The story of Tenzing the Super Tenere

[cooneyr]

Couple of people piked on the planed coffee run today so EL and I did a mission up to Lake Coleridge and back by mid day. Tried a bit of trials riding in the Harper river bed - not such a good idea. Nothing broken but clutch got a work out. Also El managed to chunk the Desert rear and I've got a couple of good slices in mine. Seems they are not that tough.

Anyway - new air filter pics below. Foam is Uni Filter foam stuck with Ados F2 contact glue. Cages are 20mm square welded chicken mesh, the plates are old 1.5mm computer cases and 3.5mm checker plate alloy, red high temp gasket goop (cause I had some in the shed) and grey closed cell foam to form a seal against the air box. Goop is to protect the green foam from the lumps of solder holding the mesh to the steel plate. After chasing El today I've ridden in enough dust to make it worth pulling the whole lot to bits to see how they are going.

Cheers R

[NordieBoy]

I don't see any #8 wire in there but bonus points for using checker plate

[cooneyr]

I don't see any #8 wire in there but bonus points for using checker plate

Two good reasons for that. We had some in the shed and the 1.5mm computer cases flexed a bit much when tightening the filter onto the air box.

Those fellas over in the Yamaha design office would probably have a hernia if they saw these contraptions.

Cheers R

[NordieBoy]

Just to whet your appetite...

What is this bike...

It is a trick(ish) question

[Peril]

Hate to pick that monster up out the sand,being 4 cylinders and all

[cooneyr]

Well its not the YZE850T being a 4 pot. I know they existed but I don't know what they are called. El found a site about them but I cant find it now. From memory very late 80's very early 90's yamaha road bike engine in chassis similar to the YZE. Have you got any info?

Cheers R

[NordieBoy]

FZT 920 - based on the FZ 750.

[NordieBoy]

More info here...

http://www.rallye-tenere.net/BgFZT750-900.html

[cooneyr]

Ah so it preceded the YZE's. What a bloody tank of a bike though, bet it truly deserved the title of PIG. Much easier to read when translated.

90hp from the 750 version. From what I understand the TRX850 motors can be tuned for 100+ so it is likely that the YZE850T's were putting out more ponies than the FZT750 but don't know about the FTZ920. Guessing the FZT920 was a stroked and over bored FZT750 being such an weird number and the fact that there was only 1 year between the two suggesting that development time re dropping in another motor would have been limited.

Cheers R

[cooneyr]

El Scooto was making noises about wanting to check the valve clearances on Ed but is out of town a lot so I decided to check the valve clearances on Tenzing to learn how to do it. After draining and stripping of the radiator (piece of cake) I had to remove the pipe between the head and the thermostat. Problem was that the single cap screw holding it on was well seized in place and it is somewhat recessed into the valve cover. After an initial attempt to remove and rounding it a little I soaked it with CRC for an hour or so and had another attempt. This time I managed to completely round it off. Damn.

I've got some easy outs but didnt really want to go there till last resort and as the head of he screw is so well recessed into the head there was no way of getting some viceys onto it or slotting the head. Fired up the www and found a suggestion of mashing a torx bit into the cap screw to remove it. Had one of those screw driver bit kits with 1/6 a dozen torx bits so found that they fit into a 1/4" socket and got the hammer out. Started with the 35 torx bit, bashed it in (genitally of course) and tried to turn it. It kept popping up and out - damn. Next tried a 40 torx bit, bashed it in and gave it a turn. Genitally genitally then crack - damn was that the cap screw moving or the bit popping out again. Put the bit back in and the bolt had moved!!!

Anyway bolt out, pipe removed and then valve cover off (not a rocket cover as there are no rockers). Whip out the crank alignment bungs, turn the crank to TDC on cylinder no 1, get out the feeler gauge and start measuring. Then do cylinder no 2. Damn of 10 valves (3 in and 2 out per cylinder) only three are withing spec. 6 are tight and 1 is loose.

Now the S10's use the bucket and shim valve adjustment system. I can see the benefits but it is also a PITA cause the cams now have to come out to get the buckets and shims out. Being the civil (not mechanical) engineer that I am I then read all I could find in the workshop manual about removing, installing and timing the cams. Book said as long as the crank is rotated to TDC put the cams in with the punch marks up (they line up with marks on the cam cap). Hmmm me things what if the crank is 360 degrees advanced from where it was when the cams were taken out, how is this going to work wrt the ignition timing and the position of the "other" cylinder. I know this isn't a problem as I could just line everything up before taking it too bits and then put it back as it was but I tend to over think things so wanted to figure this out.

Fired up the www again and found mention of bikes using a "wasted spark" concept. With the wasted spark concept the CDI is triggered (and hence spark plug fired) by the coil on the crank hence fires once every revolution. Now four strokes have to do two revs per cycle so this means that the spark plug is being fired once into fresh charge and once into exhaust gases every cycle (two revs). Nice, this means that I don't have to worry about the the spark timing. Now what about the cylinder timing wrt to the crank. Very clean screw driver down the sparkplug holes reveals that a 180 degree twin means that both cylinders are TDC (be it compression stroke or exhausting stroke) at the same time. So I don't have to worry about the other cylinder timing wrt to the cams. So in conclusion make sure the crank is at TDC then put the cams in with the punch marks up - damn wasnt that what the manual said!

In essence it seems that the Yamaha 3LD twin engine and the other 180 degree parallel twins are really just big single cylinders with a second set of cams that are 180 degrees out of phase with the first set for the second cylinder. Piece of cake to work on wrt to timing.

The worst bit of this saga has turned out to be the purchasing of new shims. I've got $108 with of metal sitting in a thimble at home. This is the new shims for both El's and my bike after mixing and matching the existing shims between the bikes. I remarked to the Don in at Pit Lane that they were the most expensive little bits of metal I've ever brought and replied "Wrong, the bits of metal in your teeth are more expensive". How true he is.

Cheers R

P.S. I'll try and put some pics of the assembly up later in the week.

[warewolf]

Just been through this very exercise with my Triumph. But fortunately I have a good relationship with my local dealer and was able to help myself to exchange the shims I needed, for a modest fee. And blagged the micrometer to measure them, in case they had worn and were no longer the thickness as marked. Which is why I pay a little more to buy stuff from them, rather than shop ex-USA.

Triumph have a tool that bolts on to the cam caps to hold the buckets down, so you can change the shims without removing the cams.

Out of curiosity, were your inlets tight? For my 12 (3 cyl 4-valve) I had 6 tight inlets (new valves & seats bedding in) and 1 slightly loose exhaust.

I much prefer the screw & locknuts on the LC4.


And, umm, don't you mean a 360 deg twin has the cyls rise & fall together? The cams are 180 deg out of phase because they are rotating at half-speed wrt to the crank. 180 deg twins are one up, one down. ???

4-cylinder Triumphs run two coils with a wasted spark in two pairs, one pair 180 deg from the other... which I think is pretty much the common thing with inline fours?

[cooneyr]

Just been through this very exercise with my Triumph. But fortunately I have a good relationship with my local dealer and was able to help myself to exchange the shims I needed, for a modest fee. And blagged the micrometer to measure them, in case they had worn and were no longer the thickness as marked. Which is why I pay a little more to buy stuff from them, rather than shop ex-USA.

Lucky you re the exchange. I'd like to borrow a micrometer but unfortunately I don't know anybody to borrow one from. Going to have to do this the hard way - put it back together and check the clearances and go from there.

Triumph have a tool that bolts on to the cam caps to hold the buckets down, so you can change the shims without removing the cams.

Now that's just cheating but I'm also guessing that means you don't have to remove the buckets, do have rockers, shims are on top of the buckets ??? I'm a little confused about this. In the XTZ's the cams act directly on the upside down buckets under which are the shims. So we have to remove the cams to get the buckets out to get the shims out.

Out of curiosity, were your inlets tight? For my 12 (3 cyl 4-valve) I had 6 tight inlets (new valves & seats bedding in) and 1 slightly loose exhaust.

Yep both Ed and Tenzing had tight inlets and either OK or loose exhausts. We didn't even have to remove the exhaust cam on Ed but the one loose one on Tenzing meant the exhaust cam had to come out. Interestingly the central inlet valve was super tight on both bikes. This is the valve that is central (ish) in the cylinder (imagine 4 valves spaces as normal and then one smack in the middle of the four).

I much prefer the screw & locknuts on the LC4.

I agree. Needs checking more often but is a quick job to carry out. One advantage of the bucket and shim system though (well in the XTZ's 3LD motor anyway) is that there is less reciprocating parts in the head i.e. no rockers.

And, umm, don't you mean a 360 deg twin has the cyls rise & fall together? The cams are 180 deg out of phase because they are rotating at half-speed wrt to the crank. 180 deg twins are one up, one down. ???

This got me wondering as well. Apart from the cams being out by 180 degrees why are they know as 180 degree parallel twins (I'm not making this up - many on the XTZ forum refer to them as 180 degrees). The crank on the 180's is effectively a 360 (or 0) degree offset????

OK done some more reading - it seems there is lots of miss info and I've been continuing the flow of rubbish. As you said it is really a 360 degree twin (as are the TDM engines, TRX are 270 degree engines).

Cheers R

[cooneyr]

...This is the valve that is central (ish) in the cylinder (imagine 4 valves spaces as normal and then one smack in the middle of the four)....

Seems I've just added to the crap as well. Five valves spaced around the outside of the cylinder with three smaller inlets and two larger exhausts.

Cheers R

[warewolf]

Now that's just cheating but I'm also guessing that means you don't have to remove the buckets, do have rockers, shims are on top of the buckets ??? I'm a little confused about this. In the XTZ's the cams act directly on the upside down buckets under which are the shims.

Ah yes, the Triumph runs shim over bucket. No rockers, the cams ride on the shims, which are 25-ish mm diameter. Yours are prolly the small ones nearer the diameter of the valve stem, shim under bucket.

Yep both Ed and Tenzing had tight inlets and either OK or loose exhausts. We didn't even have to remove the exhaust cam on Ed but the one loose one on Tenzing meant the exhaust cam had to come out. Interestingly the central inlet valve was super tight on both bikes.

I was told this is common; the exhaust valves are usually a tougher material to cope with the heat so wear less than the inlets. In addition, it was suggested I open the inlet clearances right up, to lessen the frequency of needing attention. Bigger clearance means more clatter and ever so marginally less power. As in go from 0.10-0.15mm (spec) to 0.20-0.25mm. It may be worth taking those central inlets a bit further out than the other two. And you prolly could have left that one loose exhaust valve alone.

This got me wondering as well.

I was drawing sine waves on my page mapping it out.

OK done some more reading - it seems there is lots of miss info and I've been continuing the flow of rubbish. As you said it is really a 360 degree twin (as are the TDM engines, TRX are 270 degree engines).

Many years ago I had (by marriage, would never have bought one myself ) a 1983 Honda CM250C:

(Sold it to a mate who still has it buried in the back of his shed.) It had the CD250 engine in it, a 360 deg twin. Everyone "knows" they are a 180 deg twin, it was the single coil that got me making enquiries. I also had an early 360 deg TDM 850; the TRX debuted with the 270 deg crank to make it sound/feel more like the Ducati 90 deg v-twin it was otherwise trying to emulate, and I thought that configuration was later ported back to the TDM, perhaps not until they went 900cc.

[cooneyr]

Ah yes, the Triumph runs shim over bucket. No rockers, the cams ride on the shims, which are 25-ish mm diameter. Yours are prolly the small ones nearer the diameter of the valve stem, shim under bucket.

Thinks makes more sense. We have 9.48mm cams that sit on top of the valve stem (under the bucket) inside the lip of the spring retainer.

I was told this is common; the exhaust valves are usually a tougher material to cope with the heat so wear less than the inlets. In addition, it was suggested I open the inlet clearances right up, to lessen the frequency of needing attention. Bigger clearance means more clatter and ever so marginally less power. As in go from 0.10-0.15mm (spec) to 0.20-0.25mm. It may be worth taking those central inlets a bit further out than the other two. And you prolly could have left that one loose exhaust valve alone.

Hmmm - brought the shims now. Think we might put them to spec cause I suspect the head really should come of and the valves be lapped etc as necessary in the not to distance future. Besides the 3LD motor is suppose to have the valve clearances checked every 42,000kms. Ed's have been done due to the non standard size shims but I suspect that Tenzings have never been adjusted. We should be good for another 20k km's I'm guessing.

Many years ago I had (by marriage, would never have bought one myself ) a 1983 Honda CM250C...... I thought that configuration was later ported back to the TDM, perhaps not until they went 900cc.

Seems you are right. The 900 TDM is a 270 crank.

Cheers R