650 engine vibration

Previously james_brierley wrote:

Hi all,

Further to my previous posting and thanks to all contributions, I have just finished building my 1957 Norton 99 Dominator fitted with a 650ss bottom end and standard 1960âs 99 cylinder head. Itâs fitted with a RGM belt drive, Commando clutch and rear wheel, 30mm Mk2 carburettor and Accuspark electronic trigger fitted to the 18D2 distributor set at 32 deg BTDC.

Although it starts first kick and pulls like a train, the engine feels unduly harsh when compared to my 1961 Domie 99. I have heard that the lack of a cush drive in the clutch may be contributing to this but was also wondering whether I should have had the crank dynamically balanced?

The engine has Commando rods and BHB standard 650 pistons and new RHP roller/ball mains bearings.

I realise there are many variables with this particular engine configuration but any help would be gratefully received.

Jim

Well in my opion the Commando rods are a we bit heaver than standand 650 rods and can cannot see the reason for the expence of belt drive, and commando clutch, you should alway rebalance the crankshaft after any modifircation's carillo rods will of been a better bet, as there a lot lighter, and stronger too, and lighting the crank would be benifical too, see Steve Maney web site, yours Anna J have fun !!!

Any idea what compression ratio you are running? The higher the compression, the harsher your engine may feel. I would suggest 30 degrees btdc for modern petrol and if you are running higher than standard compression ratio, 28 might be more appropriate. Of course there is a difference between harshness andvibration. If there is significant vibration, first check the head steady is absolutely secure. If all is well there, and it's bad enough to bedetrimental, a rebalance is probably your only option. The 650 rods are generally fine and of course new ones are readily available. If however you are racing (which I doubt) Carillo rods are a smart move.

No transmission shock absorber is a big no no, try a commando rear hub first, (you will have to do it sometime anyway) ,then get the crank balanced .The 99 head has no bearing on this matter .

Previously anna jeannette Dixon wrote:

Previously james_brierley wrote:

Hi all,

Further to my previous posting and thanks to all contributions, I have just finished building my 1957 Norton 99 Dominator fitted with a 650ss bottom end and standard 1960âs 99 cylinder head. Itâs fitted with a RGM belt drive, Commando clutch and rear wheel, 30mm Mk2 carburettor and Accuspark electronic trigger fitted to the 18D2 distributor set at 32 deg BTDC.

Although it starts first kick and pulls like a train, the engine feels unduly harsh when compared to my 1961 Domie 99. I have heard that the lack of a cush drive in the clutch may be contributing to this but was also wondering whether I should have had the crank dynamically balanced?

The engine has Commando rods and BHB standard 650 pistons and new RHP roller/ball mains bearings.

I realise there are many variables with this particular engine configuration but any help would be gratefully received.

Jim

Well in my opion the Commando rods are a we bit heaver than standand 650 rods and can cannot see the reason for the expence of belt drive, and commando clutch, you should alway rebalance the crankshaft after any modifircation's carillo rods will of been a better bet, as there a lot lighter, and stronger too, and lighting the crank would be benifical too, see Steve Maney web site, yours Anna J have fun !!!

Are you sure that the steel Carillo rods are lighter than the alloy Commando ones, Anna? When I fitted some to a 99 years ago the vibes from the unbalanced reciprocating mass were horrendous and I gave up with them as unsuitable for road use and built a set up similar to James's with a 99 top end on a 650SS bottom, the weight difference between the original rods and new commando ones was negligible, a piston changewould have more effect. IMHOthe vibes could well be from the undamped transmission, some people think that the belt will act as a shock absorber, but it ain't so.

Good luck James!

I have got a Model 19 with belt drive and hence no Cush in the transition. It is as smoothe as silk..

With luck the vibration may decrease, once the motor is fully run in (or you may get used to it!). A bit late now, but, although there is nothing wrong with building an engine, with parts from different models, the balance factor is going to be entirely "hit or miss". Vibration can almost never be removed entirely, but it's peak can be moved up, or down, the rev range.

If there is no improvement, there are really only two choices, live with it, or strip the engine and get crank & positions balanced.

Previously Gordon Johnston wrote:

Any idea what compression ratio you are running? The higher the compression, the harsher your engine may feel. I would suggest 30 degrees btdc for modern petrol and if you are running higher than standard compression ratio, 28 might be more appropriate. Of course there is a difference between harshness andvibration. If there is significant vibration, first check the head steady is absolutely secure. If all is well there, and it's bad enough to bedetrimental, a rebalance is probably your only option. The 650 rods are generally fine and of course new ones are readily available. If however you are racing (which I doubt) Carillo rods are a smart move.

Hi Gordon

Iâm running exactly the same flat top pistons in the 650 as I am in my 99. Both are BHB 23270 LH and 23271 RH. The 650 will be higher compression than the 99 due to the longer stroke whilst using the same type of head. With a combustion volume of 43.5cc I calculate that the compression ratio is around 8.43 to 1 which shouldnât cause the excessive harness/vibrations. Iâve checked all the engine mounts including the head steady and theyâre all tight, and as I said previously Robert, Iâve already fitted the commando rear wheel with its questionable âcushâ drive.

I did come across a chap with a similar problem with his ES2 which he had fitted with a RGM belt/Commando clutch setup. He went on to fit one from Tony Hayward with the Triumph type cush drive clutch and it allegedly transformed the ride. Iâm loathed to have to strip it down for a crank rebalance as other than the vibration itâs a lovely bike to ride albeit Iâm still running it in with only 500 miles on the clock so far. Iâd much prefer it to be a transmission issue but other than the chap with the ES2 Iâve not heard too much bad press about belt drives with no cush.

, nothing more than this, Yours Anna J

Can you use 99 barrels in a 650?

Can you use 99 barrels in a 650?

Well NO there different . you need 650 barrels witch are like Hens Teeth ! just like the genuin pistons ! Yours Anna J

Previously james_brierley wrote:

Previously anna jeannette Dixon wrote:

Previously james_brierley wrote:

Previously Gordon Johnston wrote:

Any idea what compression ratio you are running? The higher the compression, the harsher your engine may feel. I would suggest 30 degrees btdc for modern petrol and if you are running higher than standard compression ratio, 28 might be more appropriate. Of course there is a difference between harshness andvibration. If there is significant vibration, first check the head steady is absolutely secure. If all is well there, and it's bad enough to bedetrimental, a rebalance is probably your only option. The 650 rods are generally fine and of course new ones are readily available. If however you are racing (which I doubt) Carillo rods are a smart move.

Hi Gordon

Iâm running exactly the same flat top pistons in the 650 as I am in my 99. Both are BHB 23270 LH and 23271 RH. The 650 will be higher compression than the 99 due to the longer stroke whilst using the same type of head. With a combustion volume of 43.5cc I calculate that the compression ratio is around 8.43 to 1 which shouldnât cause the excessive harness/vibrations. Iâve checked all the engine mounts including the head steady and theyâre all tight, and as I said previously Robert, Iâve already fitted the commando rear wheel with its questionable âcushâ drive.

I did come across a chap with a similar problem with his ES2 which he had fitted with a RGM belt/Commando clutch setup. He went on to fit one from Tony Hayward with the Triumph type cush drive clutch and it allegedly transformed the ride. Iâm loathed to have to strip it down for a crank rebalance as other than the vibration itâs a lovely bike to ride albeit Iâm still running it in with only 500 miles on the clock so far. Iâd much prefer it to be a transmission issue but other than the chap with the ES2 Iâve not heard too much bad press about belt drives with no cush.

Hello well Part numbers 23270 LH and 23271RH are Norton Manxman 650 part numbers and the pistons fitted to the Norton Manxman Compression radio are 8:9:1 I have a Norton Manxman 650 and dose not vibrate in the ways your saying hear,, how ever there is a small buzz thought the foot rests at speed from time to time

, nothing more than this, Yours Anna J

Hi Anna,

I suppose the reason my compression ratio is slightly less than your Manxman is down to using a 99 head. It could be that I'm expecting my 650 to be similar to my 99 in terms of rider comfort but with a bit more power. Well it's certainly got the power but I must admit to being a little disappointed with the vibes.

Iâve had a quote from Basset Down balancing of £110 + vat for balancing the crank but I may just run it for a bit longer to see if it gets any better after running in. I may also try knocking the advance down to 30 deg as Gordon suggested, but I have to say it actually runs extremely well as it is apart from the vibes.

With regards the difference between 650 and 99 barrels, I ran 650 barrels on my 99 for over 20 years before I realised what the differences were. One of the numerous Norton minefields waiting to trip up the unwary.

Regards Jim

Hell yes you can run a 650 barrels on a model 99 , but not the othere way around, as it may work for some time until the barrel spilts or worse, total sezie up , if you can take the time to do some measurement you may find its just 32 seconds of a inch differnces

and by going to 30 degess is advancing the timing witch may help a softer timing you should have your timing disc set up at (0) on the Drive side cylinder thats the Left hand one , to them that do not know where the drive side is, then time its at 30 degress before top dead center Fully advanced, you should then turn the crankshaft forward thourgh its timing run, up to the firing point, *6 degress after top dead center , then check the right hand side by 360 degress .to the same point of 30 degress before top dead center and do the same as you did for the left hand side , now if you find any differnce , in the firing point of 6 degress then its is were the timing is out of balance, witch can be the cause of vibration Do not forget a engine fire's once every 720 degress. So a big Four Stroke twin fire's like a single cylinder two stroke engine evey 360 degress, So then there is two firing stroke's in 720 degress Yours The Messinger

Previously anna jeannette Dixon wrote:

Previously Jonathan Soons wrote:

Can you use 99 barrels in a 650?

Well NO there different . you need 650 barrels witch are like Hens Teeth ! just like the genuin pistons ! Yours Anna J

Different is not what would stop me doing it. There would have to be modifications that I didn't want to do.

Previously Jonathan Soons wrote:

Previously anna jeannette Dixon wrote:

Previously Jonathan Soons wrote:

Can you use 99 barrels in a 650?

Well NO there different . you need 650 barrels witch are like Hens Teeth ! just like the genuin pistons ! Yours Anna J

Different is not what would stop me doing it. There would have to be modifications that I didn't want to do. Well you will need four big cut outs to be machined out, for the connecting rods to pass, then the cam tunnel bottoms need cutting back to alow of high lift cam and hone out the barrels to so you have 3.1/2 thou between cylinder and piston skirt bare pistons , as most barrels have very thight tolerences now its the cost of all this modification , that in question!

Your Anna J

I bought this unit and up to now have not got it to run,but have had problems with other ignition parts,so may try again later. These units have to have suppression in the Ht so bear in mind the non suppressed leads that nortons have, Use surppressed caps or plugs. Also timing has to be strobed .Pos earth units are supplied if requested.

Hi James, just wondering if the belt tension is to tight.or is the belt catching the primary case anywhere under load if its misaligned. just a thought. Baz

Are you sure that the steel Carillo rods are lighter than the alloy Commando ones?

Standard 500 conrod - 340g

Standard Carrillo 500 rod - 475g

Early 650 rod - around 395g

Later stronger 650/750/850 rod - 445g

Performance Carrillo 650/750 rod - 467g

Comp ratio does not give an engine the shakes. A known good set of Commando rods will be fine especialy for the road. The balance factor should be about 85% for the f/beds to be quite smooth. The balance factor will not sort it's self out by putting some miles on it.

As regard ign timing. If you run straight from the pump unleaded you should retard about 4 deg from std. It burns different from the old leaded stuff. My road 650ss ran about 26/27deg BTDC. If you can use nice 100 octain leaded which the high comp 650's were made for then run std settings.

Previously james_brierley wrote:

Previously tony_harris wrote:

Comp ratio does not give an engine the shakes. A known good set of Commando rods will be fine especialy for the road. The balance factor should be about 85% for the f/beds to be quite smooth. The balance factor will not sort it's self out by putting some miles on it.

As regard ign timing. If you run straight from the pump unleaded you should retard about 4 deg from std. It burns different from the old leaded stuff. My road 650ss ran about 26/27deg BTDC. If you can use nice 100 octain leaded which the high comp 650's were made for then run std settings.

Iâve managed to put in around 780 miles in the last 5 weeks and the vibes havenât improved any. I re-torqued the head down and adjusted the tappets at 500 miles but apart from the vibes sheâs running great, so much so, it would be a crying shame to have to tear the engine apart and sort out the crank. I find the vibration worst at lower rpm when Iâm in traffic or negotiating roundabouts. At cruising speeds up to 80mph itâs almost normal for a 360 deg parallel twin.

The belt drive also appears to be running fine with no signs of belt run off or catching anything. It also runs a lot cooler than I anticipated with no signs of tightening up even after an 80 mile bash.

I agree that the Commando rods should be well up to the job and although they were used, I have had them crack detected for surface cracks using dye penetrant and shot peened to improve fatigue performance. It does look likely that Iâm going to have to bite the bullet at some point and send the crank off to be balanced. Is 85% the optimum balance factor that I should specify to Bassett Down or should I just leave it to them?

Hi James

About 85% is the number I try to aim for. Basset Down does things dynamically, I have only balanced cranks statically but the F/bed with a 360 deg twin appears about right with this figure.

Tony

Previously robert_tuck wrote:

No transmission shock absorber is a big no no, try a commando rear hub first, (you will have to do it sometime anyway) ,then get the crank balanced .The 99 head has no bearing on this matter .

Aside from the drive train loading, I think your problem is the dynamic balance of the engine. The 600cc Dominator was a smooth engine, when Norton punched it up to 650, the ratio of the reciprocating to rotating mass started to become unwieldy. If you have ridden a stock Atlas you will see the ultimate mess that unbalance can induce. At one time I owned both a '56 Domminator 99 and an Atlas (forget the year). The Atlas handlebars would shake as much as an inch up and down and after a short ride I had neopathy in both hands and wrists. The machine was very fast, but I would call it the most uncomfortable motor cycle I have ever encountered.

Sorry for the background chatter. I think that the solution is to strip the engine and have the crank, rods, and pistons dynamically balanced by a specialist. Mr. Tuck is correct that the head has no bearing on the problem.

Many years ago I had a 63 Atlas balanced to over 80% it was without dought one of the smoothest big twins to ride. I can only tell it as I find.

I found this little utube vidio which you may find interesting on balance. Hope you can open it.

http://www.vincentownersclub.co.uk/index.php?threads/crank-dynamic-and-static-balencing.7371/

Tony

Previously Phil Hannam wrote:

Are you sure that the steel Carillo rods are lighter than the alloy Commando ones?

Standard 500 conrod - 340g

Standard Carrillo 500 rod - 475g

Early 650 rod - around 395g

Later stronger 650/750/850 rod - 445g

Performance Carrillo 650/750 rod - 467g

Presumably that is with bolts and nuts? Out of interest, I have a set of R&R billet alloy rods on the bench, waiting to go into my 750 Proddie motor, and they are 399g c/w bolts & washers. As the original Commando ones are weighing in at 455g, am I going to need to re-balance the crank, and if so, to what factor?

Previously robert_tuck wrote:

No transmission shock absorber is a big no no, try a commando rear hub first, (you will have to do it sometime anyway) ,then get the crank balanced .The 99 head has no bearing on this matter .

Aside from the drive train loading, I think your problem is the dynamic balance of the engine. The 600cc Dominator was a smooth engine, when Norton punched it up to 650, the ratio of the reciprocating to rotating mass started to become unwieldy. If you have ridden a stock Atlas you will see the ultimate mess that unbalance can induce. At one time I owned both a '56 Domminator 99 and an Atlas (forget the year). The Atlas handlebars would shake as much as an inch up and down and after a short ride I had neopathy in both hands and wrists. The machine was very fast, but I would call it the most uncomfortable motor cycle I have ever encountered.

Sorry for the background chatter. I think that the solution is to strip the engine and have the crank, rods, and pistons dynamically balanced by a specialist. Mr. Tuck is correct that the head has no bearing on the problem.