"kindalikeawhizzer"

[cannonball2]

You are in luck on the shaft its 5/8, these can be found in various lengths. I have bought them in 12"-36" sections. Moving the final drive element to the other side of the case is not a real problem. You will have to negotiate the key way issue. You can space the drive outward a bit from the mounting plate which will move the key outward, especially since the final drive element is behind the case. I don't know how far you need to extend the key way. The crank is fairly soft so a Dremel with the right bit should be fine to do the job. None of this is a big deal.

 

[silverbear]

The keyway I need to extend is on the engine crankshaft. Only an inch or so more is needed. Besides drilling the end of that shaft for the bolt and washer, would it also be a good idea to cut a groove for a C clip?
As for that 5/8" final drive shaft it of course has the keyway, but the end is also threaded for a nut, so if I need to get a different shaft I'll need to find one that is threaded or get a die and cut threads in it.
Another consideration for that shaft is that where the bearing is right now (this is on the backside of the mounting plate, that is where a pulley would need to go to align with the sheave, so I would need to remove the bearing, cut off that much of the shaft housing, and replace the bearing further in. Don't know if that's possible, but if not then I can make up a custom jackshaft, do away with the supplied mounting plate and attach the jackshaft to the seat post. I think.

I appreciate you guys for your input as it helps me think through this. I'm glad you think drilling and tapping the end of the engine crankshaft is doable, CB2. Like Bluegoat, I had my doubts.
SB

 

[msrfan]

Hey silverbear. Glad to see you engineering this project. I go through this with every build. The main thing is not to get in a hurry to cut things up until you find the solution. I can't tell you how many times I fabbed up stuff just to throw it on the junk pile. The end of your crank should be drilled as mentioned, and the go kart people sell a drill guide to exactly center the hole. You can make a simple guide by drilling a 3/4'' hole into a 1'' X 2'' long shaft about a inch deep and then drilling a 5/16'' hole through the other end. Could be done on a drill press, but should use a lathe. And if the hole is not exactly centered, so what. No snap ring groove is needed on the crankshaft end. The bolt and washer(s) will be enough.


http://www.ombwarehouse.com/5-8-and-3-4-Crankshaft-Drill-and-Tap-Guides.html


As far as extending the keyway, I would remove the crank from the motor and work on it in your vise. Its more work and may cost you a side cover gasket (which you could make yourself), but the results will be more accurate. You may get by extending the keyway just a little and drilling some of the key out of the drive pulley. You may also be able to disassemble the drive pulley and find a place to drill and tap for a set screw to extend into the keyway. There are set screws that are made with a pilot end to go into keyways.


http://www.mcmaster.com/#set-screws/=wj9hxz


On the driven pulley by extending the shaft through the bearing an inch or so, you can buy or make a deep cup pulley that aligns back over the bearing.

After building many belt drive bikes, I've found that the rear sheave is the starting point before I mount my engine or jack shaft because of these alignment problems.

http://motorbicycling.com/showthread.php?t=27104


Lots of good advice here by everyone, but it's up to you to determine what will actually work.

 

[curtisfox]

I am also thinking,like the clutch I rebuilt for you. It didn't have a full length key ,just a short one to grab the shoes,maybe do the same here just a 1" or so we're needed..........Curt

 

[silverbear]

I am also thinking,like the clutch I rebuilt for you. It didn't have a full length key ,just a short one to grab the shoes,maybe do the same here just a 1" or so we're needed..........Curt

Curt,
You mean just use a shorter key and forget about trying cut an additional inch of keyway?
SB

 

[silverbear]

msrfan,
Thank you so much for your insight and great links. I'd have to swallow hard before sending off for that drill guide, but good to know that such a thing is made and can also be home made in a pinch. Pinched I am and do have a drill press.

Also good to be reminded about the belt guide. I agree that alignment with the sheave is the starting point on mounting the engine.

Still scratching my head over the removal and replacement of the final drive bearing on the 5/8" shaft. More staring is in order.
SB

 

[curtisfox]

Yep, most lawn equipment have just a 1" or so key in them and not full length. And like Dale said get the rear pulley mounted first then get a stick and line up from there.
The rear shaft should come right out and just get a longer on if needed. You could also cut all of the long snout off and put a flang bearing on it.
Just keep in mind that the spacing of the belt is critical for CVT to work right...........Curt

 

[silverbear]

Yep, most lawn equipment have just a 1" or so key in them and not full length. And like Dale said get the rear pulley mounted first then get a stick and line up from there.
The rear shaft should come right out and just get a longer on if needed. You could also cut all of the long snout off and put a flang bearing on it.
Just keep in mind that the spacing of the belt is critical for CVT to work right...........Curt

Good thinking! I hadn't thought of the flange bearing, but maybe I'll be able to reuse the bearing that is on it. Yes, I know the spacing and alignment on the CVT is critical which is why I'd like to use their mounting plate and not make a custom jackshaft.

This is all beginning to look more doable. Awesome Possum!
SB

 

[msrfan]

I don't think the final drive bearing should be relocated. That's why I suggested a deep cupped pulley to end up mounted on the extended shaft and located where the bearing is now. I may be able to draw a picture if you can't see what I mean. McMaster-Carr offers triple groove pulleys with 5/8'' keyed bore that could be modified to work with your extended shaft.

http://www.mcmaster.com/#6213k71/=wjappk

 

[silverbear]

I don't think the final drive bearing should be relocated. That's why I suggested a deep cupped pulley to end up mounted on the extended shaft and located where the bearing is now. I may be able to draw a picture if you can't see what I mean. McMaster-Carr offers triple groove pulleys with 5/8'' keyed bore that could be modified to work with your extended shaft.

http://www.mcmaster.com/#6213k71/=wjappk

I may not be understanding this correctly, but if I am then the keyway and set screw are to the inside of the bearing and the wider part of the cone on the stepped pulley is hollow and would sit over the bearing... is that right?
SB

 

[curtisfox]

Yep like a fan pulley on a car offset dish. I just did one for mower deck last summer. Good thinking msrfan. LOL........Curt

 

[msrfan]

Here's a crude drawing of what I'm trying to say. Obviously you would get the smallest pulley available, but you get the general idea. I would rather modify a pulley to fit an extended shaft before cutting into the jack shaft housing.

 

[silverbear]

Okay, so I don't remove any of the housing around the bearing, but use a longer shaft and reach over the bearing with the cone shaped step pulley from outside the bearing. Is that it?
SB

 

[msrfan]

Yep like a fan pulley on a car offset dish. I just did one for mower deck last summer. Good thinking msrfan. LOL........Curt

Yes curt, a steel pulley welded to a small sprocket for example. The sprocket would provide for mounting onto the shaft. Grind the teeth off the sprocket to look better or weld between the teeth. Anyway you may not have room for this, but it's worth a thought.

 

[silverbear]

Here's a crude drawing of what I'm trying to say. Obviously you would get the smallest pulley available, but you get the general idea. I would rather modify a pulley to fit an extended shaft before cutting into the jack shaft housing.

Got it! Now I need to see if I have enough clearance between the shaft and the seat post.
SB

 

[msrfan]

Okay, so I don't remove any of the housing around the bearing, but use a longer shaft and reach over the bearing with the cone shaped step pulley from outside the bearing. Is that it?
SB

You got it. Hope this info helps. We all do things differently. Some work and some don't.

 

[silverbear]

You guys are so helpful. Thank you!
SB

 

[curtisfox]

Silverbear! I would be more then happy to build it if you need it,just let me know.........Curt

 

[silverbear]

Curtis,
You are such a good friend. I do appreciate your offer, but first let me get the parts together and see if this is something I can manage on my own. If I can't, then be assured that I will come begging.
SB

 

[curtisfox]

Awesome fun to be part of any motor bike creation,be glad to help..............Curt