Hi I just bought my first cylinder mower- a Rover Scott Bonnar 45. Am pleased to join the club !
The mower started fine from the bloke I bought it from- but when I got it home it wont start. Not even a cough or splutter. I have been wading through these forum pages and have a reasonable knowledge now. What a fantastic resource !
Model number is 91202 0123 01 92100103- so i guess it was built in 1992 on 1 October?
I think this is the parts list listed below in attached files.
I will replace the spark plug tomorrow and see if that helps. As far as I can tell it works fine already but it is quick cheap replacement and rules out one possible cause of failure to start..
While I am doing that I will try the "1/2 teaspoon of petrol in the piston chamber" trick and see if that helps.
Will try drain the fuel as well.
One thing I have noticed is that when the throttle is moved from choke to fast to off the governor spring mechanism doesnt seem to change position much, in that although the linkages move the actual movement of the linkage into and out of the engine doesn't really move position much at all. It also doesnt look like the governor spring is stretching much at all. It seems to need replacement.
On page 18 of the above parts link it seems to say that the spring is part number 211 or 691289. That said, on page 24 there is also a governor spring (which looks more like the one already on my machine- it is quite long and thin and has a full loop on one end) labelled part 419- but the corresponding BS part number isn't given as far as I can tell. And then on page 25 of the parts list there is another governor spring listed - parts 692522. Any ideas which one I should buy? Perhaps I should just take the old spring and the engine number to the local mower store and hope for the best!
Happy to post pictures if thought useful.
Any idea if the repair manual for this model can be obtained online?
Some pics of the engine would be useful, I would check that the choke butterfly is closing correctly when the throttle is in that position, definitely drop a little fuel into the plug hole or carby throat to see if it's a fuel issue.
Welcome to the forum Damian - you won't regret it.
Our resident experts will definitely get you going shortly, and if you can get photos up we can all see what you've got. I'm no good to you with engines other than "fuel in there, spark on top, max choke and the rabbit" but you may be on the right track with the teaspoon of fuel in the chamber...
As for the manual, I believe if you use the search function above, you'll get an "Operators Manual" not a repair manual as such but it will be a good starting point. The same experts may be able to point you in the direction of where a better resource resides.
wce, thanks so much for taking the time to look at my post and comment in detail.
Here are some pictures. Thanks for mentioning the butterfly valve- I forgot to mention that in my original post. I think it is incorrectly set. You can see in the pictures in full choke and no choke position. In the full choke position the butterfly is not completely closed against the carby throat. You can see a clear gap at the edges. Should it be fully closed / completely shut?
Also, in the pictures you can hopefully see that that there is barely any change in the tension of the governor spring in the full choke and no choke positions. I dont know much about governor springs but intuitively it looks to me that the governor spring is basically doing nothing ie the spring mechanism isnt applying spring pressure against linkages. Maybe it is stretched beyond redemption?
I have also noticed that the linkage from the throttle shaft /plate is differently shaped to ones I have seen on this forum and in the parts list. It curves right over above and across the governor spring. Not sure if that is relevant.
Another post I have seen said try filling the fuel tank to the very top. Will try that too, I guess.
Definitely seems like a fuel problem.When I bought the mower I had to manhandle it into my 4wd. Didnt tip it on its side but certainly got it tipped sideways about 45 degrees- maybe that has caused a fuel problem.
Hi Damian I have a 3.5 hp briggs same as yours on an edger and will take a few pics and post, the bend in the throttle linkage looks way excessive from memory. First things first though and that's to establish the non firing cause, usually no fuel, stale fuel, fuel restriction, no spark. You have seen the engine run so presume compression is present ? did he do anything out of the ordinary to start it ? 1. check that you have spark 2. If spark is good put a little fuel down the throat 3. pull start with throttle in run, it should at least fire, if it fires and then dies it will be a fuel issue
The choke does need to close fully in order for enough fuel to be drawn up to start, adjust the cable so it fully closes the butterfly. Drain the fuel if your not sure of it's quality and put some fresh in and try to start. If it won't start after a couple of pulls you most likely have a fuel starvation issue which is normally only caused by a couple of things. Has the mower been sitting for a period since you bought it?
First pic, choke on no throttle second, choke off full throttle third, idle position on throttle, obviously the choke would be off if the engine was running.
Along with some of the discretions in the linkage set up which wouldn't be helping your cause, I strongly feel that the diaphragm in the carby is stretched and requires replacing. This carby style is called a "Chokomatic".
I bet London to a brick that the guy you bought if from had it going just before you arrived, thus the carby will have been properly primed and would've started again rather easily. Leave it for a few hours and let it go cold and you'll find that you'll have to throw some fuel down the carby throat to get it going just like the seller did prior to you getting there. The problem will be that it's not pumping fuel up from the tank into the carby with a stretched neoprene rubber diaphragm. This is a very common issue with these Briggs units that have been sitting around for some length of time.
To change it you will have to undo the muffler at that bolted joint so as to gain access to the small screws that hold the cover plate onto the side of the carby which has the rubber behind it. Don't lose the spring when you remove the plate.
Apart from that member wce will be your man for engine issues.
Cheers, BB.
I live a 24 Hour lifestyle, but every now and again I seem to fall asleep, well at least that's what my wife tells me.
BB, I believe some people just have the magic touch. LOL. I piked up a full crank cup pull Victa 24 a few months ago and he started it easily in front of me. When I got it home there was no way I could get the starter to catch so I removed the starter and tried starting it with the drill. No way would it start, so how did he get it to run in front of me? I pulled the G3 off and fitted an LM,modified the cup starter and it now works perfectly
BB, I believe some people just have the magic touch. LOL.
LOL !............... Certainly get that, but then there's some folks that just have the ability to cleverly orchestrate things really well to suit themselves, especially when there's the smell of plenty of money floating about.
Cheers, BB
I live a 24 Hour lifestyle, but every now and again I seem to fall asleep, well at least that's what my wife tells me.
Just trying to walk the chap through the simple diagnostics of problem solving and yes it may well have ended up at the diaphragm which is problematic after a long storage period. My experience with that particular problem is that if the diaphragm is stretched and hardened no amount of priming will get it to pump and the engine still won't continue to run after it fires.
I'm not trying to have an argument here and tread on your toes, but as the seller got it going wouldn't it just be a straight up issue that we can get to without all the trying this and trying that scenario ?
Most folks just want to get an egine running and then move on.
Anyway feel free to continue......................
I live a 24 Hour lifestyle, but every now and again I seem to fall asleep, well at least that's what my wife tells me.
First let me make something very clear, possibly even clearer than Willie Rioli's sample. I have nothing but respect and thanks for all the good folk on here like your good self who give large amounts of their time at no cost to help others. I thought it would be beneficial to the give the new member for both now and in the future the base line for simple process of elimination fault diagnosis. It's a pretty simple set of steps that only takes a minute or 2 and is designed to save time and money and quickly set you on the right track. Almost all owner manuals, workshop manuals etc have the same things in the trouble shooting section for if your mower won't start. I just think starting at step 1 not 4 or 5 is logical. A quick example, was mowing the lawn a few months back, engine cut out, wheel mower to shed, check for fuel, yes, check spark, nil, get new plug out, don't install check for spark first, all good and mowing again in a few minutes. Being a Victa 2 stroke there was a thought of a stuck float needle but fortunately that was step 3. Anyway, back on topic, I hope the advice from all Damian has received get's the engine to fire and then running nicely again. I hope is it the diaphragm, it's quicker than getting at the main jet. The engine pictured above was firing but not starting. It was a combination of bad fuel, hardened diaphragm, main jet and pick up filter screen blockages.
