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Ranwell1
Ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10304
Experience:  I Own a Lawn Mower Sales and service business (37years). Have 2-cycle and 4-cycle certification.
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I have a Briggs & Stratton 445777 v-twin intek that surges

Resolved Question:

I have a Briggs & Stratton 445777 v-twin intek that surges at idle. Here are the things I have already done to determine and repair the problem to no avail;

Verified good fuel source
removed and inspected carburetor.
cleared all low and high speed passages
cleared all air passages
verified high speed jet were installed correctly
check float height
replaced all orings, seals and gaskit from B&S overhaul kit
checked intake manafold for air leaks at the cylinders and carburetor
made static adjustment to carburetor

Once started still surges at idle

heald throttle lever to the idle screw and engine would stall
Ran idle screw up intill to 2100 RPMs and engine would remain running
tried to lower idle screw and engine would die out once below 2000 rpm
released the throttle lever and engine began surging again.

intalled spark tester on both cylinders and spark appeard to be contant.
balance test each cylinder at full throttle both were within 1%
replaced spark plugs j12yc at .030
check valve clearance and re-adjusted to .005 (no change to surging)
Performed leakdown test less than 8% leaking on each cylinder.
all leakage was into crankcase.

At full throttle and under lead engine performes normally.
It powers a Lawn Tractor with a 50in mowing deck and has no problem under full load.
Engine just continues to surge at idle.
Submitted: 6 years ago.
Category: Small Engine
Expert:  Ranwell1 replied 6 years ago.

Ranwell1 :

Hi

Ranwell1 :

The problem is still most likely in the carburetor.

Ranwell1 :

There are very small passages in these carburetors that get get restricted and cause this problem.

Ranwell1 :

Many times even rebuilding these you still have to replace the carburetor if it still doesn't work.

Ranwell1 :

I will send you my complete carburetor answer that will go through many of these things. Not all of it will apply to you, but it is good information anyway.

Ranwell1 :

Here is my comprehensive carburetor and fuel answer that may give you some ideas.


 


As engines sit or get older, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems. Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.


 


Today's gasoline's contain MTBE and alcohol. (Ethanol) They turn to "Junk and garbage" very quickly. Alcohol is partially water (H2O). And they call it "Oxygenated fuels! It is the oxygen that breaks down the organic compounds in the fuel and turns the gas to "Garbage" (Gum and varnish) The fuels we had just a few years ago had no alcohol in it and would store for longer periods of time before going stale... and fuel stabilizers do almost nothing to prevent the fuel from going bad with the changes in today's fuels.


 


Do not buy gas from the "Discount" Stations. The discount stations get a reduced price on gas because they may be buying fuel that is nearly 30 days old already. You may be getting fuel that's nearly stale right from the pump when buying from a discount station. Purchase your fuel from the well-known stations such as Shell, BP, Sonoco, Phillips 66 etc.


 


More than 70% of all of our repairs in our lawn mower business are due to this same issue. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carburetor.


 


The carburetor must be removed from the engine. Clean all parts with carburetor cleaner and blow out all the small holes and passageways with compressed air. Remove all of the non-metallic parts since the carburetor cleaner will cause them to be disfigured decompose and plug the carburetor as time goes on.


 


Wash the carburetor cleaner off of the metal parts by washing them in warm, soapy water then rinsing with clean water. Dry them by blowing it off with compressed air. Make sure that all the passageways are blown dry before reassembling.


Reassemble using a NEW carburetor rebuild kit.


 


DO NOT TRY TO REASSEMBLE WITHOUT USING A COMPLTE CARBURETOR KIT! You will just end up having to do the job again.


 


ALWAYS clean the fuel tank and replace the fuel line when doing this repair or you may have to do it all over again. The inside of the fuel line disintegrates over time and these small pieces of rubber will plug up the carburetor too. Dirt and water from a dirty fuel tank will also plug up the carburetor. Find the Model, type and serial or code numbers off of the engine and take them to your local dealer to get the carburetor repair kit.


 


If you do the work yourself, take pictures or at least make a drawing of where all the linkages, gaskets, and component parts go. Correct reassembly is critical.


 


If the carburetor still doesn't work correctly, you may have to take it to someone who has an "Ultra-sonic" cleaning machine. This machine uses carb cleaner and ultrasonic vibrations to get the very small passageways clean when traditional methods fail.


 


 


Here is where you can get an inexpensive "Ultrasonic Cleaning Machine"


http://www.harborfreight.com/catalogsearch/result?category=&q=ultrasonic+cleaner


 


If you don't feel comfortable with this kind of repair I would suggest sending it to a reputable shop.


 


Feel free to contact me here at this question anytime ...even after you hit the "ACCEPT" button ...and I will try to help further.


 


Please click "ACCEPT" or I won't get paid.

You may also consider sending a bonus if I have been helpful, Please leave POSITIVE feedback for me as this is how I'm rated. Remember, a neutral is nearly as bad as a negative. If not satisfied, contact me and I will make it right. Thanks


 

Ranwell1 :

The surging is usually caused by a lean running condition on idle. the idle passages are the ones that usually get clogged first.

Ranwell1 :

Check the spark plugs also as a defective spark plug can also cause this.

Customer:

The passages on Nikki 2 barrell carburetor that is on the Briggs V-twin are accessable and I cleared all of them.

Customer:

I have repaced the original spark plugs

Customer:

with new ones and get no change.

Ranwell1 :

The are NOT all accessable. there are some on the insise that even I cannaot get to.

Ranwell1 :

They are NOT all accessable. there are some on the inside that even I cannot get to.


Ranwell1 :

In any case. we have had some problems with the Nikki carbs. When you order a new carb , they will send you a Walbro because of the Nikki problems.

Customer:

I also put it in an utrasonic parts cleaner and still same problem.

Ranwell1 :

OK, the I suggest a new carburetor

Customer:

I will order another carburetor. I was wondering if anything outside of the carburetor could make the engien surge at idle.

Ranwell1 :

Yes, but what you have already done is what I would have mentioned.

Ranwell1 :

I hope the carburetor fixes the problem because they are not inexpensive.

Customer:

OK, thank you for your help. I will try it.

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