OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Issues with my newly restored SB45

Hi All

I have 2 new issues with my newly restored scott bonnar 45 with the original b/s 2.5 hp motor after the second use.

1: I have melted the thrust pad for the clutch.
Why would this have happened?
I changed the spring in the clutch so now the clutch is a lot tighter.
I didn't change the cork however as it seemed to me to be all intact still.
could it be heating up to much due to friction? it was almost to hot to touch.


The second problem I have is with the engine.
When I pull my pull cord there is often no resistance on it. but if I turn the clutch a small amount then I sometimes can get resistance so i can start it.
When the mower runs it is a lot smoother than before.
During the restore I removed the carbie and flushed it, removed all the covers and removed the top of the engine and cleaned about 3mm of caked on black stuff off the inside of what I suppose is called the head cover.
The gasket seemed to me to be still good to my untrained eye.

Thanks guys

The clutch question I'll leave to Deejay to explain. On the engine question it appears that you have almost no compression, probably due to one of three causes: extreme wear to the piston rings; a severe leak of the cylinder head gasket; or a valve not closing fully, perhaps due to foreign matter lodged under its sealing surface. There are other possibilities, but they are less likely (a broken piston crown, or a camshaft timing error).

Thanks grumpy,

What would you recommend my course of action should be?

The mower it self is a lot faster than before I played with it, and it is some what quieter than before too, would a cylinder leak be quite loud?
When I get it so the spot where there is resistance on the pull string it fires first or second pull, and runs till I stop it.

Head gaskets are easy to source, should I start there?

When you pull the rope is the crankshaft turning or is the starter slipping?

Na Joe the crank shaft doesn't spin at all, so I guess the starter is slipping.
There is literally no resistance.
Until I manually turn the crank shaft to find a sweet spot

Thanks for asking the right question, Joe. Suddenly the size of the problem shrinks by 90 percent.

That sounds good grumpy, but what does that mean?

There is no known internal problem with your engine, your recoil starter is simply acting up. First, please post the long string of numbers stamped on the cooling air cowl of your Briggs engine (Model, Type and Code). I'm currently guessing the Model is 80202 and the starter looks like this:


The internals of that starter look like this:


The starter engages and disengages by the use of 5 sprags: inclined planes, with balls that roll up them to jam between the internal and external inclined planes. Over time, sooner or later the central bearing will need to be cleaned and have one drop of oil applied, but unfortunately someone will either put oil in the whole thing, or spray it with WD40, thinking that will help. It won't: the oil will oxidise, forming glue, which will stick the balls in their storage compartment, so they fail to roll up the planes when you pull the rope. When this happens you have to remove and dismantle the starter, clean all traces of oil and glue from its innards, dry it off, put one drop of oil on its spindle, and put it back together. It should then be trouble free for years.

Here are the detailed instructions:
http://recoveryvehicles.tpub.com/TM-5-4240-501-14P/css/TM-5-4240-501-14P_161.htm

At the top of the page you will find Back, Up and Next buttons. 161 is the first page, so you'll need to go forward through the section by using Next repeatedly as you progress. If you have any problems, just ask us.

Thanks grumpy,
Sounds like something I might have caused when I flooded it with degreaser trying to clean it up.
You were very close with your model guess



Well I guess its back up on the saw horse and start dismantling again, with lots of photos. At least it sounds like I wont have to buy any new parts.

Your engine was made on 30 September 1975.
Here is its illustrated parts list:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6jmvGVJ1DajI.pdf

Here is its operator's manual:
http://bsintek.basco.com/BriggsDocumentDisplay/lrvvA-wU7eL7hAxB91ObQ.pdf

The important differences between the 80102 and 80202 relate to the carburetor and choke, and the engine kill switch. The 80102 is almost the same as the smaller 60102 which I think was used on the smallest of the SB45 mowers. I find that choke infuriating, I always have to start them chainsaw-style (it rich loads and stalls before I can push in the choke, after a cold start, so I have to start it twice). However the engine should be just as reliable and durable as other old Briggs engines.

I won't confirm that you don't need any parts: you are going to have to buy a new plastic thrust washer for your clutch, and perhaps another part too, to get it working properly. However that is Deejay's line of country.

Thanks so much grumpy, you guys are amazing on this site.

Yeah the choke is very annoying. But then the motor is 8 years older than me and still going strong.
I've dissembled the starter clutch and wiped it all out, there was a little black stuff inside so I wiped it all out and put it all back together with 1 drop of oil.
Just turning the shaft by hand it seems to be good and grabbing straight away.
I wont be able to tell for sure till I replace my other issue and fire it up again.
Also is there supposed to be a rubber washer or something on the oil filler plug? Mine seems to leak a bit which is noticeable on my nice new looking mower.
Thanks again grumpy

No, there is no washer. The filler plug is made of nylon, with two pins projecting upward from it. You put a screwdriver diagonally across the two pins with its handle more or less horizontal, and tighten the filler plug by pulling the handle sideways with a few pounds force. Then it doesn't leak. It will leak if you just do it up finger-tight.

Ha thats 2 from 2 for you,
It was done up finger tight.

On inspection of a parts list I have noticed that there is supposed to be a washer between the clutch cone and the thrust pad. I do not have one.
I've searched around a few sites but no one has a washer that matches that part number.
As ive melted my thrust pad im thinking that might be important, although maybe not the sole issue.

We need to get Deejay on the case. My concern is that your thrust bearing (a ball race inside the clutch) may have failed, which could be the source of the heat which has melted the plastic thrust pad. However the whole clutch needs to be assembled and adjusted strictly in accordance with the SB instructions, or expensive damage may occur (SB parts are not all that cheap). Because you have had a problem with it, I think the clutch will need to be disassembled, inspected, and set up correctly. Deejay has experience with that, including rebuilding his own clutch in detail just a few weeks ago.

Hi to grumpy and Dunks, there is no washer between the thrust pad and clutch cone. The fact that this plastic pad melted is due to incorrect adjustment of the clutch fork assembly.
There is supposed to be a slight clearance between the pad and the cone....the only time the pad fully contacts the cone is when the clutch is being disengaged.

I have to go out now, but when I get back I will take a pic of mine and explain how to set it up properly. The pad is available in the online store.

Dunks, can you clarify this statement please:


It sounds as if you are saying you replaced the correct clutch spring with a stiffer, and/or perhaps longer, one. That might be a problem. Can you tell us exactly what you have done please?

I replaced my clutch housing as when I pulled my mower apart and restored it, I discovered it was no where near 5/8 anymore. It was about 2mm off.
The guy I bought the clutch off advised me to replace the bearing inside and the spring as well, he fitted the bearing for me.
As far as my statement the clutch feeling tighter, before I changed the clutch parts when the clutch was disengaged my reel would still spin slowly, which I have since worked out must have been from the spring not being 'springy' enough to fully disengage the clutch. Even though I had tried to adjust it

It may have melted from what deejay said, when I fine turned it I wasn't paying attention to whether the cone was making contact with the thrust pad, I was just trying to find the sweet spot where it both engages and disengages.

Hi Dunks, here is a pic of my machines clutch thrust pad, clutch cone and the clutch fork in the engaged position:

As you can see, there is a few thou clearance when the clutch is fully engaged....also the hole on the middle of the thrust pad is to place a few drops of oil to keep the shaft lubricated....also the clutch cone itself has an oil hole for the same reason.
Do not over-oil, just enough to keep the shaft wet.

And before you ask, no, the oil cannot, by the design of the clutch cone, ever reach the clutch lining.
Here's a pic of the clutch disengaged....


As you know, the fine tuning is done by the screw and locknut on the clutch fork underneath the thrust pad.

Thanks deejay,
I never oiled those 2 spots when I reassembled either.
So is it normal for the clutch cone to get quite hot?

The melting of your thrust pad was caused by friction...ie. the clutch cone rubbing hard up against the plastic.
And no, I have never had a reason to put my fingers on the clutch cone after mowing, engine stopped of course...but I should imagine it would get warm but not hot enough to melt plastic unless something was drastically wrong.

A word of caution: Do NOT place you fingers anywhere near the clutch assembly whilst the engine is running.