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20hp briggs & stratton surging

#1

O

oldntired55

ok, i fixed one problem, over rich belching black smoke,,, now, i have an annoying surge...rpm rolls up and down, tried another nikki carb off my craftsman, whcih did not surge... same problem... i have adjusted governor, and checked linkages...could the springs be out of whack? i give up...help?


#2

ILENGINE

ILENGINE

Hold the throttle steady on the carb to prevent movement and see how the engine runs. If smooth then could be a governor issue. If the engine is stumbling and not running smooth than carb issue. Also you could try adding a little choke and see if the surging stops. Smooth running with some choke but surging without would also point to a carb issue.


#3

H

hlw49

Model type and code would help to identify the carb. Had a T30 MTD today that was surging. Took the carb Nikki which in my opinion sorriest carb on the market. It was a night mare to get off since I had to take the engine cover, seat and seat bracket off. Bracket that the seat bracket bolted to just to get the carb. off. Once I did found the welch plug for the idle circuit had come out. Fixed it good to go.


#4

O

oldntired55

hlw49 said:
Model type and code would help to identify the carb. Had a T30 MTD today that was surging. Took the carb Nikki which in my opinion sorriest carb on the market. It was a night mare to get off since I had to take the engine cover, seat and seat bracket off. Bracket that the seat bracket bolted to just to get the carb. off. Once I did found the welch plug for the idle circuit had come out. Fixed it good to go.
Click to expand...
thats interesting... ill have to look for that, my only question being... why would the carb off a good running v twin act exactly the same


#5

O

oldntired55

oldntired55 said:
thats interesting... ill have to look for that, my only question being... why would the carb off a good running v twin act exactly the same
Click to expand...
ILENGINE said:
Hold the throttle steady on the carb to prevent movement and see how the engine runs. If smooth then could be a governor issue. If the engine is stumbling and not running smooth than carb issue. Also you could try adding a little choke and see if the surging stops. Smooth running with some choke but surging without would also point to a carb issue.
Click to expand...
no change with choke, already thought maybe a bit on the lean side. and, as i said... this surges with a carb off a separate tractor that ran fine. im beginning to think i may have to pull the engine and check governor.


#6

O

oldntired55

oldntired55 said:
no change with choke, already thought maybe a bit on the lean side. and, as i said... this surges with a carb off a separate tractor that ran fine. im beginning to think i may have to pull the engine and check governor.
Click to expand...
also, most small engines have an anti-surge spring from gov arm to carb link... i wonder why these do not?


#7

StarTech

StarTech

oldntired55 said:
thats interesting... ill have to look for that, my only question being... why would the carb off a good running v twin act exactly the same
Click to expand...
Because the carbs be jetted differently. You can't just simply put any old carb on and expect it to run perfectly. This why you must match the correct carburetor to the engine it being installed on. This is why many of the eBay and Amazon aftermarket fail when installed. All it takes is a hundredth or so of millimeter jet to cause problems. This why you can't mix the jets on a twin barrel Nikki as there might as much as 5 hundredths of a millimeter or more between L and R sides.

Those springs are there to remove slack only not to prevent surging per say; although, worn linkage mounting can cause problem of surging. Never had a problem without them.

As IL said try holding the throttle vane steady and see what happens.

Plus on twins many have a governed idle and the carburetor first must be set minimum idle speed and the governed idle speed is set. If you only adjust the idle stop screw you can get some strange carburetor problems as governor tries to govern the idle speed but can't. I have seen an engine to very at first start up to racing after it warms just because someone adjusted the idle stop screw incorrectly. These have to be set using tach.


#8

O

oldntired55

hlw49 said:
Model type and code would help to identify the carb. Had a T30 MTD today that was surging. Took the carb Nikki which in my opinion sorriest carb on the market. It was a night mare to get off since I had to take the engine cover, seat and seat bracket off. Bracket that the seat bracket bolted to just to get the carb. off. Once I did found the welch plug for the idle circuit had come out. Fixed it good to go.
Click to expand...
mod 407777-0128-E1 000607YG


#9

O

oldntired55

StarTech said:
Because the carbs be jetted differently. You can't just simply put any old carb on and expect it to run perfectly. This why you must match the correct carburetor to the engine it being installed on. This is why many of the eBay and Amazon aftermarket fail when installed. All it takes is a hundredth or so of millimeter jet to cause problems. This why you can't mix the jets on a twin barrel Nikki as there might as much as 5 hundredths of a millimeter or more between L and R sides.

Those springs are there to remove slack only not to prevent surging per say; although, worn linkage mounting can cause problem of surging. Never had a problem without them.

As IL said try holding the throttle vane steady and see what happens.

Plus on twins many have a governed idle and the carburetor first must be set minimum idle speed and the governed idle speed is set. If you only adjust the idle stop screw you can get some strange carburetor problems as governor tries to govern the idle speed but can't. I have seen an engine to very at first start up to racing after it warms just because someone adjusted the idle stop screw incorrectly. These have to be set using tach.
Click to expand...
appreciate your reply, so...how do i proceed to set governed idle speed? mine does have 2 separate springs...on attached to a fixed point on bracket, the smaller (idle) spring on a bendable tab , also, both these carbs have the single jet fuel tube (black) , so i ruled out one of those affecting the surging... maybe im shooting in the dark, im beginning to wonder if the fuel pump is not keeping up with a filled fuel bowl... have a new one ordered as there is a small wet spot on bottom of fuel pump..


#10

F

Forest#2

After I posted this I see now that you just posted the engine info.
Below is some hints. You WILL FIND the answers to your questions about proper adjusting in the governor section of the Briggs twin Intek OHV service manual. But you need to do the test ILengine suggests in post #2 first. If you have a air leak at the manifold it will have your issue and no adjustments will correct. source of air leak is the o-ring at the intake manifold.
Appears MAYBE from your hints you have a dual throat Nikki MAYBE on a twin engine?
Model type and code would help us?????????????
Most likely not the governor inside the engine.
Have you ever seen the engine operate normal or is this a new to you engine?
Yes Bubba could have messed with the springs???

If that is a Briggs twin each time you change to another NIKKI carb you will HAVE TO go through the steps in the service manual for STATIC governor adjust then low idle the governor idle (which is bend adjustment for the gov idle spring) and then HIGH rpm limit (which is a bend adjustment) You will have to go through these steps if the donor NIKKI carb governor and throttle control is not correct when tested. (look in the correct service manual for the correct steps for such.

ILengine has some GOOD info in his post @2. Did you try that?
Sometimes on those Briggs with the Nikki you can back off little bit CCW on the CW rotation of the governor shaft when doing the static gov adjust for full throttle on the carb and get less governor control hunting. When I say little bit it's only about 1/16 of an inch difference and mostly a adjust and try because the governor shaft only rotates 1/4 turn or less full travel for the static adjust.


#11

ILENGINE

ILENGINE

Forest#2 said:
ILengine has some GOOD info in his post @2. Did you try that?
Sometimes on those Briggs with the Nikki you can back off little bit CCW on the CW rotation of the governor shaft when doing the static gov adjust for full throttle on the carb and get less governor control hunting. When I say little bit it's only about 1/16 of an inch difference and mostly a adjust and try because the governor shaft only rotates 1/4 turn or less full travel for the static adjust.
Click to expand...
Very true when setting the static governor adjustment you don't want to put tension on the governor shaft when making the adjustment. Just need to rotate shaft to stop and then tighten the arm. If tension is put on the shaft when adjusted will create a governor sensitivity surge.


#12

O

oldntired55

Forest#2 said:
After I posted this I see now that you just posted the engine info.
Below is some hints. You WILL FIND the answers to your questions about proper adjusting in the governor section of the Briggs twin Intek OHV service manual. But you need to do the test ILengine suggests in post #2 first. If you have a air leak at the manifold it will have your issue and no adjustments will correct. source of air leak is the o-ring at the intake manifold.
Appears MAYBE from your hints you have a dual throat Nikki MAYBE on a twin engine?
Model type and code would help us?????????????
Most likely not the governor inside the engine.
Have you ever seen the engine operate normal or is this a new to you engine?
Yes Bubba could have messed with the springs???

If that is a Briggs twin each time you change to another NIKKI carb you will HAVE TO go through the steps in the service manual for STATIC governor adjust then low idle the governor idle (which is bend adjustment for the gov idle spring) and then HIGH rpm limit (which is a bend adjustment) You will have to go through these steps if the donor NIKKI carb governor and throttle control is not correct when tested. (look in the correct service manual for the correct steps for such.

ILengine has some GOOD info in his post @2. Did you try that?
Sometimes on those Briggs with the Nikki you can back off little bit CCW on the CW rotation of the governor shaft when doing the static gov adjust for full throttle on the carb and get less governor control hunting. When I say little bit it's only about 1/16 of an inch difference and mostly a adjust and try because the governor shaft only rotates 1/4 turn or less full travel for the static adjust.
Click to expand...
this is a 20hp v twin intek donor engine from a junk tractor with the 2bbl Nikki with the black plastic fuel transfer tube and 1 main jet., it has been sitting for 4 or 5 years. i will check the governor settings again, both idle and high speed. and try to cheat the governor back a bit. it has the aluminum intake, so no o rings to leak. i will have to try some new intake gaskets. also will try squirting some wd40 around and check for air leaks, as i found many a leaking intake back in the garage days.


#13

O

oldntired55

ILENGINE said:
Very true when setting the static governor adjustment you don't want to put tension on the governor shaft when making the adjustment. Just need to rotate shaft to stop and then tighten the arm. If tension is put on the shaft when adjusted will create a governor sensitivity surge.
Click to expand...
i will recheck governor adjustments...and post back a reply. thanks


#14

O

oldntired55

OK, so now i am removing this engine i just installed. i wanted to warm it up BEFORE re- adjusting the governor.. it went FULL throttle, i was afraid the rods would fly out before i could shut it down..i guess maybe the governor came apart, maybe it was failing last week? who knows..a teardown will tell the story. i will repost after teardown. thanks for all the help so far..


#15

O

oldntired55

Update... i believe i found my errant governor hunting problem...parts are ordered... cant wait to get it together.

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#16

O

oldntired55

oldntired55 said:
Update... i believe i found my errant governor hunting problem...parts are ordered... cant wait to get it together.
Click to expand...
i really think one weight was off when i started it the first time...


#17

F

Forest#2

You have been lucky so far that small piece of the bad governor has not caused any major damage. It will eventually happen if you do not retrieve all.

BE SURE you retrieve ALL the small pieces from inside. I have a large metal lid/pan from the top of a 55 gallon barrel that has a lip and I take the block outside shop and put screen wire over the lid and flush the block with diesel using a hand sprayer and roll and tip the block and use magnets to search for exploded pieces. Use the replacement governor to compare to your exploded puzzle pieces to get an idea if you have retrieved all. If you don't get all the pieces the engine gears will eventually find them.:(

Also make sure the governor is orientated properly when re-installing the sump.

Hint: When first starting up that type governor engine I've been deep into I purposely set the static governor opposite of normal so as when the engine is first started so as the governor SHOULD hold the engine at idle instead of high rpms. Set throttle control at idle also or manually tie the carb to idle position. You know then when you let it have governor control it should immediately stay at low rpms and you are ready to do the ignition off immediately. After you see the governor holding the engine at idle or low rpms and letting the engine warm up at low rpms then set the governor static adjust normally by the book for the high rpms governor control know the engine should immediately start and operate correctly with governor control.
Max over speeding rpm's governor at cold startup is not a good thing even when you are trying to kill the engine.


#18

O

oldntired55

Forest#2 said:
You have been lucky so far that small piece of the bad governor has not caused any major damage. It will eventually happen if you do not retrieve all.

BE SURE you retrieve ALL the small pieces from inside. I have a large metal lid/pan from the top of a 55 gallon barrel that has a lip and I take the block outside shop and put screen wire over the lid and flush the block with diesel using a hand sprayer and roll and tip the block and use magnets to search for exploded pieces. Use the replacement governor to compare to your exploded puzzle pieces to get an idea if you have retrieved all. If you don't get all the pieces the engine gears will eventually find them.:(

Also make sure the governor is orientated properly when re-installing the sump.

Hint: When first starting up that type governor engine I've been deep into I purposely set the static governor opposite of normal so as when the engine is first started so as the governor SHOULD hold the engine at idle instead of high rpms. Set throttle control at idle also or manually tie the carb to idle position. You know then when you let it have governor control it should immediately stay at low rpms and you are ready to do the ignition off immediately. After you see the governor holding the engine at idle or low rpms and letting the engine warm up at low rpms then set the governor static adjust normally by the book for the high rpms governor control know the engine should immediately start and operate correctly with governor control.
Max over speeding rpm's governor at cold startup is not a good thing even when you are trying to kill the engine.
Click to expand...
that was my initial thought, when i get this back together thursday, to limit the throttle at the carb... ill keep you posted, thanks for the info


#19

O

oldntired55

Ok this story seems to get nothing but WORSE... now, upon inspection of the gov gear shaft, i see there is no snap ring that goes into the case. also, i notice some galling right above the lower snap ring groove... my question is, is there a part number for a new shaft with both snap rings? the ring is NOT inside the case, i looked and looked with a magnifier.the only thing i can say for certain, is the gear was 'snapped in' the case, as i had to gently pry it out. i have looked and looked, but i cant find the lower ring... the only thing i can think, is that i rinsed it out of the crankcase when i washed it out. any source for a new Briggs shaft?

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#20

F

Freddie21

Do we know that we have good, unobstructed, fuel flow to the carb?


#21

O

oldntired55

Freddie21 said:
Do we know that we have good, unobstructed, fuel flow to the carb?
Click to expand...
yes, i put new lines and filter on, and new fuel pump... pushes fuel out the outlet in a good stream. i have not done a volume test...maybe i should. i will do that, after i put the engine back together. thanks


#22

O

oldntired55

governor update!!! well, after 2 governor changes (both blew up) i believe i found the problem.if you notice the pic of the governor layin in the block, the shaft came out. i believe it was loose and moving the first time the governor blew up. and, leading to the "hunting rpm's" . after my repair, it is running fine , at low and high speed... rpms are within specs from manual now. i did some mowing with it last night... and it works fine! No surging, no varying rpms,it holds steady wherever throttle lever is.!!! hope i have solved this annoying problem for good! need to get this machine SOLD!!!! the grooves in the shaft, were put there by me, one to help hold the JB WEld to the shaft and block, the other was measured where the set screw is, to give it some holding power on the shaft. yes it was time consuming, but, i didnt have to replace the block... and it seems good now!

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#23

A

Asp

My Dixie Chopper has been surging for a while and I thought it was carb problem. Took it to shop for other problem and told repairman it was surging. When picked mower up he said I had a dirty air filter. He changed the filter and problem solved. Cheap repair.....


#24

O

oldntired55

Asp said:
My Dixie Chopper has been surging for a while and I thought it was carb problem. Took it to shop for other problem and told repairman it was surging. When picked mower up he said I had a dirty air filter. He changed the filter and problem solved. Cheap repair.....
Click to expand...
i wish my problem would have been that simple


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