New 160mm chuck backplate for the Matra

 Martha II came with a generous selection of original three-jaw chucks, made by very, very reputable manufacturers. Unfortunately they all shared one commonality: They were at least 70 years old and hopelessly worn out. 

To my big surprise Din800 M33 is still a pretty common standard on woodworking lathes. As cutting M33x3.5mm threads by hand is at the best of times "no fun", I was more than delighted to find out that cheap steel fixture plates are commonly available, but usually only up to around 125mm, with the odd one being available in 150mm/6". 

 

So in fact only the center section with the actual thread was really useful to me (for now) and a cheap 63mm (2 1/2") holesaw made relatively short work of the mild steel plate.

 

Trying the same trick on some actual tool-steel finally killed the poor holesaw and left me now other chance than to first drill and then bore the center hole to size.

 

 

Bit of TIG-magic later and a hole for a C-spanner later:

 

The thing with proper tool-steel and the right inserts is, you end up with a really lovely finish.

As the whole "using-a-holesaw-to-drill-the-center-out"-thing really backfired, I decided to do something I had put off for ages. A long while ago, I found a Morse Taper 2 reamer made in the Soviet Republic of Ukraine, still in its original wax coating and wrapper. Based on the writing the outside, I assume it was manufactured in February 1986. So, the brown stuff is almost forty year old wax and not rust. Also it is sharp enough to immediately draw first blood...

 

 

The bore cleaned up absolutely beautifully, even though I might have to face the barrel off by a milimetre or two as all the tool sit in there quite a bit deeper than before.

 

So that's it and I have to admit, even a relatively inexpensive 160mm chuck is a massive improvement over a worn out top-of-the-shelf one from more than 70 years ago. 

The SR500 sidecar build - Boring (part 5.1)

... holes and making a boring bar that works with insert tooling. If you have a boring bar, most likely of Far-Eastern provenance, you will have encountered them - import boring bars, with their little (usually dull) carbide inserts soldered on. Now one can work with them rather well actually, with some rework on the bars with a diamond file to make the inserts resemble some sort of a cutting geometry and some very, very light cuts one can get some pretty good results with them. But with the task at hand of pushing what the 6x26-mill can take in terms of cutting and doing a lot of it, this quite literally won't cut it. 

As this isn't quite my first rodeo, in the past I got a cheap boring bar and modified it as below. Unfortunately (for this boring bar), I no longer run TCMT16 inserts on my lathe and thus would have to buy inserts solely for this one bar. Not very economical, especially as I have a ton of CCMT09-inserts.

So this one started it's life as a 16mm, right handed boring bar for CCMT09 inserts. I shortened it to a reasonable length. (The shorter, the stiffer and more stiffness means less vibrations and that in turn means a better surface finish.) Then turned it down in the lathe to fit the boring head. In my case this meant going down to 12mm. Also this is where cheap boring bars shine as they are made from some butter-like alloy and turn beautifully on the lathe. 

At this point, one could go ahead and just use it, but every time you install it, you'd have to clock it to get it right on center (or actually a bit below) again. So I put it in the mill and made a little flat spot to register against. 

And there you have a boring bar where you can burn through inserts and not care much about it.

Oh and burn through inserts... I did not. For five holes, which resulted in enough swarf to fill up the whole vice and pile up left and right of it, I had to change inserts once, because it got a bit dull.

Dre-XT-Stueck - the re-Dre-XT-Stueck-ening (pt.2)

Didn't get much done on the old XT as I was mostly fixing up my new (to me) car.  That being said, I can at least show the frame off in its new paint.

Still plenty that needs to be done as both exhaust mounts are either missing the threaded boss or missing entirely. So that'll keep me entertained once the engine is done and back in, so I can line the whole exhaust up again.

The XS Triple Sidecar - gets some second hand GSXR 750 flatslides (addendum)

I had a quick hour in the workshop this morning and turned the idle adjuster down a bit, so that the spring wouldn't bottom out as that allowed me to get the old girl to idle and then sync the carbs.

With the spring base back another three or four milimetres, I can now screw the adjuster in far enough to set the idle properly. 

Only #1 carb was really a wee bit out of sync, #3 was more or less good from the get go. 

And thanks to all of that the old girl now has got a very grumpy idle...

Time for a testride, I'd say - but to make starting a bit easier, maybe first prepare the choke-rod and grind some dimples in it, so it would lock in place.

Secretly, this is my favourite shot of the whole build - safety-wired the fuel lines to the bodies as they were leaking ever so slightly. 

As the throttle housing is from a DR600 and would normally be flipped the other way round, I had to tap the hole in M5 and bolt it up. It makes a perfect point for oiling the cables though, so I guess I won't weld it up.

First testride went very reasonable. Lots of low-down torque, after adjusting the mix-screws a bit leaner there was perfect pickup from very low revs, but after a few kilometres #3 cylinder didn't want to fire anymore. Turns out the needle-jet is only a slide fit and not a press-fit anymore in its bore and I didn't notice screwing the mainjet into thin air, when I (hastily) assembled the carbs for a first testride.

So what's the verdict: Lots of grunt, which is exactly what I was after. I have to play around and maybe order some more mainjets as the full-throttle performance leaves some room for improvement. Brakes and suspension are working fine after the cleanup and overhaul, but the number of oil-leaks is starting to become a real issue. Guess I'll get by another season, but I really should have a look at the other engine-block I have and start tackling that one.

The XS Triple Sidecar - gets some second hand GSXR 750 flatslides

The plan is simple: Take carbs from an inline-four, remove one carb, put it back together, job's a good un'. Yeah right. What you see is a week's worth of work.

So I started off with a set of perfectly good GSX-R 750 carbs.

Removed the rails and the right-most carb to get a feeling, if and where the carb bodies needed to be modified and if maybe the stock throttle shaft could be repurposed.

This would have been my preferred placement for the throttle cables and idle-adjuster as they would have been perfectly accessible...

... and perfectly in the way of the fuel tank.

So shuffled the carbs around, ran the throttle cables through the frame. (Thanks Yamaha for placing this opening in just about the right spot!)

With the carbs laid out and all clearances checked, the carb spacing was finalised (88mm for those who want to do similiar things) and 15x15x2 stainless L-profile was drilled.

And it turns out there's just one spot, where things get a bit tight. Removing about 2mm from this fuel-line boss was all it took to make them clear.

In order to get the spacing on the bottom rail right, the throttle-shaft (10mm) was cut from a bit of stainless. (Stupid idea, more on that later.)

The bottom rail was then laid out and pockets milled out for the mixture-screws and the profile shortened on the engine side, so access would be a bit easier.

Drilling stainless is a royal pain. Even more so, when you have a slightly worn out Chinese drill chuck, which has got a bit of a death-wobble to it. (Unfortunately my good chuck won't grip drills smaller than 3mm and the one in the picture is a 2.0mm one...) So it broke off flush with the shaft.

Nevermind, got it out and went ahead tapping the shaft...

... bugger.

Then I went to my metal supplier and got an offcut of silversteel, enough for two carbs. Let's just say I am happy I did and the following pictures show me working with the material for the second shaft made from silversteel ...

Old machinist's trick here on how to find center, if you don't have a DRO on your mill (or want to do it quicker with just a long metal ruler) - once you've found center the ruler will be perfectly parallel to the mill's table. The longer the ruler the more accurate the measurement.

Throttle assembly is off a DR600, including the cables. These are actually bits I bought many years ago for my XT500.

And that's the carbs more or less finished. (Chokes missing in the pictures below, also the idle adjustment needs some quality time with my lathe and of course the whole lot has to be synced.)

Installed.

This is the actual second start of the XS with the carbs installed. No sync, no idle adjustment, nothing and she just purrs like a kitten.

What's left to do: Fix the idle adjustment, sync the carbs and then probably throw the O2-sensor on and see where we're at. First testride (regardless of mal-adjusted carbs) has shown a substantial increase in low-end torque, which is all this exercise has been about.