OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 13 Series - 130902 - Bent Crankshaft

Hi folks
I have a a B&S model 130902, type 1175-01 with a bent shaft. Having it straightened sounds a little risky. The shaft has a step idown to a smaller diameter and B&S do not seem to supply this style anymore either a replacement crank or a full motor.

Any thoughts on how I can get my shredder going again?
Thanks

What horsepower is that one, and horizontal or vertical shaft? I have some old B&S motors laying around but I'll have to check for model and type and let you know if I have one with a suitable crank. If I do a couple of bucks plus postage will be all.

Greetings PaulS, and welcome to the ODK Forums. We're into tinkering and salvaging here!

Model 130902 = 13 cubic inch [5hp], vertical shaft, Pulsa-Jet carby, plain bearings, rewind starter.

How 'bent' is the shaft? If you can still get the sump off, it will probably straighten OK.

Thanks Gadge
It's probably about 5 mm out at the extreme. So I reckon the sump will come off. As to straightening: sledge hammer, long bar, B&S device, lathe?

Hi Aussietrev
Gadge beat me to providing all the specs. If you have something salvageable / a straight crank of that model that would great.thanks

Paul, can you fit one of the Chonda motors from ebay, you can get vertical shaft motors from ebay for about $160, just have to watch the shaft size and you say it had a stepped shaft, get the adaptor bored to suit the shaft? I'm not a big fan of rebuilding B&S motors, not worth it cost wise

Sorry Paul, the only 5HP I have is a horizontal shaft and it is a running motor on a tiller I got from the tip which I hope to restore soon. Only other 5HP I have is a Quantum50 on a Rover base that I also got from the tip that only needed a quick clean of the carby and a new throttle cable.

Hi Norm I looked at replacement motors. The stepped shaft is necessary as it locates the chipper blades at the correct "height" and clear of the sump. I cannot see how this can be achieved without the step

Thanks for looking Aussietrev. Any advice anyone on the best way to straighten the shaft?

Well, that's about at the limit of 'straightenability', I'd say.

I would not recommend any of the 'hammer' methods which are mentioned at various sites around the Web, due to the potential to damage the shaft, and the crankcase if used with the crank still in the engine.

There are 'crankshaft straightener' tools on the market, which are a jig that bolts up to the engine, and uses jacking screws acting against a protective sleeve to apply force to bend the shaft back.

Like THIS one. Which also has a runout indicator that can be seen in the pic. Not worth buying one for a single job, though.

For a one-off, use of a press, a set of V blocks, and a dial indicator and base to measure runout [and locate the 'high spot' of the bend], would be the best way to do it. This is with the crank out of the engine.


One other thing; be sure to check the flywheel key - it's quite likely to be at least partly sheared. If it is, replace it with a new Briggs one - don't use a steel key.

Hi Paul, where in Vic are you, I used to do a lot of single cylinder motorcycle crank assemblies and rebuilds so I have plenty of gear here if you want to have a crack at it

Could always use blocks and indicator as Gadge says but use heat to straighten it. I don't know how this might affect any heat treating of the crank though.

Gadge why not a steel key? Are the Briggs one designed to shear?

Thanks everyone. Norm I'm in Balnarring on the Mornington Peninsula. Is that anywhere close?

Paul, I'm in Hampton Park, not too far, give me a ring if you want 0408350796

I'm doubtful about using heat here - these small Briggs cranks will bend cold fairly easily anyway.

Masport used to distribute a crankshaft straightener [it was a required dealer service tool in the 70's] that was basically a bench mountable steel channel base with a centre rail, two V blocks that slid along the rail, a runout indicator pointer and scale, and a small screw press. It worked very well, if the crank bend was not so great as to prevent sump removal.
Yes, it is the 'designed weak point', so that if the engine stops very suddenly, the key will shear. Rather than twisting the crank, or wrecking the shaft/flywheel keyways.
As Briggs say in one of their FAQ:

To locate the blades at the right height if you have to use another motor you could either use a sleeve above the blades, or do like they do on some ride on pulleys and have a closed sleeve welded below the pulley with just a bolt hole through it. You could possibly weld a short sleeve to the blade carrier of suitable length to do the same thing.

You learn something new every day. Thanks Gadge, I would have used a piece of steel keyway. Interesting about the straightening jig too. Thanks again.

Not too far at all Norm. I'll give you a ring during the week

No guarantees Paul, but also nothing to loose

Hi Paul, How did you go getting the shaft straight and/or finding a replacement? I just got a 6HP B&S Horizontal shaft Model 117432 Type 0551E1 that has a stepped crank. Just wondering if it is something like the one you are after. The motor turns over okay but has too many other things wrong to make it a restore possibility so if the crank is interchangeable I could strip it out for you.

The stepped area is approx 60mm long and 15mm diameter.
Hopefully someone will be able to advise if it will fit if the step is like yours.

Won't work per IPLs.

aussietrev yours is a 715238 5/8 diameter threaded.

The OP's is a 492091 which is NLA. Also the OP's is probably a 3/4 threaded.

I haven't looked at it yet, sometime in the next week or so I believe

Got it within a few thou, didn't want to play ball at first but eventually we won, I think It was not externally threaded but it stepped down about 2mm in the last 35mm

Thanks to NormK
Great determination to persuade the little blighter to bend back. Just waiting for some oil seals, new keys and a gasket then I'll get it all back together and give it a spin.
Norm deserves a medal. I offered money, beer or wine - he refused it all, just happy to help out. Great bloke and it was a pleasure to spend time learning from him.
And thanks everyone for suggestions and help. I hate to throw things away if they can be fixed. Thanks to Norm I think this is a fixer. I'll report back when I give it a whirl
PaulS

No probs Paul, hope it goes well and I hope your tea wasn't too cold by the time you got home

good to here it straight know
never use heat to make straight dangerous it make brittle and snap off

Now you tell me, next I guess you will say not to use a hammer.

hope you not heat shaft you change metallurgy. Heat affected zone make brittle very danger snap. better to use big copper hammer bend him cold lest damge to shaft

Due to changes to crankshafts composition and liability issues most of us in the US no longer straighten crankshafts. Prior method was the use of a jacking rig that used a modified bolt, an protection sleeve, and back support. The whole jig was mounted to the engine. You simply turn in the jacking bolt while checking the crankshaft straightness by rotating the crankshaft. The jacking was done until the crankshaft no longer wobbled.

Hitting with a hammer of any kind is rough on the bearing surface of the engine if the crankshaft is still in the engine.

Freebird, I'm winding you up, I did it in a press