1972 T120V Front Fork Advice Please

[Mark T120]

Hi all, I wonder if anyone can help? I recently purchased a 1972 OIF T120V . The L/H fork leg has much softer damping than the right hand leg and hangs 1/4" lower. I have swapped the springs around drained and refilled with the correct amount of oil but it hasn't made a difference. Can anyone make a suggestion as to the probable root cause of the problem ?
Thanks
Mark

 

[Rudie]

L/H fork leg
hangs 1/4" lower
than the right hand leg

72 650 parts book, pages 64/65. The physical parts that determine where the top of the slider ("Outer member") sits on the stanchion are:-

. The length of the "Damper tube" under the "valve assembly" (part 36), as the latter is in the bottom of the stanchion while the bottom of the slider is attached to the bottom of the "Damper tube".

. The length of the "Recoil spring" (part 33) that spaces the "valve assembly" off the "End plug" (part 21) in the bottom of the stanchion.

L/H fork leg has much softer damping than the right hand leg

Draining the damping fluid from the forks before dismantling them will allow you measure quantities and compare viscosities.

You should find 190 cc of ATF or similar viscosity (7.5~10 weight) fork oil is each leg, unless a p.o. has set the fluid level by height (modern method) rather than by Triumph's volume.

 

[Mark T120]

72 650 parts book, pages 64/65. The physical parts that determine where the top of the slider ("Outer member") sits on the stanchion are:-

. The length of the "Damper tube" under the "valve assembly" (part 36), as the latter is in the bottom of the stanchion while the bottom of the slider is attached to the bottom of the "Damper tube".

. The length of the "Recoil spring" (part 33) that spaces the "valve assembly" off the "End plug" (part 21) in the bottom of the stanchion.


Draining the damping fluid from the forks before dismantling them will allow you measure quantities and compare viscosities.

You should find 190 cc of ATF or similar viscosity (7.5~10 weight) fork oil is each leg, unless a p.o. has set the fluid level by height (modern method) rather than by Triumph's volume.

Hi Rudie, I have swapped the springs and put 200cc of oil in each side the r/h lis fine . The l/h takes less than half the effort to compress it by pushing the bottom of the leg upwards. It seems to have very little resistance. I know it cant be the oil or the spring. I am presuming that something in the damper assembly must be at fault .

 

[Mark T120]

Hi Rudie, I have swapped the springs and put 200cc of oil in each side the r/h lis fine . The l/h takes less than half the effort to compress it by pushing the bottom of the leg upwards. It seems to have very little resistance. I know it cant be the oil or the spring. I am presuming that something in the damper assembly must be at fault .

Hi all I stripped the fork this afternoon and @i think got to the bottom of my problem. I found two issues. The nut on the top of the damper assembly was fitted upside down by the previous owner . The the spigot which locates the bottom of the fork spring should face up . Also the O ring looks far too narrow. I have ordered another so we will see whether my assumption is correct. Because everything is now in bits I thought I would treat her to a new set of progressive springs and new bottom nuts as they were so badly chewed that If I put them back in they may never come out . Rather than the triumph tool to hold the top of the damper to allow you to release the allen bolt at the bottom of the fork leg a 20mm slimline socket ( just and I mean just)fits. Awaiting parts. then fingers crossed should get the long awaited test run next week end. Whilst I am here has any fitted the adjustable 2810 Hagon rear shocks . if so what do you think? I like to feel the front and I am thinking of increasing the ride height by either using a 13.4" or 12.9", rather than the stock shock length. Anyone done this again any feedback?

 

[JerryP]

Concerning rear shock length. A 1/2" difference shouldn't change too much in street ride. TEC offered reservoir shocks for the 900 series (2013) scrambler that came with a simple extension to the lower shaft of about 1". It didn't seem to make much difference in ride quality, but the look of more visible tire enhanced the Scrambler look. Most suspension guys though would have you adjust front and rear in equal amounts to keep the geometry balanced. I did fit TEC progressive springs to front forks so perhaps that may have helped front to rear balance. Sorting the front forks seem your priority in this case. Interesting topic.

 

[scottholl]

I have had luck re moving the fork tube bottom nut with a simple impact wrench air or electrical.

 

[Mark T120]

I have had luck re moving the fork tube bottom nut with a simple impact wrench air or electrical.

Hi Scott , Thanks for the feedback . I think the previous owner had used what we call Billy Bodgers secret weapon a "Manchester screwdriver". I managed to get it out with a 32mm socket

 

[Mark T120]

Concerning rear shock length. A 1/2" difference shouldn't change too much in street ride. TEC offered reservoir shocks for the 900 series (2013) scrambler that came with a simple extension to the lower shaft of about 1". It didn't seem to make much difference in ride quality, but the look of more visible tire enhanced the Scrambler look. Most suspension guys though would have you adjust front and rear in equal amounts to keep the geometry balanced. I did fit TEC progressive springs to front forks so perhaps that may have helped front to rear balance. Sorting the front forks seem your priority in this case. Interesting topic.

Thanks for the feedback Jerry. I suppose at the end of the day everyone has their own preferred confidence inspiring feel, personally I like to put a bit more weight on the front it helps the turn in,gives a more planted feeling . As long as you aren't excessive you don't loose much straight line stability or rear traction . With it being a 72 model then there is no easy adjustability in the front. Fork oil and spring weight are all you have ,so rather than chase my tail I thought there will be someone who has tried it and can pass on their set up.

 

[scottholl]

Hi Scott , Thanks for the feedback . I think the previous owner had used what we call Billy Bodgers secret weapon a "Manchester screwdriver". I managed to get it out with a 32mm socket

Mark I can't wait for my project, removing a 78 t140E front end and replacing it with an '83 honda CX 500 Turbo (w/TRAC feature) front end with mag wheel and double disks.. to many honda spares!!~!

 

[Mark T120]

Mark I can't wait for my project, removing a 78 t140E front end and replacing it with an '83 honda CX 500 Turbo (w/TRAC feature) front end with mag wheel and double disks.. to many honda spares!!~!

Now that sounds an interesting project and I will look forward to seeing and hearing of your progress

 

[brooke]

Mark I can't wait for my project, removing a 78 t140E front end and replacing it with an '83 honda CX 500 Turbo (w/TRAC feature) front end with mag wheel and double disks.. to many honda spares!!~!

Ok Scott , where do we find the photo of McQueen on the CX e model ?

 

[Rudie]

O ring

Cause the stiction that is responsible for the poor suspension response particularly over small bumps. If you find the new O rings are thicker, possibly a p.o. tried thinner O rings to reduce the stiction.

is Damper valve seal conversion 1971 on (pair) and ensuring the insides of the stanchions are polished (not all are).

Other proven fork upgrades:-

. 78 onwards Leak Proof fork seals instead of standard 71-77 97-4001 - initally 97-7010 as that includes the steel seal retaining rings. Thereafter, if you ever need to replace the seals (very unlikely unless the stanchions have raised rust bubbles or you do not fit gaiters), the Leak Proof seals are available on their own - 97-7079.

. 06-5743 Commando fork gaiters supplied specifically by Andover Norton.

. Proper fork oil instead of ATF.

. Progressive springs supplied specifically by Progressive Suspension. However, these might not be needed (the jury is out) if you upgrade the dampers.

. Most expensive are better dampers.

Concerning rear shock length. A 1/2" difference shouldn't change too much in street ride. TEC offered reservoir shocks for the 900 series (2013) scrambler that came with a simple extension to the lower shaft of about 1". It didn't seem to make much difference in ride quality, but the look of more visible tire enhanced the Scrambler look. Most suspension guys though would have you adjust front and rear in equal amounts to keep the geometry balanced. I did fit TEC progressive springs to front forks so perhaps that may have helped front to rear balance. Sorting the front forks seem your priority in this case. Interesting topic.

Thanks for the feedback Jerry.

@JerryP has assumed you have a Hinckley T120 ...

 

[Lordmac]

Hi all, I wonder if anyone can help? I recently purchased a 1972 OIF T120V . The L/H fork leg has much softer damping than the right hand leg and hangs 1/4" lower. I have swapped the springs around drained and refilled with the correct amount of oil but it hasn't made a difference. Can anyone make a suggestion as to the probable root cause of the problem ?
Thanks
Mark

After all is said and done, I find that spendy, synthetic fork oil smoothes things a bit, even allows the small bumps to become a little less jarring.

 

[Mark T120]

I took this picture a couple of months ago having now sorted front and rear suspension still waiting for the 7 plate clutch conversion and Spring !

 

[Lordmac]

Whilst I am here has any fitted the adjustable 2810 Hagon rear shocks . if so what do you think?

Mark;

On the subject of rear shocks made by Hagon, I can tell you that after I installed a set on my T140V, the ride was so improved I nearly fell off from the excitement! But seriously, Hagon rear shocks made a HUGE and wonderful difference in the ride.

 

[Mark T120]

Mark;

On the subject of rear shocks made by Hagon, I can tell you that after I installed a set on my T140V, the ride was so improved I nearly fell off from the excitement! But seriously, Hagon rear shocks made a HUGE and wonderful difference in the ride.

Hi Lordmac, I too am impressed with the Hagon shocks, really good value for money. My only complaint, the compression rebound is a pain to alter as the allen key adjuster is fouled by the drum brake arm, though I may be able to turn them through 180 so probably bad planning on my behalf. Also I don't know about you but I can't easily feel each click of adjustment. But again that may be me . Pity my lack of feeling doesn't extend to my aches and pains in a morning though Anyway the upgrade has certainly stopped the bike bouncing around like it did! My settings if anyone is interested I went for the 330mm centre to centre shocks and have set the preload at 2 of 3 with 8 clicks ( I think) of rebound/compression. For the forks then I have fitted progressive front springs from Les Williams with 190cc of 10w fork oil.