OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines My Scott Bonnar 33... Kirby Engine - wazzbat

Hi all. I am a new member and after purchasing a SB today then googling to find out about it I came accross this forum. I love how passionate some people are about lawnmowers. I'm inspired to find out more about my beast so I can take good care of it and perhaps replace a few parts if ever needed. I will post some photos when I get a chance but the badged model number is 33 11532 and it has a Tecumseh HK 25 engine (spec J1005/Serial 8074 4980) but the fuel tank says 'Scott Bonnar 2.5 HP 17" Model 45'. So I am guessing either a different fuel tank or engine has been fitted to a 33 series SB?

I guess I am curious as to the age of my new toy and also, if the engine packs it in, how much to replace with a new one and how hard is it to do myself? Keeping in mind I have little (or no) mechanical knowledge but am quite competent when it comes to handyman type work (I'm a sparky by trade in the construction industry).

By the way, I paid $350 for the SB and I'd say the mower itself is in excellent condition for it's age including the catcher but the engine is looking a little worn. It starts after a few pulls and when it warms up it sounds OK but it sort of purrs in waves. The guy I bought it off just spent $230 (have receipt) on it having the blades sharpened and set and a general tune up etc. When the blades are engaged it sounds quite loud like the blades are scraping against the bottom blade. Is that normal??

Anyway, any help would be greatly appreciated and I look forward to reading your replies. Cheers.

aboard wazzbat and I am sure that we will be able to help you with your enquiry. Deejay (Darryl) is our Scott Bonnar addict here and I am sure that he will offer you help with both pictures and what he has done to his Scotty.

The model that you quoted is a 33 as the 45 came later after Rover bought Scott Bonnar. We do have the parts list for that model in the parts list and manuals area of the forum.

As to the motor that Scott Bonnar used, the Tecumseh engines were one of them. I would assume that the tank or complete motor was taken from one of the first 45 model Rover/Scott Bonnar's mowers that Rover made after the take over.

I hope that this is of some help but once Deejay sees this post he will jump in and reply with some more information.

Once again to the forum.

Your description of the engine purring in waves sounds as if it may be hunting slightly - that is, the engine speed varies cyclically, with probably about 2 or 3 seconds length of cycle. If it is doing that, the carburetor mixture adjustment screw probably needs to be turned anticlockwise about an eighth to a quarter of a turn, but if you are not familiar with these engines it might be best to get the problem a bit clearer first. Find the mixture screw anyway - and note which is the mixture screw and which is the idle speed screw. The idle speed screw is on a lever and it holds the throttle butterfly slightly open when the speed control is at minimum setting. The mixture screw sticks out from the carburettor body. Both of these screws have springs under their heads to keep them from moving due to engine vibration. You routinely adjust the mixture by running the engine at normal grass-cutting speed and finding the rich limit (turn screw anticlockwise) and the lean limit (turn screw clockwise) until it runs slightly poorly in each case, then putting it halfway between those two limits. If this procedure doesn't work, always put the screw back where it was in the first place while you figure out what has gone wrong: don't adjust various things in succession and leave every one of them messed up.

Hi wazzbat, and a big warm welcome to the forum, it's great to have another Scotty afficianado onboard.

In order to help you effectively, it would be handy for you to post a pic of your machine; (we all like to see members pics) and it will assist in identification and approximate age.
From the badged model number you supplied, I am guessing it would be at least 30 years old, as the Model 33 was the precurser to the Model 45 and are quite similiar in many respects. I have incuded the only pic of a Model 33 I have as well as one of my 45 for comparison (mine has be re-engined with a Honda G100 2.5HP).

For uploading pics I use Photobucket, (free down load) and the instructions on how to use it are posted in the "Board Help Area", in "How to use the forum features" sub-forum page 2, How to upload using Photobucket. You can also resize and edit your pics.
The very first post by Bruce in the "Help" area will instruct you on how to 'access the Parts List and Manuals' area, as a manual will come in handy if you require parts.
Hope this has been some help for you, and we look forward to seeing your pics.
Once again

Wazzbat, it sounds as if your fixed blade has been adjusted recently by an expert, so it should be OK. There has to be slight contact between the rotating cylinder blade and the fixed blade to cut grass properly, but the contact should sound smooth: a sort of hiss. If there is heavy scraping or (heaven forbid) clanking, the contact is too heavy. Adjusting the fixed blade to get the right contact is a bit tricky, since it has to be adjusted on both sides of the mower, rather carefully. Because both of your blades have just been rather expensively resharpened, I suggest you study the subject a bit before attempting adjustment. Heavy contact ruins all that sharpening work in a fairly short time.

Thanks everyone for your replies. I'm not sure when I'll get time to upload photos but I will definately do it asap. And I'm keen to get a hold of the manuals/parts list.

Grumpy - Cheers, that's what I was a bit worried about (the blades going blunt quickly). I don't think the noise is all that smooth. I have a slight problem though. I don't have any lawn! Well not yet anyway. I'm rolling down some Zoysia this weekend coming (hopefully not in the rain). After that, I'll be able to give it a good run and have a closer look at it. Unfortunately I don't have a whole lot of spare time at the moment though. I will keep everyone posted.

Cheers. I will give that a go when I get time.

I had a go at adjusting the mix screw and the throttle screw and seemed to have found a pretty good spot for both but I think the problem is the bottom spring on the throttle assembly. It is well worn and I think what is happening is the vibration of the mower losens then tightens the spring/cable, therefore self adjusting the throttle speed. I'll have to searh for a new screw I think. Also the wire from the butterfly to the springy thing looked a bit dodged up. Sorry bout the explanation but like I said in an earlier post, motors aren't my strong point.

As for the blade, I fiddled around with the screws and have managed to get a nice "wizzing" type sound rather than a scraping sound. Looks like the $230 service was a total rip off. They could have at least replaced the old spring. Thanks for your help.

From your description it sounds as if that spring and wire link on the carburetor you mentioned are the engine's governor. Any friction or slight stickiness in the governor will cause the engine speed to hunt, in the same way that lean mixture often does. I don't know if you need new parts or just to carefully align the ones you have so they don't cause any binding. Comparing them with new parts (or drawings of new parts) may be the answer.

Ticked her over again today and still had a bit of trouble getting her to purr nicely. Infact I couldn't get the bloody thing to stay running at all. Then after a closer look, I found some more evidence of a dodgy service job. The fuel line out of the tank was kinked in 2 spots because it was cut too short (or they just used a cheap and nasty peice of tubing). I don't think that was helping the problem. I've managed to do a quick fix for now by turning the fuel tank around. The pull cord also broke a couple of times.

You can make a simple check on the fuel getting to the carburetor by disconnecting the fuel line at the carburetor end, positioning it close to the normal carburetor connection, putting a cup under the end of the hose, and turning on the fuel tap. If it runs a decent stream, you can eliminate the upstream bits like the line, tank, tap and in-tank strainer (if it has one).

If you have fuel to the carburetor, you could check a couple of basics like compression, spark, air cleaner and governor. You already said that visually the governor looks damaged, and this needs to be sorted out immediately. I don't like the sound of it taking several pulls to start: it shouldn't. And why did the pull cord break?

I've tried downloading some photos of my mower via Photobucket. I think it worked. I tried some close ups of the carby so you might be able to see what I'm talking about. If you click on this link it should take you to my post in the photos section of the forum. I'm still learning how to use the forum so I hope the links work?

On another note, does anyone know how much it would cost to replace the motor on my scotty with a new B&S or Honda engine and where I could get one from in Perth and/or where I could get it fitted?

wazzbat, I don't see any close-ups of the carburetor area.

Sorry Grumpy. They were in my photobucket but have only just worked out how to upload pics to the post. Theyre not the best/clearest but try these ones anyway...

This is of the dodgy old spring on the bottom


And this one from the top



And an overall view

That looks distressingly like the engine on an ancient 4 stroke rotary mower I bought (very) second-hand in about 1970. It was hard to start and didn't run very well, like yours - might be the horizontal version of the same engine (I never liked mine enough to remember what kind of engine it was. There was nothing wrong with it, but it ran like a POS. It even set fire to its own air cleaner once. I foolishly put it out - would have been more fun to watch it burn.) On yours, one of the governor springs seems to be trashed. It now thinks it's four different springs in series, each with different characteristics. It started life as a close-coiled spring, as the left-hand end of it still is, but somebody stretched it several times until it yielded severely. It won't work properly in that condition. It can be replaced by any close-coiled tension spring with the same free length and the same 'rate' - that is, how hard you have to pull to stretch it say one centimeter. Standard handyman stuff. BTW, you measure the free length by taking it off, squeezing it until it is close-coiled, and measuring the distance between the two end loops. Usually you can't get a spring the right length and you have to cut and reshape one end of a longer one. Meanwhile that crook spring could be causing all the problems you have described.

Edit: The engine in the pictures is a Kirby Lauson (Australian-made Tecumseh/Lauson).

Just visited a local mower shop and they said it wasn't worth replacing the motor on a Model 33 because they have problems with the clutch and once it's gone, you can't fix it or get a replacement for it. He said he would do it for about $400 but he wouldn't recommend it. He said it would be throwing good money at something which might not last too much longer. I was a bit dissapointed. Is this true or is there a way of fixing a stuffed clutch on a 33? Surely you could get one made? I have no idea how they go together or what condition mine is in. It could still be quite good??? Haven't pulled it apart for a look yet.

I'm all good for now anyway. The motor seems to be running very smooth now I spun the fuel tank but who knows how many hours she's got left in her???

Hi wazzbat,I have just had another look at your pics, and your machine is in great nick for it's age and properly maintained it will outlast all of us!
I think the guy at your local mower shop obviously doesn't know a lot about Scotties. Most parts are still available if you know where to look...(other than catchers for the early models)... but most mechanical bits can still be sourced.
If there was a prob with your clutch (and I'm presuming it is the cutter clutch we're talking about here) you could easily retro-fit a Model 45 clutch and engine shaft if necessary
P.S. if the clutch is ok at present, don't disassemble unless you really have to.
Was the $400 he quoted you for a brand new Briggs?
I am sure Bruce will have a comment here; over to you mate!!

Hey Deejay

Yep I did ask what engine and he said it was a B&S. He said it would be a little bit more for a Honda. I didn't ask what size or model but I thought the Honda would have been cheaper? But again, I am a novice. Maybe the B&S was a smaller capacity than the Honda he was thinking of.

He was trying to flog me off a locally made cylinder mower with a Honda for $1750 though. It looked OK but one thing that struck me as looking rather cheap and nasty was the clutch cover. It was held on by little wafer head tech screws. And the paint job was a bit chippped. I was just imagining what it would look like after a couple of years. I was thinking for that price, I would surely be able to restore my 33 to mint original condition 3 times over? Clutch Smutch!

What are the clutches made of anyway? Why would it be so hard to get a hold of one or get one made? I too was assuming he was talking about the clutch to engage the blades. I was pretty keen to take it apart and have a squizzy but if you reckon it's not a good idea? If the clutch did poop itself, would the blades not engage or would the blades always be engaged? Because I did look at a mower where the blades couldn't be disengaged. A model 45 and he wanted $650 for it by the way?

On a another note, I noticed someone on ebay selling after market/handmade catchers for SBs. All painted up and schmicko looking and they were about $100 and made of 2 or 3mm plate or something like that.

Peace

I agree with Darryl - if you replace the wrecked governor spring, you should be good to go for a long period: I couldn't kill my similar engine, much as I'd have liked to. If you keep the correct amount of clean oil in it, you are more likely to get irritated by it not running as well as a B&S than you are to have an irreversible breakdown. Watch for blue exhaust smoke; if that happens you probably need new rings. Mine also liked to drip a bit of petrol from the water-drain button under the float bowl. It may have developed a boot-print or two here and there as well, due to my general state of dislike of it.

One day you may find you've accidentally acquired all the information you need to do a good clean job of fitting a B&S engine yourself, and you may want to do the conversion for personal entertainment. However you also may become fond of the thing as a sort of pet antique; if so you'll want to keep the orignal engine and restore it to its original lack-of-glory.



As this topic is now over 12 months' old it is now LOCKED.
Please contact a moderator for it to be unlocked.