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Lucas/Price ATD Failure

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
Removed the Roy Price ATD from my Comet (it has been on the bike for around 10,000 miles) and disassembled it in preparation for modifications to reduce its operating range only to discover the cause of my occasionally erratic idle speed.

The pins on the backing plate, that are the pivots for the bob weights were real loose - both of them can be moved around and wobbled - there was also signs of wear on the ears caused by the bob weights hitting them. Now its all apart I will be TIG welding everything in place (supposed to be riveted or staked) and will be using countersunk screws and nuts with liberal use of locktite to secure the backing plate to the pinion.

Just wondering - has anyone else experienced this type of (potential) failure??

Martyn
 
Last edited:

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
Dear Martin,
Not specific to Vincent but related to the reliability of Lucas A/R units. I had a Norton Commando in the early 1970's and after not too many miles the A/R unit developed quite a bit of play requiring some weld to tighten things up. A mechanic friend who at that time serviced Commandos used by the local police force said that it was quite common for the A/R to require attention. This would have been the standard fitment Lucas unit. Maybe a few more rpm may have been used on the Norton machines compared to the average Vincent and at this time Norton certainly had build quality issues on several items.
I can't comment on the units manufactured by the late Roy Price but assume they were of a generally similar design to the Lucas unit.
Removed the Roy Price ATD from my Comet (it has been on the bike for around 10,000 miles) and disassembled it in preparation for modifications to reduce its operating range only to discover the cause of my occasionally erratic idle speed.

The pins on the backing plate, that are the pivots for the bob weights were real loose - both of them can be moved around and wobbled - there was also signs of wear on the ears caused by the bob weights hitting them. Now its all apart I will be TIG welding everything in place (supposed to be riveted or staked) and will be using countersunk screws and nuts with liberal use of locktite to secure the backing plate to the pinion.

Just wondering - has anyone else experienced this type of (potential) failure??

Martyn
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
The Price unit is the same configuration, but with thicker components. Mine is 4 years old now, so I'll check it before Spring arrives. Tom Gaynor was a big fan of them here on the Forum, I'll e-mail him with this info and see what he says.
 

cinquecento

Well Known and Active Forum Website User
Non-VOC Member
see the dramas of my ATD elsewhere. Mine was assembled without the back plate and c/s screws with nylock nuts. In itself not bad but without the back plate i was concerned about the concentrated loads where the nuts beared on the fibre pinion. As i sourced a second hand backing plate and some c/s rivets i used these as replacement.

no problems with the pins for the bob weights but the ears were all chewed up / eroded far in excess of what i would have thought through reasonable although long service. i suspect less than sympathetic 'adjustments' had previously been made which resulted in less contact area and hence accelerated wear. All i'd say regarding TIG work and bolting ATD together is of course ensure that everything moves freely on assembly and does not foul mag oil seal or crankcase.
 

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
All i'd say regarding TIG work and bolting ATD together is of course ensure that everything moves freely on assembly and does not foul mag oil seal or crankcase.

Thanks for the tips. Pivot pins welded, assembly nuts n bolts (replaces rivets) locktite and ears also welded. All bits move freely. Now back in motor with the following timing: Retarded 4 BTDC; advanced 31 BTDC.

To bloody hot to ride today at 43 C! Waiting for it to cool down - though did achieve a first kick start in the workshop

Martyn
 

ossie

Well Known and Active Forum Website User
VOC Member
trouble I had was the ears kept breaking off , I think they had a flaw from when they were formed on the press when they were made
.too sharp a corner.
im not too keen on the idea of screws holding them together as you are relying on the thread as a to and fro stop unless they are shouldered screws.
,rivets have more area to locate.
 
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