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

Hi all.

Im new here to the forum. I've recently just purchased a SB45 twin deck mower. Engine is a 90112 built in 96.


Firstly it idles quite fast so I thought it would be a simple governor adjustment. Boy was I wrong. Upon dismantling the air cleaner and fuel tank i noticed the carby has a cracked flange. you can see it just below the intake pipe in the photo. Therefore letting air and and letting the motor run lean. So i decided to remove the motor and try and JB weld the flange back together.Secondly after removing the motor i noticed the dreaded cracks in the frame. These cracks are very different to all the other photos of cracked frames i have been finding online.

First question is there any chance of buying replacement carbys for these engines. After research Ive figured out that it is a Vacu Jet carb. It has no diaphram pump and no bowl in the tank. I ask because i cant see the JB weld holding the carb, tank and air cleaner with all that vibration.

Second question is the frame able to be repaired, there are so many cracks all over? Where would i begin? Do i drill the end of each crack and weld or do i leave the cracks and weld flat bar underneath? Im unsure how to tackle this.

Other than those two issues the rest of the mower seems to be in great nic. it cuts really well and the motor has heaps of compression.

Im not looking to restore the old girl i just want a nice reliable mower. Any help and opinions would be muchly appreciated.

Thanks

Hi Nuggy,

Firstly welcome to the ODK Forums and also for joining the queue of Scott Bonnar owners that love their machines like no other.

Now to address your cracked rail situation, we only recommend the Mr.Jones method of long term rectification of cracked rails.

Please view the following thread as it clearly shows the best and strongest without compromise method of repairs.


https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/66337/Re:_MODEL_45_-_17_&_20.html#Post66337

BTW the cracks in your rails are nothing out of the ordinary, they are merely fatigue cracks that radiate in all different directions due to the vibrations instigated by the earlier style single piston type engines, both Kirby and Briggs & Stratton.

As far as your carburettor is concerned you would be correct in saying that no replacements are readily available. The only way is to obtain a second hand unit from a reputable Lawn mower shop that will have plenty laying about from previous tear downs. It would be best to go to a long standing repair business opposed to a glossy looking newish retailer.

Cheers,
BB.