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Well, at least thinking of getting started again, Cyls are back from being stripped, now looking at pistons Thinking 77mm is a nice number.
Should have a set of blank billet combustion chambers here in a few days from Decker, never did like that off set

Now if it would only drop below 90

Well, finally back to this project today, 2 month break for another broken leg. Cut a spare head in sections today to start fitting it for the billet chambers, that seams to be no problem, have everything mocked up and ready to go to the CNC shop. Perry welded up the ports to make them alittle smaller and we had to add some material to the intake port to support the rings from the new 670 SkiDoo pistons,. Roughed in all the welding in the bore and its ready to get bored as soon as the new pistons get here.
We talked about adding reed cages but lacking a good donor set of cyls with good reeds, I doubt my walled can handle that right now so looks like a piston port engine still for a while.

What I've been waiting for on this project is to get a good machinest to cut out the head and weld in supports for the billet cumbustion chambers. Well actuly the hold up was finding the cash to pay for it. So I met this guy that could do it, he tells me his kid wants to learn how to Airbrush old school flames. If I teach his kid, he'll do my head. So the result was;



Not sanded and buffed yet but maybe next week

Finally took the camera
Heres a pic of the cyl after striping, welding up the ports, and rough boring to the new size, also note the o ring groove is now gone because the bore is that much bigger. A new one will be added later


Here you can see the support welded in the intake to hold the ring, this was nessicary because of the new size being so much bigger and ring lower
Hers the new piston to get it to 600 cc


The new domes going in the head to get rid of that off center plug


Heres what the inside of the head looks like, we had to cut up a space to plan where to add bracing to support the domes.



Perry has built these engines in this form before, the goal for me was low and midrange power with a max around 100 hp
The transfer ports we changed quite a bit, to a degree, copied off some Yami factory race jugs he has. The ex port is totally different and much smaller. The new ports are made to be much nicer to the rings. The new piston which comes from a 670 rotax has dykes style rings. Part of my goal is to never see the inside of this engine again

More pic's
The first shows OEM factory transfer ports
The second shows YAMI race jug from the factory, notice the differance in front transfer. The stok designs is prone to sending much of the charge right out the pipe, the race design directs it back towards the rear wall




Heres some side by sides of both pistons, the SkiDoo is taller, ones we cut down the skirt to size, the compression height ( dist. from pin to top of piston) will be very close



Sorry, I don't know why, but in all these pictures, both posts and the ones of my SRV, the right side of the pictures gets cut off

Heres some pictures of work being done to some SRV 535 cases

Heres an update on the head with the Billet Chambers
Heres the chambers. These are ones Perry uses in Ski Doo Champ engines. Mine are same outside dementions but the chamber is now being CNC machined for 670 pistons.



Here is the head, machined out to hold the chamber, foller by a pix with the chamber in place




Here is a pix with a stock Yami head, the goal was to get rid of the old school, offset spark plug location


Now if I want I can go from pump gas safe compression to race compression by just snapping different chambers in place

ok bob i got it figured out now finally... you should have better luck posting using that Add Image Button below the box you type in

Thanks, I always like how it was before. I just had a forum put on my 120 site a couple weeks ago, of course I have no idea how to do anything on it, had a friend do it. Check it out
http://www.120sledracer.com

Bob, the work you do is simply amazing......

Thanks Chuck, ya know, I'd be rich now if that damn Reverand Jim wouldn't have run off with the plans for the DeLorian

Ok, its mid Feb, back to this project. Right now just once again trying to get the problem engine to run for the rest of the year. Last ride of last year, it just started running like crap. It had flooding issues replaced needle and seat, played with all kinds of jettimg, then tried 2 other sets of carbs , including the ones off my SRV which have always been perfict. None of that has helped, also tried different pump, nothing. The other carbs also worked fine on other sleds.

The symtoms are, starts and idels fine but will not take any power, just bogs, will not even move on its own. Clutches are good, track spins fine. Pipes are clear, many sets of plugs, tried different coil and wires, Compression good.

I'm thinking elec now. Last year replaced stator, will check that again as soon as I can hunt down whoever borrowed the V/M meter and shoot them. Tonight I pulled off the CDI box, all wires apear to be good tight and clean.
Heres my question, the numbers on the box are;
TYPE TIA01-43
8u9-19 followed by a box with 6604 in it
Does that sound right and does anyother thing cross over, Hopefully my SRV which I have a '86 box on it and a 81 box originally from it

Bob yes check your ohm readings but, do not rule out the CDI they can do funny things.....

At one time I tought I saw a list of part numbers and intercangeability on boxes, don't know where I saw it. Hope someone can find those numbers above and tell me if their right.
Everything is going to crap in a week on me here, This one doesn't want to go. Broke the crank on the cat Mon. and the kid brought the SRV home last night with a hole in the piston

Bob Bad luck does run in a row..... Any sled on the edge before Ethanol is now in the danger zone ( SRV ?)

Do you mean this list ?
viewtopic.php?f=2&t=1529

- Stators 5 different
1981 SRX (Original) P# 8K4-85500-10-00
1981 SRX (Updated) P# 8R9-85500-10-00
1983 P# 8U9-85510-10-00 without the hand warmer coil
1984-86 P# 80N-85510-10-00 with the hand warmer coil
1987-1991 P# 83H-85510-10-00Yamaha changed the charging coil in the stator to a higher output coil, by doing this the secondary coil output went up from 18,000 volts to 28,000 volts ,but you also have to use the 1987-91CDI as well as, it is different to accommodate the higher voltage of the charging coil in the stator.
F.Y.I. Double check P#'s !

-CDI's
1981 SRX 440 P#8K4-85540-10-00
1981 SRX 440 (Updated) P# 8R9-85540-10-00 it is used with the 8R9 stator
1983-86 Vmax P#8U9-85540-10-00
1987-1991 Vmax P# 83H-85540-10-00