Classic Dirt 7 Queensland 2010

[Stan S]

Geoff was the throttle man, but that thing sounds like no XS I've ever heard. In all seriousness it would be a real treat to record that engine noise in much the same manner as the H16 F1 car from 1949. if you get a chance drop over to YouTube and have a listen to the clip of pink floyds drummers car at  a track in England and you will get the idea. The exhaust note from that chair is by far one of the best I have ever heard.

Gday Bahnsy, I do totally agree about the sound of that XS engine. I asked EML about it and he said the firing order had been changed and the 2 cylinders fire like a big single. It sounded awesome.

Stan.

Thanks for the nice comments lads,

Heres a bit of info on the engine:
The firing order has been changed, however it doesn't fire as a single.
Instead of firing every 360'degrees, (parallel twin 4 stroke), it fires 270'-450'-270'-450'degrees and so on.
The right hand crankpin is 90'degrees ahead of the left one.
This is the same firing offset as a 90degree V-twin (ducati, good noise), but instead of the cylinders being 90degrees apart, the crank is.

The main objective of this was to reduce vibration, which it has done significantly.
It has turned it into a really smooth reving engine with loads of torque, and the traction is amazing due to the un-even firing pulse going through the back wheel.

Matt.

Thanks Matt for clearing that up, what EML told me was probably more like what you have explained but buy the time I related it I got it all wrong. Anyway it still sounds bloody awesome.

Stan

[270YAM]

I do not like to rev engines hard. I prefer to grab another gear and let the torque do the work, much the same as the way you use the longstroke GRM power. Reducing vibration should not be confused with reducing 'grunt'.

[GD66]

Stan, down your way Daryl Hutcheon of Professional Motorcycle Tuning in  Airport West has been playing with 650 Yamahas for years, including big bore kits and 270 degree cranks, might be worth a call if you're keen....

[Tim754]

Never had a problem with vibration ....um from the engine that is...   and on the other general item CD7 thread they have a few comments on "free hand air brushing" glad no body interested in VMX sidecars is silly enough to indulge in that rubbish. Cheers Tim754

[270YAM]

Wasp,
Moving the crank around 3 splines is a common and simple way of doing it, works out to be 83.08degrees and apparently works quite well.
To get 90degree, u need 2x #2flywheel (centre left) and a special double ended centre shaft (and a small amount of machining) to get the magic number.
Chuck the #3 flywheel in the bin, as well as the other 3 flywheels from the donor crank

[Tim754]

Wasp we  have used another tank on the track....mostly Cheers    (also the photo was really a test to see if I could properly upload hosted piccies  , Success!)

[EML]

Talking of vibration, the 880 we tried to run this year is a big drama and vibration is most likely the cause of our ignition failures. We are up to our 3rd Boyer box and 4th coil pack. On top of that we had the whole thing rewired twice and each time it has failed it has been diagnosed as something else.
I recall from back when these were raced alot that they had issues with bolts falling out and things breaking all of the time so we might consign that engine to the scrap heap.
It can't be considered poor preparation as some half-smart bastard is suggesting as we spent plenty of time and money on it.

[270YAM]

Made the cam at home from start to finish, it is made from billet 4340 steel, with adjustable sproket.
Ignition is off the shelf unit made by PROBE Indudtries in the states.

This is the cam 'rough ground' before it was stress relieved.

[270YAM]

Great idea I have a mate in Sydney with a rephased 840 in a Rob North copy frame, racing Period 5 (Forgotten Era). He has a lot of success, especailly in the wet and on tite tracks, even at Eastern Creek he gets up the 1100 Suzuki's and the Morowaki Kawasaki's, but the 840 doesnt quite have it down the strait.
That thing of yours would eat the P4 class alive.

Unfortunately the program for this cam moved to QLD as it was made by hand on a conventional lathe and a home made cam grinder!

[270YAM]

Unfortunately because I have moved to QLD I no longer have access to the gear I use to build the cams.
You can get them hard welded and re-ground, but you probly like that idea as much as i do.
In answer to your earlier question, yes the cam shaft is hollow.
How do you rephase a Euro longstroke crank? do they use the same 13 spline setup as a standard crank?

[EML]

Matt, what have I told you about talking to strange old men on the net in the middle of the night??
I heard you had a win at Proserpine but that the Norton took the trophy home. was the track as dodgy as Nick says-he reckoned it was very tight and twisty through the trees like an enduro special test.
Bloody great bunch of people though eh.

[VMX247]

The below sidecar came with no esky in the chair, as some models did at CD 7 

[270YAM]

So then what was the purpose of this bike?

[VMX247]

So then what was the purpose of this bike?

It was the all time, best ever seen fastest yellow yammie wheelie jumping machine ...
I mean they all have a purpose        

[270YAM]

Matt, what have I told you about talking to strange old men on the net in the middle of the night??
I heard you had a win at Proserpine but that the Norton took the trophy home. was the track as dodgy as Nick says-he reckoned it was very tight and twisty through the trees like an enduro special test.
Bloody great bunch of people though eh.

Yep top weekend, Great people, not so great track. Still an awesome weekend none the less.
Great to have the crew from down south come up, thanks guys.