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F: Frame Damper Refurbishment



Chris.R

Well Known and Active Website User
VOC Member
#1
Hi I have taken the dampers off the Comet and after refilling with 20 grade oil and leaving for a week to settle see oil seeping out. I have now dismantled the rear one as far as is easily possible. It appears that there are three perhaps four `o' ring seals that could be easily replaced, there appears to be no scoring on the shaft. It is obvious that the damper has been apart before as the brass threaded turning has been marked where a spanner twisted off it. When the damper was previously assembled a shellac like substance had been used to seal the thread to the aluminium casing.

`A' - Should a sealing compound have been used.
`B' - What is the regular way to get the top to which the shroud fits off the spindle without damaging the spindle: I have pondered heating it at that point as it must be a threaded fit?
`C' - What size `o' rings are required?
`D' - If a bump stop is added as I have read it can be what should be used?
`E' - Or should I leave this job to others?
Chris _DSC0511.JPG
 

powella

Website User
VOC Member
#4
To get the top mounting off you need to tap out the small locking pin just under the bush.
Do not try to remove the mounting without first pushing this pin out as the twisting action will ruin the threads at the top of the Piston Rod.
Lastly when the small locking pin is out - put it in a safe place as it is an unusual size and shape.
 

Bill Thomas

Well Known and Active Website User
VOC Member
#6
filling vincent damper Morning Chris, Go to top right corner " Search " Put that in the top then press search, Don't put anything else on there. There is a bit from Paul that tells you what the big oil seal is.
Cheers Bill.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
#7
Option 1. If you are looking for complete originality you can find improved seals and parts to rebuild your own damper. The design already incorporates a hydraulic bump stop so I'm not sure about "`D' - If a bump stop is added as I have read it can be, what should be used? " as mentioned in your first post.
Option 2. You could buy one of the four units available from the Spares Co.
Option 3. If you actually plan on doing some significant riding same yourself a lot of time, frustration and money buy an AVO damper unit. It will improve your ride quality far better than option 1 or 2.
Others may be able to suggest more options.
 

vibrac

Well Known and Active Website User
VOC Member
#8
filling vincent damper Morning Chris, Go to top right corner " Search " Put that in the top then press search, Don't put anything else on there. There is a bit from Paul that tells you what the big oil seal is.
Cheers Bill.
I have a copy of the full Paul Ennis damper mods he gave me at the Annual Rally I think that includes most of the mods of the last 50 years and then improves on it I certainly will be building one for my Grey Flash I did have a unit with the recirculating valve mod & some sealing changes for many years on the racing Comet and it was a great improvement.
 

timetraveller

Well Known and Active Website User
VOC Member
#10
I think that I heard that Mauhan's will do a full rebuild and update but whether they include all of the Paul Ennis mods I do not know. Their telephone number is 01529 461717.
 

Chris.R

Well Known and Active Website User
VOC Member
#12
Any chance of putting it on here, I think Chris is a new member, So may not have old MPH s.
Cheers Bill.
You are quite right I do not have access to MPH681. I have into the Millenium and will look at that. I do not have 40 years and 10 more years they had sold out when I asked about them, `I hope they are both reprinted'
 

hadronuk

Well Known and Active Website User
VOC Member
#13
The original Vincent Damper is fixed orifice, a design that gives the worst of both worlds, being soft and wallowy at slow suspension speeds and too stiff at high suspension speeds. The Paul Ennis mod is an improvement but cannot change this inherent fault. Every Vincent damper that came after it uses pressure relief valves to give a much better characteristic.
But to be fair, when I did some back to back testing of different dampers fitted to the Girdraulics the Vincent damper didn't seem bad!
I think other problems with Girdraulics such as the high friction make it harder to feel the benefit of a better damper.
At the back, it's a totally different story. A well matched damper and springs can utterly transform the ride.
I certainly would not want to have to return to an original rear Vincent or Armstrong damper unless I was giving up actually riding the bike.
 
Last edited:

Chris.R

Well Known and Active Website User
VOC Member
#14
The original Vincent Damper is fixed orifice, a design that gives the worst of both worlds, being soft and wallowy at slow suspension speeds and too stiff at high suspension speeds. The Paul Ennis mod is an improvement but cannot change this inherent fault. Every damper that came after it uses pressure relief valves to give a much better characteristic.
But to be fair, when I did some back to back testing of different dampers fitted to the Girdraulics the Vincent damper didn't seem bad!
I think other problems with Girdraulics such as the high friction make it harder to feel the benefit of a better damper.
At the back, it's a totally different story. A well matched damper and springs can utterly transform the ride.
I certainly would not want to have to return to an original rear Vincent or Armstrong damper unless I was giving up actually riding the bike.
Yes understood, I cannot remember what riding was like in the 60s when I last had a Vincent, I guess it was what we had back then initially I am likely to restore what I have but will think on. Thanks Chris
 

powella

Website User
VOC Member
#17
Hi Chris
Like politicians who never answer a question directly there seems to be no definite reply to your enquiry - so read on .

A " Wellseal " has the looks and consistency of Shellac and is a very good sealer. No one outside of the electrical industry will know what you are talking about regarding Shellac and has`nt been heard of since Glovers Cables of Manchester used it in their Varnished Cambric insulation .

B Tap the small pin out and the top mount will unscrew from the top of the Piston Rod. This is threaded 5/16 inch BSF.

C For the Piston Rod seals you need " Sealmasters " Quad Ring seals ( sometimes called X seals ). These give 2 wiping edges per seal i.e the bottom lower left and the bottom lower right of the " X " give 2 edges.Two of these seals give 4 wiping edges. There is no need to replace any other seals .
Order Quad Ring Q4-013 NBR part number 09QR13N19.
Order for the filling plug Bonded Seal 1/8 inch BSP part number ( Concentrate on this one ! )
57SM45020MS16N. Phone number is 02920490711 or the web www sealmasters co.uk.
The modern replacement 1/8th BSP Blanking Plug uses a 12mm spanner.these are obtainable for any plumbing shop.

D Already has one ( hydraulic )
E Have a go ! if you can unscrew the brass plug at the top the rest is easy and save yourself hundreds of pounds

Extras - the top Brass threaded plug is a 1 1/14 inch TAPER GAS thread .
use Paul`s idea of approx 3 inch x 2 inch bubble wrap round the outside of the piston body.
use Automatic Transmission Fluid to fill . If this proves to be too soft then go to 20 , 30 etc until the
ride is right .
the seals are 0.30 pence each and the bonded one 0.25 each.

Hope this helps - Regards Alan.
 

Chris.R

Well Known and Active Website User
VOC Member
#18
Hi Chris
Like politicians who never answer a question directly there seems to be no definite reply to your enquiry - so read on .

A " Wellseal " has the looks and consistency of Shellac and is a very good sealer. No one outside of the electrical industry will know what you are talking about regarding Shellac and has`nt been heard of since Glovers Cables of Manchester used it in their Varnished Cambric insulation .

B Tap the small pin out and the top mount will unscrew from the top of the Piston Rod. This is threaded 5/16 inch BSF.

C For the Piston Rod seals you need " Sealmasters " Quad Ring seals ( sometimes called X seals ). These give 2 wiping edges per seal i.e the bottom lower left and the bottom lower right of the " X " give 2 edges.Two of these seals give 4 wiping edges. There is no need to replace any other seals .
Order Quad Ring Q4-013 NBR part number 09QR13N19.
Order for the filling plug Bonded Seal 1/8 inch BSP part number ( Concentrate on this one ! )
57SM45020MS16N. Phone number is 02920490711 or the web www sealmasters co.uk.
The modern replacement 1/8th BSP Blanking Plug uses a 12mm spanner.these are obtainable for any plumbing shop.

D Already has one ( hydraulic )
E Have a go ! if you can unscrew the brass plug at the top the rest is easy and save yourself hundreds of pounds

Extras - the top Brass threaded plug is a 1 1/14 inch TAPER GAS thread .
use Paul`s idea of approx 3 inch x 2 inch bubble wrap round the outside of the piston body.
use Automatic Transmission Fluid to fill . If this proves to be too soft then go to 20 , 30 etc until the
ride is right .
the seals are 0.30 pence each and the bonded one 0.25 each.

Hope this helps - Regards Alan.
Hi Alan Simple solutions are usually best and the Vincent damper seems a simple beast, presently I have driven out the pesky and small pin and replaced the larger of the three O rings with new, at the other end of the piston shaft I have placed one of the lipped seals that Paul suggests on page 71 of into the millennium into the screw cap in place of the brass fitting and two seals. I could have said Hermatite rather than Shellac I suppose I am using a locktite paste which takes time to set just as Hermatite used to in the old days. I will however obtain the parts you suggest and comment that I was a trained plumber not an engineer and have neither a lathe or press in my garage. Thanks Chris
 

powella

Website User
VOC Member
#19
Hi Chris

Should have said £ 0.30 pence not 0.30 pence - at 1/3 rd of a penny that really would be a bargain !

If you get stuck for the seals I have " Spares " here.

Regards Alan.
 

everiman

Website User
VOC Member
#20
I tried and failed to re use the old locking pin on the top mount, as it turns out it was the same diameter as welding rod, so insert welding rod after sharpening it a bit, carefully saw it off on each side. Use stainless rod if you want to get fancy :)
 


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