fuel tank prototype

Prototype using the LOST FOAM method, where you do a layup around polystyrene foam, and then pour in some acetone to melt the foam away. I encased the foam in packing tape with PVA coating so that the interior lining of the tank is not too ugly. Not sure about this technique, because it leaves a surface that'll need a lot of fairing.

airbox fab.

Originally, I had thought to just attach a couple pod filters to the carb, but there's not enough room with the monoshock there. Plus I've read that pod filters can make it a real pain to get the jetting correct. Also, with no aft attachment place, the carbs are more prone to wiggling. So I decided to use the existing air boots on the inlet side and attach them to an airbox of my own design.

The original airbox was rotted out from neglect and had all sorts of ugly bits that would normally be obscured by side panels. So here's an attempt to make a cleaner airbox with a bit more filter surface area for sucking.

Construction approach was to do a final layup around a male mold and cut around the circumference to lift the halves off. Using this technique allowed me to do a small layup around this circumference beforehand, so that I had a good mold to make a joint piece from.

Anyway, here's the foam plug getting shaped:



The plug waxed and ready for the layup:


Here is the joint piece assembly:


Layup done, vacuum bagged to minimize voids:



Outer surface need a bit of fairing once the resin cured:

I marked the circumferential cut with masking tape and took my DREMEL OF FEAR to it:

BAM!!!

Fitting the two halves together with the joint interior, then epoxying the joint to the forward side



I fabbed up a little backfire screen that the air filter will rest against. This is still twice the surface area than the stocker. Ought to be good enough for the time being



I then made a spring loaded "cage" that will be used to press against the foam filter element along the edges to form a reasonably tight seal along the backfire screen edges.

Here's where it sits now; hope it fits!

one reason to love thumpers.

top end tear down.

With oil looking like it did, the inner workings of the engine didn't look as bad as I imagined. Still could use a rebuild.


Cam chain tensioner had one MEAN looking spring holding it in place..."That'll be a fun bastard to install" I thought to myself...

In a pinch, pancake batter can substitute for engine oil.

Step one, drain the engine oil...HOLY CRAP! WHAT IS THIS???

Apparently this happens when water gets into the engine oil. Lovely. I'm sure it also makes a wonderful foot soaking medium.

More Cleaning

With the engine sort of running after the carb rebuild, I continued some deep cleaning work, trying to remove the baked on mung between the cooling fins of the cylinder. This is when I noticed one of the 6mm Hex head bolts attaching the rocker box cover to the head was loose. Well, actually it wasn't loose, more like the threads were stripped out. It would need a helicoil at least, and I worried there might be more damage in the cylinder. Instead of ignoring, I decided this was impetus enough to take the motor apart, send the top end to XRs Only and have them refurbish it with a valve job, etc. Anyway, more cleaning and prep work to get the engine out of the frame (sadly, you have to remove the whole engine in order to get the top end off since the frame backbone gets in the way!

kuoba link

Instead of chopping the rear shock, I got a lowering link for the rear, made for an XR650L. It fits this bike, okay, but the end caps need to be turned down on a lathe or something.