OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Advice needed re newly acquired SB45

Hi guys

I have just bought a SB45 17" Engine ID 80102-0224-01 73061801
It would not start when I bought it but the seller told me it was due to stale fuel (come in spinner! ... I know!!) All photos are at the bottom of the page.

Anyway, I paid a courier to deliver it to me ...unbeknown to me, he laid it down for transit ...but I suspect that just put the boot into what was already a dead duck.

When it arrived:
- I drained and changed the oil (SAE30) (although could only do air temp change due to failure to start)
- Siphoned out old fuel and replaced with fresh unleaded
- Cleaned air filter as per maintenance instructions
- Gave unit a very light exterior clean up with WD40 lubricant
- Replaced chain case screw (one was missing)
- Did not replace spark plug as existing one looked new
- Trawled your very informative forum for tips
Once I had done the above I tried to start it - to no avail. My Lawn mowing contractor co-incidentally arrived this morning so had him try to start it. No good! He checked the spark - no spark. The attempts to start have also caused leakage from the choke (see photo)
My lawn guy suggested I take it to mower shop to get it fixed but that will turn a cheap mower into an expensive one. I dont have experience with engines - I'm just a lady with a can-do attitude. I did have a SB45 I inherited from my Dad years ago but sadly gave it away when I lived in a unit. It was beautiful and gave not trouble - even with the Kirby engine :-) I replaced the pull start component at one stage and that was very easy. Changed the oil myself but left the rest to the shop. But this is a bit more complicated and if I can do it myself I would like to. From what I have read in your forum the carbi sounds like it might need attention. If one is methodical (and very careful) is it possible for me to do it? What else is contributing to the lack of spark do you think?

I notice the engine mount is cracked and has seen prior rectification work. Im not sure to what extent though. The engine clutch body does not seem to be original. I wonder if the cracked engine mount was responsible for this? I also notice the spark plug and throttle cable have been replaced (it would seem recently) I wonder if these were done just prior to giving up with a "terminal" prognosis. The front roller seems to have a gap in the end caps where it sits. Will this be a problem?

I loved my previous mower and hope I can get this one back to a reliable machine which provides a very good cut and starts first or second go. I really look forward to your sound advice.

Many thanks & best regards
Jen

Hi Jen, welcome to Outdoorking.

That is a serious crack in your new SB45's front frame rail. At this point I do not know whether it has been repaired from underneath the hollow rail. If it has not, it will need to be repaired before you can use the mower - it is not safe to use it in that condition.

There is no reason you cannot get the engine going yourself if we go through the process together carefully. You may run out of patience or determination along the way - I cannot predict that, and wouldn't if I could, but if you stick to it, the job is doable.

As a beginning, here is the Operating and Mainteance Instructions for your mower's engine, which you can download free from here:
http://bsintek.basco.com/BriggsDocumentDisplay/lrvvA-wU7eL7hAxB91ObQ.pdf

Here is the Illustrated Parts List, also a free download:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6jmvGVJ1DajI.pdf

The engine was made on the 18th of June 1973, and is most likely the original engine fitted to your engine in the Scott Bonnar factory in Thebarton, a suburb of Adelaide. That would mean your mower was probably manufactured at about the end of 1973. Our Scott Bonnar guru Deejay will tell you more about the mower when he can, but he is involved in some family matters at present and is focused on those.

I suggest that you read the Operating Instructions first, that will help you to get focused on how to look after the engine after you get it going. The Illustrated Parts List (IPL) will be referred to repeatedly as we move forward with this, along with the Briggs and Stratton Service and Repair Instructions 1984, which you can view free page by page here:
http://recoveryvehicles.tpub.com/TM-5-4240-501-14P/css/TM-5-4240-501-14P_78.htm

It is a very long book - a couple of hundred pages - and I will help you find the right page each time we need it.

For the present, I suggest that you read the above operating instructions, then remove the vertical screw in the top of the air cleaner and post a picture of the urethane foam filter element you will find under the top cover. It may have become completely soaked in oil due to the mower being laid down in transit.

Hi Grumpy
I opened the air filter immediately when the mower arrived and I was surprised it was in such good condition. Just a bit of black dirty air particular matter at the intake holes but great otherwise. It is also a genuine Briggs & Stratton foam filter so not sure how long it has been there - but not crumbling or showing signs of age. Anyway, I washed it with detergent and thoroughly dried it, then soaked it in fresh oil then squeezed it out "like superman turning a rock into a diamond" (I saw someone post that on one of your other threads-made me laugh). Anyway did all that and have already downloaded the Operating and Maintenance Instructions and the Illustrated Parts List already from previous threads. I have spent many hours on your forum looking for answers - in the end figured I would just send you a message directly. I appreciate the link to Service and Repair Instructions 1984. That will keep me busy. :-)I think I can stick with it - with your help. That crack will be something I definitely cant fix myself - it will be interesting to see how that goes. Let me know if you still want me to send a pic of the air filter foam? I should also send you a photo of the chains etc I guess. In for a penny, in for a pound!
Cheers
Jen

Hi Guy's,

I'm not trying to discourage you, but that front rail has some really serious issues and truthfully I'm not sure if it could really be repaired, due to some butcher hitting it hard with an Arc welder and a grinder. The complete rail is badly distorted and from where I'm sitting will require a very skilled welder to fabricate another section to replace the magotted attempt that's been left behind by someone else.

Sadly what has happened is that that the original clutch half that you can see was replaced no longer sat correctly on the output shaft of the engine and this induced a vibration into the chassis which inturn has lead to the fracturing of the metal around the engine mounting holes. Now what has been a reoccurring problem due to the front rail not being straight has re-fractured the rail after the botched attempt to repair it, thus it has cracked again and now the whole machine is running out of balance.

This is only my own opinion and that is I would address the rail prior to anything else as the engine I'm sure with a bit of Grumpy's attention to detail will be in running order without too much issue but the chassis rail really is the deal breaker and will determine whether this project is worth pursuing (value for money) or finding another chassis with a US motor and mating up the best of the two machines and coming up with a very serviceable machine.

Again this is just my opinion and I'm not trying to tread on anyone's toes here. I'm just trying to avoid some serious disappointment in the long term.


Cheers,
BB

Thanks BB, you have far more experience with broken SB45 chassis rails than I do, and your comments will be useful ultimately in figuring out how to proceed with that part of the project.

Jen, you have done considerably more work on this project than I realised. I'm sorry for mentally classifying you as a dillettante. The reason to inspect the interior of the air cleaner was in case it had flooded with oil (through the breather tube) when the machine was being transported laying on its side. Please put it back together, and remember for future reference, you cannot run that engine without the air cleaner's central screw in place: it plugs a hole in the carburetor.

The next question is why there is alleged to be no spark. The IPL tells us that your engine has the old type of "kill switch" (ignition-off switch) consisting of a piece of aluminium, pivoted at the bottom on the cylinder head, which can be tilted so the top of it is pressed against the metal top of the spark plug. To run, the piece of aluminium is clicked into the position where it does not touch the spark plug, and to stop, it is tilted so it touches the spark plug. Not very high tech, and it sometimes gives you an electric shock when you snap it over against the plug with the engine running, but you get used to that (I don't say you get to like it much, though). Please disconnect the spark plug lead from the top of the plug, then remove the spark plug. Reconnect the lead to the plug and hold the plug's metal base (not the cap where the lead is connected) against the cylinder head. While holding it in that position, pull the starter handle briskly. Simultaneously, watch the gap between the electrodes at the base of the spark plug, where the thread is. See if there is a steady string of sparks between those electrodes. If there is, "We have ignition!" If not, we have our first malfunction challenge.

Hi Grumpy & BB

Thanks for coming back to me. No worries about "dilettante". Ive been called worse.

I think mine is a Choke-A-Matic. (Throttle in 'start' position opens choke and there is no kill switch on spark plug). Have a look at my photos in my first post to confirm ... in case I have it all wrong

I will check for ignition as per your instructions. Fingers crossed.

BB, your frankness is greatly appreciated. Im cross with myself really because I had an uneasy feeling the chassis rail would be a problem when I bought it. What a pity I didnt know about this forum BEFORE I bought it! Oh well.

Cheers
Jen

Hi Jen, yes, that is a Choke-A-Matic, as you say. Just one thing: when you set the speed control as far as it will go to maximum, and the choke handle is pulled out, that closes the choke, it doesn't open it. Immediately after the engine fires, you must pull the speed control back far enough for the choke to be pushed all the way in, which is the open position, suitable for actually running the engine. Do you begin to see why there was stuff running out of the carburetor when you kept pulling the starter with the choke fully closed? That will have flooded the carburetor. With that nasty Choke-A-Matic unit, you have to be very quick in opening the choke after the engine fires, or it rich-loads and stalls. Then you have to restart it with the choke open, and all is well.

Also, now that I actually look at the engine instead of the IPL, it has a plastic boot over the top of the spark plug, so it can't have the old flip-lever kill switch. That means it must have a kill switch in the governor plate mechanism, since it doesn't have the one shown in the IPL. Lack of spark on Briggs engines is frequently due to a malfunction of that kill switch. Hence you need to sort that out, if the spark test shows no spark. Remember though, because you have a kill switch, whenever the speed control is set to minimum speed (the opposite end of the range to the end where it closes the choke), the kill switch operates automatically, so there will be no spark. So, test for spark with the speed control in the middle of its movement range, or if you prefer, at the choke position: stay away from the slow speed position. Please do the spark test, and if there is no spark, we'll need some pictures of the kill switch area. I'll get to that in a moment, but meanwhile you should bear in mind that your engine was made in 1973 and hence has a breaker-points-and-condenser ignition system: electronic ignition was not introduced until 1982. Here is what you are up against:


Don't despair, even if there is a problem in there, it probably won't be hard to fix, and if it is, you just fit a Magnetron electronic ignition unit: it is fully interchangeable.

Here is a not-very-clear illustration of the kill switch on your engine (that is, an early version of the Pulsa-Jet carburetor with Choke-A-Matic):


Here is one of your pictures, cropped and with the kill switch circled in green:


So, if your engine fails the spark test, we will need some detailed pictures of the mysterious object labelled "STOP SWITCH" in Figure 52, and circled in the above picture.

Hmmm...I dont know what my lawn contractor was looking at - but there is definitely spark.

That is good news, Jen, but I'm not surprised. Now since you've already serviced it, the next step is to see if it will start. Remember the limitations of that coupled choke system: we don't want either to flood it, or to under-choke it. You've just been pulling it over with the spark plug removed, so hopefully any excess fuel in the cylinder has been blown out by now. I suggest you install the spark plug (doing it up moderately tight, so it won't leak air) and connect the lead. Set the speed control at maximum so that the choke is pulled out fully (full choke) and, of course, the kill switch is not operating (it operates at the other end of the speed control's movement). It is safest to flip the clutch lever over so its handle is toward the engine, so that the reel will not rotate when/if the engine starts.

Remember, the most you can hope for is that the engine will fire a couple of times then die in agony. It cannot run with full choke. If it fires, and you have superhuman speed and strength, instantly move the speed control to mid-range before the engine dies. More likely it will die by the time you get there. Don't worry if that happens, just put the speed control lever in that mid-range position and pull the starter immediately. It should start, and run properly. To stop it, move the speed control fully to the opposite end of its range from the choke position: that should operate the kill switch, and stop it. If it starts but won't stop, you'll have to pull the black plastic cap on the spark plug lead upward off the spark plug.

Please let us know what happens, of course.