Misaligned crank?

In a previous thread about Dommie cylinder lubrication, one reply mentioned the possibility of the crankshaft not being parallel to the crankcase mouth joint face. Apparently it's a common problem and may be up to 15 thou in bad cases.

My engine shows a misalignment of 15 thou, and I wondered if this might be a possible cause of its tendency to seize the left piston, (though why only the left I can't imagine).

It occurred to me that slightly different length conrods could also be a cause of this misalignment so I swapped left for right. This halved the measurement to 8 thou, so it seems the fault is a combination of conrods and crankshaft/case alignment. This works out as a tilt to the left of 0.0612?.

My question is: is this within acceptable tolerances, or should I try and have the crankcase mouth milled down to level things up? I have a spare 40 thou thick steel compression plate lying around. Would it be possible to mill this to make a spacer sloping from 40 thou on the right to 32 thou on the left.

Well you do not measure the connecting rods in this way , there measured from large end journal to the small end journal when there removed from the crankshaft. And when splitting and crankshaft you must mark the crankshaft alignment by punch marking along a steel angled ruler or long set square so the crankshaft is in line with the left and right hand sides and the center flywheel before you remove any of the bolts that hold the crankshaft together and making extra sure you re-assemble it back in the same way as you dis-assembled it. and then you can measure the connecting rods and check there weights too and recording this as you go and check and record the said part before reassembly. then you have and record of weight's and length and width of the parts in question , and it may-be that your crankcases are out of line or do not match each other , just trying to help, yours anna j

Anna has a point here because crankcases need to be a matched pair. The crankshaft and camshaft bearingsneed to beline-bored - hopefully at 90deg to the barrel bores!

But Rob has the cases he has...As Anne suggests, checking once as shown might just indicate one rod being slightly shorter than the other. But since half the defect remains when the rods are swapped over, the crank alignment must be the issue. So a taper pack ought to bring the barrels into right angles to the crank. Are there specialists who can measure this sort of thing with special equipment?

hello yes a slided rule or a vernier caliper would do the job . if you know how too use one. yours anna j

Hi Rob,

How or where are you measuring to establish a 0.015" alignment error?

If you can find someone with a large enough lathe you could mount the crankshaft (with the crankcases assembled) between centres, then clock up the crankcase mouth by attaching the dial tast indicator to the carriage of the lathe. This would check for parallelism between crank and crankcase mouth. making a tapered base gasket is, IMHO, a bodge.

Ifeverything is within toleranace with the 99 crank fitted (which it appears at a glance to be), the problem lies with your 88 crank. Something as simple as the flywheels being the wrong way round or even a bit of muck under the crank cheek when the crank was last reassembled could be the problem. It's unlikely (but not impossible) that the 88 crank is distorted. Might be worth a quick strip and check. The crank that is...

It sounds to me like your 88 crank has not been ground correctly (concentric with the original journal) after metal spraying and that along with maybe some distortion has lead to your problems. The 50,000$ question is did the barrel sleeve and rebore get done by the same outfit that metal sprayed your crank? If the answer is yes, then an independant check of roundness, size, surface finish and parallelism would be worth investing in. Can you let us know who this outfit is so we can all benefit from your experience?

The bearing should not be as tight on the shaft as that .A simple bit of hand fetling with blue black emery was needed.Crankcase halves do not always go back together with the surfaces flush. Rods can go out of round, Manufactured on old worn machinery anything is possible.My opinion is it will be ok with a bit more clearance in the bore. Dommies are prone to drive side siezure, Look up old posts.There are a few differing theories as to why this happens. The 88 is the better motor,i was happy to cruise at 80 on mine ,The 99 is rough by comparison.

"The 88 is the better motor,i was happy to cruise at 80 on mine ,The 99 is rough by comparison."

I have ridden good and not so good 88s and good and not so good 99s. They are both good rides when put together properly.

I would also check that the ignition timing is the same on both cylinders if you are running a distributor or a mag, this is a known issue.4 and a half thou should be ok for the pistons although you may experience a bit of cold slap.. The final hone grade should match the type of ring material. Check the ring gaps in the bore ,they sometimes are nil!.

The barrel sleeve and rebore were done by S.E.P. (Service Exchange Parts) of Kegworth, who were recommended to me by two vintage bike enthusiasts. They seem to do quite a bit of old bike work. I don't know yet how good their work has been, but they came across as knowing what they were talking about. Even so, they disputed that my 88 crank would have been balanced to 80%, but when they checked it that's exactly what it was. (By the way, it was balanced in 2004 by a chap called Dave North in Leicestershire, who I believe used to race Nortons).

Regarding your idea of checking the crank in the cases on a lathe, my friend said he could try that, but another way would be to upend the crankcase (minus studs of course) on its barrel joint face on a flat surface and measure to the crankshaft ends with a height gauge.

Hello Rob Now after reading your threads on this problem of yours, Theres a cupel of issues here S.E.P are one of the best engineering company's you can get in this country, the first thing that comes to my mind is the Gardie pistons you have, Have you weighed the and measured both of them for there lengths and the next thing that comes to mind is the Crank could of been in the past reassemble wrongly and too balance a crank right you need V bocks and 4 clocking dial guages , Mercer dial guages are one of the best you can get just take look on E-bay garage tools and my advise too you is too take all your engine part to S.E.P and tell him what you like him to check out . and see what He thinks too the situation you now have, as at the moment your firing blanks in too the thin air, and getting no where , he has the expert know how, too do all the measurement checking and re-balancing the crankshaft but you need too take all the bottom half of the engine including the barrel ,and do not forget the taking the pistons as well, then you know that the job will be done right , then you can get on with enjoying you rides out, But in the Classic and Vintage world there is now a big thing going on with showing your nice machine , as the Bristol Branch have shown with there Win of Best stand in the Show , so we all need to take more apart of this showmanship on apart for your Club and Branch , well I do hope you take my advise and get your nice model 88 sorted out , Yours Anna J Dixon

Hi Alan, 10 thou ? sounds about right,(without looking it up!) , remember to stagger the gaps around the piston (i forgot last time),might be worth checking that the pins are able to move in the piston easily when hot, I have had a tight one.

Anna

Thanks for the reassurance about S.E.P., I'll be more confident about going back there in the future. Probably soon, with all my bits to be checked.

They did check the balance factor of my 88 crank (so that I would know what factor to apply to the 99 crank if I want to use it again), but maybe they wouldn't have noticed any misalignment if they weren't actually doing a re-balancing?

I have actually weighed the new GPM pistons (with gudgeon pin, rings and circlips) and there was a difference of just 1.2 grams. Never thought of measuring the length though. But I don't see how that relates to the recurring left piston seizing problem.

I prefer riding to going to crowded shows, but after restoring it in 2009 (after 37 years of ownership) I did show the bike at the National Rally at Donington, and at Stafford on the Historic Police Motorcycle Group stand, and on the November page in the 2011 NOC calendar if you still have a copy. Some time I must write up its history for Roadholder, it's quite unusual being a 500cc police bike.

well as pistons go there not all the same length I have a number of Hepolie pistons and the in pairs but there not one pair that the same lengths as you have GMP piston they may two different lengths there sent you but only by a very small amount of difference, the original pistons for norton were BHB brico-covo all apart is the British heavy Industries witch Hepolie and earlier Hepolex , Brico-covo did there piston rings at one time. then every thing was brought in to one industry under Automotive Engineering , and then in the 1980s copys of AE pistons were done by JP pistons in Australia and GMP piston in Italy both theres are copys but to my mind JP piston have the edge over the GMP piston, as these are heaver than the Original british made ones so you have to rebalanced your crankshaft any way , to compensate for the exter weight , so its a trip to S.E.P . as for the seizing up problem by using GMP piston are a different metallurgy too the originals and they have more lightly too of been re-bored the original specification for over size piston ,but not taking in account the expansion rate of the GMP piston and these need a extra thou for the expansion , yours anna j

The crank was balanced for the previous pistons which were also GPM.

Are you saying GPM pistons need 0.0055" clearance?

I've read forum posts on both JP and GPM pistons and I think it's true to say opinion was divided. Andover Norton have decided to go with GPM. It's true my previous left GPM piston seized, but so did the Heplex in the 99 barrel, and whatever was fitted when I bought the bike in 1972, possibly Hepolite but not, I think, GPM.

well I no idea what your bore size is now , but from standard the expansion clearance would be better at 0.003 thou as Norton were bored to narrow a tolerance for the expansion of the piston , and gpm piston have a different metallurgy to the original pistons , and they will expand quicker than the original pistons , but after reading your threads there something not right with this engine and it need some looking into by S.E.P the man with experience off all types of engines , yours anna j

Bore size is now back to standard 66mm for an 88, in new sleeves.

I took the engine to S.E.P. today so I hope to know in 2 or 3 weeks what's what.

His first impression was that crank misalignment was unlikely to be causing this problem and only on one side. Maybe a bent con-rod? Other suggested causes are weaker mixture on the left or different ignition timing each side.

On the oil burning issue, he thinks the valves are too loose a fit in the guides, the inlets being Commando items as recommended for all twins from Andover Norton. He says it's usual to have to ream guides to fit the valve stems but these were loose from the start. I have an old pre-1960 head spare and the valves are a nice fit in the old guides in that. But I suppose that's a subject for a different thread.

well let hope you now get it sorted soon and you find that Bronze Valve guides are better than your cast iron valves guides Carlbro valve are some of the best, I get my parts from RGM motors and up to now I am happy with there service but then there our Steve Maney performance parts , yours Anna J

Previously Rob Bradley wrote:

Well, the engine's still at SEP 7 weeks on. So much for their 2-3 week estimate. I've been promised it next week, but that promise has been broken twice already so we'll see.

As far as I know, the only misalignment was in the crankpins, which has been corrected by re-grinding to -.030" from -.010". I believe oversize valve guides are to be fitted and reamed in the hope of controlling the oil burning. Seems the new guides I fitted earlier from AN weren't up to much.

Anyway, we'll see next week what the final verdict was (or the week after, or the week after that...)

Hello Rob Make sure the oil ways are cleaned out on the inlet side of the cylinder's and cylinder head and the crankcase as well , this is the one that runs down the back of the cylinders from the inlet side of the cylinder head, This is most important as this is where it gets blocked and then there is a build up of oil in the cylinder head around the inlet valves then is only try's to find its own way out , mostly down the valve stem and into the cylinder chamber too be burned with the fuel , the end result of you think you need a rebore, as when the engine is running you have white or blue smoke coming out of the silencer ends, and the other place that get a oil leak in to the cylinders is from the rocker tunnels where they meet in-between the cylinders and cylinder head it get by the gasket and gets sucked into the combustion chamber on the downward stroke, this is very common on Norton twins so be-aware of this problem , Yours Anna J Dixon Technical officer for the EASY YORKSHIRE BRANCH

For an undersizesd valve guide, what I did was this (purists look away now). Screwfix do a cheap set of engineers drill bits. I selected one which was a good sliding fit in a correct valve guide and then used it carefully to open out the undersized guide. Worked a treat. I can hear the howls of outrage already.

Rob, I have trawled through this thread again and I think the problem is with the left (drive side) end of the crank which was metal sprayed. It would seem that following the metal spraying, this was ground slightly off centre. It would account for the measured error varying depending on the position of the crank. I am not a great fan of metal spraying. I had a metal sprayed crank which was fine until the sprayed bit lifted at speed seizing the engine. I was not amused. Sorry to hear of all your tribulations. It might be worth trying RGM or SRM or one of the established specialist bike restorers rather than a general machine shop. They should have theappropriate expertise.

Stripping and reassembling the crank won't put it out of alignment, so go ahead. Just make sure you mark the flywheel with T and D for timing and drive side (or something similar) to make sure it goes back the way it was. Not that getting it wrong should make much of a difference. The crank that failed was a BSA crank bought expensively from a dealer down south - paid the price as it was advertised as standard journals. Only when it arrived I discovered it was standard because it had been metal sprayed and reground. A shame he forgot to tell me that. The sprayed big end let go causing the instant seizure and an S shaped con rod. I must have got a couple of hundred miles out of it before it failed.

The grit could have been in the bag before they put the crank in it. Having now had the crank reground true, has the regrinding process gone through the metal spraying on one side of the journal? Your regrind has gone from -0.010" to 0.030" that's a 0.010" cut (20 thou off the dia) what you need to know is how thick was the metal sprayed surface before you started and being as the journal was not true before the grind then the metal sprayed band will vary in thickness. Sounds to me like SEP is to be avoided. If you don't want to seperate the crank a good wash in clean petrol should suffice.

You might want to examine the conrods a little more closely for the small end being parallel to the big end in two planes. That would/could give you the seizing problems if the piston is cocked in the bore. I'm sure you have spent a fortune on this crank. Two new conrods might be money well spent, particularly as the originals could be 50+years old

The grit was packed into a corner of only one side of the flywheel casting and had to be scraped off, so it couldn't just have been lying around loose in the bag.

The metal spraying on my crank was done to stop the drive side main bearing inner race from being loose, so once on it should stay put; Gordon's was on the big end journals which is a bit different.

SEP say they checked and the conrods are straight. Not that that fills me with confidence. I agree with David's assessment of SEP.

I always mark mating assemblies before I dismantle them, so I know the cranks and flywheel go back together the same way round.

Anna Dixon's reply in this thread on 24 March implied the crank could become misaligned after dismantling, but I couldn't follow her explanation of how to avoid this. SEP said there's a chance of misalignment when the bolts are loosened because there's only one locating dowel on each side. But I must say it doesn't feel to me as if there's any potential for movement once the cranks are located on the dowels and the bolts are in even loosely.

Well the 1954 Dominator Crank I did did not have T and D on each side of the fly wheel in the center of the Crank So you had to puch mark it so you know where its all fitted before you took it apart,

I would of though this would of made some sence ! The first 650 was built on November 7th 1960 and this Is No where in Roy Bacon books or anything much about the 650cc Norton Manxman , We had to do all the reseach on this machine as even the Norton Owners Club as Not even bothered to do any reseach on this motorcyles as they where export machines its just like other Norton motorcycles that where for export, like the 1950/51 model 77 .500cc machine that was exported to Australia and New Zeland , And the EC member do not seem to that much bothered about any of the History of Norton motorcyces from day one, why we have this Executive commttee that dose not seam to be in tune with any thing Norton, yours Anna J

But anyway - can you add anything to Rob's questions about details of crank assembly please, Anna? Are all the holes the same size, and are all the studs + bolts supposed to be the same size or is there a pair of studs/bolts acting as dowels in there somewhere?

Well 5/16 studs seem to be standard on most early Norton Cranks and punch marking in-between the stud and nut is the best way of locking the thread two or three pop marks should do the trick, Now back to Roy bacon Book yes there is a bit of a mention on the Norton Manxman but that's just out of curtsey to the mark , there not much else in there but the colour but No colour codes or any thing they did not do a Manxman deluxe model as He says or a sports model , just a very fast cruiser and a very nice bike to own and ride, he did not say any of this did he, and he is out with the year numbers by months earlier than he say that they are, its like he says the first 650 was number 100200 , but its is wrong the first 650 was number 93601 built November 7th 1960, nearly one year out, that's a long time to be out on Norton's manufacturing ,What else is out of data in his books too , And to say for a long time the Norton owners club took this book as the bible on Norton twin restorations, But did not question this book of Roy Bacon , And for a long time no one had even thought of doing any research on the 650cc machine, and it was taken for granted that Roy bacon book was right information on the Norton models , Until me and Phil Hannan started to dig up some information on them and found that the previous information was bit out of date to say the least , I think its high time to do a better job of his books and start all over again and get some real data first, and do some better listing of parts and part changes and there dates that would be more helpful to a Norton owner and restorer and some better date on colours to, and there years and colour changes and some paint codes or very close matches but this need to be a team effort and coming from with in the executive committee or members that can work as co-ordinators to a book for the Norton owners club to be published by the Norton owners club and not some outside source, yours Anna J Dixon

The tight fit bolts were a Bracebridge St fitment, Once the production was switched to the AMC works they did things their way,Probably dropped the idea.They were dismissive of the way things were done at Nortons.John Hudson (a fine Engineer) was equally dismissive of the AMC ways of doing things.

Previously David Cooper wrote:

Rob - are all the holes the same size as well? You say 'one won't even go through one of the holes'... I remember some of mine were very tight and I was worried that bits might get scraped when tightening it all together - with the risk that the cheeks won't be in proper contact. I did'nt measure anything, partly because I didn't expect any problems, and partly as I hadn't read Bacon's remarks. My bike was from Plumpstead in 1963.

ARRRRR ! now he tells us Its a Plumpstead job no wonder you having a hard time with this crank if the bolt are tight fit use a reamer to the right size and have the holes in the crank reamed out, then you get a good fit, and are the number on the left and right crank webs the same numbers because you just could have two different crank web half's and it will give a slite out of alinement

yours anna j

If the threads have not been deformed i would re-use them. A genuine 88ss crank is stronger than a standard one with a different core size. Hard to replace ,so look after it.