8 valve head conversion

Thanks.
It was not clear if these were actually included. Or what was indeed required.

Sill wondering if the required cylinders are stock 850 type.
Or if the stud pattern is something special to suit these particular heads. ?

It sounds as though they are special Rohan.
Too special for me Foxy.
How many Bags to the acre over there.?
AC.

AussieCombat said:

How many Bags to the acre over there.?
AC.

Click to expand...

That depends on how much wool is on the sheep,...... ooooh I see you're not refering to bags of wool.

Gday AC, off topic but seeing you asked , 8.5 bags. Not enough seeing its at give away prices! Too many overseas countries subsidising their farmers pushing the price down!! :cry:

here`s one in the uk ,,,,,,,,,,,,

http://www.youtube.com/watch?v=4FnEp2mFLKw

Thanks for posting the link ritosfx, but what a tease! Thoroughly enjoyed the vid, although it being a fleeting glimpse! Do I assume right that you have a strong link to this beautiful and most desirable machine? If so more pics please and of course information on its build plus performance! :mrgreen:
foxy

I think my old 500cc short stroke Triumph would have benefitted from twin spark plugs in each cylinder It was basically a 650 fitted with a 63mm stroke billet crank and shortened barrels. I used 12 to one 650 pistons which gave a final comp of ten to one. After a long time racing, it was clear that the carbon build-up was bigger on the crown of the piston away from the spark plug side. In my 850 commando, the head is offset forward on the barrels giving a squish band (as standard) And because the chamber is actually smaller, the size of the crown of high comp pistons is smaller. The weight of hi-comp pistons must still be higher than with a flat top. limiting the revs you can use , and the way the motor spins up through the gears. I don't use high comp pistons, only standard comp, and I still run methanol fuel. The Norton head is much better than the Triumph head. Even when Triumph 650 motors were fitted with Rickman four valve per cylinder heads, they did not go much quicker. In general ter ms the difference between running four valve heads on a sing le cylinder motor is that the power increase is about ten per cent. I think they are popular on four cylinder machines, because of this power increase, and the higher permitted revs due to the light valve weight. In the end it all comes back to what gear box you use , and the loads in the bottom end when you spin the motor. My crank is balanced to 72 %, the bike rocks when idling, but when revved it is very smooth. With the CR box, it spins up extremely quickly, and is a danger to itself. I never do anything which will reduce its torque characteristic if the change will substantially decrease the usable rev range by moving it too high. I always try to change at 7000revs, and it always gets to 7,500 before the next gear arrives, even with the close box.
I have a set of spare crankcases with a plate welded over the drive side main bearing. It was cracked by someone over-revving a commando with a standard crank balanced at 58%.

I guess all things need to "allign" perfectly when such mods are performed.
The early seventies Honda XL Trail bikes in 250cc and 350cc were 4 valve OHC Heads.
Not saying it made them any better or more powerfull, but the 350 head became
a usefull addittion, as a Conversion, for the Jawa 500cc 2 Valve Speedway engine.
Just saying.
AC.

Hi

I found that my 8 valve Rickman T120 may not be much quicker than my friends race T120 (it is )
What it is though is a far nicer bike to ride & pulls from everywhere.
Still say the Commando Piper head looks like a couple of house bricks.
Pete Lovell is still the man to speak too.

Chris

Hi

I found that my 8 valve Rickman T120 may not be much quicker than my friends race T120 (it is )
What it is though is a far nicer bike to ride & pulls from everywhere.
Still say the Commando Piper head looks like a couple of house bricks.
Pete Lovell is still the man to speak too.

Chris

Thanks for the comment about the 2 valve Jawa a nd the XL350 head. My brother owns this :
http://www.youtube.com/watch?v=XoWlC8wzA7g

More 8-valve footage and pictures here:
http://nochangegiven.com/ncg/manx-norto ... ousel-1381