Best source for a replacement head?

I know this probably isn't an uncommon question, but I need to replace the head current fitted to my 1973 850. I love the ones produced by Full Auto but sadly they're about $1000 outside of my maximum budget. Is there a good source for decent used heads?

The reason I need one is because a previous owner of my bike had the head shaved by a few millimetres and broke a heat sink fin, so I'd like to go back to original spec with no cosmetic damage.

As always, thanks for any advice!

Can I have your old, shaved, broken ugly one?
Ta.

Such a crap shoot with used cylinder heads. You could get what seems like a decent one only to find cracked fins, stripped exhaust threads, stripped spark plug holes, etc. That extra $1,000 or so might seem like chump change after spending good money on one that you thought was solid only to be right back where you started.?! That being said I'll keep my eye out for a good RH10.

Branch said:

I know this probably isn't an uncommon question, but I need to replace the head current fitted to my 1973 850. I love the ones produced by Full Auto but sadly they're about $1000 outside of my maximum budget. Is there a good source for decent used heads?

The reason I need one is because a previous owner of my bike had the head shaved by a few millimetres and broke a heat sink fin, so I'd like to go back to original spec with no cosmetic damage.

As always, thanks for any advice!

Click to expand...

Good 850 heads are getting a little hard to find. A lot of TH4s are cracked and RH10s are scarce and bring a premium price.

I can fix a broken fin so you can't tell it ever happened.
An extra thick headgasket or a shim under the barrel can be used to restore the low compression. Jim

I had to emergencey head shop for Peel when C-head lost over a yr after sending to M.A.P. Cycle and their shop decided to ignore any more Norton jobs w/o notifiying M.A.P. I suggest go Technical post section and go down list of vendor world wide inquiring what they have or know about and keep eye on ebay. Much as this forma has great resources its a drop in the bucket of world wide scope and parts so happy hunting and making new friends rescuing a Commandos. Btw a 750 head can be modifited to work on 850 and bigger which tends to give smaller chambers and more squish band area for faster combustion and velocity in ports. I was laughed and put down 10 yr ago on other forums telling me I paid WAY TOO MUCH, $450 for ready to run 28.5 head but it turned out to be key to Peel power and still ready to go again if my Trixie head wears out.

comnoz said:

Good 850 heads are getting a little hard to find. A lot of TH4s are cracked and RH10s are scarce and bring a premium price.

I can fix a broken fin so you can't tell it ever happened.
An extra thick headgasket or a shim under the barrel can be used to restore the low compression. Jim

Click to expand...

You'll never be able to tell where the fin was fixed. No one will see the spacer or head gasket. With the extra money you just saved have Jim clean up the head and maybe do the exhaust ports too. If the rest of the head is good you'll have something better than anything you can find.

swooshdave said:

.......You'll never be able to tell where the fin was fixed. No one will see the spacer or head gasket. With the extra money you just saved have Jim clean up the head and maybe do the exhaust ports too. If the rest of the head is good you'll have something better than anything you can find.

Click to expand...

+1... he can even fix/replace the sparkplug threads too, and put it in the tumbler to clean the whole thing up.

There's an auction for an RH10 happening on eBay right now.

Thanks for all the tips and advice here, it has really helped. @Comnoz, I'll send you a message now.

I have a 850 head for sale which I'll put up on eBay again tomorrow, located in Australia. I fitted a Fullauto head to my Mk 3 so I don't need the original.