Wanted Ohlins YZ360 Kit / Barrell (Noleen in USA)

[Rookie#1]

From my conversations with Peter (billet yz) regarding the 360 yz I get the impression he loves it, don't think his wr500 has seen much dirt since he's had the yz up and running.

[SON]

Why not just get a KTM 360/380  with all the hard work done for you?

YAMAHA Dealer with a new YZ250 2 smoke and a rider capable of using open class 2 stroke power
Homage to Peter Doyle and Sharky at Broadford.

[JohnnyO]

The short stroke/big bore combination will surely limit it's potential compared to a properly designed motor, but you'd think that it would still be able to out-perform a 250 if the rest of it was right.

The combination doesn't work, they don't produce any more power than a 250 and don't rev. You're very busy on the gear lever because they don't pull for long in each gear.
I had a $10,000 360 Mugen which is the same setup, I tried everything to make it work..different compression ratios, different port heights, different carby's and ended up selling it because my 79 cr250 was faster and pulled longer in each gear.
There isn't a short stroke big bore engine around that does work..

[JohnnyO]

From my conversations with Peter (billet yz) regarding the 360 yz I get the impression he loves it, don't think his wr500 has seen much dirt since he's had the yz up and running.

No doubt he does like it, it's rare and cool and would be fun to ride compared to a WR500 dinosaur but in a mx race against 89 CR & KX500's... good luck!

[Lozza]

Why not just get a KTM 360/380  with all the hard work done for you?

YAMAHA Dealer with a new YZ250 2 smoke and a rider capable of using open class 2 stroke power
Homage to Peter Doyle and Sharky at Broadford.

Cast up some covers with Yamaha on them  You should ring me about this literaly anything is possible today.

The short stroke/big bore combination will surely limit it's potential compared to a properly designed motor, but you'd think that it would still be able to out-perform a 250 if the rest of it was right.

The combination doesn't work, they don't produce any more power than a 250 and don't rev. You're very busy on the gear lever because they don't pull for long in each gear.
I had a $10,000 360 Mugen which is the same setup, I tried everything to make it work..different compression ratios, different port heights, different carby's and ended up selling it because my 79 cr250 was faster and pulled longer in each gear.
There isn't a short stroke big bore engine around that does work..

Pipe, ignition and head shape is where the answer is.

[SON]

Call in next time your driving past
I was going to call you once I had a barrell

[JohnnyO]

Why not just get a KTM 360/380  with all the hard work done for you?

YAMAHA Dealer with a new YZ250 2 smoke and a rider capable of using open class 2 stroke power
Homage to Peter Doyle and Sharky at Broadford.

Cast up some covers with Yamaha on them  You should ring me about this literaly anything is possible today.

The short stroke/big bore combination will surely limit it's potential compared to a properly designed motor, but you'd think that it would still be able to out-perform a 250 if the rest of it was right.

The combination doesn't work, they don't produce any more power than a 250 and don't rev. You're very busy on the gear lever because they don't pull for long in each gear.
I had a $10,000 360 Mugen which is the same setup, I tried everything to make it work..different compression ratios, different port heights, different carby's and ended up selling it because my 79 cr250 was faster and pulled longer in each gear.
There isn't a short stroke big bore engine around that does work..

Pipe, ignition and head shape is where the answer is.

I still don't believe it will work, bore and stroke is all wrong. A KTM 250/300 has an 8mm longer stroke by comparison..

[SON]

Johnny it will work when I stroke long rod and balance the crank
Lozza has programmable ignitions that work
Doesn't need to rev if it's pulling your arms out
250cc 2 strokes have to be revved
400cc 2 strokes are just right

[JohnnyO]

Yeah SON I agree it will be much better with a longer stroke crank..

[Nathan S]

Apart from the weight of the piston, what stops a 360 from revving as hard as a 250 with the same stroke?

The old Husky 360GPs were short stroke - they certainly didn't have a problem with not revving hard enough.

[JohnnyO]

Apart from the weight of the piston, what stops a 360 from revving as hard as a 250 with the same stroke?

The bigger volume it has to compress. A longer stroke also has more leverage to turn the crank easier.

[OverTheHill]

in terms of what works & what doesn't--the old SC500 is way oversquare with a stroke from the 360 of 70mm & bore of [not sure without looking] 90mm or something, which is 10mm over the 80mm 360 it was stretched out from--plus a 4 speed box come to think of it. Rode one occasionally in big flat or rolling grassy miniature tt's we use to call them & on the day [my good day haha] was quicker than my mates RN400. In fact our Hugh Anderson beat Ivan Miller for the nz mx champs back then on the SC & Ivan on the RN--was a great day that.
What's the stroke of the "89 250 your stretching to 360. Yams were typically 70x64 till [i think] went to 68x68 which i suspect this ["89 is] & YZ400F piston is 82mm, the only year they ran 82mm [have one in my old RT2-360.
I do have a 'way' oversquare 250 Yam that's 80x64--well--a 250 with a 360 cylinder, long story but turns on up top. Actually--actually forgot where i was now as a mate turned up on a mint original XR500 twinshock while writing this, & now [i want one]. Cheers.

[OverTheHill]

i hope people aren't getting confused between 'long rods' & 'long stroke'. I'm old [& confused most of the time] but gather long rod has something to do with piston dwelling longer at top & bottom of stroke. Lozza would be the man to explain but would a long rod plus long stroke be 'the go'.!! Thanks

[Lozza]

Apart from the weight of the piston, what stops a 360 from revving as hard as a 250 with the same stroke?

The bigger volume it has to compress. A longer stroke also has more leverage to turn the crank easier.

Heat(or lack thereof)in the pipe limits the rpm. Not so long ago GP125/250's ran 19:1 compression and they would not rev past 11,000, untill tuners started wrapping the pipe in heat wrap. A few years later after exotic leaded 124 octane Elf Blue Gas was banned, comp ratio's dropped heat in the pipe increased so no need to wrap the pipe any longer.

Johnny it will work when I stroke long rod and balance the crank
Lozza has programmable ignitions that work
Doesn't need to rev if it's pulling your arms out
250cc 2 strokes have to be revved
400cc 2 strokes are just right

Taking about a proper cylinder not the rubbish that Japan Inc has been serving up recently. A friend in NZ has prototyped a 350cc disc valve engine with modern features like a cassette gearbox and water cooled cases. Should be a right weapon.

[SON]

in terms of what works & what doesn't--the old SC500 is way oversquare with a stroke from the 360 of 70mm & bore of [not sure without looking] 90mm or something, which is 10mm over the 80mm 360 it was stretched out from--plus a 4 speed box come to think of it. Rode one occasionally in big flat or rolling grassy miniature tt's we use to call them & on the day [my good day haha] was quicker than my mates RN400. In fact our Hugh Anderson beat Ivan Miller for the nz mx champs back then on the SC & Ivan on the RN--was a great day that.
What's the stroke of the "89 250 your stretching to 360. Yams were typically 70x64 till [i think] went to 68x68 which i suspect this ["89 is] & YZ400F piston is 82mm, the only year they ran 82mm [have one in my old RT2-360.
I do have a 'way' oversquare 250 Yam that's 80x64--well--a 250 with a 360 cylinder, long story but turns on up top. Actually--actually forgot where i was now as a mate turned up on a mint original XR500 twinshock while writing this, & now [i want one]. Cheers.
Pleased you have told this story as I have an ex Ivan Miller RN