Monday, 24 July 2017

The XS Triple Sidecar - sync'ing and rejetting and rejetting and...

Good things sometimes take a while and with the VM36-carbs on the XS Triple sidecar it was no different...

Let's talk about jetting carbs. First step after soldering the cables was to make a base-setup of the carbs. This requires a bit of experience and lots of jets. Depending on what the carbs come from, it can quite easily be, that you slap them on and fire the bike and see what's going on. As these VM36s came off a two-stroke Skidoo both the pilots and mains had to be swapped out.

Next set the throttle-slide-stops (i.e. the idle adjustment) to the same level. A rather crude way to do it is to simply slide in a drill under the throttle slide cutout and then set all three of them so they just touch it.

Then the next step is to fire the bike up and see what happens. If you're lucky it will fire up and you will have to work the throttle and the air- or mix-screws a bit to make it start, run and finally idle. Be aware that just because a bike idles means absolutely nothing in terms of how well it is set up. (Spot the missing mainjet in this picture... yes it came loose and lay around in the float chamber, still the bike idled.)

Next you try to sync the carbs (assuming you have both idle and at least midrange) - I did this with my trust vacuum clocks, but you can of course also just do it via the cables.

As you might have noticed, the pictures look a bit different than usual, that's because I've been using my trusty old DSLR instead of my normal camera, so it would have been rude not to play around a bit.

Some backfire through the #1 carb

Once sync'ed and rejetted a few times, it started to sound more like this...

So are those VM36s are simple install and why isn't everybody doing them? Well firstly they are an incredibly tight fit as you can see in the pictures below, I had to remove some of the breather tubes as the carbs were touching each other.

... and then there's this thing with the cable splitter under the tank, which is huge and there's no off-the-shelf solution for. But is it worth it (after a testride): Hell yeah, she's a gas guzzling, fire-breathing, two-wheeled hoodlum that will reward exactly one-smile per mile, because it goes all the way!

Friday, 21 July 2017

Ms. Braaaaaap - gets a new exhaust

To (incorrectly) quote Mark Twain: Reports of my death are greatly exaggerated. Or in the case of Ms. Braaaaaap, I did toy with the idea of selling her, but as there were no (serious) takers, I guess she'll stay around a bit longer.

She suffered from a few (smaller) issues like the tail-light not working correctly, which by now all have been remedied (more or less, but more on that in another post). Except for a very, very, very noisy exhaust. And those who know me, are aware that I am not exactly very girlish in such matters.

So here we have the (old) offender, which was the very first exhaust I made, back then with a stainless steel electrode.

As I normally don't have the sidecover off the next two photos show my homegrown airbox-lid and a modified MZ TS250 inlet rubber (no pre-silencer on this one anymore) to make getting the carb in and out much easier!

As it was MOT-time, I though, well I still have that old beaten up Sebring, which I could "just" slap on and that's it. So I took the old exhaust and wanted to fit the Sebring, but nope... won't go over the seal on the stainless downpipe.

While I was at it, it seemed rude not to extract the broke bolt that was stuck in there.

So as that clearly didn't work, I decided to say f*ck it, I'll build a new exhaust straight away. These universal 1.75" silencers are a sort of personal favourite and I had an old waterjet cut mounting plate left over.

Test fitting a 90 degree bend behind the rear shock, following the idea, that some sharper bends would slow down the exhaust gas and thereby reduce the exhaust-crackle notably. 

The bracket was only partially useful and needed some tweaking with the bandsaw. 

After a bit of drilling I welded the cut-off-part onto the silencer...

... and there you go. Might be a bit long for the taste of some, but it's quiet (enough) and doesn't hamper performance, which means I can use the bike regularly again. 

That's what the exhaust looks like, when taken off the bike.

And after a nicely spirited ride to the MOT man, who failed me again, as he thinks no exhausts without "E"-markings are allowed anymore. (Which is wrong, but no amount of arguing with him could convince him. So I guess, I'll do a few more modifications, including re-installing the diskbrake-frontend and then get all those mods added to the paperwork, so I can enjoy the XT without remorse.)

Before you ask, there's nothing substantially wrong with the drum-brake frontend, it actually stops quite well, for a drumbrake (running some rather soft Ferodo shoes) and even when compared with the stock XT600 diskbrake, but I didn't forget the amount of maintenance work involved to keep it that way, if you actually use the XT regularly.

Tuesday, 18 July 2017

Everyday TR1 - rejetting and syncing

Lately I have been playing around a lot with getting the everyday TR1 (the Traktor) dialed in perfectly. It's been 90% there, but still... until I found out, that maybe a year ago or so, I tried a flatter ignition curve, because I had some heat issues. They weren't cured by less ignition advance, but I never got round to setting the curve back to the values, I used before. And as I tend to alter my ignition curves by always choosing the previous one and then make some alterations... well you get the picture. The result was relatively simple: After going back to that old curve, I now had to raise the needle one notch as it was pinging a bit at 3000 rpm. Not shown, but at the same time I also swapped out the mains for #170ies, instead of #175s as it was a bit rich on max rpm and now it revs to 7500rpm in 4th (couldn't go any faster yesterday).

Unfortunately, when you take off the carb tops, you will eventually mess up the synchronization. But as a lot of people asked me, how I go about sync'ing cable-operated carbs, my loss is your gain, I guess.

My setup (sorry for the dark picture, I've used a different camera...) is an old moped-fuel tank hanging off the ceiling and feeding both carbs.

First step is to fire up the bike, open the cable adjuster on the throttle grip and turn that up until the RPM increases. (This way you make sure you're actually sync'ing the cables and not the throttle stops.)

I've drilled holes into the cast inlet manifolds of my cylinder heads, so next step is to unplug the sync ports.

The actual cable adjustment will have to be done via the cable adjuster on top of the carb. 

With the clocks plugged in, you will probably see something like this. (I simply assume you know how to hook up the clocks without damaging them, if not, RTFM.)

Now the only (slightly) counter-intuitive thing you have to know: If you the vacuum is bigger on one port than it is on the other, this means the throttle slide is LOW and you have to raise it. (It's simple physics, if you don't believe me, try it out for yourself.) And after a bit of fiddling, you end with something more ressembling this picture.

Then you tighten down the locknuts on the carb tops without disturbing the settings and you're done.

Friday, 7 July 2017

The other XS Triple Sidecar - fuel petcock adapters

If you're thinking something along the lines of... "didn't he say he was done with the bike and it's ready to be sold" you're totally right. BUT firstly with an old bike, you're never done and secondly the original fuel taps were at least 30 years old and after turning them on and off a few times they decided that leakage was the way forward.

I've built some fuel-tap adapters in the past and remember one set of baseplates that I ruined ages ago, by drilling the hole too large (as in 19mm, where it should have been 16...)

Well then, grab a bit of 20mm ally roundstock, turn it down to 15.90mm and thread it M16x1.

Prepare it for parting off. (My parting tool is an old HSS-blank, which I should really upgrade to some good carbide tool rather sooner than later as I have a few ideas, which involve stainless...)

... and after sound all so professional realize, that the backside better be flat, but with a light chamfer. *doh*

Nevertheless the thing that can be learned from this mishap: a bit of painter's masking tape and a very gentle hand on the chuck can save things. Ideally don't f*ck the part up in the first place and you don't have to freestyle your way out. 😉

Wednesday, 5 July 2017

The XS Triple Sidecar - making those VM roundslide carbs work

The uni year has ended and this means on the contrary that I am back in the workshop and making some progress.

One of my big misconceptions with this whole VM36 setup out of a skidoo was to think it would be quick 'n' easy. Apparently even when those carbs look 99% like standard Mikuni items, there's a few funny differences compared to a stock VM36/38 carb.

 It's the literally millions of tiny modifications, e.g. the needle is held down with a special clip in the slide unlike as on any other Mikuni VM, I've ever seen. Next the carb-top-cable-adjusters had to be drilled out to 3.5mm to make the cables go through (they were originally part of the throttle-cables) and the list goes on like that...

Lots of measuring was involved in order to get all the cables to the right length and yes it took two attempts (of course).

Once the cables were done at the right length it was assembly time, which presented it's very own problems as in space under the tank was a bit tight and stock routing was absolutely impossible.  (Also to make sure, I didn't have to route the cables in sharp bends...)

So was it worth it...? It took a few attempts to make it fire up and the carbs will require quite a bit of fettling to get them right, but I am pretty convinced that the final result will be worth it.

Sunday, 18 June 2017

The new TR1 motor - Introduction (part1)

As you might have guessed by the apparent decrease in posting frequency: Exam time is upon us poor students. The mere mentioning of these perilious times sends shivers down the spines of even the most brave students... but I digress.

The XS Triple isn't even remotely done (yet) and still, there's a new project dawning on the horizon. I have recently started to gather the parts for a new motor for my trusty old everyday TR1. Originally I had only planned to bore the cylinders to the next oversize and slap the engine back together. But truth be told, the most worn out part of the whole engine are the cases. Nearly every thread of a bolt holding on the sidecovers has been stripped and helicoiled and there must be some small crack on the left side somewhere between the alternator cover and the neutral switch.

Luckily I still have a good set of cases under the bench and then I literally fell over a parted out XV1100 engine that I managed to pick up really, reallly cheap.

 Together with some new (used) rods and fresh bearing shells the bottom end is pretty much sorted. Additionally I also managed to score a set of XV700 cylinder heads, which I got today, cleaned up and inspected and then put next to an old XV750 head I still had lying around to show you the differences.


The interesting feature about those XV700 are the two squishareas, whereas a normal XV750 only has got one (larger) squish-area, which also creates an uneven load on the piston and that can be seen with the small ends of the conrods wearing out unevenly. 

Of course, one of the new heads came with the mandatory damage to one of the fins... Guess we'll see a bit of ally welding soon.

As you can see the on the new XV700 heads, the combustion chamber is basically shifted 5mm to the right. I haven't cc'ed the combustion chamber, but I suspect it might be a bit smaller, but it's also recessed by about 0.5 - 1.0mm so overall the compression ratio should end up the same or only marginally higher.

An absolutely essential part is to clean up all the parts. One of the best methods (I found) to remove old carbon deposits is to use some industrial gasket remover spray, let it do its thing for five to ten minutes and then just brush it off with a soft brass brush and the combustion chamber cleans up nicely.

The other part (as you might have noticed in one of the first pictures) is that one head was increadibly oily and dirty and I found typical kitchen cleaner to be the most effective way to clean off that grime.

As I mentioned before: the next two weeks I'll mostly spend with my books, so only expect some minor updates (if any at all). The next update on this project will most likely be, when I measure the crank and rebuild it with fresh bearing shells and some good (used) rods. To be fair though, it'll probably be at least another four weeks until you hear about this project as I really want to get done with the sidecar before I start a new project.