Saturday, 4 December 2021

The XS Triple Sidecar - XS1100 swingarm installation

It all started with a comment from Ralf that he fitted an XS1100 swingarm and final drive into his XS750 sidecar. To be fair I had the same idea a while ago, but it always only came back to mind, when I really needed the old girl to be working and doing her thing on a daily basis. 

The hard facts: approx. 7 percent shorter gearing, which should fix the issue with a slightly long first gear, when pulling a sidecar and as an added bonus 30mm more wheelbase due to a longer swingarm and being quite a bit sturdier than wouldn't do harm either. 

It's rather apparent that not only the XS1100 swingarm (on the left) is beefier than its 750 counterpart, but also quite a bit wider.

19mm wider to be precise. Luckily due to the way the swingarm mountin is arranged on these bikes the odd millimeter up or down wouldn't make a differents as the swingarm runs on adjustable pins.

With the in mind, only way to do this - get the angle grinder out and hack that swingarm to bits. Sounds dramatic, but I knew that the outer bearing cup was originally only welded on (for those who want to do the same, the lip is about 5mm deep), so cutting it off sufficiently far away from the cup made the rest a rather simple job.

Clocking it up in the lathe using the original bearing cup of the swingarm bearing as a reference was a tad nerve wrecking, but I got it within 0.02mm between high and low spots.

Then turned it down to a nice press fit inside the swingarm tube

A final sanity check with the cup pressed in and it ended up spot on in terms of the width. Same 281mm as my stock swingarm.

An old 17mm rear axle out of a XV750 had to sacrifice it's thickened part, where it normally is clamped in the swingarm to act as a draw bar and alignment tool for the swingarm. 

I admit, my TIG weld looks nicer than the stock MIG weld that was there before. It's probably also a lot stronger. (There were some penetration issues in the original weld that became apparent, when I shortened the swingarm.)

Fitting the swingarm was a royal pain as it is rather heavy and obviously imbalanced and there's not a huge deal of room to wiggle it in. Also some idiot forgot to put the rubber boot on.

Swingarm out again - aside from the width, the indent on the right and the brake brace mounting point had to be modified.

Next stop was the splash guard on the rear wheel. Turns out with it installed the rear wheel doesn't clear the final drive housing.

The bolts dig into the housing and if you were to replace them with countersunk bolts the studs of the final drive housing eat into the shroud.

Once you look at both the triple and the 1100 units, it becomes rather apparent why it won't work as the 1100 unit is more or less flat and the triple inner cover has got the wheel coupling sitting a notable bit further out, giving plenty of room for the shroud.

In the end it all aligned rather nicely.

Let's waste no more time and tackle the elephant in the room: Was it worth it? Oh hell yeah. First gear is now short enough that I can take off without touching the throttle on level ground. First and second gear as soon as the engine gets into the power band makes the rear wheel light up and me grin like an idiot. And in the end, ain't that what it's all about?

Thursday, 25 November 2021

The XS Triple Sidecar - back to snowmobile carbs

So I am going back to 31mm* snowmobile carbs and no it's not that I wasn't happy with the modified Gixxer flatslides, but to be honest I will need them next year on a mighty four that has been lurking way too long in another shed. (*Yes, previous iterations used 33mm snowmobile carbs, but I have sufficient carbs to make a 4-carb rack of those and only a single 31mm rack with three carbs, also torque is more important than outright horsepower on a sidecar once you reached a certain point.)

As usual they were properly mangled and not much use to me in their stock form.

This time I tackled the task differently than last time, because I wanted to use all the original inlets or at least the cast bosses as first I broke through the casting last time on one carb and second a fuel line in the way of the throttle cable during installation is no fun at all. 

The one bit not shown is how I aligned the casting in the mill with a drill bit snuggly fitting into casting before milling the remnants of the pressed in fitting flat and then drilling it out.

Tapped M8x1.0 (standard hydraulics banjo bolt and banjo) and then after tapping gave it one more lick with a milling cutter to make sure the surfaces were square.

Milled down the boss on the left carb and there you go, enough room for the fitting. Don't think you could get it out with the carbs as a rack though. (But then again that was not the objective.) Also spot the challenge that came from turning a right into a left carb. The throttle-shaft hole is plugged.

Luckily in terms of the right carb, it is only plugged and can be knocked out with moderate force. (It's a nice press-fit though.)

It's a completely different story on the other end of the rack. Turning a left into a right carb involves a fair bit of thinking and machining. 

The first step was moderately easy once I summoned all my bravery to just drill into the casting. (As can be seen, I first tried to do a sort of lineboring job, but that didn't work, so I aligned a 16mm endmill with the casing and did what I had to do.)


Fun starts with the insert that needs to go in there. Because it has to be an inside and outside press-fit and has not too much wall thickness left, so each of the two will affect each other, if I c*ck it up. (Spoiler from this point onwards I do consider myself a proper engineer.) So turn it to 16.55mm as the bore in the case is slightly out of round and measures 16.52mm at the widest point.

Then took the seal out of the carb body. It's a relatively normal 10x14x3mm lip-seal and if it weren't for a lockdown, I could buy one of these over the counter, if I screwed up. As can be seen, it checks out to 14.08mm and goes into a 14.00 hole. (So Mikunis press-fit was chosen a lot tighter than mine.)



Test fit on the lathe - wall thickness around 0.75mm (16.55-14.00mm) and yes, it distorts with the seal inserted. So I gave it another lick on the lathe and at least at that point it was round again.

Pressed into the casing, thanks to a light taper on the backside, it centered nicely and started with finger pressure.

Couple of tap-taps later and it sat all the way in and the shaft didn't bind up.

Making a solid 4mm tall, 14.00mm plug for a 13.95mm hole was almost relaxing at this point. Also, MGEHR-tools leave a beautiful finish. The 14.00mm were hit going straight down from 15.1x and this was the moment, when my ego politely pointed out that it was due for its own postcode.

Same trick, slight taper on the backside to get it started and the a few love taps to drive it all the way in afterwards.

The plan (obviously) was to use the throttle shaft I made for the Gixxer carbs and to be fair, I think that wasn't too outlandish to think it would work. Well, it didn't all holes are just a tad off to these. 

So I did it all again (sorry no photos, it's boring...)

Not sure, why I altered the throttle cable mount last time, but it clears just fine, so it'll stay (almost) stock.

And that's the finished product - aside from painting the carb tops black and making an extension to the idle adjuster shaft. 

Fuel line is now a pretty straight forward affair and the horizontal section will be zip-tied to the rail.

So there you have it - bit more work necessary to get it finished and I have to come up with something smart regarding the throttle cable to give it the 90 bend it needs for perfection, but in all honesty this should be the hard part done.

Sunday, 21 November 2021

The XS Triple Sidecar - unplanned maintenance

To be fair to the old girl right away, it was only unplanned, because I had originally expected to get through this Winter on the new sidecar. (Regardless of whether we're talking about the SR500 or the XV-sidecar.)

I checked the valves last year and the inlets were a bit on the tight side (I thought), but the exhaust valves, aside from the center cylinder one, were "about there". How wrong I was. For some weird reason I was absolutely convinced that on an Yamaha XS Triple, you run the common-place 0.10/0.15mm valve lash. For some reason today I decided to have a look into the book of lies and lo and behold it said 0.20/0.25mm, some frantic checking and rechecking of various resources on the net confirmed the finding and as a result making the notes below even more concerning.

How to read the chart, I and E stand for inlet and exhaust, the bottom number is the shim thickness installed, the number above is the initial valve clearance and the top value the valve clearance after the shim swap. Now I am in possession of a lovely box full of shims, but if you're not and check your valves, you go back to this handy chart and then can work out which shims to order.

So I rolled the old girl into the workshop, removed the fuel tank and got crackin'.

The big trick on an XS-Triple, you have to remove the camchain-tensioner, which usually ruins the paper gasket, but if you lubed that gasket up like this is part of some kinky massage-thingy, see below. 

Also when re-installing the tensioner, use the lock-bolt on the side to lock it into the rear-most position for easier installation.

With everything assembled and the sun slowly setting on the old girl, just one question remains:

Why hasn't anyone snatched this beauty up yet?