HM100 1" Crankshaft Help

[mustangfrank]

Hoping someone has done this or has the specs. I can't find any line drawings or information after a couple hours on the interwebs.

In the simplest way to ask, will a 35442C crankshaft interchange with a 35372A crankshaft?

I have a LH358XA-159493Y (HM100) new generator engine with the tapered crank I'm converting to a 1" for my Super Bronc. The 35372A is available but only in used and welded up/reground new-ish but over 2-3/4" PTO length. The 35442C is available NOS and looks shorter, I'm hoping closer to 2-1/4" PTO length this engine is replacing.

 

[mustangfrank]

A little more research...they use a one digit apart part number connecting rod. Not sure if the stroke or crankshaft pin changed over the generations.

Found a 35443A crankshaft is a 1" diameter 2-1/4" PTO and will definitely work for my conversion but same poor availability.

Hopefully someone has some information on the 35442C, it's my best option if it's a direct fit.

 

[oldcarcbx]

Check out the Tecumseh flathead manual link at the top of this thread. There is a section in the back of the manual with all of the specs including journal diameters. For hm100s with solid state ignitions it lists the same stroke for all ,but two different spec cranks with different crankshaft journal diameter,crankshaft main bearing diameter, crankshaft pto main bearing diameter and, connection rod crank bearing diameter. Its also footnotes to "check to determine crankshaft bearing diameters".

It sounds like you need to measure the specs on your engine and physically measure the specs on the replacement crankshaft to determine compatability. There were some old threads that talked about cutting down tapered generators cranks, but that was Yellowhand, may he RIP.

 

[mustangfrank]

Good info, figures the last place I search is this forum.

I know a retired machinist with a lathe and a Bridgeport in his garage that has done similar but something about cutting the gennie cranks down to 3/4" just feels wrong. Seems like I'd be creating the weakest link with more than double the torque of an engine that normally has a 3/4". Plus I have new 1" clutches, although that's a 80 buck fix.

 

[chrisr]

I have a few newer 8 and 10hp Tec with 3/4 and 1" PTOs and have had no issues. The one in my avatar is a 10hp 3/4 Tec that is thrashed off road and once broke a driver mudding but I think it would hard to break a 3/4 PTO .

 

[mustangfrank]

I have a few newer 8 and 10hp Tec with 3/4 and 1" PTOs and have had no issues. The one in my avatar is a 10hp 3/4 Tec that is thrashed off road and once broke a driver mudding but I think it would hard to break a 3/4 PTO .

You're totally right, it's more economics, a 1" crank costs as much as I'll probably have spend turning the tapered down to 3/4"...plus I can get a couple bucks for it.

Then again why didn't they just make all cranks 3/4" for simplicity?

 

[mustangfrank]

Still hoping someone has info or specs on the 35442C. Might be a no go because of a change made on later models to the crankshaft connecting rod journal going .0010 bigger. Planned on running an ARC billet rod so maybe they'll have some info.

 

[mustangfrank]

Wound up buying a NOS 35442C because it was a deal plus I am yet to call ARC and see what crank rod journal they designed their billet rod on (or when). Picked up a complete Ariens engine with the 35443A crankshaft and I've got my eye on another clean used 35443A crank only I think I'm going to jump on.

My dial caliper is a POS but if anyone else wants info for this conversion I'll either have a better tool sooner than later or I can at least measure the difference side by side when I tear into the Ariens or get my grubby hands on the spare.