Saturday 18 June 2022

Dre-XT-Stück - BigBoreBadAssery (Deluxe)

Some people tend to make create problems for themselves. Take a perfectly good running motorcycle, a bit sluggish perhaps, but good running nonetheless. I confess, I am one of those people. Please don't get me wrong, there's nothing fundamentally wrong with that 95.25 setup, aside from maybe the fact that after a 620cc high-comp bigbore setup the old girl was feeeling "a tad" lame. 

That being said, some may recall I originally got myself a beautiful Wiseco 97mm piston with stupid high compression. (IIRC 11.5:1 - in the picture below it's the one with the carbon buildup.)

The other one is a Mahle out of a KTM LC4 620, but the more modern 640 is the same as they only increased the stroke. Also, this puppy is a whopping 101mm bore-size, which incidentially is exactly the same as on a XT660... bad ideas? Me? Nah... For those going down that rabbit hole, the SuperComp and SXC models ran a forged Mahle, the standard models a cast piston. Compression ratios are the same on both. 

After maybe giving one of you fellas some bad ideas, back to the main topic. As some may recall, I run a XT600Z (1VJ) carb on my XT. Which was pretty good on the first bigbore, but a bit of a pain with the stock piston. At the time of writing I am already contemplating, when to find some time to put it back in, at least for the initial break-in period. BUT, as luck would have it, I got my dirty paws on another XT600 carb, but this time the most desirable one, by the opinion of many folks I have spoken to, a 2KF version. 

Up to this point I was convinced that the differences were only in the jetting and base setup, but it turns out that for example the slide in the primary carb is also slightly different (you can see a port in the back, not present in the 1VJ-carb on the left).

 So I installed the 2KF and... well, things didn't quite go swimmingly. 

It turned out that a big flake of something was stuck under the needle as somebody had removed the screen over the float valve. Luckily I had a semi-broken carb at my disposal and could take the screen from that one. 

I merrily went about my usual business with the old girl and life was fairly good until the main fuse mechanically broke and I lost all my ancilliaries. (Yay for battery-less ignitions!) Then again, why it took me nearly a decade to come up with the clever idea to drill a hole into the top of the (former) battery tray to route the fuse down there... not my brightest moment. 

... and then a few days later a parcel from my favourite (used & new) XT and SR parts supplier arrived and was expedited in style to the workshop. 

Said box contained: a slightly used JE 98mm piston, with an not overly excessive 10.5:1 dome and a freshly bored and honed cylinder to put it in.

Friday morning (9:22): Dre-XT-Stück is ready to be the center of attraction for the better part of the day.

9:28: The old girl strips quicker than an exotic dancer confronted with hundred dollar bills.

 9:35: Quick chat with grandma and the other old girl is on the stand and the engine is loose.

Put the piston on TDC to check my timing marks

9:45: Engine is stripped down far enough only to miss having the pistons swapped out and start reassembly. (Narrator's voice from the off: It was at this point, when he wondered if he might have worked on those XT600s a bit too often lately.)

Quick side-by-side of the two pistons - the size difference in real life is much more notable, when you have both in front of you.

"Couple of rags" to prevent dropping the clip into the engine. Something which has never happened to me (yet), but has been frightening me ever since.

Shortly past 10:00: Cylinder going back on.

11:15 (and quite a few rude words): another one of those M6 threads that hold the camshaft down have failed and needed a timesert.

11:45 (almost) Ready to roll.

Whilst I was at it, I quickly experimented with an XS650SE fuel tank - sits too high, but in general the oldskool Scrambler look could be a nice alternative for those days, when large tank and panniers is not the way to go. 

A quick first rideout was had, which revealed:

  • carb desperately needs a rejet as that 633 is pumping a lot more air through than the almost stock engine
  • this is going to be a good un'... even though it was running lean there was a lot more oomph down low already. 


Monday 13 June 2022

The SR500 sidecar - even more post-reggo work (Part 15)

 ... and we haven't even gotten to the frame reinforcements. The TM36 carb below is by no means the only reason, but it played an instrumental part in me making sure that I do not get to said reinforcements just yet. 

When money is no objective, you can just go ahead and order the right one from the Mikuni supplier of choice. This one is NOT the ubiquitous TM36-31, but a TM36-50A, meant as an aftermarket carb for a Husqvarna TE410. With the biggest difference being the adapter on the back, which came off relatively easy with a hotplate and a drift.

In order to make it work with the stock throttle cables, all you need is one extra M5 nut as the carb is operated the other way round. Jetting at the moment: 12.5/130/1.5 turns/accelerator pump still enabled but turned down a lot. 

Next job was to turn down the sidecar mounting balls on the "equator" to make installing and removing the sidecar a bit easier. Thing is, somebody might have chosen the perfect size balls for the job, which meant that I almost had to remove the jaws of the sidecar clamps to get them off.

At the same time, all the sidecar mounting blocks was hung from wires and got a lick of paint. It's not like I don't trust my zinc plating, I just think it could do with a bit of help. 

Another one of those minor jobs, which in the end makes one hell of a difference, is to mount rigidly mount the footpegs to the frame and remove the rubber isolators. A bit of POM roundstock did the trick nicely. A certain, well known supplier also offers an aluminium kit, but the thought of steel, aluminium and salt didn't quite inspire confidence.

They are slightly oversized in the frame and as they compress a bit, when being installed, the footpeg-backplate-bolts that go through are now a press fit in the plastic. Trust me when I say, THIS is a gamechanger.

Dimensionally, I turned them from some 30mm roundbar, center hole 12mm, the recessed part that goes into the frame is 10mm tall and 20.10mm in diameter. The locating hat is 3mm thick. 

Next step was to make the tail-light work. The contacts of this (brandnew) el-cheapo Guzzi V7 taillight are so bad a solution had to be found. I decided to go with cables directly onto the LED-bulb. 

As it is one of the more decent LED bulbs, it actually works decently enough to be used, as in it is nicely visible from all sorts of angles and uses a lot less power than a conventional filament bulb. (Which due to the vibrations lasted the better part of 100km.)

One of the things I forgot, when installing the rear brake shaft in the bike was to put a stop in, which resulted in the rear brake lever sitting up very high and thus causing a rather unpleasant seating position. 

Much better - now I can put my right foot flat on the peg and not have to turn it out to the right in order to avoid the brake lever. 

Ultimately the bike looks almost the same, but the freshly painted black mounting blocks are a nice touch, if I am honest.

So what's up next: More dialing in of the flatslide, quite some thread repairs on the forks (the front mudguard acts as a sort of fork brace), solid handle bar bushings and a one-piece handle bar clamp, repair the shock-mounts on the swingarm and then most likely I'll finally get to those reinforcement plates.

Wednesday 1 June 2022

The SR500 Sidecar - post rego is pre-ride-o (part 14)

Contrary to the title, the story actually starts a few days before the old girl made her trip to the local DMV to get her official inspection. For a start let's bask in a bit of the awesome looks.

Now if looking awesome would have been part of the registration process, yup the old girl would have totally nailed it. Unfortunately good looks don't quite do, for a start, within 5km of doing testrides the old girl would ruin a tail-light bulb. And not just ruin it, obliterate is probably more to the point.

... and another. Turns out, if you install the holder the right way round, the bulb doesn't touch the lens.

That's a nice tach - what's wrong with it today? Oh the two screws came loose? Yeah, just take the glass off. Easy fix.

Yeah, nah. (Bought another tach, fitted it, job's a good 'un.)

Then the sidecar seat was definitely missing a decent locking mechanism. I wanted it beefy and rust free. Over-engineered? Would be rude not to. 

Another thing I discovered, as I had several rotors and stators, is that not all work equally well with each other. Resulting in a top-speed of about 80-85kph and REALLY difficult starting.

See how the big coil is in a different position? And so is the triggering nose on the outside of the rotor. (Take this as a sort of public service announcement that at one day might come in handy...)

Then asked the ever so helpful Günther (you know, who you are), whether I could borrow his trailer, loaded the old girl up and got all the paperwork in order, which was pleasantly unexciting, if I am honest. (Aside from having to get up at 5AM as I had to drive quite a bit to pick up the bike and trailer then get back to the DMV and then drop of the bike and return the trailer...)

Got this really expensive little book to go with the bike...

... and then registered the old girl.

First shakedown run went as good (or bad) as one would expect, made it all the way from the workshop back to Linz to pick up some bolts and longer rivets for the tarp and made it back with no real drama. 

Also swapped the rear brake adjuster for something that can be used without tools.

Now I have to express my hearfelt sympathy for all sorts of noise regulations out there. Really, some stuff is just obnoxiously loud. But the old girl with my homegrown was now 10db (or about 3 times as quiet as the paperwork allowed), yet the header pipe was bluing faster than I could spell the word blue. Or in other words, a more free-flowing solution had to be found. 

 Take a big M14 washer and put it in the lathe...

... some 1.75" tubing and a bit of TIG-magic...

... and another washer with what looks a lot like a nipple. So exhaust gasses have to go round a corner once. Result a bit louder, but still under the registered limit due to a really old testing method at only half of the max. RPM, which in other words is just slightly faster idle on the old girl.

At the same time, the header pipe lost its support, to make installation a bit easier. 

With the exhaust side sorted, it was time to tackle the inlet and I started (for now) by removing the airbox-snorkel. 

As the rear brake lever hit the exhaust pipe, I gave that a bit of a tweak and guess what, when you can press that lever all the way, that drum brake is more than just "quite alright".

Now if you happen to buy Konis... make sure you buy them from a reputable source. My only saving grace was that I had bought the exactly same type before and as such I still had a spare.

Oh and a bit of eye-candy - replace the manky old breather port bolt with a nice, shiny M5x12 stainles allen head.

Time to use the old girl "in anger" for the first time and about 90km in a go. Final score:

Speedo cable came loose multiple times.

Lower front engine mounting bolts (M8x20) - both gone.

Taillight bulb - death by good vibrations.

Long bottom engine mounting bolt - almost on the way out.

Two new bolts, all locknuts replaced with new ones and a fistful of torque sorted things right out. Just the taillight... well that LED-bulb will have some wires soldered onto it directly, because the contacts are just rubbish.

First oil-change revealed no nasties.

Two new bolts.

Angled greasy nipple on the pivot, so I can get to it with the greasegun.

Verdict-time, how does it stack up against the brutish XS850? It's obviously quite the different animal. It's light, probably just a bit over 200kg all in all and ready to go, plenty of torque. I sprayed gravel into the workshop on the first few testrides and dug some nice 4" wide trenches in my granny's driveway no problem at all. Obviously it's a lot slower, which quite frankly sounds a lot worse on paper than it is in real life. With the triple going 100kph at all times was no problem, probably even going 110-120kph no big deal, with the small thumper, 80kph feels like hitting the sweet spot. And then there's fuel consumption, even though it has probably got almost the same frontal area, it's only a single and it sits at feel-well rpms most of the time, the first refill yielded an average fuel consumption of 5.66L/100km which is almost on par with a Solo SR500 or just a wee bit more thirsty than my XT600. 

Coming up next: There's still the matter of the frame-reinforcement plate for the headstock, I think after some playing around with the jetting some holes in the airbox-lid might be beneficial and probably a 15T instead of the current 16T sprocket may work wonders for top-speed. Also the new tach seems to have an issue, as it doesn't read anything over 4000rpm.