who can identify this???

hewhoistoolazytologin · Sep 30, 2005

Thinking of getting this thing running so I can give it a try....had it about twenty years and don't know what size the barrels are...or who made them. Nice fellow had it in a chopper. Would be nice to get an idea if I can still get rings etc for it. Barrel is aluminum...note strange bolts used to attach it to the housing...really thick base too. Thanks for any suggestions!

L.A.B. · Sep 30, 2005

That is the barrel from the Paul Dunstall big bore kit for the 750 Commando available from about 1972 and should be 810cc.

I cannot give the actual bore size but if the stroke is the standard 89mm then the bore size should be somewhere around 76mm?

hewhoistoolazytologin · Sep 30, 2005

Super!

How can you see this? Have to assume the rings etc will be available then. Is this a relyable sort of upgrade...or were they prone to problems? My standard motor works just fine....I just have always had plans to give this baby a try. Bought 34 Amals...Mark2s?...at one time too, to fit on it.....guess we all have our dreams... :wink:

L.A.B. · Sep 30, 2005

How can you see this?

= The shape of the barrel.

I am not sure if rings are still available although it may be possible to get replacements from a piston ring supplier like Cords Co. etc. ?

It may be an idea to contact Mick Hemmings or Norvil, possibly they could give you more information as I think Dunstall stopped making these parts some while ago?

http://www.woodgate.org/dunstall/covers+.html >1970's = top left and top centre pics.

hewhoistoolazytologin · Sep 30, 2005

good idea...thanks...will check out RGM too. Have to assume the bores will need attention.....I've never even turned the motor over......stupid me.. There's a 73 roadster too out there...same story....that will indeed be a trip to get going again

...just have to find it...under the piles of junk...but I know it's out there somewhere...........I think. :lol: :lol:

Ron L · Sep 30, 2005

The 810 cylinders had a 76mm bore (73mm for stock 750). These alloy barrels are notorious for pulling out the threads for the head bolts. They should have thread inserts put in before you attempt to use them to avoid major headaches later on. As I have said before, the Dunstall stuff for Commandos was pretty, but very poor quality.

British Cycle Supply had some pistons and rings and sleeves are available from LA sleeve. If the pistons and bore are OK you might get rings from Total Seal.

TheFrib · Sep 30, 2005

Those Dunstall 810 cylincers were of such poor quality that the cast iron sleeves in the cylinders cracked or broke and ruined your motor, they were too thin to begin with!!!!!! Junk, kinda like the Drouin superchargers!!!!

VA Rebel · Sep 30, 2005

The Frib is correct. If you need pistons/rings, the best way to go would be have your barrels resleeved down to 73mm bore and use stock 750 pistons/rings that are readily available.

hewhoistoolazytologin · Sep 30, 2005

Hummmmmmm..........

My nose would indeed grow a bit if I said " Thanks guys....just what I was hoping to hear!! ". Better not say it then. And that statement about Drouins.....my god!! Pray he doesn't see that....it will be worse than the Little Big Horn once he gets going....if you don't tell him....I won't!! Haven't we learned from the Boyer vs points thing? Some things are better left unsaid if you get my drift.......remind me not to visit this forum for a week or two...till the dust settles :lol:

Soooooo..........Who else has some comments on the Dunstall barrels?......nows the time...lets get it over with!!

Don't worry....I don't hold grudges.... :wink:

hewhoistoolazytologin · Oct 27, 2006

Well...took me long enough. Got it down from the storage area and found the plugs were in finger tight, and the pistons were at bottom so I gave it a good juicing with oil in there, and gave it a turn. Stinker is free! And no strange sounds in there. Gave it a few turns and it started to squirt oil out of the breather, so I wiped my face off and moved to the side. Son comes over and stands where I did a moment before, puts a finger over the plug hole and says Wow! It's got a lot of compression......just in time to get a dose of oil from the breather himself...at least my dose wasn't in the mouth... :wink:

So....I had a look see and I see the PO had a few bad habits. Notice the plugged off oil feed to the head....and the cool tach drive modification......phillps head screw in the block too. So I will have to pull her apart and see what else he did to it.

What should I look for...any typical problems with this motor type? See Photo of number. Are the head gaskets, and base gasket the same as standard? Know the threads might need helicoiling in the head. What did the Dunstall head work look like? Any problems putting 34MM Mk2 Amals on this..have the inlet ports got to be 34mm too? etc...etc...

I think it would run as is...as it is nice and free (after 25 years sitting in a box) but I might be smart to pull it apart to see that it hasn't got any trick things inside, like it does outside. Was this thing worth the 80 dollars? Any ideas welcome...Thanks!

L.A.B. · Oct 27, 2006

The kit was supplied as a straightforward bolt on kit, and could be nothing more than that?
Although other Dunstall parts could have been fitted as he (Paul Dunstall) recommended a Dunstall camshaft and head to get the full benefit of the conversion. Have a look down the inlet ports, is there any evidence of any porting work?
I suspect the base gasket could be standard as there is no machining work involved in fitting the kit, the head gasket was supplied with the kit so could be non-standard? The barrel base and head studs were also supplied with the kit as they are different to the standard ones and had to be changed.

dave M · Oct 27, 2006

It looks like you got a good deal on this motor, any one of the major components from crank shaft, to cases, head, timing gear etc would be worth $80. The barrell itself would undoubtedly fetch a premium as, notwithstanding the adverse comments about the Dunstall quality, sufficient enthusiasm remains for these products and they are becoming increasingly rare.
I would be inclined to dismantle the engine to see what the condition inside was like and to make sure that all was well prior to recommissioning it. Such things as the crankshaft sludge trap can be full of rubbish which might come loose and find its way into the oiling system if left unchecked.
As L.A.B. pointed out the Dunstall aftermarket equipment was sold separately by numerous vendors, Dunstall themselves sold relatively few complete bikes and a 'Dunstall Norton' could actually consist of a bike with replacement side panel decals and nothing else or the whole cafe racer kit installed. I suspect most of the bikes out there were 'bolt ons' rather than having had the full Dunstall treatment by the man himself.
Congratulations on owning a rare piece of Norton history.

norbsa48503 · Oct 28, 2006

If you ever need to bore or hone the jugs be sure to use plates top and bottom with the bolts at full tightness. I run a set of alum jugs but there were many false starts. The fit of the pistons is also much different .0025 total clearance with cast pistons. As Ron said, not doing inserts is only a delay of what must be done. I like (Keen serts) they have the tabs you drive in. If there was no risk of blowing it were would be the fun?

nortonf1 · Oct 28, 2006

Ma NORTON FATSBACK de juin 1970 a le numéro de série 135321 donc il y a de forte chance que ta NORTON soit aussi une NORTON FATSBACK de fin 1970 !
Elle a de jolis cylindres de 750 DUNSTALL !

hewhoistoolazytologin said:
Well...took me long enough. Got it down from the storage area and found the plugs were in finger tight, and the pistons were at bottom so I gave it a good juicing with oil in there, and gave it a turn. Stinker is free! And no strange sounds in there. Gave it a few turns and it started to squirt oil out of the breather, so I wiped my face off and moved to the side. Son comes over and stands where I did a moment before, puts a finger over the plug hole and says Wow! It's got a lot of compression......just in time to get a dose of oil from the breather himself...at least my dose wasn't in the mouth... :wink:

So....I had a look see and I see the PO had a few bad habits. Notice the plugged off oil feed to the head....and the cool tach drive modification......phillps head screw in the block too. So I will have to pull her apart and see what else he did to it.

What should I look for...any typical problems with this motor type? See Photo of number. Are the head gaskets, and base gasket the same as standard? Know the threads might need helicoiling in the head. What did the Dunstall head work look like? Any problems putting 34MM Mk2 Amals on this..have the inlet ports got to be 34mm too? etc...etc...

I think it would run as is...as it is nice and free (after 25 years sitting in a box) but I might be smart to pull it apart to see that it hasn't got any trick things inside, like it does outside. Was this thing worth the 80 dollars? Any ideas welcome...Thanks!

hewhoistoolazytologin · Oct 29, 2006

Going to have to guess...he says his is a 70 Fastback and due to the number on mine...that mine might have been in a 70 Fastback too?

Google Translates...

My NORTON FATSBACK of June 1970 thus has the job number 135321 there is strong chance that your NORTON is also a NORTON FATSBACK of at the end of 1970! She has pretty cylinders of 750 DUNSTALL!

Coco · Nov 1, 2006

Don't you love on-line translator sites.

I for one, he now would like Dunstall of 1970 years to Fastback model she is and now looks object to job number of Norton. :wink:

biggles · Aug 12, 2009

hello, first time poster. i have a 1972 750 commando (e#204475) with a quite similar (or the same) cylinder. the bike also came with an extra dunstall 810 cylinder. there are differences in these two pieces. one is clearly marked "dunstall" cast into the front mounting flange. one has no markings at all. note the two casting "lumps" in front over the tappets. on the unmarked cylinder they seem to be reinforcement for the tappet slots but on the dunstall cylinder these lumps do not exist. because of heavy smoking and bad pinking (@ 28 deg btdc) i pulled the head. what i found was what appears to be stock 750 l.c. pistons (dished dome) and a 73mm bore. is it possible who ever made cylinders for mr. dunstall offer a "big bore kit" for 650s or did p.d. just think stressed aluminum cylinders were better than the cast??? will 650 dominator cylinders even fit to commando cases? my budget is such that i am going to try resleeving as the pistons are in fine nip and the price of a stk bore 750 cylinder, whew. this is a very interesting bike with some period mods and a hoot to ride. e.g. airhart triple discs on kimtab rims. thanks for listening. any ign timing suggestions appreciated. biggles

Nortasaki · Aug 12, 2009

Here's some pics when I had my Dunstall apart:

The "DUNSTALL" in the casting.

Yea it's a "HEMI" :mrgreen:

Barrell removed

Note the "M" stamped on the head fin; DUNSTALL Mod
I did eventually put new coils at the #9 and #10 holes, some day I may do the rest as they do tend to pull up.

who can identify this???

hewhoistoolazytologin

L.A.B.

Moderator

hewhoistoolazytologin

L.A.B.

Moderator

hewhoistoolazytologin

Ron L

TheFrib

VA Rebel

hewhoistoolazytologin

hewhoistoolazytologin

L.A.B.

Moderator

dave M

norbsa48503

nortonf1

hewhoistoolazytologin

Coco

biggles

Nortasaki

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