Wednesday, 27 February 2008

Crisis, What crisis?

ONLY six weekends left before the first SuperMono Round at Snetterton, and the bike is still in large chunks. In the next fortnight we need to have it up on its wheels and running. This will give us just enough time for a practice session at Mallory and any insuing remedial fettling.


Uncle Boyd

Wednesday, 20 February 2008

No Woe!

So we are idiots. The frame's not twisted, just my dour Scottish outlook always expects the worst. One is rarely, in such cases, disappointed...
However, I think the motor's mounts are not where we want them to be... Or rather the lugs on the frame are for a differernt motor. Possibly an XT? I know that it previously held an SRX lump, the current cases are XTZ.

Anyway, here are some pics for the anoraks to show what I mean.
These were posted further to a bit of discussion on the forum of the ThumperClub.

From above. You can see that the head mount is central, but the centre of the cases is offset to the left (look at the mating surface cf the rear shock mount)

The rear of the engine has 2 mounts, upper and lower. The upper mount requires spacers to me made up, so is currently a (laterally) sliding fit. The lower mounts (left one is the ally "tab" you can see here) is a welded piece which locates the motor, each side of a boss cast into the rear of the cases.

And here's the one on the right hand side of the motor...

From underneath, it looks something like this:

The right of this picture is the rear of the bike. The motor is to the left of the image. Centrally, (vertical in the image) is the lower frame tube, running between the left and right "spars" of the frame. The two mounts to our right are for the rear shock linkage (the pivot of the rocker). These are central to the frame. This illustrates nicely the offset nature of the two "tabs" I described above. I am presuming that these should be central (ie each equidistant from the left and right rocker mounts). Are you with me??
I haven't yet measured up what I think the offset is, but I'll get the vernier (or the "very near" out and get some figures tonight. I do know that the cylinder head mount is central...

Sunday, 17 February 2008

Oh Woe!

Boyd arrived bright and early yesterday morning. Bringing with him such goodies as a frame, front end, pipes, cans, and our little ally fuel tank.

After I had lightly bolted down the head and cambox, we had a motor-shaped object. It will take a bit of time to get the valves sorted, but the motor is certainly getting close to Team Thumper’s exacting standards. We are professionals, after all…

In a jiffy, Boyd had assembled the front end (one nut and bolt!!) and slipped the rear spindle thru so she was on her own 2 wheels again.

First thing we noticed was that the front engine mount was fouling the XT barrel fins.

So a little judicious use of the cheap n nasty £15 Aldi Dremel-copy reduced the bottom fin to allow the ally mount to bolt onto the two front mounts.

All good so far! And without too much further ado, we soon had the engine in the frame, resting against the cylinder head mount, supported by the lower rear mount.

Interestingly, the lump is off-centre in the frame , it appears to sit closer to the left spar than the right.

After some recreational sawing…

…I put the carbs on, while Boyd tried to hide convince me that “hide-and-go-seek-seek” was more fun. Silly man!!

I found him easily! We sized up the tank against the frame

and made sure it cleared the carbs.

And although appears small, it actually holds over 5 litres.

However, whether or not this is enough remains to be seen. UK Supermono races are approx 20 miles, so maybe we’ll have to weld an extra box onto it. We also talked about the possibility of making a still air box. We’ll need to make up a support for the rear of the tank, so maybe this could somehow the tank could rest on to top of an airbox?? Despite Boyd trying to chat up the pretty 3rd member of Team Thumper and her playing all coy, we soon got back to work. However, it wasn’t too long before our dreams of victory dissolved into despair.

We couldn’t get any more engine mount bolts in. Despite giggling, pushing pulling, and modifying the front mount, we started to suspect that the engine wasn’t going to bolt up after all. To our untrained eyes, it would appear that the frame may be twisted… Which would explain why we cant get any more than 2 mounts secured at any one time. This is a definite blow to Team Thumper’s schedule to get the bike built by mid march and tested by the end of that month for the first race at snetterton . I’ll try to get it to the Maidstone Motoliner asap, and get their opinion…

The clock’s definitely ticking pretty loudly now. I thought I had my work cut out to get the head built up and bolted down. Now its become a lot more complicated for a number of reasons. Ally frames are a pain to straighten. Especially slightly fragile 17 year old ones which have housed tuned large capacity singles. And in order to straighten the frame, ideally the motor should be bolted up. But we cant do that yet. And I can’t get on with finishing the head until it (goes to and) comes back from the motoliner man.

I will give him a call on Monday, and see what he advises. Either way, this isn’t going to be cheap. Or easy. Is it ever??! Will we be racing in april? Here’s hoping.
Andy n Boyd

Saturday, 16 February 2008

A litle more progress (snail's pace!)

Last week, I received a parcel from a new friend in the States. Chris Hunsicker shipped me some springs, collets, Ti retainers and bottom cups; thanks also to Bill Jurgenson for his help with this. I also took advantage of a favourable exchange rate and bought a DID cam chain.

As Boyd was due down on Saturday morning, for a “dry-fit” I thought I had better try to get the motor together.

The RD springs came with a bit of paperwork specifying the Installed Height, and how to obtain it. The correct height of the spring retainer to the bottom cup; this can be decreased if necessary with the shims supplied to place UNDER the bottom cup. However, my installed height is between 1.5mm and 2mm greater than the specified limits. I have 4 shims, each of 0.34 mm. I’m unsure on how to proceed with this and will try to ask those who have played this game before…

Anyway, it did mean that when Boyd arrived on Saturday morning, the head still wasn’t on! No problem, I quickly assembled the “empty” head and cambox on top of the barrel…

…and he seemed pleased to see me anyway. What a handsome pair!

New piston

It’s a Wiseco item, brand new, and its on the Carillo rod now. It’s a flat top, 98mm bore, so it won’t be a brutally high compression, but if the motor is good we can up the performance a little later in the season. I used 3 Bond from Rex Caunt Racing (look thru their site, some lovely classics...) on the new genuine Yamaha base gasket. And then torqued down the new nuts onto new studs, with new washers from Slipstream and Kedo.

I also blocked off the oilway from the cases to the barrel, with one of the little plugs Alain made for me.

No piccies here, simply too boring!!

The Devil is in the Detail...

…and that is why I have cleaned up the new valves. I’m not sure if it will really make any difference, but in theory its got to be better. Not least because A. Graham Bell reckons it’s the thing to do (according to “Performance Tuning in Theory and Practice”)

So I dropped in on Alain Antoinette, who runs Spacesavers Plus in East Finchley. Specialising in light engineering, engraving, signmaking and CNC laser cutting in various media he’s been a great source of advice. He let me use his lathe and tools to remove the sharp edges from the valves, clean up the surface, and give them a little polish. What a guy, thanks Alain!

On the left is the untouched valve, on the right one of the inlets after our attention.

And here is a close up. You can see both the smoother profile and the polish on the surface. I used Scotchbrite, then fine Wet n Dry (first dry, then polished wet)

The polish had touched the seating area of the valves, so I very lightly lapped the valves in again, just to be sure! Boring? Pedantic?? ME???!


Sunday, 3 February 2008

Return of the Anorak

I have just forked out a big wodge of hard-earned for 4 Yamaha valves. I had received some pattern ones, but I thought them a little suspect- heavier than standard, tighter radii, and rather prominent “corners” where its been machined.

So I got my precious treasure home. And compared it to the standard valves. I have it on hearsay that this head was built for the Singles TT, and is a little bit special (or was at one point).
Anyway, that was many moons ago, the exhaust valves had been replaced quite recently, and the inlets much longer ago. The (recently replaced) exhaust valves were standard. However, I noticed that the inlets (possibly quite old) had had all of the edges close to the seat machined off…

You can see the difference between the new Yamaha valve on the right, and the valve which came out on the left.

Edges have been removed (arrowed) and I also think the seat is a little thinner. I haven’t weighed them, but I am certain that the old valve will not only allow better flow; it will also be lighter.

The photo on the right attempts to show the thinner seat of the modified inlet valve which was in the engine. So I have decided to grind in the new valves, (so we know where it actually seats) then take them for some light "recontouring"- both on the inlets and the exhaust. If a job’s worth doing….

Valve grinding- a Great, British, Sunday pass-time. When you missus is away… The "Chemico" paste looks like its come right out the 1950's, and would be more use lapping in valves on a Manx! Ahhh, to dream!