RH6 Cylinder head

[Madnorton]

Do they exist? and wondering if anyone is using one.

 

[L.A.B.]

RH6 was one of the two heads used after the Combat series ended. If you put RH6 into the search then you should find several references. As the RH6 was such a common head I'm curious to know the reason for the question.

Examples:

Post in thread '1973 Commando Roadster MK V: Combat Motor?'

Feb 7, 2020

Thanks for the link.
How can you determine if the head is an RH5 or RH6?

I too have seen RH5 and RH6 a bit more haphazard stamped on the heads. Not neat like the 850's. Look for an R and a 5 or 6 on top of the head
RH5 squish band depth is standard .125", the RH6 will be cut 20 so .100" squish band... both "approx"...

• dynodave

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Picture:

C

Post in thread '1973 Commando Roadster MK V: Combat Motor?'

Feb 9, 2020

Tell us more please. How did you find the bike ... and how much did you pay? Sounds like you have more than a "little" back ground in Nortons. Even a Norton mechanic; back in the day? How cool is that

My oldest son came across the Roadster on Facebook Market (of all things), and the owners said they had it posted for about 1.5 months, with no real interest. Bought it within two days of finding it, and paid $3k...for a Roadster with 21,121 original miles on it. Many thanks to my son for making the 12 hr. round trip, from outside if Nashville, TN to...

• CommandoMKV

• 

 

[marinatlas]

I have one , actually on a 750 engine .

 

[marshg246]

Do they exist? and wondering if anyone is using one.

I have a bike with an RH6S ("S" means cast iron 850 valve guides)

 

[Shelby-Right]

My bike is a 1973 mk5 from its numbers and its registration and it has a RH6 head .

 

[Ron L]

I have them on two 1973 MkV 750, one I have owned since new. And another RH6 head on the shelf for a possible future build. More compression than the standard 750 head (or RH5) but a little less than the Combat head. 32mm intake ports. My favorite 750 head for street use.

 

[L.A.B.]

As far as I'm aware due to previous discussions the RH6 was the head generally fitted on US post Combat 750 models which still leaves me somewhat bemused by Madnorton's original question "do they exist" as there must have been hundreds made originally.

 

[Madnorton]

As far as I'm aware due to previous discussions the RH6 was the head generally fitted on US post Combat 750 models which still leaves me somewhat bemused by Madnorton's original question "do they exist" as there must have been hundreds made originally.

Now that is what I thought, but we see many of the other RH heads, mind you we seem to see many early 750's here and a lot of 850's.

The reason being is that we are looking at head design and a 750 head that will suit all 750's would make sense. The RH6 seems to have a little more increase of the CR than the 'standard' head but not quite as much as the RH3, so this with modern fuel will think will be ideal for the 750 head. Port design has already been agreed upon. On the original drawings the head was not only skimmed to increase compression, but also the height of the combustion chamber to gasket face was also reduced.
I have now found a high temp / low ex alloy that will replace the RR 53, it is readily available to order from the smelting plant.

 

[L.A.B.]

Now that is what I thought, but we see many of the other RH heads, mind you we seem to see many early 750's here and a lot of 850's.

The reason being is that we are looking at head design and a 750 head that will suit all 750's would make sense. The RH6 seems to have a little more increase of the CR than the 'standard' head but not quite as much as the RH3, so this with modern fuel will think will be ideal for the 750 head. Port design has already been agreed upon. On the original drawings the head was not only skimmed to increase compression, but also the height of the combustion chamber to gasket face was also reduced.
I have now found a high temp / low ex alloy that will replace the RR 53, it is readily available to order from the smelting plant.

Alright, although I don't know why you didn't just say that in the first place.