norton dunstall 810

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valdemar

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Jan 29, 2012
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im new to this forum
im in the tail end of finishing the 810 motor and what a project its been.but worth it as i was able to improve the reliability of the 810 barrel.resleeving it to 750+.60 thou for a thicker sleeve that wont break, to using loctite 635 to lock in the threaded inserts so they dont work loose(i dont understand why the inserts werent helicoil).loctite 635 is permanent it wont work loose,can only be drilled out,this was used in conjunction with spray primer (hardener).more data available if required
 
Welcome to the forum.

I'm sure there are others besides me that would like to see pictures...
 
I believe you are on the right track in working around the weaknesses of the 810 cylinder. They are porous and frail. I have pushed using a Dunstall Cylinder to the right on my project list. I wanted to include studs that fully engaged the threads of the cylinder before any torque is applied. The thin sleeve of the 810 kit are a disaster. BTW, the OD of the 810 liner and an Hepolte liner for a 750 cylinder are the same. 76 mm in a liner that was designed for 73mm. Any wonder!
All the best on your project. Send photos. Inquiring minds want to know.
Rj
 
I will follow this thread becoz I'm seriously considering manufacturing the Dunstall cylinder. I know I know , there are heaps of people making these so dont bother telling me that.
If the problems cant be sorted with the 76mm bore then I was thinking maybe leaving them at 73mm, I know it kind a defeats the purpose, but if I had a choice of either stock iron 750 cylinders or Dunstall alloy 750 cylinders I know which I would prefer, I think this thread has a long way to go , I'll be watching.
 
i put a 750 +60 thou sleeve which gave the sleeve an extra .75mm thickness
i was also advised by the engineer that made the sleeve metal technolgy has come a long way since 1970
ive taken photos of the comparision of old sleeve and new sleeve and theres heaps of difference
i also found when i removed the threaded inserts for the head bolts they are different length reach sizes
and that brass shims are fitted to compensate
 
ps how do i submit photos
i taken heaps of photos have tried but unsuccessful
can someone help val
 
its val again
by using +60 over sleeves which wont break it gives it 74.5 mils
i think this is approx = 775 to 780 cc
so its still bigger than standard 750 and give a throatier sound .i had stainless steel studs made to bolt to the cases
im using a brass base gasket,ive hade allen head bolts made in stainless
and when more financial redo the header pipes to 1 3/4 to breath better thus hopefully reduce
engine heatup
 
norton dunstall 810


Im sure this one suggested 1 7/8 o.d. , screw in bored inserts , plug in pipes , m-x type spring & hook retainers .
The old 1 3/4 is ok on a 650 Triumph . 3 in Cooper Ex pipe for 36 Buicks . :D
 
madass140 said:
I will follow this thread becoz I'm seriously considering manufacturing the Dunstall cylinder. I know I know , there are heaps of people making these so dont bother telling me that.
If the problems cant be sorted with the 76mm bore then I was thinking maybe leaving them at 73mm, I know it kind a defeats the purpose, but if I had a choice of either stock iron 750 cylinders or Dunstall alloy 750 cylinders I know which I would prefer, I think this thread has a long way to go , I'll be watching.
Click to expand...

The most popular alloy race barrels are surely Steve Maney's..... http://stevemaney.com/products.html

750, 850 and 920.....and like you say there are other choices....will you be able to do a quality product cheaper?
 
valdemar said:
its val again
by using +60 over sleeves which wont break it gives it 74.5 mils
i think this is approx = 775 to 780 cc
so its still bigger than standard 750 and give a throatier sound .i had stainless steel studs made to bolt to the cases
im using a brass base gasket,ive hade allen head bolts made in stainless
and when more financial redo the header pipes to 1 3/4 to breath better thus hopefully reduce
engine heatup
Click to expand...


From what has been said on exhaust ports I am not sure larger diameter pipes, beyond say 1 1/2 ID are going to make a lot of difference, particularly for road use, but whatever diameter remember that it is pipe volume that is important...larger dia pipes need to be shorter, and you may then have problems with mounting silencers if using conventional routing.......

1 1/2" ID by 28" worked on 850s! and smaller diameter (1 3/8") 32" pipes worked on 750s....way back when............
 
"The most popular alloy race barrels are surely Steve Maney's..... http://stevemaney.com/products.html

750, 850 and 920.....and like you say there are other choices....will you be able to do a quality product cheaper?"

I'm not looking at race barrels, my intention is to produce barrels for road use , Dunstall replicas supplied with the same Dunstall cam followers , stellite faced BSA style, Actually the cam followers will be the single biggest costly part to produce.
Do Maney barrels come with cam followers?
 
madass140 said:
"The most popular alloy race barrels are surely Steve Maney's..... http://stevemaney.com/products.html

750, 850 and 920.....and like you say there are other choices....will you be able to do a quality product cheaper?"

I'm not looking at race barrels, my intention is to produce barrels for road use , Dunstall replicas supplied with the same Dunstall cam followers , stellite faced BSA style, Actually the cam followers will be the single biggest costly part to produce.
Do Maney barrels come with cam followers?
Click to expand...

I only refer to the fact these are race barrels because that is Steve's business, and I don't go to events where many road bikes go. I see no reason why Maney barrels cannot be used on road bikes. Certainly Steve will supply them honed to the size and clearance you want, cast or forged pistons or whatever.

I don't see why cast iron is not the most appropriate solution for road bikes either,but then again I never really understood why Dunstall bothered!, but that really is just me. For me, black iron looks right, especially with closed through bolts, and I don't thenk the weight and heat dissipation are real issues for stock bikes. As far as I know some racers prefer cast iron anyway!

I guess if I think about it I see little need for a capacity of around 780 to 810 either, when there is an easy 828 solution available, Dunstalls product disappeared quickly when Norton launched the '850'. But maybe its just the technical challenge of casting barrels and inserting liners you are after, I am sure it will be fun to do if you can. :D

Concerning cam followers, the answer is no, Maney's don't come with the barrels, but I don't think they come with anyone elses barrels either!

Standard Norton Cam followers are stellite faced and I know that from experience when that 'friction welded' stellite comes off, it causes a mess.... Of course they are flat not curved like BSA style followers, and from Jim Schmitt and Steve Maney practice, surely you will need to look at your cam profile if you go for curved followers? Maney needs follwers that are to be used with his cams to be reprofiled, so again the follwer needs to suit cam profile.

Andover Norton standard followers are pretty pricey, so you don't really want to grind new ones.....and I don't think they come with that 'high performance sand' they used to contain when Norton made them.....clean internally and externally before use!
 
SteveA said:
valdemar said:
its val again
by using +60 over sleeves which wont break it gives it 74.5 mils
i think this is approx = 775 to 780 cc
so its still bigger than standard 750 and give a throatier sound .i had stainless steel studs made to bolt to the cases
im using a brass base gasket,ive hade allen head bolts made in stainless
and when more financial redo the header pipes to 1 3/4 to breath better thus hopefully reduce
engine heatup
Click to expand...


From what has been said on exhaust ports I am not sure larger diameter pipes, beyond say 1 1/2 ID are going to make a lot of difference, particularly for road use, but whatever diameter remember that it is pipe volume that is important...larger dia pipes need to be shorter, and you may then have problems with mounting silencers if using conventional routing.......

1 1/2" ID by 28" worked on 850s! and smaller diameter (1 3/8") 32" pipes worked on 750s....way back when............
Click to expand...

BUT....after having those pipe dimensions in my head since late '75....I have just read them in Paul Dunstalls tuning manual....but since there was no 850 when he wrote it, he actually says for 650 and 750 sizes are the same but that the bigger ID shorter length is race cam, and the longer pipe smaller ID is for street cams....so maybe you need to look at your cam choice first?

I chatted exhaust dimension with Peter Williams in '78 and he said the 1 1/2 ID, 28 that I had been using was right for my 850 with it's ex Thruxton cam....so it seems to still stack up...except that Maney, from eyeballing his system, uses a longer and bigger ID pipe, but I have yet to measure one of his exhausts, and anyway they are 2 into 1 and a bit more 'sound concious'....

I have ridden a 750 PR copy Commando at Cadwell Park with one fitted and, a guy with lots of Seeley Norton experience changed to one last year and recorded an improvement over his previous system...

But for road use, do you need even 1 1/2 ID?
 
"Standard Norton Cam followers are stellite faced and I know that from experience when that 'friction welded' stellite comes off, it causes a mess.... Of course they are flat not curved like BSA style followers,

the stellite faced Dunstall followers are flat not curved
 
From what has been said on exhaust ports I am not sure larger diameter pipes, beyond say 1 1/2 ID are going to make a lot of difference, particularly for road use, but whatever diameter remember that it is pipe volume that is important...larger dia pipes need to be shorter, and you may then have problems with mounting silencers if using conventional routing.......
My first race bike had a Steve Maney bottom end, crank, ported & lightened head, 4s cam, Maney pushrods, twin 32mm Mikunis going into a 2 into 1 exhaust with 1 3/8" head pipes. It put out 52 hp when we put it on the dyno, right before we did some work on it. Herb made a 1 3/4" head pipes 2 into 2 exhaust and put twin 38mm Mikunis with long inlet tracks. The only engine work we did was to put a 7s cam in. Back on the dyno it now put out 67 hp. I would say big bore pipes would help you but mostly if you've got more air going in too. I have that dyno sheet print out with both graphs on it.
I've got a set of 810 pistons stamped Dunstall on the bottom that are out of street engine I just had taken apart. The guy had bored stock barrels until they were paper thin at the bottom to make them work- the bike ran fine but that paper thin bore at the bottom was not going to last. I had the motor rebuilt as a 750.
Click to expand...
Click to expand...
 
This is a subject of great interest to me as Im about to make up some pipes for my 1360 Vincent. Ive always thought (wrongly perhaps) that people tend to go too large on pipe diameter and end up losing exhaust velocity and some performance.

I recall reading that Paul Dunstall tried all different sizes of pipe on his racing Dominators and finally decided that the smaller 13/8" size gave those bikes the most power and greatest top speed.
. Later on, Dunstall was a consultant to Norton for the development of the first Commandos. One piece of advice he gave was to use 1 3/8 pipes on the Commandos, so that is what Norton did.
On the subject of long inlets, I have always thought (again, perhaps wrongly) that stock Norton twins have terrific throttle response due to the short inlet that engine type has. A Vincent has a longer inlet trac and it seems to be a little slower engine to rev. Both engines have heavy flywheels in stock form.
One well known Vincent is in a Seeley frame. The act of shoehorning the Vincent into the Seeley was documented in a British cycle mag about twenty years ago when this was done. The article was entitled "big job" which it was.
Due to the positon of the frame tubes a very long inlet stub was required for one pot, so the owner/builder, made the other stub of equal length.
That bike is one of the slowest accelerating Vincents Ive encountered. It did eventually show some power from 5 to 6 k (all done at 6k) but by the time it got up there the rest of us were already in the next town!

Btw Doug, I have the 650ss that Herb rescued from a junkyard in Ontario a few years back.

Glen
 
im not trying to make my 810 a track bike
i just wanted to try and improve on the weaker parts so i have a 810 dunstall
that hopefully will be reliable and not damage bottom ends by the sleeve breaking
and hopefully the inserts in the barrell wont work loose and cause problems
but still have a fairly fast norton that will the do business

thans val
 
Val, if your main goal is simply to end up with an 810 Dunstall, then I think you are going the right direction in mods to improve its reliability. Back in the '70s I built a race bike with a set of Dunstall 810 cylinders that I sleeved down to 750. Because Dunstall made the cylinders in both 810 and 750 bore sizes, LA Sleeve stocked replacement sleeves in both sizes. It was pretty simple to just replace the 810 liner with the 750 liner. It worked fine for a couple years, with the only problem being the need to regularly tighten the base nuts, because they would sink down into the soft alloy Dunstall used. Eventually the alloy cylinders cracked between two of the fins, and I had to replace them with iron cylinders, but the engine had suffered a lot of abuse on the race track before it finally gave up. Good luck with the project.

Ken
 
Doug MacRae said:
From what has been said on exhaust ports I am not sure larger diameter pipes, beyond say 1 1/2 ID are going to make a lot of difference, particularly for road use, but whatever diameter remember that it is pipe volume that is important...larger dia pipes need to be shorter, and you may then have problems with mounting silencers if using conventional routing.......
I just had a good test of that theory. I had two similar fresh builds. One was 850 ccs with 1 3/8 inch pipes and normal peashooters. The other was 880 ccs with 1 3/4 inch pipes and hollow peashooters. [ no center tube-very loud]

Both bikes had the same cam [street performance] ,compression ratio and cylinder head mods. They were both fuel injected.

Both engines hit the torque peak almost identical. Above the torque peak the big pipe 880 went downhill. At 6500 RPM the 850 with small pipes and mufflers with a center tube made a good 15 horse more than the big pipe 880 with open mufflers. The difference was dramatic. Jim
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