New Xr Project

[vintagemx]

So I have this '83 XR100 frame, front-end and swingarm. The original plan was to use those parts to upgrade my sons XR75 so it would last him a few more years. Thing is in two years I'm going to need another XR75 for my younger son. Rather than swapping parts around I've decided to just build a whole bike around the XR100 frame.



I'm putting together a list of all the parts needed to complete this project. I'm going to use an XR80 motor, which would still make it legal for the XR75 class. I'm also going to try and do a better job tracking the build process. My last build project spanned the technology jump from 35mm film to digital. One day I'll find the time to scan in that shoebox full of photos.

[PlanetMinis.com]

[vintagemx]

Here's the XR100 frame.







Something doesn't look quite right?







The bad news is the frame is bent...







Bummer!



The good news is I can fix it. These early XR stamped and welded frames are flimsy. There isn't a lot involved with straightening them as long as you have the tools to make sure it's aligned properly. The trick is gusseting the frame so it doesn't bend again. For that you need all the parts for a mock assembly to make sure the gussets don't interfere with other components. I've made that mistake before.



Time to find some parts.

[Luckystar64]

So I have this '83 XR100 frame, front-end and swingarm. The original plan was to use those parts to upgrade my sons XR75 so it would last him a few more years. Thing is in two years I'm going to need another XR75 for my younger son. Rather than swapping parts around I've decided to just build a whole bike around the XR100 frame.



I'm putting together a list of all the parts needed to complete this project. I'm going to use an XR80 motor, which would still make it legal for the XR75 class. I'm also going to try and do a better job tracking the build process. My last build project spanned the technology jump from 35mm film to digital. One day I'll find the time to scan in that shoebox full of photos.

Looks like it'll be pretty cool. What series has an XR75/80 class? If AHRMA had some pitbike class-- I'd like to build one myself. ---L*64

[vintagemx]

What series has an XR75/80 class? If AHRMA had some pitbike class-- I'd like to build one myself. ---L*64

The Hammer & Tongs series here in the Northwest. I've never understood AHRMA. You need a law degree to understand half of the rulebook and it seems like there's a class for every age group and motorcycle made... Except for kids and minis. It's a real shame too. The XR75 had a huge impact on the sport.

[hobbeekid]

Looks like your frame got run over by something heavy at some point in it's life like maybe a pickup truck?! anyhow I'd just find another frame to mess with instead of that thing.There's too many of em out there.I know that socalvmx is starting a xr75 racing class for 2012.who knows if this gets popular enough, maybe AHRMA won't have a choice but to take notice. I hope they start a 2cycle mini class open to bikes 86and earlier but I believe that's too much to ask at this time......

[vintagemx]

Looks like your frame got run over by something heavy at some point in it's life like maybe a pickup truck?! anyhow I'd just find another frame to mess with instead of that thing.There's too many of em out there.I know that socalvmx is starting a xr75 racing class for 2012.who knows if this gets popular enough, maybe AHRMA won't have a choice but to take notice. I hope they start a 2cycle mini class open to bikes 86and earlier but I believe that's too much to ask at this time......

I was able to straighten the frame. Working on the gussets now. Those early XR stamped frames are pretty flimsy. Add 35+ years of abuse, by kids and adults, and finding one that's not bent or cracked is akin to searching for the proverbial needle in a haystack. Actually this applies to a lot of vintage bikes unless you're lucky enough to come across a former factory bike. Since getting into the vintage scene my skills with hydraulics, fixtures, welding and machining have been put to good use.



I'm not going to hold my breath on AHRMA. Our local series has an XR75 class for kids, which is what I'm building this one for.

[Luckystar64]

I was able to straighten the frame. Working on the gussets now. Those early XR stamped frames are pretty flimsy. Add 35+ years of abuse, by kids and adults, and finding one that's not bent or cracked is akin to searching for the proverbial needle in a haystack. Actually this applies to a lot of vintage bikes unless you're lucky enough to come across a former factory bike. Since getting into the vintage scene my skills with hydraulics, fixtures, welding and machining have been put to good use.



I'm not going to hold my breath on AHRMA. Our local series has an XR75 class for kids, which is what I'm building this one for.

Ahhh. For kids. Wonder why not for adults too? Why should the kids get to have all the fun? --L*64

[vintagemx]

Ahhh. For kids. Wonder why not for adults too? Why should the kids get to have all the fun? --L*64

There's a 100 class for adults and the rules state:



"INTERMEDIATE & EXPERT 100 Classes - vintage & evo - will allow 120cc four strokes, in line with Ahrma's Rule."



No reason an adult couldn't run hot-rod XR75 in the class.

[vintagemx]

So it's been a while since this project first started. Got the frame straightened and have collected a bunch of parts. Since these parts come from different bikes from different years I figure I better mock everything up and make sure it fits before painting/powder coating. Had to trim the tank stops and the rubber bumpers. Used the bumpers to support the back of the tank. The seat is a tight fit but it does fit. Tank and seat are from '77 or '78 XR75. More stuff to come. I also need to repair the steering stop tab that's tweaked. Probably from the same crash that bent the frame.

[vintagemx]

This project stalled once more as I was busy trying to keep the '74 XR75 running. Lost a couple e-bay bids for an engine, so that killed my mojo too.

This week I plan on getting all the parts painted so I can start the assembly. For the time being I'm going to use the engine, and some other parts, from the '74.

The '74 will get repainted to stock colors, black frame, gray tank/side panel with gray fenders. Hopefully by then I'll have another motor.

[vintagemx]

Swingarm and brake arm blasted, primed and painted.

[vintagemx]

Tank after two coats of paint. Got some peel on the second coat, so I'll do some wet sanding, adjust the gun and apply another coat. Then graphics and clear coat.

[vintagemx]

Frame bead blasted and ready for priming then paint.

Straightened the tweaked steering stop and brazed the crack. Might touch it up on the grinder. I have a feeling I'll regret not replacing it.

[vintagemx]

More progress...





Back in Black



First coat

[hobbeekid]

Frame bead blasted and ready for priming then paint.

Straightened the tweaked steering stop and brazed the crack. Might touch it up on the grinder. I have a feeling I'll regret not replacing it.

Who knows you might be satisfied with the way it came out.If it's straight, why bother spending money you don't have to... looks promising Keep up the good work!

[vintagemx]

Thanks, progress has stopped once again, but this time for a good reason. Going on a cruise Monday. Hanging out in Galveston catchin' some rays and havin' some drinks now.

[vintagemx]

Back in business... Sort of. Just finishing up clear coating the frame swing arm and tank. Took the xr100 forks apart and found the right fork tube was bent. So I'm looking at alternatives. Ordered all the parts I need to start putting things together.

[vintagemx]

Okay so this thing is moving slower than molasses in winter, but today I made some progress and started fitting all my e-bay/CL parts together.

Still have some things to work out. Ended up with '83 CR80 forks and MR175 triple clamps. Everything bolted up, but now I'm going to need longer shocks in the back, or maybe lower the forks 3-inches.

Waiting on some things that are coming, like a motor, and I need to get the wheels powder coated, polish the hubs and lace them with new spokes. One thing I still need is an exhaust. Could've snagged a nice Bassani off e-bay, but someone beat me out at the last minute.

[vintagemx]

Mo' stuff... courtesy of Mr. ShapeShifter. All that's needed now:

• Modify steering stop to keep forks from hitting the tank.
• Rebuild one of the XR80 engines in that box o' stuff.
• Rebuild and shorten the forks.
• Longer front brake cable.
• Fenders and side panels.
• Put all this stuff together.

[vintagemx]

No updates to report on The Project.

Been busy working on the '74 XR75 (stocker). Got tired of the engine pissing oil all over the garage floor. One of the weld repairs to the case was leaking. So I looked at both the XR80 engines I got from ShapeShifter and picked the best one.





It fits!





79 cubic centimeters

Had to repair the broken rear air box mount. The carb hit the frame using the intake off the 75, so I bolted up an XR80 intake off e-bay. It's about an inch too short from attaching to the air box.





DOH!

I could just put a pod filter on, but would like to keep the air box for the wet season. Made a little adapter and will connect it using some radiator hose and hose clamps.