer than a mower with a fixed speed engine?


In my opinion not necessarily, these engines and equipment are designed to operate at specific RPM's both for safety and efficient operation. Slowing the RPM's down causes engines to run hotter and affects the mowers ability to process the cut grass. 

Slowing the engine down to cross rocky driveways or lowering to an idle while one moves obstructions or does whatever may be nice and save a little fuel. If you want to really save, simply kill the engine and restart when you are ready to proceed.


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## cleverlever (May 13, 2009)

If this is true then why don't we remove throttles from all lawn mowers?


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## 30yearTech (Sep 14, 2006)

cleverlever said:


> If this is true then why don't we remove throttles from all lawn mowers?


If What is true??


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## Rentahusband (Aug 25, 2008)

cleverlever said:


> The EPA information you post is correct but I really thing the government has larger problems than chasing a guy that removed a couple thousanths of an inch from a carb jet in his lawnmower


I agree. The way the motor was running was not very efficient, so I feel by doing what I did helped its efficiency. I also wondered about the fixed throttle I do not care for them. IMO I do not think starting any gas engine at full throttle is good for it. I always give it a bit to warm up. Bottom line is the unit is running the way it should.
Dean


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## 30yearTech (Sep 14, 2006)

Rentahusband said:


> I agree. The way the motor was running was not very efficient, so I feel by doing what I did helped its efficiency. I also wondered about the fixed throttle I do not care for them. IMO I do not think starting any gas engine at full throttle is good for it. I always give it a bit to warm up. Bottom line is the unit is running the way it should.
> Dean


Bottom line is it's running. If it were running the way it should, then you would not have had to modify the carburetor. It may be running better then it was, but doing what you did, just side stepped whatever the real cause of your problem was. If the issue ever gets corrected, then the engine could be running too rich. 

These engines have governors and do not ever run at full throttle unless the governor has been circumvented. They also have fairly loose tolerances so running at higher rpm's when cold is not an issue to be concerned about.

Dean, I generally agree with what you post, and I seriously doubt that the government will ever track you down and fine you for modifying a carburetor. Although, you did admit to doing so on this forum. I was only stating that it was against federal law to do so. I am not the EPA police and I don't care if anyone does it, I just do not endorse it. It's my opinion that if you had to modify the carburetor to make it work, then while you made it run, you did not fix the problem.

Oh yea, anyone and everyone is welcome to disagree with me, it's just my opinion.


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## pyro_maniac69 (Aug 12, 2007)

don't fight with 30year, YOU WILL LOSE

I've done it more than once lol


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## 30yearTech (Sep 14, 2006)

pyro_maniac69 said:


> don't fight with 30year, YOU WILL LOSE
> 
> I've done it more than once lol


I am not trying to pick any fights, just expressing my opinion based upon my experiences. I will from time to time disagree with others posts or advice. This does not make them or myself right or wrong... Just different in our opinions and advice.


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## cleverlever (May 13, 2009)

http://www.cleverlever99.blogspot.com/

Thought you guys might be interested in one of my other modified carburetor schemes


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## 30yearTech (Sep 14, 2006)

cleverlever said:


> http://www.cleverlever99.blogspot.com/
> 
> Thought you guys might be interested in one of my other modified carburetor schemes


Wow 8 carburetors, how do you sync them?

Does this engine run backwards??


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## Rentahusband (Aug 25, 2008)

No hard feelings. I am not trying to pick a fight either and as 30year stated difference of opinions. Is it possible that the bowl nut was not manufactured properly? While diagnosing the problem I come to the conclusion that the engine was not getting enough fuel. What else should have I checked? 
Dean


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## cleverlever (May 13, 2009)

30yearTech said:


> Wow 8 carburetors, how do you sync them?
> 
> Does this engine run backwards??


There are reverse rotation camshafts used in twin screw boats that allow motors to run in opposite directions but this is reverse flow induction. Motor runs same direction as stock but the air flow is reversed.

The visual impact draws huge crowds when we go to car shows.


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