Dunstall 810 cylinder with broken lining

I have a Dunstall 810 cylinder which has been laying on the shelf for many years. The reason for this is that one of the cylinder linings is broken. see pictures below. I assume it would be possible to fit new linings if I could find some. Does someone know if these are possible to find?
Does anyone have some procedure for this? Heating temperature for dismantling and and pressing in new liners for example? There seems to be some fixation of the linings, a small screw or the like. See photo below. Just drill it out? Is there need to fill the resulting hole with some welding once the old lining is removed?

Finally, is it worth the trouble? Will a standard 750 run better, or is is just improved looks?

Try LA sleeve. I think they stock 810 and 750 liners.

A lot of guys with high performance engines have blown up the 810 barrels although there are some people that report long life from their kits in normal street use. The weight savings and lighter cam followers are the biggest advantages so fitting 750 liners gives you a more solid cylinder as the 810 are minimal with no room for rebores down the road.

I think I prefer the stock Norton cam lifters design over the Dunstall version riding in the alloy cylinder casting:

There are 2 ways to remove the liner.
1/ As the existing liner is broken it should be cut off just proud of the cylinder base flange. Machine a large bung/drift that is about .010” smaller than the OD of the liner, put the cylinder in the oven for at least 30 minutes at full heat. When fully hot remove the cylinder and place on a stable support, (not the fins). The support must allow the liner to be driven through. Drop a couple of sponges into ice water, then push the wet sponges into the liner. The cold sponges should shrink the liner. Next sit the bung on the liner and drive the liner out. Or if you have access to a press use that.
2/Take the cylinder to an engine reconditioner where they can bore it until the liner collapses.
Refitting a new liner is much simpler. Heat the cylinder in the oven as before. The new liner (cold) should just drop in all the way . The cylinder will contract around it.
Those screws appear to serve no purpose. Is there any reason they cannot be unscrewed.
I have relinered my Dunstall cylinders. I can also say that I have virtually no wear in the lifter tunnels after about 80,000 miles.
ando

ando said:

Take the cylinder to an engine reconditioner where they can bore it until the liner collapses.

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+1.

Take it to the machine shop you trust. They will remove the old liners and fit the new one of your choice.

Also note the dowel hole in the top hat of the liner; this prevents the liner from rotating. You do not want the cut out clearance in the sleeves for the rods to move around.

You'll need to have a machinist bore out the new sleeve anyway so have him turn key the job.

RennieK said:

Try LA sleeve. I think they stock 810 and 750 liners.

A lot of guys with high performance engines have blown up the 810 barrels although there are some people that report long life from their kits in normal street use. The weight savings and lighter cam followers are the biggest advantages so fitting 750 liners gives you a more solid cylinder as the 810 are minimal with no room for rebores down the road.

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+1, LA Sleeve fix it right up.

Thanks for all the answers. LA is a bit of distance from Stockholm, hopefully I can find someone closer to do the job. I don´t have the equipment to do the bore, so I need a shop anyway.
But first I need to decide on 810 or 750 and if I should try to find Dunstall cam followers as well. Bob prefered stock ones, any specific reason why?

Do you think I should be worried about the old pistons if I choose 810? New rings of course, but does anyone have the dimensions/tolerance top an bottom for theese?

concours said:

RennieK said:

Try LA sleeve. I think they stock 810 and 750 liners.

A lot of guys with high performance engines have blown up the 810 barrels although there are some people that report long life from their kits in normal street use. The weight savings and lighter cam followers are the biggest advantages so fitting 750 liners gives you a more solid cylinder as the 810 are minimal with no room for rebores down the road.

Click to expand...

+1, LA Sleeve fix it right up.

Click to expand...

You mention LA sleeve. They seem to be picky who they sell to....
I tried to buy a standard catalog item from them and after several follow ups by me, over a years time, I never did receive one or a phone call..... :cry: my engine is still broken and sitting on the shelf.
Unfortunately my future plans don't include LA Sleeve.
Dave

If you should decide to buy a replacement 810 sleeve from LA Sleeve, the part number used to be FL-227. That's for a 76 mm bore, and the sleeve is only .062" thick. As others have reported here, it's not very reliable. A better choice is to sleeve it to 73 mm and just run it as a 750. LA Sleeve used to supply a sleeve for that purpose, but I don't know the part number for it. I bought a pair of them and converted an 810 back to 750 some time in the late '70s or early '80s for a race bike. If you have the proper dimensioned liner, it's pretty easy to do as ando explained and just replace the old liners with new ones. I don't recall if the LA Sleeve liners come with the cutouts at the top for the two locating set screws. I don't think they do, and I'm pretty sure I didn't use any locating method when I installed them.

If you do go ahead and use them, I'd suggest that you check the casting for crack after you have the old liners out. The last blown up 810 engine I worked on had seen the liner crack and the lower part fall down into the crankcase, trashing the crank and rods, but I found the alloy casting was also cracked around the circumference of the bore, about 2/3 of the way down the bore. A quick check with a dye pentetrant kit is cheap insurance.

Ken

I purchased my liners from http://www.westwoodcylinderliners.co.uk I chose an oversize liner and machined it back to suit. I believe that I used the WCL 16FL liner. I received them within a week of placing an order. Westwood will also provide specials, machined to size but you must provide the dimensions. The liner quoted above is only suitable for the 76mm bore (or +40” 750 pistons) as it has a nominal bore of 74mm
My dunstall cylinders were not fitted with the screw at the top.
If you do not have the dunstall followers they will be very difficult to find. It would probably be easier to have them made, and easier still to use a standard commando barrel and lifters.
ando

Mikael,

You also asked this:

Finally, is it worth the trouble? Will a standard 750 run better, or is is just improved looks?

Which didn't seem to get much of an answer....

Dunstall developed his 810 prior to Norton building their 828 (850) model. Intent would have been extra capacity of course and reduced overall weight, including valve train weight, (the followers). I guess he succeeded, and he probably prompted Norton to do what they did. All very interesting stuff, but perhaps not that useful in a road bike, and almost certainly not worth the investment for looks alone. (and certainly not if like me you always preferred the look of a through bolted 850 barrel in black!).

The cast iron barrel has a weight disadvantage, but a stability advantage, less expansion, and it is more reliable. And surely that weight is only of interest to racers, and even then some may argue that in certain frames the extra weight over the front is not such a bad thing!.

The ideal solution for a 750 long stroke build these days is a new barrel, perhaps an expensive option, but likely to be a one time purchase. You have the choice of an Andover Norton cast item (bolt through design like an 850 anyway) or a Steve Maney alloy item, designed on the lines of the Dunstall item. Both quality items.

A used 750 barrel may be a little fragile aroud the flange and may need sleeving anyway if well worn and previously bored to max. The other route is to find a recoverable 850 barrel and sleeve it to 750. There is one of these on the bike I raced two weeks ago. Works well. You still need a donor barrel and sleeves, but there are a number of suppliers of suitable sleeves as far as I can see, including RGM in the UK.

I don't think a well built 750 is going to disappoint for a road bike.

My current choice for a 750 short stroke I am building is a used 850 barrel at standard bore! not many about! It will get honed anyway, to give clearance on forged racing pistons.

It really depends what you want to achieve, if you are fitting other Dunstall items to recreate a Dunstall Commando, then it has value.

But overall, in my opinion, no, it is not worth it, only as a talking point....or an engineering exercise....but my bet would be that even if you do a pretty good job of it, after fitting them you will find yourself lifting the barrels again in a much shorter time than you would if you go with a decent cast iron solution.