Mikuni TM38s over the years have undergone quite some iterations in their design. As it turns out, the newer style floats (left and middle) only offer more buoyancy for as long as they don't fill up with petrol and then are better described as sinks than floats. The older design (on the right) is of rather elegant simplicity and is a direct swap. Only downside: They will fall out of the carb, if you don't turn it upside down, when removing the float chamber.
Older versions used longer studs with o-rings on the end to prevent the floats from falling out, but that is a rather bearable price to pay. Talking about price: They are also substantially cheaper and readily available.
Next, I finally got my wideband lambda (afr) gauge working and instantly put it to good use on the TR1. (It will really shine on the XS-Triple to iron out the last niggles on that, but testing it against a known quantity was meant to give me some rough insights in how (well) it would work).
That's 11.3:1 at idle, which correlates perfectly with my observations: a tad too rich down low and pretty much spot on from the middle upwards.
And then there was a certain someone's brilliant idea to "quickly" repaint the metal bits and make a new rear mudguard. The latter worked just fine, but the paint... different story.
It all started so well...
If you look closely you will undeniable notice quite a few scratches on the new tank. That's because it decided to jump off its painting hook.
The really annoying part came, when it turned out, that one batch of the clear coat had somehow become chemically incompatible with the paint and started dissolving the affore-mentioned.
Heat gun and scraper: actually works a treat. It made a huge mess, but it was all cleaned up again in about an hour or so.
The rear mudguard then went on without any notable hickups and looks fabby the way it is. Also if someone is looking for inspiration: The usage of an old (and somewhat hardened) breather tube and R-clamps to route the cable of the rear light on the inside of the guard is to be highly recommended.
Then I decided to make some fresh gaskets to go between petcocks and tank and that's where trouble started again. I specifically used some thicker rubber, thinking that it would seal better than my normal recycled motorcycle innertubes.
Well the next morning I was in for a bit of a fix-it-in-the-morning-before-going-to-work workshop session...
The leakage in itself was bad enough, but after draining the fuel from the tank – I had of course filled the old girl up good and proper...
... the fuel had dissolved the paint.
More by chance than by perfect planning, I had bought a set of (used) XVS650 petcocks a while ago, only to find that (for my application) the spouts were pointing in the wrong direction. Still, I decided it would be better than nothing.
As is rather apparent in the picture below, this petcock was leaking as well. Luckily this time it was only, because all the gaskets had shrunk quite a bit. Still some rather rude words might have been uttered in my workshop...
A couple hours later the o-rings had swollen back to their regular size and all is well again. Plus there's new filters and fuel lines on the bike.
Next stop: Time to get the exhaust on the XS-Triple built.
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