Project 2-4: Installing a 2-Stroke Motor in a 4-Stroke Frame, Part 6

Jun. 06, 2011 By Rick Sieman
Let's bring you up to speed so far on our project bike. We started out with a YZ 426 rolling chassis, less the engine. We were able to buy this complete bike for $1000 even. For another $250, we were able to get a running 1979 RM 250 Suzuki motor.

We used a heat gun to soften the plastic. The gun costs about $15 from Harbor Freight. We were careful not to melt the plastic; we just heated it up enough to where it became pliable. Then we put a thick towel on the press to keep from messing up the plastic on the tank, and we then used a block of wood to press down on the area that we wanted for clearance. Discreet use of the heat gun was required, and we were very careful not to rush things.

Our goal is simple: we want to make a bike that was lighter, easy to maintain, cheaper to build and performs well. In part five, we finally got to the point of fabricating an exhaust system, and now it's time to do a whole lot of detail work that's got to be done before we could even think about starting the bike.

Here is the bottom of the tank with the area pushed down about an inch and a half to clear the spark plug.

Most of the plastic on the bike was in really good shape with the exception of a few scuff marks and scratches here and there. We used Krylon sun yellow paint, and found it to be a perfect match for this Suzuki colored plastic. Before we sprayed the plastic, we sanded it very lightly with 400-grit (wet or dry) sandpaper until it was perfectly smooth, and then we cleaned that surface with some contact cleaner. A few fine coats of the sun yellow paint made the plastic look like new.

When we got to the right shape, we sprayed a little cold water on the plastic to literally “freeze” it into the contour we wanted. Here is a side view of the tank.

Project 2-4 Installments
Part 5

Part 4

Part 3

Part 2

Part 1

We had one real problem to take care of still, and that was the bottom left side of the gas tank where it made contact with the spark plug. While we could ride the bike as it was, there's no way we could remove the plug without taking the tank off. This meant that we had to do some sort of correction on the actual shape of the tank directly above where the spark plug went.

So follow along as we did this and some other very important detail work.

Now the spark plug clears the tank and can be removed.

The tank can now be bolted into place.

Here’s a brake-side view of the project at this point.

The stock right side shroud is bolted into place.

Since the stock shroud was meant to direct air to the radiators, they'd no longer have to be as big as they were but would still offer some protection to the electrics and the aesthetics as well.

The shroud was cut quite easily with some ordinary tin snips. You can make it any shape you want, but here's the shape we've settled on.

Any rough edges or sloppy cuts can be shaped up with the use of an ordinary bench grinder.

With the shroud cut down and in place, the bike started to look good.

The same was done on the shift side of the bike.

But the tank now looked a little bit barren, what with being a flat black color and no decoration at all. We solved this by taking a simple mylar number plate sticker and cutting out the shapes we wanted.

Here's the shift side of the tank with the very simple shapes that we cut out applied.

Here’s a closer look at our artwork.

The front number plate got a coating of Krylon.

Left rear number plate got the same treatment of Krylon sun yellow.

The brake side of the bike also got a nice yellow number plate, and at this point all the little details that we have done were starting to add up to make the bike look good.


Project 2-4 Installments
Part 5

Part 4

Part 3

Part 2

Part 1 Newsletter
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