OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers Scott Bonner 45 issue

Hi all I have a Scott Bonner 45 with a 3HP Briggs & Stratton motor that I can't seem to get going anymore have check if I have spark and seem to have compression but don't know where to go from here. Hope you can help. I'm not sure where to go from here. This was my dads lawn mower and it is as old as I am so I'd really like to get it to work again. It has been sitting in the shed for 8 years that I know of untouched. Hope someone here can't give me some direction on where to go from here. I am doing a mechanical fitters apprenticeship and I'd like to accomplish this project on my own terms.

Also I'd like to ad pictures but not sure how to go about it

Hello Swiftdevil

A warm welcome to the ODK forums.

From the history you have told us about, it may be that the problem
lies with fuel & carburetion. After 8 stagnant years, the carby would
need cleaning and the fuel pump diaphragm would need replacing.

If you are not comfortable with engines, or have little experience,
then professional help will be the way to go. But, to help you further,
we do need more information ...

We do need photos and the Model, Type and Code from the engine.
For info. on how to upload images click HERE.

The Model, Type and Code will be found here:-



Hope this helps.
-------------------------
Jack

Thanks Jack ill get this done but i don't think my engine has this sticker. I think mine has it stamped on the the engine

Just added some pictures to show everyone what I have at this stage.

cheers

G'day Swiftdevil,

Yes, your engine doesn't have the sticker, but have a close look at the carby side of the cowling - the stamped numbers should be there, and they will be in the Model/Type/Code order.

Sometimes a bit of wire brushing and a rub with chalk is needed, to make them legible.

Ok thanks Gadge I'll take a look and let you all know

Thanks.

Hi all so if taken a few more pictures and was also able to get a picture of the numbers of the engine.
I was also able to get it to fire using and help start spray so I know that the engine will fire and run. So I'm now up to looking at the carbie I have got some pictures of all angles and parts of the carbie too.

Great work, Swiftdevil.

Model 80202 Type 0879-01 Code 79022703

So what we get from those numbers is that it's an 8 cubic inch horizontal shaft engine with Pulsa-Jet carby, plain output bearing, recoil starter. Made on 27th February 1979.

The Illustrated Parts List for your engine is downloadable from HERE.

I was going to suggest seeing if it would fire if a teaspoonful of fuel was tipped down the carby, but the starting spray has answered that question. Though we don't recommend ether sprays for regular use on small engines, once is OK.

Clogged fuel pickup tube screens are a common problem with these carbies, but yours look fine.

These Pulsa-Jets are a very simple carby. All it should need is a clean out, to get rid of any gum residue from old fuel, and a new fuel pump diaphragm, and carby-to-tank and carby-to-engine gaskets. Give the fuel tank a good rinse out too.

If using commercial carby cleaner, keep it away from nylon parts like the fuel pickups.

Initial setting for the mixture screw is 1.5 turns out from fully closed.

I would also check the valve tappet clearances, while you've got the carby off. They are under that small plate just below the ports on the engine.
Factory specs are Intake 0.005-0.007" [0.13-0.18mm], Exhaust 0.009-0.011" [0.23-0.28mm]. Check with piston at TDC, at end of Compression stroke, engine cold.

BTW, the Workshop Manual for this engine is P/No CE8069, 'Repairman's Handbook For Out of Production engines 1919-1981'.
The later P/No 270962 manual doesn't cover points ignition engines.

Hi Swiftdevil and Mod Gadge,

Your problem is clearly the fuel pump diaphragm which is the very thin black rubber type item that is clearly fuel affected and thus is not allowing the carby to pick up fuel from the tank.

This is the most common issue with most Briggs engines of that era.

If you follow Mod Gadge's advise you can't go wrong and you'll have it up and running in no time. I will say though that these small parts are not cheap so be prepared for a bit of a shock on that part as they are around $11 ~ $15 depending upon where you purchase it from.

Cheers,
BB

Thanks for that input, Mod bonnar_bloke.

At those prices for over-the-counter parts, it could be worth ordering from the ODK Shop , even with postage cost.

Search tip: Enter briggs followed by the Part Number, in the 'Search' field of the Shop homepage, to find specific parts easily.

Thanks everyone with your advise.
Where the nylon tubes go into the tank the long one is in the main part of the tank and the other is in another little pot (not sure what this is for) when I tried to crank the engine over I was told to prime the engines is to pull the start cord slow a couple of times, once done put on cold start choke out and then try and start it. This did not work but when I pulled apart the carby from from the tank I noticed that the small pot was full of fuel and it stated spilling over the top of the fuel tank.

Regards Scott

One thing we should have mentioned, is that it's vital to get any old fuel out of the tank, as far as possible, and refill with fresh stuff.

That long pickup tube shows signs of gum from old fuel around the screen, but a good rinse in fresh fuel should clean it up. If need be, it can be gently scrubbed with an old toothbrush.

I'd also replace the spark plug as routine here; NGK BM6A is my favoured type, or Champion CJ-8 is Briggs' OEM. Gap set to 0.030"/0.75mm.

Hi all could I get some feedback on what I'm planning on ordering as parts for worn parts some I know I need others I think ill need please help

NGK Spark Plug BM6A $4.92
Briggs & Stratton Foam Air Filter 27987S $15.40
Briggs & Stratton Carburetor Kit 495606 & 494624 $31.00
Genuine Briggs & Stratton Cap Spring 690766 $6.66
Genuine Briggs & Stratton Spring Pump Diaphragm 692206 $8.79

Any other suggestions or changes to be made.

Regards
Scott

Hello Swiftdevil

Generally the cap and spring would not need replacing.

-------------------------
Jack

Unless they're missing entirely?

Okay thanks Jack and Gadge they are there just thought I'd replace that whole section anything else I should look at.

Thanks Scott