Bride of Frankenstein - a cure for leftover parts cluttering the workshop.

Tanshanomi

Well-Known Member
Rear wheel installation is complete. Rather than reduce the width of the spacer to compensate for the added chain adjuster plate, I simply used an old, banged-up screwdriver against the sprocket carrier to pry the swingarm apart, just enough to slip the existing spacer into place. The inner side of the chain adjuster is only 3mm thick, so the amount of movement required was quite minor, and didn't take much force at all. Overall, I'm happy with this solution; I think I have a safe and sound configuration.

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At this point, I could cut the chain to length. With the chain on the sprockets and the wheels still in my makeshift alignment jig, I adjusted the chain for about 1-1/4" deflection, then tightened everything down.

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On the right-hand side, my M10 rod ends arrived, so I drilled out the hole in the caliper bracket for an M10 x 1.25 tap, then added the torque link. I had to angle the caliper to the rear more than I intended; otherwise the bracket fouled the square upper swingarm tube running to the shocks. My use of threaded rod looks a bit bodge-y; I'll either cut threads in smooth rod stock at some point, or just slip an appropriate length of alloy tube over it to hide it. For now, it's functional.

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Tanshanomi

Well-Known Member
Taking a cue from the first-gen GSX-R, I’ve mocked up what a foam dash panel might look like. This initial go is just a rough cut out of some yoga mat I had left over from upholstering Bultakenstein’s seat. In fact, I’m not even totally sure what instruments I will end up using.

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The NOS John Deere snowmobile tach is my first choice, but it may not work for some unforeseen reason. The engine is a 1-spark-per-revolution wasted spark ignition, so in theory a two-stroke tach should work, but there’s no guarantee. The knockoff CT70 speedo should work fine, but without knowing the bike’s top speed, I wonder if the 0–50 MPH range will be adequate. [Wishful thinking, I know!] I do have a GPS speedometer and digital tach/hour meter that are self-powered. The electronic mini gauges are likely all I use initially. I will consider the bigger dial instruments after the bike is running. Ideally, I would like to have them all hooked up at some point to verify the gauges’ accuracy.

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Meanwhile, the punch sheet is getting smaller, and there doesn’t seem to be not many big, hairy technical issues left on the list.

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Tanshanomi

Well-Known Member
With oil in the crankcase a bit of gasoline in the tank, I attempted to start the Bride’s engine. There’s no CVT pulley on the crank, but I wanted to play with the throttle without the centrifugal clutch engaging. It was a rough first start. Pulling the rope only got a few pops at best. After a bunch of tries, I discovered that I could get to run with a very specific drill: choke on, a couple of pulls with the throttle closed, then whack the throttle open just as I pulled, and it might light. I was able to get it to run twice, but the idle was uneven, with lots of surging and some pops from the exhaust. I was not able to get the engine to run without the choke on.


A few unexpected things I noticed: the carb end of the intake tract got quite cold, the exhaust is louder than I’d hoped, and I discovered that the kill switch leads, surprisingly, do absolutely zip — I had to pull the spark plug cap to kill the engine.

It’s at this point that I am rudely confronted by my inexperience with carb tuning. I’ve never had a new carb run this poorly from the first go. From all of my past experience, jetting can be off pretty darn far and the engine can still idle fairly nicely. I looked at the plug several times, and the end never looked wet from fuel, so the hard starting isn’t from flooding. So I don’t know if it’s lean, rich, bad/old gas issues, or whether the super-long intake tract is causing issues (although Mike Festiva has demonstrated that it shouldn’t). The carb I’m using is a Keihin PE24 clone from Nibbi Racing. Nibbi is a fairly high-end manufacturer that I’ve had good luck with before and their PE24FL is a popular choice for modded Predator/clone motors. Perhaps I need to check my gaskets and make sure I don’t have an air leak somewhere? I am guessing there’s a lot of head-scratching ahead for me.

But hey, it has run, which is something I couldn’t say when I woke up this morning!
 

Tanshanomi

Well-Known Member
Could the super long intake be causing all the problem? Long way before it gets into the engine
Mike Festiva has a very similar intake on his Predator-powered XR100, and it runs great. I've talked to him, and he said he had no jetting issues getting it to work. I think his might have been a narrower diameter pipe, but his carb was also slightly smaller, so perhaps my particular setup is wrong.

 

GustoGuy

Active Member
A built Predator 212cc makes plenty of power even for a motocross motorcycle. I have a resto-mod Rupp Roadster 2 with built Predator 212cc and a Suzuki k10 fork and hydraulic shocks in the rear and I let my wife's 34 year old nephew ride it in July and he said he used to ride Yamaha 125cc dirt bike so I thought he could handle it. I warned him not to gun it since it hits really hard off the bottom and has enough power to wheelie up. Evidently he didn't listen and he wheelied it over bent up the seat pan. He told me that he didn't realize how powerful it was and he cracked the throttle and Supermanned my bike and wheelied it over. Now instead of riding I been fixing my bike. Don't let newbies or little kids ride Built Predator 212cc powered bikes since they could get hurt.
 
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Tanshanomi

Well-Known Member
My suspicion that my intake tract wasn’t airtight proved to be correct, and the reason was quickly and painfully obvious. I had totally skipped the build step of creating a gasket to fit in between my head adapter and intake pipe. I had assembled it with nothing between the two metal surfaces. To make matters worse, the two countersunk bolts, by necessity, sit slightly below the mating surface. You can see here that there is very little material surrounding them, so there is plenty of opportunity for air to sneak past in the best circumstances.

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I cut the gasket I needed from a sheet of high-quality gasket material (Fel-Pro 3157 — 1/32″ rubber-fiber, fuel/oil safe). I can seal things up further by adding a flush skim of RTV silicone over the screw heads with the adapter installed and torqued down, if that turns out to be necessary.

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I checked all the mating faces by coating them with layout blue and then and then lightly rubbing them on a plate covered with 220 grit emery paper. In the above photos you can see that the adapter flange was spot-on flat. The two end plates of my intake tube were not quite as true (after all, they had been welded), but likely good enough for a bit of gasket material and properly torqued bolts to keep things acceptably sealed.

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I bolted everything up, and it did, indeed, start and idle much better. It still needed choke and wasn’t perfectly smooth, but much, much better.


I must sheeplishly admit to why my kill switch leads weren’t functional. I had plugged them into the wrong connector. The wires at the rear of the engine are the kill mechanism. I think the identical connector at the front is an oil level sensor, perhaps? In any case, touching them together kills the engine now.

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Unfortunately, there’s enough play in the mounting holes that the carb was positioned just a skosh higher after re-installation, and the choke plunger touched the bottom of the tank. The choke kept spontaneously snapping shut — er, open. I loosened up the carb bolts, shifted its position slightly, and tightened them back up. I started the engine and let it idle a bit longer. This time the choke stayed on. When I went to shut it off, I saw a small piece of black plastic lying on top of the engine. Oops, I guess I was a bit too vigorous in re-tightening the carb bolts.

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The carb is so far away from the engine block that it really doesn’t need an insulator, so I might re-make this out of alloy. Somewhere in that process, I might be able to create more space between the tank and the choke knob in the “up” position. I will also make some sort of brace or bracket for the intake pipe, so it doesn’t vibrate itself to pieces. So, there’s still plenty of work to do.

I will need to develop some carb tuning skills. The jetting is clearly way off; the engine won’t rev smoothly and won’t idle without choke. I have very little experience with the sort of methodical diagnosis required to get a bike fueling well across all throttle positions and engine speeds, so it’s another opportunity to learn. Or perhaps to just make negligible progress for an extended period of time. We’ll see.
 
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Tanshanomi

Well-Known Member
With an hour or so to spend in the shop, I was able to make a couple of guide brackets for the rear brake line that attach to the torque link. The rubber grommets are actually designed to fit 3/4″ diameter truck marker lights, but I had some in my parts cache and they turned out to be ideal — just the right size for the banjo fitting to pass through. The way I have them installed on the torque link doesn’t make logical sense, but it was a quick and dirty install to see how they’d work. I’m happy with the result. I still need a couple more brackets further forward, where the brake line passes under the engine. However, a couple of simple P-clips might be all that’s needed there.

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Once those were done, I started on a replacement for the plastic carb insulator I broke. I got as far as laying out the shape on 3/16″ alloy.

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At this point, I had one of those “well, duh!” moments. Why did I need any spacer at all? I could just bolt the carb directly to the intake runner. Why have an o-ring and a gasket, when one mating surface would do?

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Why, indeed. I got a couple of slightly shorter bolts and cinched the carb in place. There’s no clearance problems with the throttle cable, and as you can see in the photo, the choke knob is pulled up without hitting the tank. There’s enough leeway in the bolt holes that I bolted the carb on slightly low on the intake tube, in order to provide that extra bit clearance. It looks sloppy, but I doubt that will cause any functional problems. The engine started on the third pull and settled into a very even idle, so I am calling that satisfactory.
 
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GustoGuy

Active Member
With an hour or so to spend in the shop, I was able to make a couple of guide brackets for the rear brake line that attach to the torque link. The rubber grommets are actually designed to fit 3/4″ diameter truck marker lights, but I had some in my parts cache and they turned out to be ideal — just the right size for the banjo fitting to pass through. The way I have them installed on the torque link doesn’t make logical sense, but it was a quick and dirty install to see how they’d work. I’m happy with the result. I still need a couple more brackets further forward, where the brake line passes under the engine. However, a couple of simple P-clips might be all that’s needed there.

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Once those were done, I started on a replacement for the plastic carb insulator I broke. I got as far as laying out the shape on 3/16″ alloy.

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At this point, I had one of those “well, duh!” moments. Why did I need any spacer at all? I could just bolt the carb directly to the intake runner. Why have an o-ring and a gasket, when one mating surface would do?

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Why, indeed. I got a couple of slightly shorter bolts and cinched the carb in place. There’s no clearance problems with the throttle cable, and as you can see in the photo, the choke knob is pulled up without hitting the tank. There’s enough leeway in the bolt holes that I bolted the carb on slightly low on the intake tube, in order to provide that extra bit clearance. It looks sloppy, but I doubt that will cause any functional problems. The engine started on the third pull and settled into a very even idle, so I am calling that satisfactory.
Amazing fabrication skills you have. I like how you are building a bike from the ground up with leftover parts and motorcycle parts.
 

Tanshanomi

Well-Known Member
I have the bike starting easily on the choke and idling smoothly. I still cannot get it to idle without the choke. I tried playing with the air screw, but it doesn’t seem to have much effect. I am left to suppose that either the float height is low, or the pilot jet is too small. I’ll have to continue playing with it.

In order to feel some sense of accomplishment, I also filled and bled the front brake. (brake line vacuum pumps are a stupendously wonderful tool to have, BTW.) I rolled it down a hill in the yard and it stopped the bike firmly at the end of the driveway, keeping me from rolling out into the street. So, that’s a win.

Since there really aren’t any meaningful photos to document any of this, here are a couple of general progress photos:

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