Seeking East Valley Machine Shop

[CouesPursuit]

I have a 160cc/5hp Honda that needs a crankshaft diameter reduction and possible lengthening to fit a custom PTO for a project. 

 

Any recommendations on someone capable in the east valley ? Thank you.

[mattys281]

To lengthen the stroke you will need someone that has a crankshaft grinder.  I’ve seen stuff where people rigged offset fixtures and did it on a lathe before, but to be done properly it needs to be ground.  Crank journals are very high precision.  I’d call a motorcycle shop and find out who does their engine machining, or try to get in touch with someone who’s into motorcycle racing that could recommend a good engine builder.  If that’s not done properly the guy in the saddle will be sitting on a grenade.

when I was younger I was into road racing motorcycles and trashed a couple engines while learning.  Sometimes you get big dividends by just going to a pro right from the start.

[mattys281]

Pictures finally loaded on my phone after I already made my first response.  I see now you want to reduce and lengthen the output?  You might find a fab shop with a welder and o.d. Grinder or lathe with centers that can pull that off.  For 5 hp it’s probably not that dangerous/critical, but I’d still think it’s worth talking to someone who specifically does custom bike work and get an opinion.  Good luck with your project!

[Delw]

It would be easier if you used a smaller sized adapter than turnign the crank. Like matty said turning the crank is a pain in the butt. and its not needed. plus you will have to take the crank out. and those ends are hardened they are not soft so grinding is almost the only way.

have a machine shop make a smaller diameter adapter for the crank end. of goto mcmastercarr.com and buy a sleeve/ bushing to match.

[CouesPursuit]

Thanks guys. I could write a novel here, but essentially, this Honda that I purchased used on a screaming deal is supposed to have a 3/4" diameter and 2-7/16" long shaft according to any spec list and photos I find online. However, after purchasing a longtail mud motor kit based on that 3/4" spec (and the largest PTO offered for the kit), the shaft on the Honda ended up being 7/8" and the PTO won't slide on. Not sure how or why but it is what I have in front of me.

 

It isn't the PTO manufacterers issue as I did specify 3/4". They don't offer a 7/8" but I sent them an email asking anyway. I don't want to buy another motor or swap a crank if I don't have to so I'm still looking for a professional to attach the PTO to my existing engine so I can move on with the build. 

 

Regarding adapters and bushings, I am not sure how far I can extend the PTO off the engine and still have the rest of the kit and shaft fit together. Not sure how difficult honing out this 3/4 to 7/8" would be either but it beyond my skill set.

[mattys281]

How long is the part in that picture?  Depending on how hard that part is you can probably just bore it out.   You’d likely also have to face down the key that engages.  As it would be too tall to fit in that end.  That’s a lot more doable than screwing around with the crankshaft.

i could probably modify that for you (depending on the hardness of the shaft), but can’t take responsibility for the engineering/integrity of it.  It’d be work done per customer instructions.  My shoot from the hip is that the shaft your holding is probably very soft compared to the crank journal it mounts to.  It’s more desireable for that part to wear and be replaced than it is for the crank, plus a drive shaft that is too hard becomes brittle and will likely crack under torsion.  Those types of parts are usually pretty soft to maintain toughness.

[CouesPursuit]

Great info, thanks Matt for your offer to help.

[mbiewer]

give Az custom machine a call. If he can't do it, Tim might be able to direct you to someone that can