Cylinder head to barrel fitment problem

Tony, you say your cylinder bores are 3/16" closer together than they should be. With an error of this size I cannot see how you're  going to get the barrels over the pistons , even if you manage it I feel the pistons will be at the limit of their horizontal play . I think this sounds like a non starter as the error is too large. Just my opinion, unless you've  already tried.

A 750 barrel would have the bores closer together. By about 2.5mm each side or 5mm in total. 5mm is very close to 3/16".  Has somebody made a cock-up???   Check that the head gasket fits all the barrel and head bolts holes nearly perfectly.

Is that a downdraught head ?.Perhaps the issue is with the head.

Hello Tony, thinking about your problem, you say you have bought a NEW head and barrel the bores of which are closer together by 3/16" than they should be. When you refer to flame rings on the barrel I assume you're  speaking of location spigots atop the barrel. What I'm failing to under stand is ,  if your error is as great as you say  the head would need to be machined because no ammount of scraping could correct a 3/16"error ,and you now say that the head and barrel are united.  Are they brand new or just new to you ?                    The normal distance between the 99 bores is about 3/4" inside bore to inside bore. Puzzling indeed, I shall continue to watch . 

Makes you wonder if a barrel was machined to fit liners and somehow  the centers got changed , from the posting that could have been the old scrapped barrel? As the replacements seem to match the new head.Perhaps we are off the beam here.

Orriginal barrels had the appearance of having liners because of the way the  cylinders extended into the cases. But they were a one piece casting .

Tony..........check out this list of cylinder head casting numbers. For your single carb head these will be on the top.

22707 (usually plus single suffix letter) - all alloy plus raised cross-hatching between the rocker spindle plates. These are late 1958 to  late 1961 heads.

T2225 (some with suffix letter M but no cross-hatching) - these have full alloy finning across the front between exhaust ports. The area between the rocker spindle paltes is plain.

T2225 (no suffix letter) -  also full alloy finning but stepped up between the exhaust ports. These are generally 1955 to 1957ish.

T2225 - same as above but all iron. 1950 to 1955 heads. Mostly found on Model 7s and early 88s.

T2212 - Available in iron or to special order in alloy. No suffix letter. 1953 to 1955

Definitely liners,but I don't suppose the original  bores would be truly concentric with the castings. As long as the bores are parallel to each other  I would put it together anyway.I have seen much worse liner installations If the pistons enter the cylinders and it turns over freely.. Give it a go.I would.

hello  Can put up some better photos of all the bottom end of the barrel and top end of the barrel  AS the part of the barrel in these photos look like someone has fitted a set of sleeve wrong  this looks like they have machined down the centerline, where Norton barrels where machined off set to the centre of the barrel So you get a measurement difference  So if this is the case then the barrels you have bought from Yeomans are at fault And I would return them  As there Not fit for purposes and as Yeomen are a dealer  the will come under trading standards act of resale,     Yours Anna J 

A sleeve must be concentric to the original hole it is copying!

Tony, Since the engine  is all in bits I have the following suggestions. If you have the equipment or have a machine shop handy, make a mandrel of correct diameter to fit the rods with the bearings removed. Fit the rods onto this mandrel with the same distance  between the rods as when they are mounted on the flywheels. Fit the pistons without the rings. Turn the barrels upside down and lower the pistons into the bores. If the rods are not in the centre of the pistons the barrels are cactus. You could do the same using the crankshaft but it would be heavy and unwieldy. A quick visit to the cave has discovered a piece of 1.5 inch outside diameter exhaust pipe. Fit an old set of bearings and maybe a bit of masking tape and you have a 10p mandrel.

Hope this quick and easy fix helps. Anything you care to leave under the plate will be gratefuly accepted.

I think I would just fit the barrels  to the engine and check that the rods are close to  central in the bores. Unlikely that they will be perfectly central anyway. As long as the piston pin bosses are not tight to the small ends you will have a working engine not untypical  to what the Industry produced most of the time. Should be able to measure the gap rod face  to bore surface and compare to piston boss.

Its very important that the flame rings stay in position. If they can be hit by a piston or are otherwise insecure they can wreck the motor. If they are in doubt I have heard of motors being run without them and not to have a problem.

The best way, but not necessarily the easiest way, to find out what the bore centres need to be for your bike is to measure the big-end journal centres. They may or may not be to original factory specs but your bores need to match your crankshaft.  Space between bores isn't an accurate way to measure.  As Anna says, measure the bore centres at the top and the bottom to make sure that any previous work hasn't boogered it!

You are doing the right thing,checking carefully and questioning everything that was done before.Don't assume anything is right .  You will waste some time but the satisfaction when it works well is more than enough reward.

Some new liners are supplied with a small exterior lip / flange on the top edge.  This lip sits up against the gasket and prevents the liners from coming loose and dropping into the crankcases. Other barrels need to be machined to accept this lip. On spigoted barrels similar replacement liners have a stepped spigot machined. Thus saving the liners from having to be pegged/pinned in place.  See attachment.

Remember to anneal it before fitting.