Briggs and Stratton kicking back

[Potash123 26]

I took the 375 engine that was running well off of a rusty deck and fitted it onto a new deck. I also fitted a brand new carb that I had. It started once then cut out, now it is kicking back on the pull start like an old BSA motorbike, almost smashed my knuckles to bits on the recoil. I thought the timing was factory set. It was fine before removal. Info appreciated.  

[Stormin 4,458]

  If you've not touch anything, except for fitting a new carb, I'd try it with the original carb before doing anything else. A possibility is the fly wheel key has sheared. It's only aluminium for the reason. Don't fit a steel one in it's place.  

[Potash123 26]

Must admit I did clump on the blade boss, would that have sheared the flywheel key. ?? Many thanks

[Chris 642]

Flywheel key for sure

[Potash123 26]

Thanks Chris, job looks easy. End of thread, merry Xmas.

[Potash123 26]

Easy I thought. All the sprints I have worked on have a nut holding on the flywheel. This one must be older as the starter mechanism is fitted over the flywheel. I have pullers but cannot see how it comes off so I can change the key.

 

Thanks lads. 

[Wristpin 399]

Presume that you are referring to the starter clutch. It is screwed to the crank, conventional right hand thread and should be undone using a special tool. However, with care it may be undone with a large stillson  or a hammer and hard wood block against the lugs that the top screen screws to. Take care as those lugs were not designed to tak impacts - just a steady pressure.

The "bronze" wrench, one in from the right, is the clutch removal tool and the "half moon" one beside it is the flywheel holder . The two cup shaped ones above them are clutch tools, early and late, for use with a torque wrench or breaker bar.

[Potash123 26]

Easy I thought. All the sprints I have worked on have a nut holding on the flywheel. This one must be older as the starter mechanism is fitted over the flywheel. I have pullers but cannot see how it comes off so I can change the key.

 

Thanks lads. 

Many thanks, what a superb set of tools, a bit like my Norton BSA kit.

[Wristpin 399]

It is worth considering that while a sheared or even partial sheared flywheel key is the likely culprit , a sheared blade boss key or a slipping blade can produce the similar symptoms. The key will be obvious but if the blade is retained by a friction mechanism such as friction washers compressed by a big bellville washer , it can appear tight but actually slip a bit under starting conditions. A contributor to another forum who had completely overhauled a rotary mower engine but was unable to start it  was mightily relieved  to find that a properly torqued up blade did the trick.

[Potash123 26]

Easy I thought. All the sprints I have worked on have a nut holding on the flywheel. This one must be older as the starter mechanism is fitted over the flywheel. I have pullers but cannot see how it comes off so I can change the key.

 

Thanks lads. 

Many thanks, what a superb set of tools, a bit like my Norton BSA kit.

 

I fitted the boss but not the blade as yet. Have put my tools away for the next couple of days.

 

Merry Xmas to everyone.

[Wristpin 399]

7 hours ago, Potash123 said:

 

 

I fitted the boss but not the blade as yet. Have put my tools away for the next couple of days.

Merry Xmas to everyone.

 

In which case forget the flywheel key for now and put the blade on - may well solve your problem.

BS vertical shaft engines specified for rotary mower applications have a light flywheel to take account of the flywheel effect of the blade. Sometimes you can start one without the blade but more often than not they will bite.

 

Edited December 23, 2016 by Wristpin

[Potash123 26]

Fitted the blade and job done after a slight carb issue which I have just posted on another thread.