Piston slap?

Err, I have a slightly raised eyebrow when you say you have completed a restoration but haven't looked inside the engine. To me that is the fundamental aspect of a restoration, long before the shiny bits. Anyway, compression can be good if the rings are a good fit even if there is excessive piston/bore clearance. Really, you need to take a look inside to see what's what. You shouldn't need to fiddle around with extra breather valves. The standard set up is perfectly fine with a properly fettled engine. Cast iron guides are just fine for road work. Norton fitted them as standard for a reason. Once you have completed your engine strip and sort, then your rebuild will be pretty much complete. Assuming of course that all the other mechanical and electrical aspects are OK...

Oh, there is controversy about the effectiveness of triple electrode plugs. The spark only jumps one gap at a time, not all 3. I am of the opinion that they are simply a marketing gimmick. Gordon.

I agree with Gordon but would add that your description doesn't sound like piston slap. Take it apart.

Funnily enough I have never had much success with Champion N4 plugs. I suspect that any Bosch plug is better, regardless of the number of electrodes. I use NGK B7ES quite happily. As an aside, all the piston aero engines I have had dealings with have had single electode plugs. As indeed, all the jet engines too - yes, turbine engines have spark plugs (called igniters). You can hear a great irregular cracking sound from them as a jet engine starts. Gordon.

Previously wrote:

Hi everyone - I'm a new member: after a 25 year layoff from riding, I've just finished restoring a '67 Dommie 650SS that's been in the family from new and sat in my cousin's garage for 27 years with 35k on the clock.

Once stripped, I found the bike in pretty fair condition, aside from a set of very well worn monoblocs - soon sorted by a re-sleeve from Alverstoke Restorations in Gosport. It must be something to do with the reg. prefix - NMY is shared by many of the Routemaster buses still in daily use in London - the bike came from a Camberwell dealer on 1st February 1967, close to Camberwell bus garage - must be something in the air round there!

I'll confess up front to the following (before I turn up at the Hampshire monthly meet): I've restored and fitted all the '60's aftermarket goodies that were in store with the bike - alloy tank & oil tank, John Tickle rear-sets and clip-ons, Manx seat, swept-back pipes and Dunstall silencers - and I'm now working on the Dunstall half-fairing. but I have all the original Norton parts and I think the huge fenders can be recovered by metal-spraying!

The bike runs fairly well, and now ticks overincredibly slowly (should I wish it)after fitting a set of the Bosch triple-electrode plugs (thanks to Anna for that tip!). However, once warmed up, a merry ringing tapdevelops from the right pot, which I strongly suspect to be piston slap - when riding,it goes away under load (so it certainly isn't pre-ignition) so my guess is that the piston probably nowfits like a demob suit.

There's no smoking that I can see, and the exhaust residue isn't oily - but the crankcase breather is pretty incontinent and spits green goop. I'mmachining a discreet little housing to fit an industrial reed valve which ought to be something of an improvement on the timed breather disc, which isn't, as I recall, all that efficient at stopping the pistons drawing in air on the up-stroke.

The one thing that doesn't add up is that the compression is good, so there's unlikley to be ring blow-by - or is there, in the experience of other members?

My guess here is that it's wear in the valve guides - presumably the exhaust valves are the ones - given that the seals are pretty rudimentary and the guides are plain cast iron, I guessI shouldn't be too surprised.

So it looks like I'll have to do a top-end strip, which I think I'll leave until the winter bites - and at £186 a pop ex-VAT, a set of pistons and rings from Norvil is somewhat jaw-dropping - given that Commando pistons are £86 a set - still,I suppose it's based on numbers sold, and also at 46 years on a set of pistons it works out at just £4 a year!

So what I'd like to know from the collectiveknowledge of the NOCis whether any one has any experience of piston wear on their bikes and what it sounded like, and whether anyone has experience of wear in the timed breather disc causing similar incontinence to mine!

Finally, to end this diatribe, does anyone have experience of the Colsibirio iron valve guides that are listed by RGM- or are less exotic bronze guides a safer bet?

Thanks

Hello Dave Well I can tell you that its Not Piston slap as you would get it under load , And Do Not Buy Pistons From RGM or Norvil,or Andover parts there GMP pistons and there heaver, these pistons will put your balance factors out, fit BHB pistons at was fitted Originally, or Hepolite pistons there out there if you look hard, alway check the piston numbers there stamped on the top of the piston, Give Dale Middelhust a ring He,s The Club Heavy Twin Expert .and he just loves the 650 twin he will see you right , As for Valve Guides I fitted Colisboro bronze valve guides you need to cut the seats after you have fitted these guides ,you find its easer to lap the valves in afterwards , alway do a seat check by turning the head over fit a old spark plug slot the valves in with no springs fitted and fill the bowl in the head will white spirits or meths and see if you have any leaks any were .when you have no leaks anywhere then you can fit the valves with the springs etc Green-spark-plugs.co do a colder Bosch tri-Electrode plug equivalent to N4 Champion NGK BP7ES is equivalent to Champion N7Y Cold Plugs with extended noise electrode Tri-Electrodes are for modern petrol easy starting and that last longer and they have a cleaner burn less hydrocarbons in the exhaust gases , as for you taping noise try looking at the rockers and you may find that is Thackeray washer thats gone weak, this lets the rocker arm tap the side of the head inside

Ferodo AM4 linings were green. Not very effective until they reached 120 deg C. Not a lot of use on a back brake then. I have used GMP pistons from RGM and Norvil on my last 3 engine rebuilds (88, 99 and Atlas) and am very happy with them. I have a box of failed Heploite pistons - one split 200 miles into running in - so have rather gone off them. Gordon.

From a previous post:

The VMCC "shop" is nothing but a retail outlet for W.E.Wassell, so most of the goods are sourced in the far East and India. The trademark "Hepolite" was recently purchased by Wassell and is now used to pack Far East pistons in nostalgic "Hepolite" look-alike boxes.

I am not surprised the prices are "reasonable", but whenever something is very "reasonable" you should be aware this may be because the materials/quality may also be "reasonable". If you want better than "reasonable" you should insist on Genuine Norton Factory Parts- but these tend to be, admittedly, more realisticly priced.

Previously wrote:

From a previous post:

Posted byjoe_seifertat October 22. 2012

The VMCC "shop" is nothing but a retail outlet for W.E.Wassell, so most of the goods are sourced in the far East and India. The trademark "Hepolite" was recently purchased by Wassell and is now used to pack Far East pistons in nostalgic "Hepolite" look-alike boxes.

I am not surprised the prices are "reasonable", but whenever something is very "reasonable" you should be aware this may be because the materials/quality may also be "reasonable". If you want better than "reasonable" you should insist on Genuine Norton Factory Parts- but these tend to be, admittedly, more realisticly priced.

GMP pistons are Not Original factory parts, and a one of our member has a Big 4 he removed the GMP piston that was making a Noise in his machine and he fitted the Original BHB piston , and He weighed both pistons against each other and the GMP piston was 92grams heavier than the BHB piston that the same weight as a extra gudgeon pin , and these are member in question words not my ones , and he is a Engineer. yours Anna J

Of course GMP pistons are not original - but when you think about it nor are the new Hepolite ones. I can only relate my experience - the GMPs have proved excellent in service, the Hepolites have not. Of course, an engineer's opinion must be superior. Am I an engineer? It depends on your definition.

Previously wrote:

Previously wrote:

Previously wrote:

Hi everyone - I'm a new member: after a 25 year layoff from riding, I've just finished restoring a '67 Dommie 650SS that's been in the family from new and sat in my cousin's garage for 27 years with 35k on the clock.

Once stripped, I found the bike in pretty fair condition, aside from a set of very well worn monoblocs - soon sorted by a re-sleeve from Alverstoke Restorations in Gosport. It must be something to do with the reg. prefix - NMY is shared by many of the Routemaster buses still in daily use in London - the bike came from a Camberwell dealer on 1st February 1967, close to Camberwell bus garage - must be something in the air round there!

I'll confess up front to the following (before I turn up at the Hampshire monthly meet): I've restored and fitted all the '60's aftermarket goodies that were in store with the bike - alloy tank & oil tank, John Tickle rear-sets and clip-ons, Manx seat, swept-back pipes and Dunstall silencers - and I'm now working on the Dunstall half-fairing. but I have all the original Norton parts and I think the huge fenders can be recovered by metal-spraying!

The bike runs fairly well, and now ticks overincredibly slowly (should I wish it)after fitting a set of the Bosch triple-electrode plugs (thanks to Anna for that tip!). However, once warmed up, a merry ringing tapdevelops from the right pot, which I strongly suspect to be piston slap - when riding,it goes away under load (so it certainly isn't pre-ignition) so my guess is that the piston probably nowfits like a demob suit.

There's no smoking that I can see, and the exhaust residue isn't oily - but the crankcase breather is pretty incontinent and spits green goop. I'mmachining a discreet little housing to fit an industrial reed valve which ought to be something of an improvement on the timed breather disc, which isn't, as I recall, all that efficient at stopping the pistons drawing in air on the up-stroke.

The one thing that doesn't add up is that the compression is good, so there's unlikley to be ring blow-by - or is there, in the experience of other members?

My guess here is that it's wear in the valve guides - presumably the exhaust valves are the ones - given that the seals are pretty rudimentary and the guides are plain cast iron, I guessI shouldn't be too surprised.

So it looks like I'll have to do a top-end strip, which I think I'll leave until the winter bites - and at £186 a pop ex-VAT, a set of pistons and rings from Norvil is somewhat jaw-dropping - given that Commando pistons are £86 a set - still,I suppose it's based on numbers sold, and also at 46 years on a set of pistons it works out at just £4 a year!

So what I'd like to know from the collectiveknowledge of the NOCis whether any one has any experience of piston wear on their bikes and what it sounded like, and whether anyone has experience of wear in the timed breather disc causing similar incontinence to mine!

Finally, to end this diatribe, does anyone have experience of the Colsibirio iron valve guides that are listed by RGM- or are less exotic bronze guides a safer bet?

Thanks

Hello Dave Well I can tell you that its Not Piston slap as you would get it under load , And Do Not Buy Pistons From RGM or Norvil,or Andover parts there GMP pistons and there heaver, these pistons will put your balance factors out, fit BHB pistons at was fitted Originally, or Hepolite pistons there out there if you look hard, alway check the piston numbers there stamped on the top of the piston, Give Dale Middelhust a ring He,s The Club Heavy Twin Expert .and he just loves the 650 twin he will see you right , As for Valve Guides I fitted Colisboro bronze valve guides you need to cut the seats after you have fitted these guides ,you find its easer to lap the valves in afterwards , alway do a seat check by turning the head over fit a old spark plug slot the valves in with no springs fitted and fill the bowl in the head will white spirits or meths and see if you have any leaks any were .when you have no leaks anywhere then you can fit the valves with the springs etc Green-spark-plugs.co do a colder Bosch tri-Electrode plug equivalent to N4 Champion NGK BP7ES is equivalent to Champion N7Y Cold Plugs with extended noise electrode Tri-Electrodes are for modern petrol easy starting and that last longer and they have a cleaner burn less hydrocarbons in the exhaust gases , as for you taping noise try looking at the rockers and you may find that is Thackeray washer thats gone weak, this lets the rocker arm tap the side of the head inside

Thanks indeed Anna for the considered and detailed reply - and I'm heartened to see someone else keeps the same anti-social hours as me - oh, the joys of being on-call 24 hrs and having offices in India and the USA!

I'll try for the pistons you suggest, although with my more "mature" style of riding after such a long layoff, the additional vibration would probably appear higher in the rev range and perhaps be less obtrusive - but ifI can, I'll stick to the designed spec in terms of piston mass.

Ifthe ringing tap does prove tobe the small ends, what's the advice on re-bushing (ie sources, materials,method of fitting and reaming etc)?

I'll certainly go with your advice on phos-bronze guides - I had goodreports of these when we turned up a set for a Gilera 150 some years ago - while Gordon pointed out that cast iron was good enough for the original design &productionteams, I'm not constrained by the need to work to a budget imposed by management (beyond the usual benign oversight from the domestic authority!) and given the superior oil-retention of PBand the closer expansion characteristics of PB and steel I'll give them a try - any advice on valves if the stems turn out to be worn - unlikely at 35k miles, hopefully?

I got a set of the Bosch tri-electrode N4 equivalents, andthey do seem to make for easier starting - but I cheated a little by fitting the RGM folding kickstart when I rebuilt the gearbox (as the original was appallingly rusted), and it's a tad longer - am now trying to teach my 20 year old son how to start a big twin - the look on his face was wonderful to behold!

Finally, your point about the Thackeray washers bearing (or not) against the rocker shouldersdoes seem likely - I'd forgotten about those andit's an even bet that they've lost temper with the passing years and the shock of returning to useful work!

DA

Well you be surprised how little extra weight you need to put the balance out these machine were balanced to take over size piston to plus 40 over size , the Manxman were plus 30 over size. going beyond this is frort with danger the top spigots get thin and crack or brake off , I do not think your machine needs new pistons and a rebore , I think your Noise is coming from some were else , in the valve train .you need a stethoscope and check carefully with the engine on tick over do not rev hard just give it a little throttle very carefully until the engine starts to pick up just do this in different rev ranges but do this in a constant way do not rev quickly . just go very steady with it and you find it as the engine changes note . good luck you may need some one to assist yours AJD

Re-bushing small ends. FIne if the bush itself is worn. However, sometimes you may find the bush slack in the rod. This is a hint that the small end eye is elongating and the con rod is not long for this world. Piston weights. The factory wasn't known to be fastidious about crank balancing, especially in Plumstead days. If you want a really smooth engine (don't we all?), you should re-balance the crank regardless of what pistons you fit. Gordon.

P.S. I had a look at my box of failed Hepolite pistons yesterday. There are rather a lot in there.

Engine noisescan bequite difficult to diagnose. eg a rumbling can be the mains on their way out or just a loose rotor. Tapping, clicking or ringing can be caused by a whole multitude ofproblems and not always what appears to be the most obvious.

I would suggest, strip the engine and check everthing including looking for:-

loose rocker spindles, wear ridges at the top and bottom of the barrel, loose gudgeon pins, a knackered small end, worn camshaft follower tunnels, a valve head touching a piston, loose timing chains.

A few years ago I helped a fellow rider sort out a noise from his timing cover that turned out to be caused by a new repacement chain. To savepulling out the gears and pinions he had bought replacement chains with links in them. The link on the magneto chain was too wide and hence catching the small boss for the lower magneto bolt.

Final thought.........I am fairly certain that tri-electrod plugs are not a new idea and seem to recall them being around in the early 70s as alternatives for Champion and NGK plugs.

Previously wrote:

Previously wrote:

Engine noisescan bequite difficult to diagnose. eg a rumbling can be the mains on their way out or just a loose rotor. Tapping, clicking or ringing can be caused by a whole multitude ofproblems and not always what appears to be the most obvious.

I would suggest, strip the engine and check everthing including looking for:-

loose rocker spindles, wear ridges at the top and bottom of the barrel, loose gudgeon pins, a knackered small end, worn camshaft follower tunnels, a valve head touching a piston, loose timing chains.

A few years ago I helped a fellow rider sort out a noise from his timing cover that turned out to be caused by a new repacement chain. To savepulling out the gears and pinions he had bought replacement chains with links in them. The link on the magneto chain was too wide and hence catching the small boss for the lower magneto bolt.

Final thought.........I am fairly certain that tri-electrod plugs are not a new idea and seem to recall them being around in the early 70s as alternatives for Champion and NGK plugs.

Aha! I'm going to strip the engine and do the full inspection properly now that winter's arrived - but when I had it apart orignally I noticed some apparently fresh scuffing on the lower mag bolt boss - and the chain in there has a split link - and I don't recall checking the back of it.

In my innocence I had assumed the split chain was standard, but Idid thinkto myself "there's a potential point of failure" (puns about weak links spring to mind - so sorry!),"I wonder if I can get an endless chain" - so that's on the to do list now! I'll also root out the ex-luftwaffe stethoscope I acquired many moons ago, which has a useful selection of somewhat frankenstinian probes - just need to make sure the sons aren't watching when I use itor there'll be dark noises off about Dad's mid-life crisis bike and growing eccentricity - they're of the generation that expect to dump data from an ECU, and have their cars serviced by technicians instead of fitters and mechanics!

DA

Hello Magneto and Cam chains are endless Chain as Standard This chain you have with a split link is not a standard chain it as been made up by some one . and need replacing asp Is I said earlier I would not think it will be your pistons , if you do strip the motor take of the piston rings very carefully and my sure you place them down as they came of the piston try not to get them mixed up its is important . then fit the piston back down the bore , about half way and with a feeler gauge take a reading and do this up and down the bore from top to bottom writing down each reading then you find how much ware there is if there is any more than 0.005 thou a rebore will be necessary . your ajd

does the noise go once warmed up?, my 99 with rebore and new pistons with 4.5 thou clearance slaps when cold.