"No Regerts" - Triumph Mongrel 904 Choppah, planningoncrashing-style

This is a non-update update to say that I've accomplished absolutely nothing with this bike and that I don't plan to for a few more weeks yet.

I may be tearing the frame completely apart, since I apparently erased all of my project files (ever), and with them, such trivial things as the drawings I did with all the angles and tube lengths to get everything back in shape. First, I get to redo that.

Instead, here's a picture of an old Gold Wing with its bodywork removed, since that's what I have been working on.

Update time!

Work has been done!

(Kind of.)

The first order of business was to remove most of the back end of the bike, since the tacks broke when the frame fell off its stand a couple of months ago and the alignment was all out. I also removed most of the rust. Here it sits on my high tech welding stand (itself once a frame).



From there, it was simply a matter of setting it back up on a rail, getting the back end close enough to in line with the front, and tacking everything back in place.





My 1/8" and quarter-degree tolerances for straightness would be crazy-loose on a real motorcycle, but for this ridiculous bullshit, they're overkill. It may be straighter than that, but I didn't feel like getting out the real tools to measure.



The lower hoop was a simple retack job once the top was welded up straight.



"DO NOT MAKE ANY MODIFICATIONS TO THIS TRIUMPH FRAME. MODIFICATIONS SUCH AS WELDING OR DRILLING MAY WEAKEN THE FRAME RESULTING IN AN ACCIDENT." Being a moron, I didn't put down a wet towel when I welded the fill plate into that hole, so this sticker is now ruined. Triumph doesn't seem to sell it separately. Damn it.



It was snowy out, so I brought everybody inside.



It's been a few years since I've laced a motorcycle wheel. The front came together on the first try. I had to unlace and relace the rear three times. It's fortunate that these aren't important parts, since clearly I was paying zero attention to what I was doing.



... and we have a roller. Fits right in.

I still need to finish a few welds that are (heavily) tacked, and I have five or six brackets to weld on... still plenty of work to do, but man... having wheels on it makes me happy.



The next step is, of course, sorting out this mess.



Here's the original problem. The starter idler gear spindle exited the original case without ceremony. The underlying metal was... not awesome. I've since ground it down to install a plate, but that's kind of a mess. I have a set of good cases, so I'm going to use those instead. Don't get me wrong. I'm super-bummed about not putting the original cases back into service. It's just not practical at this particular moment, and I need to get the engine together.

Swapping the main bearings from the old cases provided the right clearance and now the crank turns freely.

The problem now is that there's too much drag in the trans, so I'm going to have to play with bearings and spacers to get that sorted out. Not the end of the world. In the mean time, I'm packing the engine away, because two of the case bolts have wandered off, so I'm $2.20 in metric fasteners from being able to actually button this thing up.



And here they are, put to rest for a few more days.






With bolts on order, all that's left are a few odds and ends, like a lightened flywheel and an EFI conversion...

One step forward, two steps back.

Did you know, when they tell you to loosen the case bolts in a specific sequence, they mean it?

I always thought it was just a sealing thing, so that the cases would mate up nicely and not leak oil. I mean, I do it anyway as it's good practice, but seeing as I care absolutely zero about small oil leaks, and that I'll probably have a slow seep from at least one of the gaskets on this motor regardless (seriously... if I built a birdhouse, it would leak oil), I didn't think much of running some random cases I bought on fleabay. After a week of assembling, disassembling, measuring, and reassembling the gearbox, on repeat, and there's still too much friction in it, I had second thoughts. Sure enough, put the top case half on plate glass, and it rocks just a little bit. Bottom half is fine. Old cases are fine. Transmission runs fine in the old cases. The old lower and new upper are trash, but the bores in the new lower case and old upper are allllmost perfectly aligned...

Almost.

Damn.

Sooo... plan 'R' exhausted, we're now on to plan 'S', I think...?

I guess find another motor?

Nope. Don't want to sink a thousand more bucks into this.

The original cases are going back into service. The two options I'm weighing are making a patch out of a chunk of thick aluminum, LIKE THIS or, possibly, just running it as bump-start only. The bump-start would also solve the battery problem (namely, I hate big batteries) and would likely be a fair theft deterrent, but it would mean I'd need to go to standard controls, because bump starting a foot clutch on the regular is a bit above my pay grade.

Hmm... More thought needed... Probably should work on the other bike for a minute.

... instead, I decided that it was time to procure the highest-quality food available in my neighborhood after 10 PM, and devote further consideration to what exactly I should do with the engine...



I really want a jockey shift and foot clutch, and there's really no reasonable way to bump start a bike with a foot clutch.

I really want a jockey shift and foot clutch because I have a really cool jockey shift lever...



A REALLY cool jockey shift lever (pictured here with my fancy front brake setup and my BMX foot pegs)...

When it comes down to it though, I want a jockey shift and foot clutch because it's so impractical in city traffic, and being a dork, I think that's cool.

Jockey shift / foot clutch ain't got nothin' on bump-start-only for impractical.

I think that one's pretty well decided, then.

"That frame is gonna' crack."

No. Seriously. I've looked at a lot of bikes, studied a lot of frames, and built a few things myself, and I'm pretty sure that by keeping the build light overall, it'll hold together just fine. Race bikes use thinner tube than this pretty regularly, and they don't break their frames.

"No. Seriously, race bikes have suspension, and if you think running a sprung bike on a smooth racetrack is harder on a frame than riding a hardtail in the city, you've lost your damn mind. That frame is gonna' crack right there [at the steerer], there [where the down tube gusset will be], and there [at the seat pivot mount]."

Why?

"Twins vibrate. Oil in frames had bigger backbones that was twice as thick and they crack at the neck. The new ones don't buzz so bad, but you got half as much metal holding that together, plus a hardtail. Your joint is too tall, which means there's more leverage from one side to the other. It's gonna crack. It's gonna have to. There's no other way for it to get rid of the stress. You boxed in all your triangulation, so it'll be too stiff. Even without that, it'd probably still be too stiff. These frames need to flex if they're gonna live."

What if I...

"You do what you do, but I'm tellin' ya', that backbone's gonna break. Want that bike to be safe? Redo it."

-------------

Well... shit. Dude is right. Dude is totally right. I'd considered this strictly from a strength perspective. I hadn't thought about vibration or that this thing might NEED to flex in some way I hadn't considered.

That was not the bar conversation I expected to have with a stranger when I hit the place up the street for a beer last night.

It also makes cutting the tip of my thumb off with a paper cutter a couple of weeks ago look like a minor setback.

Alright. Guess it's back to the drawing board on this one. I think it's time for the Yamaha to get some love while I sort this out.