The pretty one - fixing stripped head bolt threads

 The pretty one is my dad's XT500T 4 valve. What it is, is essentially a XT600 2KF, but with a smaller bore (87mm) and the cylinder head off a JDM XT400. This means it has got smaller valves and a smaller combustion chamber  than a stock XT600. Whilst in a sense it is good that Yamaha put the effort in to make the engine work decently with the smaller bore, it also created its own set of problems. Whilst engine parts for the 600 are comparatively cheap and definitely plentiful this is definitely not the case for the 500 version as it was pretty much only sold in Austria. This should answer the question why we didn't simply get another cylinder and be done with it. Also yes, you can convert it to 600cc, but that would still mean you'd have to bore out the engine case and quite simply my dad didn't want this. (Remember when I did a frame swap, i.e. registered a new bike, because that was easier than converting Dre-XT-Stück to 600cc? There might be an explanation hidden in there somewhere...)

So the story with the headbolt threads follows a very classic recipe: The headbolts are M8, they are torqued to 30NM and they go straight into the aluminium of the cylinder. The cylinder in question has already been helicoiled three times, but there were two installation failure as I found out during the repair. A more permanent solution was needed and it came in the form of a handful of homemade threaded inserts. They are M12 on the outside and M8 on the inside and the ones I ended up using where 20 and 30mm long.

After taking the head off, it was pretty obvious where the headgasket leak was.

I (wrongly) assumed that the biggest challenge with this repair would be to install the recessed threaded inserts... as the first one had spat out its helicoils this was a very straight forward job. Nerve wrecking, but simple enough.

On the second one, the helicoil was still in there, but as I found out, the locking tab hadn't grabbed correctly and I just pulled it out. 

Installation was simple enough: an M8 bolt, a nut, a spacer and the insert. (Yes the spacer is also made from a bit of turned down M12 threaded rod. 

Just to be really sure the inserts were glued in with some high strength locking adhesive.

Test fit with the locating dowels in place worked a treat.

Somewhat inspired by all of this, the next day I decided to upgrade all remaining headbolt threads as well, including the one with the only working helicoil of the previous repair attempt. It did not go well.

As the previous attempt of getting a helicoil out worked rather well, I didn't think much of it and snapped my drill about 10mm below the surface when it locked up. Those were two not very funny hours.

... the final one was a case of "more of the same" was every bit as pleasantly straight forward as one could have hoped for. (And yes, I had made a new spacer in the meantime.)

The finished product.

What followed next is the "usual" assembly of an XT engine, though I have to admit that there's a distinct difference between a completely sh*gged example and a well-cared for two-owner bike. 

Apparently last time I swapped the headgasket I made the same mistake as on the Dre-XT-Stück with choosing the wrong time mark (talk about consistency), so that was rectified in the same go.

... and that one bit where I decided it was time to ruin the purity and replace some mangled JIS screws with some stainless M4x25 allen heads.

The first startup was pleasantly unexciting. Let's hope it stays this way. 

Merry Christmas dad. 😌

(Yes there's plenty more work that needs to be done to make it usable, but at least for now it seems as if the head's going to stay where it is supposed to be.)

Been out to the Sölkpass SR/XT meeting

... and my dad and my humble self did more km on the XTs in a single rideout than he did in the entire last year.

Now there's a distinct reason, why my dad's XT is called "the pretty one" and mine's called "Dre-XT-Stück".

A few corners before reaching Pyhrn-Pass.

If it's called "Kirchenwirt", it's only stereotypical that the local church official has got his own reserved parking spot.

The meeting itself is rather small and at the end of gravel-track (hence us riding on the ol' XTs), but the turnout was good and a lot of old friends have been met.

Even though not quite an SR/XT 500, that BSA B31 was probably the sexiest bike at the meeting (at least in my opinion. Even though my dad heavily drooled over the endearingly well-used Guzzi LM4.

We only paid a short visit to the actual bike rally as there was another action item that had to be tackled. On top of the Hengstpass is a little hut, which amongst other things sells some rather delicious Kaiserschmarrn. (Sort of a sweet omelette served with homemade fruit-jam)

Unfortunately on the way home at an intersection we had a bit of a misunderstanding that caused a bit of bent metal, a broken mirror and some bruises.

But as we had some discussion, why the performance of the pretty one was somewhat lacking a bit compared to the Dre-XT-Stück, I dug out a well perforated airbox-lid. As I suspected, the old girl was running rich in all places and that extra bit of air made her very, very lively.

So lively in fact, that I decided that the old Dre-XT-Stück will eventually get the same treatment, especially as she's awaiting a 600 engine transplant some time later this year.

Project "pretty one" - Another XT500 4 valve and the Italian Beauty

So my dad probably can't help it, but he's got a soft spot for his very first XT 500 4 Valve, which is an odd-ball model and is a smaller bore XT 600. Now ever since this one turned into a smoke bomb, we said we're gonna investigate and fix the f*cker.

So here we are. The most harmless reason would have been that either the scavenge oil-pump (XT600s are a dry-sump setup) is leaking or for some other reason not sucking enough of the good juice back to the oil tank resulting in too much oil in the crankcase or that the check valve in the clutch cover is stuck resulting in the oil tank emptying itself into the engine, when park for a (longer) while.

That's said check-valve. Poke it with a stick to see if it's stuck. (It wasn't.)

Next step was to work towards the oil-pump. For this the clutch has to come off as it's driven from a gear on the backside of the clutch basket.

With the clutch basket off, a yellow-ish gear becomes visible, which is the oil-pump. Unlike on the older 2-valve XTs and SRs. It's fixed with nice hex-bolts instead of the old philipps, which always put up a terrible fight.

Undo those three bolts and pull out the oil-pump. There's a pretty self-explanatory check procedure to check the lobe-clearances between rotor and housing and even though the pump was working fine, it's over the service limit.

This means the Dre-XT-Stück will be degraded to a parts donor for the pretty one in the rather near future. Either it will donate the complete engine, if I can't find anything obvious, when I take the engine apart further OR I'll just swap over parts.

Now why did my dad park up this fine XT for several years AND didn't show quite the enthusiasm to fix it? Well the reason comes from Italy and you've seen her before. It's his Moto 6.5, a bike so nice, he only rides it whilst wearing a shirt. And it got even nicer now that we've added some progressive fork springs, which together with the modified SV650 rear-shock makes the fine Italian lady quite a respectable weapon in the twisties. (On the first rideout I managed to get it down to the pegs in a roundabout with great ease, just saying...)

The mark is to check the sag with my dad on it and it's perfect: slightly less than a third of the overall travel. (30mm vs. 130mm overall)

And as I wrote before, a bike so nice, you have to ride it wearing a shirt. Luckily it's pretty much sorted by now, so all that's left to do for my dad is to enjoy it this Summer and probably do an oil-change at some point in the not too distant future. 

The Dre-XT-Stück - more work that needs to be done

Back in pre-EU days Austria was a weird country when it came to motorized vehicles. The one most apparent in this particular case was the fact that Austria only knew two tax-classes for motorcycles: sub 500 cc and from 501 onwards. As such motorcycles such as an XT600 would have cost the same to insure as an old Zed thou or the like. Consequently various manufacturers offered sleeved down models in Austria to circumvent this situation. My dad's XT500 is exactly such a case. It's a model 55A, which most closely corresponds to the international 43F-model.

Whilst overhauling the carbs the last time, there was still some more left to do this time:

• Adjust the float height correctly

•  Overhaul the front-brake and fit it with a stainless brake piston and new pads

•  Put on some nicer used sidepanels and headlamp mask

• And lastly tune the carbs and test-ride the lot. Just for those interested - the secondary carb is supposed to open at 7mm slide movement of the primary carb plus the odd extra turn on the adjuster to make the transition go smoother. 

And trust me you can spend a whole afternoon trying to get those carbs *JUST* right...