Saturday 28 August 2021

Everyday TR1 - TM38-86 (revisited)

Now I don't like failures or giving, especially when I know there's an actual solution to the problem. As such it seriously annoyed me that I didn't find a way to have the old TM38-86s run nicely on my TR1. So I bought another set. 

Additionally I bought (per carb):

  • 2x M3x10
  • 2x M4x16
  • 4x M5x20

 Plus a 40 degree throttle-cable bend and a 2in1 throttle cable 51-6506.

I started with unscrewing the splitter and then GENTLY clamping the cables in the vice using the splitter as a funnel to oil both sets of cables. 

Then hooked up the cable and replaced all the hardware for stainless allen bolts with plenty of copperslip on the threads. Also a bit of grease goes a VERY long way on the paper gasket of the carb top and prevents it from sticking to the carb body and subsequently tearing apart.

The stock jetting of #22.5, #230, 1.5 turns on the airscrew is probably a good starting point, if you run huge velocity stacks or something like that, but for me a more modest #17.5, #185 and 2.0 turns stopped the smoke and yielded some rather respectable performance on the way home from the workshop. (Mind you my exhaust is far from stock...)

Out with the old VM38-9s ...

... and in with the fresh TM38-86.

The difference between 1.5 turns fluctuating between 11.0 and 11.6, because it wouldn't run cleanly.

And 2.5 turns out, running a stable 12.2 to 12.4:1 at idle.

On the way home I noticed that the idle had crept up considerably and now with some slight detonations on a very hot engine, probably around 2.0 turns out would be more the right ball-park for the setup. 

But even with quite some room for improvements this is where we're at at the moment:

Addendum: Air-screw 2.0 turns out from a soft seat and idle set to roughly 1400rpm, when hot did the trick. Bike runs better than ever and I can't hear any detonation or notice any stumbling or hesitation in the rev-range.  I also went ahead and sync'ed the carbs once more and shot a little video of it, especially for those, who keep telling me they can just "eyeball" it. (I can't - at least not to this degree.)

So the next step will be to find out how good or bad the fuel consumption is. 😏

Wednesday 11 August 2021

Dre-XT-Stück gets drilled and new ears

 ... something, something rude joke. The by now rather trusty XT600 has got a slight airflow issue, stemming from the fact that someone (me) put a huge mudguard in front of the engine, which hasn't got a single hole to let air pass through. 

... and then when rummaging through various boxes and stuff, I found these folding mirrors, which I had bought originally for my old XT500, but didn't give the seller. That being said, these aren't the real deal ones, but Chinese knock-offs, so once that single is buzzing properly there's not much one can decipher in the mirrors.

To be fair, aside from quite a bit of riding, not a whole lot is going to happen to the old girl in the coming weeks. Eventually I will make the pannier rack for it, but there's no imminent need for it at the moment and there's a new project in the shed that I have to turn some wrenches on...