OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Model 45 - Service Needed

Hi all,

First post. Great information here!

Watched a youtube video from Deejay last night which inspired me as I've been desperately trying to set aside time to fix a couple of issues with my Briggs & Stratton 3HP SB Model 45.

My gear lever to engage the reel operation stopped working a while back, so I've just been firing it up with reel engaged. Hope that's not bad. I'd really like to fix it myself, and assumed it was the plastic thrust cap which has deteriorated. After removing the engine bolts, I can't work out how to knock the cotter pin out. From the video, I've unscrewed the nut to the top of pin, then tried hammering down as shown, but it doesn't want to budge. How much force do I use?

This is just round 1 of what i'd like to get an answer for - but I won't push my luck just yet

Thanks in advance,
Stew

Hi Stewart,

Firstly a big warm welcome to the ODK Forums

Your issue can be a multitude of things, but as you say we'll tackled one thing at a time.

Starting the mower with the clutch engaged will have an absolutely dramatic affect.............................on your arm , nothing else so no issues there.

Could you please take a shot of the thrust pad side of the clutch before you remove the assembly and post it here ?

As far as the cotter pin is concerned, you can't take it out until you've taken the clutch assembly off the PTO shaft of the engine, only then will it slide out as the cotter is an interference type item that acts as a wedge against the shaft.

As far as your engine is concerned it is a replacement for a Series one Scott Bonnar that you have there. Your original engine would've been a Kirby HK25.

Anyway your engine was manufacture on the 20th of May 1988. It was made in Briggs' Plant 3, their engine plant at Rolla, Missouri.

Cheers,
BB.

Hi BB,

Really appreciate the response, and thanks for the welcome

Yes, it has been a little heavier to start ha!, but I'm glad I haven't been doing any further damage **phew**!

I just went out to the shed and took a couple more pics, and one of them is on the thrust pad side (sorry, the picture is with the motor off). The shaft has a few knocks in it and wobbles against that rubber housing to the chain drive, and as you will notice, no thrust pad

Just to clarify (sorry, not as mechanical as I'd like to be), I can't actually get the clutch assembly off the motor shaft. I assumed it was because of the cotter pin not down far enough, but maybe it is and the clutch assembly is "stuck"?

Just inserted a couple of photos of the chain drive, which to me looks in need of love - but only you gurus could tell me for sure.







Thanks again &

Stew

Ok some updates to this... I've been learning about my mower and playing Removed chains, inspected and cleaned. All good.

Made a decision to get the reel and bedknife sharpened, since I'll get the clutch sorted at some point anyway, might as well make the disassembly worth while

Taken reel sprocket off, removed right side bearing cover screws, gone to do the left side and they're tight as. I've done some searching around on here information wise, and most things lead to taking the mower to professional or try use heat - or hole punch hitting into it counterclockwise. I seriously don't want to kill these screws so if there's anything I've missed?

Thanks
Stew

Hi Stew,

This mower hasn't done a lot of work as can be clearly seen by looking at the cutter sprocket. It's very very good considering the usual ones I get to see.(cutter sporocket that is)

You didn't supply us with a thrust pad photo, just the shaft which has a few strange vice grip type marks on it.

As far as the bearing carrier halves are concerned, this is one of the only places where I use a hammer.

Place a screwdriver that fits the slot in the head very snuggly without any slop and while pushing down very firmly and applying anticlockwise twist, tap the back of the screwdriver rather firmly also ensuring that the screwdiver doesn't slip out of the slot which would flare out the edges of the slot, something we don't want to happen. Keep tapping until it comes undone which it will. Apply some "Penetrene" or "CRC C56" prior to starting the process of undoing these set screws.

As far as the clutch assembly is concerned before you remove it from the PTO shaft can you tell me whether it rotates without any wobble at the outer circumfrance as you pull on the rope starter gently so that the engine doesn't start. If it rotates straight then your clutch half will be reuseable if not then a replacement will have to be sought.

Your clutch half is the original unit which is made from cast iron. These are usually the best units made and if the cotter has beeen kept tight there shouldn't be any wear in that area. To remove the only way is to use a larger 3 jaw puller. These are available from Asian type tool shops and won't be that expensive and you'll use it later on in many different applications.

Also again apply some "Penetrene" or "CRC C56" before attempting to remove it. This is always good practice in mechanical engineering.

If you have any quieries don't hesitate to ask, no matter how large or small the issue is.

Cheers,
BB.

Hi BB,

Was so glad to see your response yesterday, thanks a lot.

Reading your opinion on the mower's drive sprocket, and that it is in good knick is great news as i was really hoping you were going to say that

So, the thrust pad photo - yes, the reason i couldn't give you one of them is because there is no thrust pad - just the fork. I gather this is a major contributor to drive reel not disengaging.

Thankfully, following your advice, those screws came out (mainly thanks to the hammer and right screwdriver as you suggested). I'll need to buy a couple of new screws as i've damaged them using a poor screwdriver earlier. You live and learn

I checked the clutch using the pull rope process, and it's straight as a dye. Purchased a cheap 3 arm gear puller, and the clutch half has come off PTO now - Didn't realise how stubborn it could be could be to get off! Checked the cotter pin, and again, was in great condition.

Had some fun taking the clutch assembly apart to check cork, spring etc. I don't know exactly how they're supposed to look, so i'll try find some more information around here to help me before putting back together. Feel free to chime in if you want.

The reel has been taken to local mower shop to be sharpened, but the bedknife needs to be replaced. Should get it back tomorrow

Will post some photo's here of before and after just incase anyone will find it interesting.

Here are the before's






Till next time!

Cheers,
Stew

Hi Stew,

Well no thrust pad takes out about 5 mm of throw length and thus your clutch was never disengaging. I can't understand why it's not there. I reckon that when the previous tenant of the machine did the engine swap that they forgot it and thought bugger it I'm not going to pull it all apart again. Your original one was a brass unit but they've since been replaced with a black plastic replacement. You'll have to buy yourself one and install it on assembly, they're not expensive.

As far as the spring cork and bearing are concerned you'll find nothing wrong with the spring at all, the cork only needs to have around 1.5mm to 2mm of thickness on it to be OK and the bearing I would submerge in petrol to wash out while spinning it, then dry it out thoroughly and then submerge in oil for about 5 minutes. Pull it out and try to work out all the excessive oil as you don't want spare oil being flicked out inside the clutch housing as that will work against you.

Those cast iron clutch housings are like GOLD and you want to move heaven and earth not to have to move away from them and go to a die cast unit if you can help it.

I must admit that I would've thought that the bed knife could've gone another round after re-grinding but it does look rather thin on one end.

I'm glad that I've been able to help you with this one, but that's what this forum is all about.

Cheers,
BB.