5hp B&S Ind/Comm on a Sarlow mower...carburator question...

[jsflynn603]

Many years ago I rescued a Sarlow 24" self-propelled mower from the dump. The mower blade shaft/bearing was gone, and the engine appeared seized, but it wasn't... some patience, $60 for a bearing assemply and Marvel mystery oil in short order it was up and running has been for over 5 years now.

It runs beautifully, often starting on the first pull but lately it's been doing something odd, it's cycling rpm-wise, high, low, high low... On the carb there is something that has two springs and whatever that is is moving back and forth at about a two second cycle. Worse, it causes the pull rope to somehow get stuck and start to screech. (Note: Recently it was doing this, so I took it apart and cleaned off the small balls and did NOT lubricate, so this seems odd--the balls were free wheeling two weeks ago.

I'd love to simply buy a new carb but I doubt that is possible. Perhaps someone can give me an idea, why there are two springs (one very thin, and one thicker) what attaches to the thing that moves back and forth. Even with a hint, I probably can fix it.

The engine is model 131782 type 3125-01, vertical shaft with a PTO--so very expensive to simply replace. The Sarlo hi-wheel is a real workhorse, and I use it to mow 1+ acre of fairly rough lawn.

Perhaps someone can point me in a direction that explains what that connector to the carb does, how it works...?

Any ideas would be greatly appreciated.

Btw...the carb is totally cleaned--no gunk or varnish in it.

Thanks,

Steve

 

[ILENGINE]

From the parts diagram it looks like there is a spring that loops around the throttle linkage and is attached from the governor arm to the carb throttle shaft, so purpose is to keep slack out of the linkage. the other spring is the governor spring which is used to increase the engine speed. Now to the solution, you have some sort of debris or blockage in the idle ports of the carb which is causing the surge. Probably doesn't surge under load does it. The only fix may be to replace the carb, since most of the newer carbs have passages that are impossible to clean. I would disassembly the carb completely and spray carb cleaner through every hole you can find and that may fix it. If not replace the carb.

 

[jsflynn603]

From the parts diagram it looks like there is a spring that loops around the throttle linkage and is attached from the governor arm to the carb throttle shaft, so purpose is to keep slack out of the linkage. the other spring is the governor spring which is used to increase the engine speed. Now to the solution, you have some sort of debris or blockage in the idle ports of the carb which is causing the surge. Probably doesn't surge under load does it. The only fix may be to replace the carb, since most of the newer carbs have passages that are impossible to clean. I would disassembly the carb completely and spray carb cleaner through every hole you can find and that may fix it. If not replace the carb.

Thank you. I disassembled the unit, and couldn't find anything amiss, but there is no fuel filter, where there should be an inline one, so what you say makes sense.

This carb is from the 70's, and in the past I've been able to spray cleaner, and using a tiny needle to clean out all the passageways, when I found it the carb was a mess, after cleaning it, it was fine.

I'll try what you suggest, thank you.

Btw, can a carb be purchased for such an old unit? I don't even care if it is the same, as long as it is mountable, so the carb to the engine mounting must fit. I'd love to purchase a new carb, know where I could possibly buy one?

 

[ILENGINE]

The part number for the fixed jet carb is 490886 and the adjustable jet carb is 490934. Both are available through any Briggs dealer. Stocking at certain parts warehouses may be limited but both are available for them to order through east coast distributors.. Suggested list price is $65.62, but is subject to local pricing changes.

 

[jsflynn603]

The part number for the fixed jet carb is 490886 and the adjustable jet carb is 490934. Both are available through any Briggs dealer. Stocking at certain parts warehouses may be limited but both are available for them to order through east coast distributors.. Suggested list price is $65.62, but is subject to local pricing changes.

Many thanks, you may have just saved me a grand! I was thinking that one could not buy a carb for such an old engine, and the PTO on a vertical shaft motor would probably cost me $500+, the mower still rocks--and almost all problems come either from the carb or the pull thing.

A few questions if you don't mind Ilengine...

What's the difference between a fixed jet and adjustable jet and which would you recommend?

Does a carb come with an air filter assembly, or must I purchase that one separately, or will the carb be identical to the one that is on that engine?

I'm gonna take the carb apart and see if I can clean what is blocking it...

Again, many thanks!

Updated question: Please ignore the air filter question, I took it apart again and see that the carb is separate from everything around it, so that a replacement would just fit back with the existing parts.

Updated again ~5PM. I pulled the carb off, and used a 3cc/23ga needle, and sprayed inside all fuel-ways. Everything is clear, there is no blockage.

Put it back together, started right up, then within 4 seconds, it started surging with the arm that goes under the flywheel moving back and forth, faster and faster until the rope inside the pull started gets somehow hung up and something starts to screech. I stop it, pull on the rope which is hung up a bit on the inside, pull it out, but then it retracts smoothly.

What is that "arm" which goes under the flywheel? Is that a centrifugal governor? Could something be wrong with wherever that goes, under the flywheel?

Aarrgh.... I've pulled it apart three times this weekend, well, at least I'm getting pretty good at that.

Any suggestions? I'd hate to buy a new carb just to find the same problem.

Thanks