Slowly but surely . . .

This project is taking a while (cash flow).

 

[Frogslayer]

Also going to have to cut the fork tube cups off and redo them. (wrong size: face palm)

Damn it!

 

[Randall]

Damn it!

I know, right?

 

[FNTPuck]

Glad you posted to remind me to come back here...

If you do go the jackshaft route and try a kit, do NOT use the bearings they come with. They are absolute trash and when I ran the numbers and compared online they are freaking wheel barrow bearings not even meant for motorized use.

I tried them out and they have a dramatic amount of excessive bearing play under load - as soon as I started giving it gas from a ~15mph roll the bike got a nasty clunking vibration and snapped the short crank chain since the jackshaft actually moves forward ~1/8" due to bearing play which brings the sprockets out of alignment. Added a half link thinking it was just too tight and tested with final drive chain disconnected so I can free rev it and it did the same thing - you can see the movement that causes the sprocket teeth to hit the side plate of the chain, which snapped a link. Even though I was only going like 10mph when it happened it was still very unsettling.

I am replacing them with proper sealed flanged bearings and supporting them with ~1" of a bearing race tube on each side, with a ~1/2" hold drilled in each tube so I can still use inner lock collars instead of just outer. Only ~$20 extra for priceless amount of piece of mind.

 

[Randall]

Glad you posted to remind me to come back here...

If you do go the jackshaft route and try a kit, do NOT use the bearings they come with. They are absolute trash and when I ran the numbers and compared online they are freaking wheel barrow bearings not even meant for motorized use.

I tried them out and they have a dramatic amount of excessive bearing play under load - as soon as I started giving it gas from a ~15mph roll the bike got a nasty clunking vibration and snapped the short crank chain since the jackshaft actually moves forward ~1/8" due to bearing play which brings the sprockets out of alignment. Added a half link thinking it was just too tight and tested with final drive chain disconnected so I can free rev it and it did the same thing - you can see the movement that causes the sprocket teeth to hit the side plate of the chain, which snapped a link. Even though I was only going like 10mph when it happened it was still very unsettling.

I am replacing them with proper sealed flanged bearings and supporting them with ~1" of a bearing race tube on each side, with a ~1/2" hold drilled in each tube so I can still use inner lock collars instead of just outer. Only ~$20 extra for priceless amount of piece of mind.

Thanks FNT.

Yeah I think I am going to go the route of pillow block bearings and 5/8ths shaft (size of the sprockets). I dont think I trust
my fabricating techniques just yet. Critical area not to have any misalignment or bad welds. I'm going to fabricate the mount
though (easy peasy).

 

[Randall]

Okay so the pillow block jackshaft is a fail. Not enough room to mount it (another facepalm). The seat tube is too close. Should have taken better measurements. OY! BUT, I was able to grind a little bit more material on the slots with a die grinder on the motor mount and push the engine the 1/8th - 1/4 inch that I needed to align the sprockets. YAY!!! (lol) Hooked up the chain and she's now rolling under power! I will have to post a video here soon. No brakes yet so I will have to show it going up hill (lol).

 

[FNTPuck]

I'm jealous of your tire clearance! I have like barely 1mm lol, gonna heat up and dent the chainstays to get a tiny bit more clearance on that side so I can throw thin washers behind the sprocket to bring it out a little more since it lightly grazes the tire and gets rubber dust everywhere. Just 1 under each bolt would be fine, its that close.

Glad you were able to line it up easily! If I could get away without the jackshaft I would too, just adds more complexity and drivetrain loss.

My bearing race w/sealed bearings worked much better than the hanger plates and cheap bearings did, but while test riding it twisted the whole thing around the seat post by almost ~1/2" which threw the chains out of alignment so I had to gusset it with 1/4" thick plate to the motor mount brace. I had planned to gusset it anyway during final paint+assembly, but thought it would be fine to test ride just a decent bead to the reinforced seat post - guess not lol.

Big 4stroke+converter is a TON of torque which loves to break stuff, be careful.

 

[Randall]

I'm jealous of your tire clearance! I have like barely 1mm lol, gonna heat up and dent the chainstays to get a tiny bit more clearance on that side so I can throw thin washers behind the sprocket to bring it out a little more since it lightly grazes the tire and gets rubber dust everywhere. Just 1 under each bolt would be fine, its that close.

Glad you were able to line it up easily! If I could get away without the jackshaft I would too, just adds more complexity and drivetrain loss.

My bearing race w/sealed bearings worked much better than the hanger plates and cheap bearings did, but while test riding it twisted the whole thing around the seat post by almost ~1/2" which threw the chains out of alignment so I had to gusset it with 1/4" thick plate to the motor mount brace. I had planned to gusset it anyway during final paint+assembly, but thought it would be fine to test ride just a decent bead to the reinforced seat post - guess not lol.

Big 4stroke+converter is a TON of torque which loves to break stuff, be careful.

I would weld a piece of flat bar on the outside of the smashed tube to reinforce it.

My bearing race w/sealed bearings worked much better than the hanger plates and cheap bearings did, but while test riding it twisted the whole thing around the seat post by almost ~1/2" which threw the chains out of alignment so I had to gusset it with 1/4" thick plate to the motor mount brace. I had planned to gusset it anyway during final paint+assembly, but thought it would be fine to test ride just a decent bead to the reinforced seat post - guess not lol. --- DAMN, that sucks.

So what kind of frame are you working with?

 

[Randall]

I now need to find some very good hydraulic brakes to stop this beast.

 

[FNTPuck]

I would weld a piece of flat bar on the outside of the smashed tube to reinforce it.

My bearing race w/sealed bearings worked much better than the hanger plates and cheap bearings did, but while test riding it twisted the whole thing around the seat post by almost ~1/2" which threw the chains out of alignment so I had to gusset it with 1/4" thick plate to the motor mount brace. I had planned to gusset it anyway during final paint+assembly, but thought it would be fine to test ride just a decent bead to the reinforced seat post - guess not lol. --- DAMN, that sucks.

So what kind of frame are you working with?

It was at one point a Sun Revolutions beach cruiser but almost all of it has been replaced, modified, or reinforced. Everything behind seat post was cut off and replaced with heavy tubing making it 1" longer and wide enough to fit 4.5" tires, headtube replaced with larger chromoly one and boxed, and seat post has a thick steel tube stuck down the whole length of it and rosette welded on 3 spots on both sides - bottom diagonally into the BB, in the middle, and in the top where the rear upper tubing attaches to seat post. In front of seat post the center of the frame was stretched 7in and has a 1" square tube across the bottom that the motor plate is welded to.

The tube is thick walled tubing same size used to make small hardtail motorcycles(think 70s Triumps and small Harleys) so even with a slight dent of around 1mm it is still way stronger than bicycle tubing, the wall thickness is more than that so it will barely deform lol.

 

[Randall]

It was at one point a Sun Revolutions beach cruiser but almost all of it has been replaced, modified, or reinforced. Everything behind seat post was cut off and replaced with heavy tubing making it 1" longer and wide enough to fit 4.5" tires, headtube replaced with larger chromoly one and boxed, and seat post has a thick steel tube stuck down the whole length of it and rosette welded on 3 spots on both sides - bottom diagonally into the BB, in the middle, and in the top where the rear upper tubing attaches to seat post. In front of seat post the center of the frame was stretched 7in and has a 1" square tube across the bottom that the motor plate is welded to.

The tube is thick walled tubing same size used to make small hardtail motorcycles(think 70s Triumps and small Harleys) so even with a slight dent of around 1mm it is still way stronger than bicycle tubing, the wall thickness is more than that so it will barely deform lol.

Oh, gotcha. Yeah, that should work really good once its up and moving.