650 Mod's 78 Fighter Build

Devin, not the same frame or drive, but I took 0.300" off my Cush drive. But before doing so I spaced the front sprocket over the 5/8" I thought I could get away with, then spaced the hub away from the swingarm until my straight edge on both sprockets lined up. Threw the chain on to check clearances. Made the front sprocket and measured clearances again with the chain on, paying close attention to the chain at the tire to know how much I could cut the Cush drive. Then took an equal amount of spacers off the axle that I had cut off the Cush. Checked everything again, and then cut new axle spacers. Im running a non o-ring 530. If I could start over I would have bought a 525 front sprocket.

Alan

Bob- The chain I had bought was a 530 O-ring chain as the rear wheel I bought already has the 530 pitch sprocket on it. Going with the O-ring chain probably wasn't the best idea... I just bought a non-O-ring chain today.

Al- I currently have .125 shaved off the cush. Still have .125 clearance to the tire with the O-ring chain. I'm thinking I should gain .0625 or so by switching to the non-O-ring chain. I'll then have 3/16th clearance to the tire. Shave the cush down another .0625-.125", and I should be ok. This will give me .0625 clearance or so to the tire, which should be more than enough.

As soon as I have a little time to tinker in the shop, I'll get an update up. Thanks for the input, guys.

Devin

I changed the chain out for a standard 530 pitch chain, no O-rings. Gained 3/16th of an inch or so. Which brought the chain closer to where I need it to be to have the proper clearance to the frame. Ground down the welds on the inside of the frame around the engine mounts, and the chain JUST grazes now. So the next move will be to shave another 1/8th off the cush drive to give me more than enough play to the frame.

Another small hiccup in the progress... It's getting there though

I am about to be going mono shock with that same swing arm and finding this thread extremely useful, just want to say thanks for all the input an knowledge from everybody here!!!

Awesome! Glad you found everything helpful here I'll be back in the shop soon too, so more will be up as progress carries on. Hopefully this makes things very easy on your end!

650mod wrote: Awesome! Glad you found everything helpful here I'll be back in the shop soon too, so more will be up as progress carries on. Hopefully this makes things very easy on your end!

The pictures help lots, I'll be trying to copy your top shock mount, or something very similar. By the way what was your total offset measurement for the front sprocket, I'm getting 5/8 but it's hard for me to tell being that the swinger I have is so stretched Im having a hard time with finding a straight edge long enough to get a nice measurement !

don't overlook using a string as a straight edge.

remember the term"straight as a string".

leon

Yepper, use some bright colored dryline (masons line). Very strong and stretchs out nice and tight.
Wayne

531blackbanshee wrote: don't overlook using a string as a straight edge.

remember the term"straight as a string".

leon

Jmoney: I'm unsure of total offset right now- but I'm thinking I'm somewhere around 5/8ths. I've shaved 1/8th of an inch off my cushdrive to let the chain ride in closer to my tire. I'm hopefully in the shop over the week, so I'll have the sprocket all welded up then and I can get a rough idea. But I think I'm going to be somewhere around 5/8ths or so- seems to be the standard offset.

And fully agreed with Leon and Wayne- the string is a quick way to see if your chain has any pitch in the middle (left to right misalignment).

Devin

Looking good Devin. Please do keep us updated on your progress.

your 78 Fighter conversion is being featured in the BikeBuilds.net
directory here: 650mod's 78 Fighter build

We’re currently displaying only a reduced-size photo (similar to what you’d find in Google
Images). We'd like to ask for your permission to publish the original full-size image with your
build listing.

If anyone would like to have a build of their own listed, just send me a message with a link to
the build thread and we’ll take care of the rest.

Al

Hey Al!

Absolutely, feature whatever you would like on the site Giving people tips on their builds is always welcome. Hopefully this weekend I'll be back in the shop, The summer was super busy for me, so winter will be my crunch time to get her done. Thanks!

Devin

Alright, guys. I'm back! Things got super busy for me in June/July with my Master's Thesis work, but that's COMPLETELY out of the way now Now I have more time to focus on important things, like building bikes

I got into the shop today with my welder and we tackled the last really large bit of the build- getting my offset lined up properly and welding up the sprocket. We decided to take the cush drive off again, and shave even more meat off of it to get the sprocket to sit closer to the tire, In total, we've shaved 1/4" off the cush to drag the chain closer to the tire. Total offset on the sprocket is 21/32", a little more than 5/8ths said and done.

We got the cush off, took the sprocket lugs out, and threw it in the lathe to shave another 3/16" off it.



After that, we put a few of the sprocket lugs back in, put the wheel back on, and checked to see if we cleared the frame and tire- we have about 1/8th of an inch on both frame and tire side- perfect!



It was then time to weld the sprocket up and get this thing solidified.



I'm really happy my friend is helping me out so much with all the welding- I couldn't ever weld this smoothly. He does amazing work. Picture of the outer face of the sprocket.



Picture of the inside face of the sprocket. Nice smooth beads.



We went to move onto getting the foot rests sorted out, but I forgot some of those pieces at home... This will be the job for next time.

Maybe Leon can answer this one- when it comes time to harden the sprocket up, I think you said to heat it cherry red then dunk it in a bucket of oil/mineral oil?

I should be back in the shop fairly quickly as I now have plenty of free time to spare Updates should be up more often.

Devin