English French German Italian Spanish

Mercury ignition system

Submitted by chas_goupillot on Thu, 05/04/2018
Forums
Heavy Twins

Hi all,

Coming to the end of a long rebuild of my '68 Norton Mercury.

With regard to the ignition system, to those unfamiliar, the Mercury has an aluminium casting (canister?) with a steel cap held by a wire loop situated where the magneto would have previously been fitted. The points etc are contained within.

I am currently re-assembling the drive for the ignition system on the timing side and have noticed considerable end play (4mm) on the shaft to which the drive sprocket attaches

My manual features only magneto and distributor systems and with reference to the distributor refers to a spacer fitted behind the sprocket.

Should the Mercury have something similar to take up the end play?

Best regards,

Chas

Submitted by howard_robinson on Thu, 05/04/2018

Permalink

hello Chas - I'm fairly certain that there is a small tufnol bush that locates on to the shaft before the sprocket is located. On mine there is very little end-float when the spring pin is inserted with the chain on the sprocket. Are you running the Lucas auto advance unit or a Boyer or Rita sender ? These do need to be tight on the taper in the shaft. Have you also checked that the thrust spacer inside the housing is properly located against the housing bearing ? In my parts list the only contact-breaker housing bush is 033069 but that could be the inner bush or the outer. Unfortunately there is no diagram of the item. A quick e-mail to Lawrence at RGM me thinks. Cheers, Howard

Submitted by chas_goupillot on Thu, 05/04/2018

Permalink

Previously howard_robinson wrote:

hello Chas - I'm fairly certain that there is a small tufnol bush that locates on to the shaft before the sprocket is located. On mine there is very little end-float when the spring pin is inserted with the chain on the sprocket. Are you running the Lucas auto advance unit or a Boyer or Rita sender ? These do need to be tight on the taper in the shaft. Have you also checked that the thrust spacer inside the housing is properly located against the housing bearing ? In my parts list the only contact-breaker housing bush is 033069 but that could be the inner bush or the outer. Unfortunately there is no diagram of the item. A quick e-mail to Lawrence at RGM me thinks. Cheers, Howard

Hi Howard, haven't as yet pulled the unit apart, but it is running a Boyer system. Hadn't thought to check that end of the shaft. Will have a look.

Best regards, Chas

Submitted by chas_goupillot on Thu, 05/04/2018

Permalink

Previously robert_tuck wrote:

On the earlier 18d2 dissy too much end float would wreck the ADVRTD and the cap,

Hi. Robert, this was my main concern, although the unit was working well prior to stripdown. Just about to pop into the garage and remove the unit, will check it out over the weekend. Regards to all Chas

Submitted by alan_osborn on Mon, 16/04/2018

Permalink

Previously robert_tuck wrote:

On the earlier 18d2 dissy too much end float would wreck the ADVRTD and the cap,

The end float of the 18D2 is adjustable with a washer between the back of the sprocket and the distributor body, easy enough to sort out. A couple thou is about right, if you haven't got the right washer I have resorted to 'thinning' a washer on an oilstone before now. The original washer 'Lucas' had three or four little dimples I though to allow oil to flow between the washer and the distributor body, but as they wear down down very quick you end up with large end float. So a plain washer is acceptable.

Submitted by chas_goupillot on Tue, 17/04/2018

Permalink

Previously Alan Osborn wrote:

Previously robert_tuck wrote:

On the earlier 18d2 dissy too much end float would wreck the ADVRTD and the cap,

The end float of the 18D2 is adjustable with a washer between the back of the sprocket and the distributor body, easy enough to sort out. A couple thou is about right, if you haven't got the right washer I have resorted to 'thinning' a washer on an oilstone before now. The original washer 'Lucas' had three or four little dimples I though to allow oil to flow between the washer and the distributor body, but as they wear down down very quick you end up with large end float. So a plain washer is acceptable.

Thanks Al, will proceed as you suggest. Current end float is 4mm, so may need to use several washers. Can't see any problem with this. Will aim to limit end float such that there is no possibility of contact between static and whirly bits.

Best regards, Chas

 


Norton Owners Club Website by 2Toucans