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 G&S 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.

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, utilzing the three bolts of the OEM tank. All the electrical stuff except the rectifier, which you can see in the bottom of those three pictures, will be placed on this pan which should protect it from the weather keep it relatively clean. The pan will close the to seat frame underneath. When I am satified 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 one. 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 switches a Bosch 16A. relay which turns on the +12V. main to everything but the starter.
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.
























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.





















Of course the exhaust system is still missing.
When I do make the aluminum tray, the arrangement of the parts will probably be different. I intend to use a LiPo battery. As soon as the bike is running, I plan to test what minimum size is necessary to start the engine which has no decompression unit.
If possible - it is a question of height, the LiPo battery will be set at the front end of the tray, right behind the oil tank and as close as possible to the rectifier and ignition switch. The SilentHektik unit would then go roughly to the place the big battery now occupies. Of course the LiPo battery could go where the Hawker is at the moment.

to be cont'd.