"BS 18HP model # 917.255912."

I'll try to help you but that is not a B&S number, it is a Sears number so I don't know WHAT 18 hp B&s engine you have. There are 3 different ones that I can think of and none of those have 3 bolts holding the starter. Model number is on the engine.

Walt Conner

note to Walt.

MODEL NO. 422437, TYPE NO. 0721-01

This is the horizontal shaft opposed twin that is installed on the large GT 6000 mower. It has the 6 speed gear transmission. The engine delivers power on the flywheel side and the pto side. I believe these were sold around 1991.

I have never worked on the starter on the horizontal engine - so I cannot comment.

I thought I saw a thread specifically stating that the engine in this machine must be raised in order to service the starter. I couldn't find the thread I wanted but I am posting a link to another thread in which a comment is made alluding to the need to raise engine off chassis to get starter off/on. Click link and scroll to the pics posted by colt357, it is in that section of thread you'll find the comment. By the way, accessing a component is seldom the goal of the designers when the machine is in the planning stages. Sorry to bear the bad news!

Here is a link that might be useful: Hint on starter buried herein

I am not familiar with how the engine sits in your tractor but I expect the starter is inside the frame rails.

The good news is you don't have to remove the flywheel. You will need to take the cooling shroud loose and slide it away from the engine so you can reach the two bolts holding the starter. One is easy to get to, the other is under the flywheel. A 1/2" open end wrench will do it. You may have to turn the flywheel to find a recess in the under side of it where the bolt can be lifted up and removed. Nimble fingers help.

By the way, the starter of a 42 series B&S engine mounts the same regardless of whether it is horizontal or vertical.

You didn't say WHY you were replacing the starter, burnt out, not enough power to turn engine (may be something else), starter gear worn out?

Walt Conner

Oh, Sorry, you did say why.

Walt Conner

Thank you all for the info. Yes it is a Sears mower and it it is a GT 18 6 speed. I can not find a engine number other than what sears put on under the seat giving me the model & serial. It is a 2 cylinder opposed with the drive and power take off belts on both ends of the engine. As I look at it; it would appear that this engine will have to be lifted in order to service starter, Thank you for that thread as it also said the same thing. I will try and find a manual or a mechanic to advise me on this model. I hate to tear into something when it is not necessary. Lifting the engine means taking alot of stuff apart. I took the left cylinder cover off and can see it is the plastic starter gear that is my problem.

You can get an IPL at the link below.
The gear should be Briggs PN 280104

Here is a link that might be useful: IPL

The starter is out. Yes you do have lift the engine up & out of the frame and the engine mounting plate. The fan shroud also has to be loosened. It is a bear of a job. I just took the engine out as it was about the same amount of labor. If only the people who design these things could think of maintenance that is going to be done at a later date!!

hokesailor