# 4 HP Briggs problem



## Adster (Feb 29, 2008)

Hello all,
I have an old Bolens 22" self propelled walk behind mower that needs some adjustment. It was one of the first mulching mowers of the 1970's and it has stood the test of time. It has a 4 HP Briggs & Stratton engine Model #110988, engine type 0324. I have the original manuals and have downloaded the Illustrated Parts List from Briggs so I can at least identify what I'm asking of you guys. You can grab it too if you need to at:

http://www.briggsandstratton.com/pdf/illustrated_parts_list/100\MS6317.pdf

Anyway, I'm mowing away with this thing at full throttle last weekend and all of a sudden the throttle goes from full down to about 3/4 of full...just like that. After she cooled down I pulled off the plastic shroud and air filter assembly and could see the problem. The governor spring (B&S Part #260875) that connects the throttle adjustment assembly to the governor link had broken. Luckily the spring broke right at the end loop where it connects to a little hole in the throttle assembly. I just took needle nosed pliers and made another loop from the end link of the spring and re-connected it.

That allowed me to get my mower back on the lawn, but the problem is that although the mower is throttling up much better that it obviously did with the broken spring, it's not quite as many RPM's as before any of this happened. I need like another 10% of maximum RPM's. I know this because I feel that the mower is now needing to be "pushed" by me rather that the pace I was used to at full throttle doing the same lawn with the same mower for many years.

I'd really like to play around adjusting the maximum throttle speed up a bit but don't really know where to start. BTW, the physical throttle control (the cable) for FAST/SLOW/STOP is set properly and the carb mixture is good.

Where should I begin? Thanks.


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## 30yearTech (Sep 14, 2006)

The lever where the governor spring attaches to that is controlled by the throttle cable is simply bent to increase or decrease tension on the governor spring to set the maximum governed RPM. You should use a tach when setting to make sure that the engine is not set to run faster then it should.


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## Adster (Feb 29, 2008)

Thanks 30 YT. Can you recommend an inexpensive one for the home hobbyist that will hopefully be accurate enough? Are the induction ones any good? How about those really inexpensive ones that work on vibrations?


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## 30yearTech (Sep 14, 2006)

Look at the Tiny Tach, it's really meant to be mounted to an engine to monitor run time and engine rpm's but you don't have to mount them and they are reasonable. The vibra tach's work good as well as the hand held digitals but are kind of expensive.

Just do a search on "Tiny Tach" and you will find them all over and on ebay as well.


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## geogrubb (Jul 28, 2006)

You are trying to complicate a simple solution.
Why not just replace the broken spring, when you created a new loop in the end you changed the functioning of the throttle/governor system, if you will notice on the IPL part#209 has two versions for diferent RPM. Have a good one. Geo


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## Adster (Feb 29, 2008)

Thanks for the recommendations 30YT. Good point also geogrubb, but here is what I found and I don't quite understand why. Maybe you could shed some light on this for me? In manually playing around with the governor system while the engine was running yesterday, I discovered that more tension on the spring causes a higher maximum RPM. Therefore, in making the new loop on the spring, I effectively increased the tension on the spring slightly. This should have gotten me back to where I was (RPM wise) before the break and then some. Why it put me at a lower maximum RPM I can't seem to figure out. 

BTW I did see the notation about the two springs. I believe you use the engine type code to choose between the two. Mine uses the first one.

Getting a new spring is a good idea also and I plan to do that too. I just wanted a quick fix for now, is there a reseller on the Internet that stock lots of these older Briggs parts that you guys can recommend or should I just have a Briggs dealer order it?

Thanks for the help...I always learn a lot here. :thumbsup:


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## 30yearTech (Sep 14, 2006)

More tension should increase rpm's, but you may have stressed the spring when you made the new loop. As long as you have it adjusted to the proper RPM's it does not matter if you replace the spring or not, there are several different springs for different engine applications. This is an air vane governor, anything that affects air flow around the cooling fins on the engine can change the operating rpm's so make sure the air intake and cooling fins are clear of any obstructions or restrictons.

It would be a good idea to replace the spring, if it broke once it may be fatigued and may break again. Any Briggs dealer should have or be able to get you the proper spring.


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## Adster (Feb 29, 2008)

Thanks 30 YT. The cooling fins and air intake I always try to keep clean. I see what you mean about it being an air vane governor. The other end of where the governer spring connects seems to "float on air" when the engine is running. In reading a bit about this I discovered that the system is there to govern maximum speed over a wide variety of loads and throttle settings. I still really don't understand how the system works though. Could you give me a basic readers digest version of how it works or maybe point me to a link?


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## 21tgs (Oct 26, 2006)

The spring on the governor pulls the throttle plate to wide open. As the engine picks up speed the fan moves more air which pushes on the air vane. The vane overcomes the spring tension and pulls the throttle plate closed to keep the engine from over speeding. As you apply a load to the engine, the engine slows down which reduces the amount of air being moved by the cooling fan. The governor spring opens the throttle, the engine speeds up and the increased air flow holds the governor and the throttle plate in the new position. And so the cycle continues based on engine load and throttle position.


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## 30yearTech (Sep 14, 2006)

21tgs said:


> The spring on the governor pulls the throttle plate to wide open. As the engine picks up speed the fan moves more air which pushes on the air vane. The vane overcomes the spring tension and pulls the throttle plate closed to keep the engine from over speeding. As you apply a load to the engine, the engine slows down which reduces the amount of air being moved by the cooling fan. The governor spring opens the throttle, the engine speeds up and the increased air flow holds the governor and the throttle plate in the new position. And so the cycle continues based on engine load and throttle position.


This is pretty much it, in a nutshell!


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## Adster (Feb 29, 2008)

Thanks everyone... new governor spring and VibraTach on order. I'll give it a shot soon as the parts arrive. :thumbsup:


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## Adster (Feb 29, 2008)

Well the new governor spring came today. Popped it on and fired up the old Bolens. Ran pretty well almost from the start. The old spring was pretty stressed I guess (as you mentioned). Then I put the VibraTach on and was amazed how simple and well it worked. I re-adjusted the carb mixture and tweaked the low idle to 1750 RPM. Then I found the high idle was a bit fast 4000, so I opened up the governor spring ring a tad and she pegged at 3700. I'm good to go. Just one more question...would it be a real no-no to run high idle at 4000 instead of 3700 on the old girl?

Thanks everybody,
Bob


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## geogrubb (Jul 28, 2006)

IMHO, if the engine hasn't been abused in the past the additional 300rpm shouldn't hurt it. Glad to see you installed a new spring. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

RPM's on lawnmowers are actually set for maximum blade tip speed of 19,000 feet per minute, and of course should not exceed the engine mfg specs. for the engine.

Your mower I believe is a 22" cut width.

To calculate blade tip speed you would have to take the length of the blade say 21" and multiply that by the engine or spindle RPM's say 3200 then take the result (for this example 67200) then multiply this by 3.14 (pie) (211008) and then divide by 12 (inches in a foot) = 17,584 Feet Per Minute.

The maximum blade tip speed as set by government standards is listed as 19,000 feet per minute.

Blade length X RPM's X 3.14 / 12 = Blade Tip Speed in Feet Per Minute.

If you want to figure out maximum rpm's based on blade size then you could do this

19000 (divided by) the result of (Blade length X 3.14 (divided by) 12) = Max RPM's

Example:
For a 21" blade the formula would look like this:
19000 / ((21 * 3.14) / 12) = 3457
It carries out several decimal points, but you can just round down for the maximum blade tip speed.

The maximum RPM's you should set a 22" mower for is 3300.


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## Adster (Feb 29, 2008)

Wowee 30YT...never been much for arithmetic, but you laid it out simple enough...I'll have to print that out for future reference. :thumbsup:

While I'm at it...how can I identify the kind of carb I have? I'd like to pick up a rebuild kit (if they are still available). 

Do you think it would be OK to spray a little Gumout through the carb throat while on high idle and maybe a little fuel cleaner in with the gas? It runs pretty smooth now for a 30+ year old mower, but could be better.


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## 30yearTech (Sep 14, 2006)

You most likely have a pulsa-jet carburetor and all the parts for it should still be available.  Sure you can spray some gum out through the carburetor while it's running, I don't think that will really do much, but I can't think of a reason that it would hurt anything. 

If it's running alright then it may be best to leave well enough alone, usually have to work on these when the diaphragm starts leaking or the fuel tank gets warped and the automatic choke does not work properly.


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## Adster (Feb 29, 2008)

30yearTech said:


> If it's running alright then it may be best to leave well enough alone


Good advice "if it ain't broke don't fix it" 

Here's a dumb question...do I have a horizontal or vertical shaft engine?


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## 30yearTech (Sep 14, 2006)

Adster said:


> Good advice "if it ain't broke don't fix it"
> 
> Here's a dumb question...do I have a horizontal or vertical shaft engine?


You have a vertical shaft engine

Just think of Horizontal = Horizon and this will help you to remember that the shaft comes out of the side of a Horizontal shaft engine and that leaves the Vertical shaft coming out of the bottom.


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## Adster (Feb 29, 2008)

OK...so the old Bolens 22" Mulcher is back in service. I have about 8500 sq/ft to mow. I've been doing this with this mower for years. I paid attention to how it ran. Low and high idle seem fine. They "sound" fine and I checked them with my VibraTach also to be sure. Only thing that concerns me is that the high idle (under actual full mowing load) seems to surge ever so slightly and my gas consumption seems a bit increased. I used to get all 8500 sq/ft mowed in 1 tank of gas. Today I ran out before I finished. To be fair, I will say that it rained 2 days ago and I would have let the grass get really dry, but rain is predicted again for tomorrow so today was it. The grass would be too long to mulch if I let it go any longer. Although it wasn't wet...I really prefer it be dryer than it was. 

While mowing I didn't smell gas in the exhaust, but I did adjust the carb last week. I used low idle (1750 RPM) found the best point between too lean and too rich and then tweaked it a 1/4 turn toward rich and left it. I'd really like to eliminate that small surging and get some better gas usage...but all in all I'm happy she's still hanging in there and doing a darn good cutting job for a mower born in the 70's. :thumbsup:

Any suggestions on how to proceed next? Thanks all.


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## 30yearTech (Sep 14, 2006)

The surging could be a small air leak in the seal to the intake tube or where the tube mounts to the cylinder. A worn throttle shaft in the carburetor could also be the culprit.

Does the choke open up all the way when the engine is running as stay open? or does it flutter back and forth?


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## Adster (Feb 29, 2008)

30yearTech said:


> Does the choke open up all the way when the engine is running as stay open? or does it flutter back and forth?


Yes, the white plastic choke plate opens up and stays open with throttle pegged at fast. The governor spring and lever assembly (not throttle cable side) move back and forth a little when she surges...which I might add is intermittent with the throttle position. 3/4 throttle is the worst.

To check out what you asked me to, I tried starting it today (cold, damp day) without the air cleaner assembly on and it was spitting gas a few drops at a time directly out of the carb straight up with every pull. It would not start that way. I pulled the plug, cleaned it of gas, and let her sit awhile. Then I put the air filter back on and after a few pulls she started very, very slowly...putt-putt-putt...almost as if she was going to stall out but then started up and warmed up in about 4-5 minutes. 

The link below is to a close up photo I took right after I checked out the carb today (engine was now shut off for the picture). It won't be up long, so I suggest downloading it to your computer if you'd like. This is the Pulsa-Jet right? Thanks for your help!



http://galleries.cigarweekly.com/Cloud9Bob/PotPourri/pulsa_jet?full=1


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## Adster (Feb 29, 2008)

Here is a link below to short movie (with sound) of the surging engine. 

1.39 MB so it may take a few minutes to download of you are on dialup.



http://galleries.cigarweekly.com/Cloud9Bob/albums/PotPourri/surge.avi


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## 30yearTech (Sep 14, 2006)

*Dial Up whats that???*

Is this the way it runs with the air filter installed?

Running it with the air filter screw out of place can cause fuel to be drawn into the carburetor from where the air filter screw goes. It's open directly into the fuel tank and without the screw in place sometimes extra fuel gets drawn into the carburetor. 

You may have a valve problem, if the intake valve is not seating good or if it does not have sufficient clearance you can get some fuel spitting back into the carburetor and you will never be able to get it quite right if thats the case.


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## Adster (Feb 29, 2008)

30yearTech said:


> Is this the way it runs with the air filter installed?


No, it runs much better with the extra resistance of the air filter in position. Just surges a little then. It also won't start very well (or at all) without the air filter installed. I found I need to start it and let it warm up completely with the air filter in position and then while it's running I can take the air filter off to check the choke or to adjust the carb etc.

What do you make of that governor spring getting tighter/looser as she surges? Is this a Pulsa-Jet as you thought? 
Should I try anything else?


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## geogrubb (Jul 28, 2006)

Doesen't this thing use the same diaphgram as other top of tank carbs, I haven't seen a model and type number so will post anyway.

You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.
Here we go;
Here we go;
Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble) with a small screwdriver pry out the main jet(carefully) and clean it, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem. Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo


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## Adster (Feb 29, 2008)

geogrubb said:


> Doesen't this thing use the same diaphgram as other top of tank carbs, I haven't seen a model and type number so will post anyway.


Hi Geo....model and type # buried in the first post of the thread.


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## 30yearTech (Sep 14, 2006)

geogrubb said:


> Doesen't this thing use the same diaphgram as other top of tank carbs


No Geo, you are thinking of a pulsa prime carburetor that has the push primer on the front of the carburetor. This is a Pulsa Jet carburetor, it does have a diaphragm but it's a little different. This carburetor has an automatic choke, the diaphragm has no gasket and is used to pump gas from the tank to a secondary chamber (much like the pulsa prime carb) but vacuum from the engine running also draws the diaphragm down and a little rod attached to the diaphragm pulls open the choke plate and holds it there while the engine is running. This carburetor also has a metering adjustment screw.


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## 30yearTech (Sep 14, 2006)

Adster said:


> No, it runs much better with the extra resistance of the air filter in position. Just surges a little then. It also won't start very well (or at all) without the air filter installed. I found I need to start it and let it warm up completely with the air filter in position and then while it's running I can take the air filter off to check the choke or to adjust the carb etc.
> 
> What do you make of that governor spring getting tighter/looser as she surges? Is this a Pulsa-Jet as you thought?
> Should I try anything else?


It should start just as easy without the air filter in place. The surging can be due to many different reasons or a combination. It may in fact be time to replace the carburetor diaphragm, you may also have low compression and as old as this engine is I would not be surprised to find valve issues with it. Air vane type governors tend to be a little sensitive so a little variation in rpm's is nothing to be concerned about 100 or so rpm won't make much difference in overall performance.

If you decide to replace the diaphragm, when you take the carburetor off of the fuel tank, pay special attention to the area where the choke portion of the diaphragm is (th part with the little spring attacthed) if there is any fuel at all in the well where the spring sits, this could indicate a warped fuel tank. There is a special kit with a little pin and teflon washer to help out with this.


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## geogrubb (Jul 28, 2006)

Sorry 30yr, it was a quick guess that I keep as a rough draft. I learn from you. Have a good one. Geo


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## Adster (Feb 29, 2008)

30yearTech said:


> It should start just as easy without the air filter in place.


But it sure made a heck of a difference today. :freak: 

Would any of the reasons you gave (low compression, bad diaphragm, tank warpage, etc.) cause harder starting (or no starting) with the air cleaner off, but allow pretty good performance when on???


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## 30yearTech (Sep 14, 2006)

Adster said:


> But it sure made a heck of a difference today. :freak:
> 
> Would any of the reasons you gave (low compression, bad diaphragm, tank warpage, etc.) cause harder starting (or no starting) with the air cleaner off, but allow pretty good performance when on???


It's possible that all of the situations I listed "could" cause this problem, also if the carburetor is just adjusted a "little" to lean.


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## jsouth (Jan 31, 2008)

Go to any auto parts store and pick ypu up a can of seafoam,and put a ounce in the gas tank,do this every once in a while,and you will be good to go.

Jerry


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## jbrow1 (Aug 18, 2005)

Good thread. I was just looking into governors the other day and didn't find much. 

I ended up switching the gas tank/carb from an older mower onto my say 3 year old push mower and she's good to go now. Just have to set the full throttle so it doesn't grenade itself. :thumbsup:

Good info guys, thanks.


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## santa (Jul 14, 2008)

Sorry I'm late to the party,

Look I saw your picture, the problem was right there in your face. The spring was installed incorrectly. This is very important, believe me, I did the samething.

OK, you need to install the loop on the throttle side so that it is vertical. The end of the loop needs to be on the engine side, pointing up. 

Does that make sense? 

On the Air Vane side, the loop will be horizontal with the end of the loop on the bottom of the spring. Its very important to do it this way or the governor won't work correctly.

BTW I got this from a old briggs and stratton repair book that you can still purchase today. It has some great pictures, but I saw this info online as well.

-paul 




jbrow1 said:


> Good thread. I was just looking into governors the other day and didn't find much.
> 
> I ended up switching the gas tank/carb from an older mower onto my say 3 year old push mower and she's good to go now. Just have to set the full throttle so it doesn't grenade itself. :thumbsup:
> 
> Good info guys, thanks.


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## dawgpile (Apr 28, 2008)

Look at the attached pdf. It is what the previous poster was referring to and it comes from the B&S service manual. It shows how to remove and install the gov spring on your engine. Hope this helps!


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## collarman2 (Dec 14, 2009)

*NEED help*

hi i have a 4hp B&S 110998 cant line up timing marks


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