Wednesday, December 29, 2010

Swapping clusters

Last year, I wrote about various clusters:

I did not go into what must be done to change the 3YF transmission into a 4SU unit.
3YF is the XTZ , the engine used in all MuZs, 4SU is the Belgarda SZR and the engine used in that bike which was assembled by Minarelli in Italy. Minarelli also builds the new 4-valve XT660 engine.
In that posting, you can see the different ratios and that the only difference between the 3YF and 4SU is 1st gear. Everything else is identical.
So, for those MZ riders desiring the better cluster (that the Skorpion should have had to begin with!) the easiest way to go is to obtain an SZR cluster thru eBay or similar source. They are not offered very often, however, and the price can be unrealistic as are the prices of many XTZ parts at eBay.
Lacking the complete cluster, one can order the mainshaft and loose 1st gear for the 4SU from any Yamaha dealer:
Mainshaft: 4SU1740100 list price 125.00€
1st. gear: 34K1721100 list price 40.00€

This is a 4SU cluster. The mainshaft is at the top, 1st gear at the right on it. This gear is milled directly onto the shaft. That is why the mainshaft must be exchanged. 2nd gear at the far left is pressed onto the mainshaft. This presents the main problem when rebuilding the 3YF cluster with the 4SU mainshaft. A suitable press is mandatory and one must make (or find) a piece of steel pipe into which the whole mainshaft will fit, allowing 5h gear -second from the left - to rest on the rim of the pipe. Thus set up, the shaft can be pressed thru the 2nd gear and fall free.
All the parts can are then assembled in the same oder onto the new mainshaft and the 2nd gear pressed back on. For this job, it is best to have a different piece of pipe into which only the shaft itself fits, allowing 1st gear to rest on the rim. Being observant of course, one will have measured the axial tolerance of 5th gear to turn freely as well as the exact amount the shaft stands proud of 2nd gear. Turning a small piece to fit exactly flush with the end over the shaft before disassembly will make assembly nearly fool-proof.
I have reassembled several Skorpion clusters with the 4SU mainshaft and it is not higher science but you do need, as I said, a suitable press and the mandrills to insure the the parts are moved straight. It is not necessary to heat the gear at all.
Bottom line:
As I have repeatedly written, it is a must-do for anyone riding a Skorpion hard. Apart from needing to the break the engine completely, the actual job takes only about 30 minutes, a couple of cheap and easy pieces of pipe, a lathe and the press.
The total cost for the parts (here in the EU) ±170€ plus the scraps of pipe. 200€, even 250€ are thus acceptable for a used cluster in good condition if one does not have the machineshop at hand.

If and when one does get into this, one could consider going for a shorter 5th gear; see chart below.
Slipstream offers (or at least offered the pair of gears for 270£. Here in Germany, Joachim Pethke has made pairs and such pairs do turn up in the ESA (european supermono assoc) scene.
I am using a used pair myself.
Obviously, the pressing is the same to change 5th.
At one time, OVER made racing clusters for the XTZ engine, used both by theirselves and marketed as Yamaha works clusters. These cost 2500DM in the 90ies. They now generally go for over 2000€.
Koehler here in Germany made clusters for MZ and these very occasionally turn up. I have installed one.
Slipstream offers (-ed?) a close ratio cluster as well, on my dated price list at 1500£.
Again, the ratios of the OVER and Koehler clusters as well as the shorter 5th gear are on that chart:

I do not recommend either of the race clusters for street use; I have extensive experience with the OVER myself.
For serious track outings, tho, they cannot be beaten if the motor has been freed up and the ignition suitable without rev limiter.
For street use and the rest of us (including me now) the longer 1st of the SZR together with a shorter final ratio opens up a whole new world of fast Skorpion riding - and big game chasing.

Oh, and one more thing, another important must do for anyone running the 3YF or 4SU hard:
One must replace the gear on the crankshaft for the balance shaft with either that of the new
XT660 part no. 5VK-E1536-00
or of the Raptor 700 pat no. 1S31153600
Both fit, Shown in the picture here:

is that for the Raptor. The XT660 gear is a 1:1 replacement; the thick steel washer behind the gear must remain in place.
The Raptor gear is as much thicker as the washer is thick, so the washer must be removed. The gear as far as size and module is identical. I prefer this solution.

Saturday, August 21, 2010


Now that the 1000km break in are done, I can push it as I am used to doing. The oil tank is a complete success. I already wrote about the temperature in actual use. One thing I could not judge before now: I use practically no oil now. This can only be attributed to the form of the tank, i.e. to the fact that the returned oil does not foam up and is allowed quietly sink to the bottom of the tank. Also the oil itself is still recognizable as having been red when new. It is of course dark greyish red, but not opaque black at all. This is still the first filling for the new engine. I admit that I have not changed it yet, something I normally would have immediately done after the break in. It is Castrol Power Racing 1 10W/40. I use a K&N #145 oil filter. I also always add 2-stroke oil to the gas, always fully synthetic, usually Castrol, but most any will do actually. About 25cc to the 15ltrs filling.
This engine is definitely better than last years aircooled and I think perhaps the my best street-use engine to date. I can live with the vibes which are nowhere near bad as with the balancerless engine of the blue bike.


Today, after finishing the parts I need for the customer engine on the workbench and mowing the lawn (brownie points!), I went for my usual ride in the Swabian Woods (Schwaebischer Wald) which take me up what was the official Heilbronner Bergpreis (hill climb stretch, was a national event until 1983) and on to Sulzbach an der Murr, turning towards Schwaebisch Hall on the B14 (national highway) which is a favorite "hill climb" because it is relatively new and in good condition and because there are almost never any sheriffs present. Who knows why...
I take this to Mainhardt and then turn onto the B39 back towards home. coming by the "Loewensteiner Platte" where I usually stop for a coffee if it is not too full.
Despite the good weather, there was still room to park which I did and immediately caught notice of three Vuns! Three of a bike you normally do not see once a year around here!

This is Cristina Baio: 2004 champion, Italian female superbike series, Hers was one of the three Vuns there.
A friend of mine, Oliver Thiel - Ollie - instigated this. Since I last talked to him, he has gotten a CR&S consession (and sold a Duu that is not even on delivery yet) and had been at the Nuerburgring with some Vun owners the day before. One of the three present was his demonstrator, the others, that of Cristina and of John van Houten.
Ollie greated me with, "grab your helmet and take it out for a test drive." Didn't need to be told that twice; not all that often you get a chance to ride something as exotic as a Vun.
What can I say? It looks and feels very light. Actually, tho, it is only a couple of kilos less than my Skorpion SP. Riding position is good: this is very first bike with a super bike bar (ape hanger in my eyes) that I actually liked. I later rode John's which has LSL clipons and it was MUCH better. The BMW Rotax has quite a bit of punch up to about 6500 and is easier to drive at 5000 than my engine, but it is not at as good at low (2500-3500) or high and is probably down a bit on top end performance. No measurements, just my very subjective feeling. The Brembo radial clamp with racing pads is decidedly 1-finger only but easy enough to use and VERY effective. Biggest impression for me, tho, are the BST CF wheels. All three Vuns had these wheels. Steering, braking and acceleration are all extremely quick, seemingly effortless. These wheels are becoming a obsession with me. They would bring the weight of my bike down to 140kg, reducing the weight where it counts most. Costly dreams............
After more discussing at the "Platte" we rode together to Oillie's shop, John with mine and I with his. Riding home from there, that is riding mine after just having ridden the Vun, was a pleasant surprise.

I had lots of fun with both Vuns. What I did not like? The throttle response from idle in and around town/street use is very grabby, to put it mildly. I am used to flatslides and they are quick, but this was extreme. I would probably get used to it after a day or two. OTOH, I might possibily dump the injection for dual flatslides... I would definitely want narrow clipons like my Gilles GP Lights and also a smaller Ø front wheel pump. And of course I would reverse the shift pattern as always.

What else I liked?
My own baby was not so far off from this highend product. Franco (from CR&S) in particular was quite impressed with some of my technical stuff and took a lot of pics. He was pleased to see that I had somany Poggipolini products on mine as he a the owner are friends. John commented (he rode mine) that it immediately felt very light and that the steering was extremely light. He wasn't fond of the vibes but then he didn't get a chance to really rev it out and shifted far too soon. After riding he also commented on the very quick throttle response and ease of riding on residential streets and he found my riding position good.

Unlike so many things I have test ridden that were hyped up by the press, the Vun is not a let down at all. I am not sure it is a must-have, but it certianly comes close. Given their policy of building to customer specification, I can readily imagine that "my" Vun would be exactly as I want a bike to be. Things to dream about...

Saturday, July 3, 2010

Picking up from the last entry, the bike is running and passed MOT without any trouble at all. I did cheat by installing the the quietest DB eater - which I then removed right after MOT.

It took ages to get the 101 Wiseco flat top piston. The barrel was bored and honed to 101.05. I needed to make a 1,5mm alu spacer under the cylinder to match the compression height. The cylinder (3AJ), which I got "as is" with the XTZ (3YF) sleeve in place, was turned on a lathe after shrinking in the liner. Obviously, a little too much had been removed. No problem, tho.
The head (2KF) with the new valves from GS Valves fits of course. As before, I am using the beehive springs from RD.

From my "collection of cams" ranging from stock to Megacycle 266/4, I chose the 266/4 because it is a billet cam. Thus the rockerarms do not stand at such an adverse angle to the valve stems and they normally do with "reground on customer core" cams.
I milled the mating surface of the Y-manifold so that the carb doesn't hang as low as it did, leaving at least a little room between it and the plus connector of the starter.
Otherwise everything is as before or as described recently.
I actually did get the tiny LiFePo battery

I mused about. Although it is rated only at 4.6Ah, it delivers 150A start current or more. It weighs in at 650grams instead of the 2700grams of the Hawker placed next to it to get an idea of the size.
If anything, the motor (remember, no deco!) starts better than with the Hawker SBS8.
Tuesday, after it was back together, the first attempt:
-two twists of the grip for the accelerator pump to squirt some gas in;
-pulled choke;
-turned on and pressed the botton;
-WUMS! at the first turn.
In this warm weather, it starts without the choke.
So at least it does start and the battery is indeed strong enough.

The oil tank I talked about at length last time looks to be a success. Summer weather, hot (for here) with temperatures above 30ºC, stop and go and traffic lights; I measured the oil temperature immediately on return and it was 105ºC. at the top, i.e. the oil coming from the engine. dropping to about 90 at the bottom. There is no foam visible and the oil is still remarkably clear. Remember last year I never got over 80ºC. I did stupidly have an oil cooler because I listened too much to others and did not think for myself. 80ºC ist simply way too cold for modern oils. No wonder the SRX/XT clan think 30000km is a good distance for an engine!
So the new cylindrical oil tank does manage the oil better and it also contains more oil.

Now to drive in the new rings and valve stems and take it from there.

I am pretty sure the present can is not the best there is. For MOT, I had inserted the longest DB eater and the motor was unwilling even at 6000, also starting more poorly and idling roughly. With the shorter pipe, everything improved greatly yesterday.
When I have run in the rings, I can test for performance above 7000. Last year's engine would not turn above 8000. Quite posssbly the the small TM40 carb is just too small. I plan to try a TM42 but probably there will be no way around fitting a TM34-B65 on longer intake pipes. Before any of that, tho, I will probably get that SR-Racing can($$$) I wanted all along.

anything else just now?
I drove over to the farmer's cooperative in the next town where I can weigh my bikes on their scales inside, the one use for pallets and bags, not the big truck scales outside:

148kg = 326lb with half-full tank.

We're getting there...

here is a little demonstration how fast it starts when cold:

A few people who bought the TCIP4 have complained about their bike's poor starting and were wanting to blame that on the iginition, especially the last setup I did with it. I have the TCIP4 with the last setup and there can be no question about poor starting here. No choke was used, just one or two squirts with the accelerator pump and then pressing the button which I do with the left hand normally so that I can immediately respond with the twist grip. When cold, idle with the reather extreme cam is anything but good and short gas bursts are necessary usually to keep it alive for a short time at least.

Saturday, March 20, 2010

Update SP 2010

Long time since I've updated here. There has not been too much to tell since the last time.
For several reasons, I dismantled the Skorpion last November. Most important of those was the wish to pursue the air-cooled engine further. But there was also the the racing cluster to contend with. After the season's use, I had to admit that as nice as the cluster was in high-speed use, it was very trying in everyday traffic. Thus, I removed the engine completely and exchanged the OVER cluster for a standard SZR trans, albeit with a shorter (ex-Kehrer) 5th gear. I also exchanged the right crankshaft ball bearing for a roller bearing.

When I reinstalled a lightened balancer last year, I replaced the original drive gear with the cushdrive for a solid gear.

The cushdrive is the main reason for the abnormal deterioration of the woodruff key in the crankshaft. This is the case when the engine is pushed very hard, particularly downshifting into corners at higher RPM. The cushdrive stores the energy of the balancer shaft and gives it back to that key. The solid gear behaves better and the engine runs quieter as well.

Last year's engine was based on an early TT bored out to 98mm. While this ran well enuf, upon dismantling I saw that the changes Yamaha made between the early versions and the last ones were necessary. These are changes in the oil feed and heavier (9mm instead of 8) head bolts with a wider spacing. The E-start motor also has no manual deco. I put the TT head and cylinder out to pasture. (=trash)
This year I have a last version XT600E cylinder with 100mm XTZ barrel giving me the original 660cc. The head will have custom-made valves from GS Valves . As in my blue bike, I will use a probably a stock piston with a stage 2 cam shaft and the RD beehive springs I had in the TT head. The Grizzly manifold with 40mm Mikuni will also remain. I also have a TM42 which I may just try out. Basically, tho, the engine is similar to last year's but with 660cc.

The Skorpion's plastic oil tank has long been a sore point for me, not so much because it is plastic but because of its shape. So this winter I decided to finally do something about that. I measured and pondered and came up with a cylindrical aluminum oil tank , as high as possible to fullfill the standard requirements that an oil tank be at least 1/3 larger than the filling.

This is an example of a typical car dry sump oil tank. Much higher than wide, notice as well, that the return connection on the side at the top is not centered. Rather it is "tangential" so that the return oil stream runs along the inside wall to the bottom to help prevent foaming.

Here is another state-of-the-art example of such a tank installed with a racing V-8, the brand-new Roush-Yates built Ford 360 for sprint car racing.

Unfortunately even the smallest of these readily available tanks is much too large for the bike so I "designed" one myself from 140mm Ø aluminum pipe and 4mm sheet material. It hangs on the two front seat mounts of the seat frame (orignal but much modified) and is supported by the two back airbox grommets to which the battery box was attached before. The airbox was thrown out years ago.

I turned an aluminum fitting threaded to accept the Skorpion filler cap and modified the in-hose sieve fitting to be welded onto the bottom of the tank. The oil feed line connects to this and runs straight to the engine. The return line which cannot really be seen here, runs up to the return connector on the left side at the very top of the tank. 

The filler cap fits so closely under the seat, that it cannot unscrew even if it is loose. Several riders have lost that filler cap from the OEM tank; I know at least one rider who has a separate heavy wire latch to prevent it from unscrewing. I needed a new cap because the red one shown here which fits the aluminum part would simply snap loose if tightened even a little bit too tight.  The clear tube between those blue fittings shows the oil lever at a glance; the dip stick on the cap does not reach the oil since the top 1/3 of the tank only air.

With the OEM oil tank gone, the seat frame is empty. I am in the process of making a prototype shallow pan of 6mm waterproof plywood to fill the entire space, utilizing the three bolts of the OEM tank. All the electrical stuff except the rectifier, which you can see in the middle picture above, will be placed on this pan which should protect it from the weather and keep it relatively clean. The pan will close the to seat frame underneath. When I am satisfied with the pan design, the prototype will be replicated from sheet aluminum and anodized black.
My harness is home-made anyway as I must have related more than once. I use the Silenthektik solid state fuse box with blinker and ignition relays. I also use an Ignitech rectifier and the Ignitech Sparker TCIP4 ignition box. The ignition key is on the right side below the seat and  turns on the +12V. main to that fuse box. The starter is directly connected to +12v. The fuse box has a built-in relay switching +12v when its pin is connected to minus. I use this relay as the ignition switch supplying +12v to the ignition box and coil directly. That relay is switched by the kill switch on the right clipon.
In the meantime, I have made a prototype tray of 6mm waterproof plywood; easy for me to do and easily modified if necessary. When I am satisfied, the prototype can be replicated in aluminum or fiberglass.   
:-)    Nothing is so permanent as a temporary solution  :-)

Another shot showing that tray from a different view and also the 4,5Ah LiFePo battery I am now using. You can easily see the difference in size. The difference in weight is substantial. The Hawker SBS8 weighs 2.8kg, the LiFePo 650grams.  A LiFePo = lithium iron phosphate is not to be confused with a so-called lithium or lithium ion battery so do not be mislead by advertising hype. A LiFePo cost much  more. This one, made for me by Akkuwerk in Heilbronn, is 5 years old now, has never once been charged and has never failed to start my motors which have no decompression unit.

All the electric stuff is placed together as one can see. The space in the seatframe is entirely filled.
The underside of the tray is clean; apart from the reservoir for the strut, there is nothing there.

The side view is completely clean and unobstructed.

to be cont'd.
edited  Sept. 24, 2017