Vintage Yamaha 360, Woods Riding!

[Uniflow]

Yes I'll start a new thread. Some quick answers. Yes runs well now. idles smooth, starts well when the day is hot or engine is hot. Ethanol won't vaporize well when cold so I use a little petrol squirt bottle to start from cold, first kick usually. Injection timing is critical around transfer opening. Injection can be staged to minimize fuel loss out the exhaust, at least a lower engine speeds. Throttle uses a TPS. Crankcase pressure is sampled by a small valve connected to the crankcase, is only reads pressure ( or vacume ) when the injectors are on. So far only "seat of the pants" tuning. Yes rotary valve case moves with RPM ( this is a very good feature for a rotary valve engine). The "new" engine will be a made up unit ( for the YZF ) . I'm also doing a "converstion" for a YZ250 T for the local Yamaha shop. I think it will be too dear to sell as a kit, but lets just see if it works first.  Yes I have access to a dyno but they cost so I've decided to get it tuned as close as I can first.

[SachsGS]

Fascinating!

P.S. Are you related to Herbert Schek by any chance? You make that old Bighorn look like an 80.

[Uniflow]

I have to stand on the foot pegs to start it, buggered hip. citabjockey, have you had any trouble with that RT2 gearbox? Have you a picture of the RT parked?

[citabjockey]

The bike is an RT3 (1973 model, RT2 was 72 with a 19" front, mine has the 21). Absolutely no issue with the gear box. Shifts like the proverbial hot knife... The whole bike is built like a Sherman tank -- very tough and over engineered. Puts a huge grin on my face every time I ride it.

[Uniflow]

Very nice. I had one ( 2, one in a box for parts) years ago but in a fit of shortsightedness scraped it! ( them ). I always thought mine was an RT2, it had reeds. I think the RT1 was piston port? The gearbox on mine was not too good. I ended up changing the gear clusters out of a DT 400. The 400's had undercut drive dogs where as the RT's and DT360's did not. Fromm memory I had to change the clutch as well?

[Uniflow]

This is a DT360 I used to race in VMX a while ago.

[Uniflow]

This also had  400 gear clusters, clutch and the DT400 head. Because it had a central plug.

[citabjockey]

 Interesting point regarding the undercut dogs on the 400. Is this the case for both the DT and MX400 models?

So can you wrangle up some video of that bighorn? I for one would love to see and hear that monster running.

[Uniflow]

This is montage of racing at Wakatane two years ago. Somewhere in the middle is the bighorn running. This was with the lower comp head and the mechanical fuel injection ( similar to a Hilborn system) , never the less it did win one race and second in an other. You can see that the old guy riding it needs to try a little harder!

[Uniflow]

This video is pre the vairable rotary housing. The bighorn is coming to pieces  this weekend, as I was taking the photos for you with the throttle body off I noticed the rotary valve is lose. There is a pin that drives the valve and it's had some damage in the past, it seems I didn't do a very good job of fixing it, I'll need to pull the crank out and remachine the drive pin hole out to a larger size. Make a stepped pin to suit. Next time I'm out with the old girl I'll get some video. Our racing starts in a month so it has to be running good for that. I'm going to run in the pre 75 open class with this EFI engine first, untill someone complains. I might have to go back to the old mechanical injection engine you see in the video.

[Uniflow]

This is typical of a VMX racing  in New Zealand, mostly natural terrain. Right up to 1985 bikes.

[2T Institute]

This video is pre the vairable rotary housing. The bighorn is coming to pieces  this weekend, as I was taking the photos for you with the throttle body off I noticed the rotary valve is lose. There is a pin that drives the valve and it's had some damage in the past, it seems I didn't do a very good job of fixing it, I'll need to pull the crank out and remachine the drive pin hole out to a larger size. Make a stepped pin to suit. Next time I'm out with the old girl I'll get some video. Our racing starts in a month so it has to be running good for that. I'm going to run in the pre 75 open class with this EFI engine first, untill someone complains. I might have to go back to the old mechanical injection engine you see in the video.

I can see the engine has spent some at Kaitemako Rd Tauranga    I have a Big Horn motor myself a Skidoo cylinder could easily fit onto the Big Horn cases.

[SachsGS]

How do you pressurize and time the fuel with the mechanical system? Also, why are there so few Euro bikes in the vintage and evo classes in NZ? I think I saw one CZ in your video and that was it for non Japanese bikes. Here in NA it would be a sea of Maicos.

You got it right those old RTs and DTs were built like tanks, 300 lbs of over engineering.

[Uniflow]

Well well, who do we have here? Yes Wobbly and I talk and there has certainly been some input from him. We build some stuff for him and his RZ based engines.
Fuel in the MFI system was pressurized by a small pump run off the flywheel side of the crankshaft. Based on a Honda 50 oil pump. Continuous flow to a tapered needle in the throttle body with a vairable flow back to the tank. When it worked well, it worked very well but when it didn't ( most of last season ) it was a disaster. That's why I started playing with EFI. From what I know now I think I could go back to MFI with a little better results, still not as accurite as EFI.
We didn't see many Euro bikes in NZ, not sure why? Cost maybe? USA sucking up all the stock?
The ones we did see usually ended up broken and were expensive to fix.