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i’m restoring my first Triumph, I have a 76 Bonneville any recommendations on the type of fork oil I should be using ?
Fork oil
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Hi 76barnfind, Book calls for ATF. I’ve used ATF F & ATF Decron II & III, Mercedes 134A.
To me they feel the same.
I find ATF is very close to 7 to 7.5w Belray fork oil. A change of only 2w can be decidedly felt while riding. 10w Belray will make fork feel more harsh than ATF.
My preference is 5w Belray. I find it makes fork more comfortable & wheel follows road surface better allowing better control, especially heeled over on bumpy curves.
Belray was recommended to me by my coworker & his friends that are racers & suspension gurus. It seems slipperier than ATF to me.
On a side note, the damper piston oring creates great stiction. LP Williams phenolic rings cures that 100%. Well worth the higher cost.
Genuine Leak Proof Classic fork seals really do resist leaking. They also have much less stiction than normal seals such as Emgo.
I most strongly recommend both these no matter what weight oil you choose
Also make sure the fender stays fit tension free. If stays have to be flexed to get bolts in it will increase stiction.
These forks have reputation for harsh action. The above will allow fork to work to it’s potential. When set up like this they really feel & work well. The better ride & improved handling substantially reduces fatigue on longer rides. I was surprised by that.
I use the recommended 190cc.
Don
To me they feel the same.
I find ATF is very close to 7 to 7.5w Belray fork oil. A change of only 2w can be decidedly felt while riding. 10w Belray will make fork feel more harsh than ATF.
My preference is 5w Belray. I find it makes fork more comfortable & wheel follows road surface better allowing better control, especially heeled over on bumpy curves.
Belray was recommended to me by my coworker & his friends that are racers & suspension gurus. It seems slipperier than ATF to me.
On a side note, the damper piston oring creates great stiction. LP Williams phenolic rings cures that 100%. Well worth the higher cost.
Genuine Leak Proof Classic fork seals really do resist leaking. They also have much less stiction than normal seals such as Emgo.
I most strongly recommend both these no matter what weight oil you choose
Also make sure the fender stays fit tension free. If stays have to be flexed to get bolts in it will increase stiction.
These forks have reputation for harsh action. The above will allow fork to work to it’s potential. When set up like this they really feel & work well. The better ride & improved handling substantially reduces fatigue on longer rides. I was surprised by that.
I use the recommended 190cc.
Don
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Hi
The leakproof seals will need to be purchased as a conversion kit for 76 forks.
If you fit them correctly to stanchions and fork sliders with surfaces in good order, it is likely that you will not have to worry about leaking forks again.
If you are feeling experimental the amount of oil in the fork can be varied, once the forks are properly sealed, the amount of compressible air in the top of the fork can be changed by adding or removing oil.
If you are of heavy build or ride 2 up regularly, more oil can give a stiffer spring effect, inversely, if you are of light build less oil can give a softer spring effect.
Of course care must be taken that the damper mechanism is not out of the damping oil at full fork extension if you lower the oil level significantly
Small changes in oil level can have a noticeable effect.
Regards
Peg
The leakproof seals will need to be purchased as a conversion kit for 76 forks.
If you fit them correctly to stanchions and fork sliders with surfaces in good order, it is likely that you will not have to worry about leaking forks again.
If you are feeling experimental the amount of oil in the fork can be varied, once the forks are properly sealed, the amount of compressible air in the top of the fork can be changed by adding or removing oil.
If you are of heavy build or ride 2 up regularly, more oil can give a stiffer spring effect, inversely, if you are of light build less oil can give a softer spring effect.
Of course care must be taken that the damper mechanism is not out of the damping oil at full fork extension if you lower the oil level significantly
Small changes in oil level can have a noticeable effect.
Regards
Peg
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102 Posts
Thanks Don I appreciate your insight I’ve already contacted LP Williams. I’ve bought and aftermarket seals and O-rings and already installed them. The forks are still dry I think I’m going to make the switch to the LP Williams. Thanks
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102 Posts
Hi Peg thanks for your response, I purchased some aftermarket seals and installed them they slid right in perfectly they seem to fit well but they’re definitely not like the original ones that I took out that have a metal plate on the top that basically hold them in place. Seals seals went in almost a little too easy although they were snug. I was a little concerned that they would not seal that’s why I asked the question. I think I’m going to take Don’s suggestion and buy those seals from LP Williams overseas.
Cheers
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Hi
It might be that your forks were already converted, or have later sliders fitted.
I have made a quick list of the T140 forks seals that were originally fitted by year.
1973 97-4001
1974 97-4001
1975 97-4001
1976 97-4001
1977 97-4001
These are a single seal, they have a reputation for leaking badly and require replacement on a regular basis. They are upgradable to the later versions. Upgrading kits similar to the 1978/79 versions are available and easy to implement.
Upgrading to the post 79 version requires new sliders or a circlip groove machining into the existing slider.
1978 97-7010
1979 97-7010
Two piece seal kit consisting of a floating seal and a thick hammer in retaining washer.
These seals have a reputation of not leaking and a long working life.
1880 97-7079 + 97-7093 thin washer + 60-7269 circlip.
1981 97-7079 + 97-7093 thin washer + 60-7269 circlip.
1982 97-7079 + 97-7093 thin washer + 60-7269 circlip.
Easy fit floating seal retained by a thin washer and circlip, The slider must have a circlip groove machined into it to fit this seal
These seals have a reputation not leaking for long working life.
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Dust covers or fork gaiters are not mentioned. There is a general agreement that fitting Norton Commando dust seals or fork gaiters (from Andover Norton) is preferable to fitting Triumph branded items.
Most upgrades kits will be 1978/79 type with hammer in thick washers, the washer should be inserted until the top of the washer is flush with the top of the slider. The seal should float loose under the washer.
There are two types of seal hard and soft. If the soft type is fitted, these can be replaced without having to remove the washer.
The 78 onward seals have sealing surfaces on the inside and outside, both the fork stanchion and inside of the slider where the seal sits should be in good condition. The slider inner sealing surface can be easily damaged by careless removal of the original seal. Extra care must be taken not to scratch the sealing surface if a lever is used to prise out the original seal.
The upgraded floating seal often looks loose once installed, this however is normal.
It is important to get the seal the correct way up.
Leak stop and Ariete are two known seal brands.
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If I was already in contact with LP williams then I would definitely take Don’s very good advice on also fitting the Phenolic rings instead of the damper ‘O’ rings.
regards
peg
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Interesting that you said make sure you get the seals the correct way up I put the aftermarket seals in that I got with the smaller tapered side up and the thicker part down into the stanchion hopefully that’s correct
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Hi 76barnfind, Sounds like you got the Leak Proof seals. I don't know the difference between soft & hard ones. I've installed several sets of Leak Proof, but always used the genuine Leak Proof in their packaging. I'm afraid to use any others as these have worked so good.
Absolutely worth taking dampers out to use phenolic LP Williams damper rings. Spread them gently, don't wind them on, but spread with thumb nails. Lube them well. They will fit damper very loose. You'd think they'd not work good, but they are fantastic.
You can just unscrew allen bolt in slider & push damper rod out the top. Keep track of dowty washer in slider, but it generally stays put. Very careful visual inspection through bolt hole & you can see if washer is in place. I just did the through the top on a set I installed recently. Hold slider full up. Push long screwdriver or piece of rod/dowel up bolt hole. Engage rod into bolt hole of damper rod. Guide rod down to slider. I often use a 3/8 drive spark plug socket & extension from top to help push down damper rod. If handle bars are in place restricting access Just use a long rod or screwdriver. This method you don't have to unscrew the retainer nut on stanchion or remove slider & have to work seal over fork end.
Sealant on allen bolt head is always a good plan. I've seen so many leak even with new dowty washer. Sealant on spring nut threads also or they will leak.
Gaiters are a good thing. Keeps water, dirt, bugs at bay. I don't use them because my bike didn't have from new. I want to keep it visually stock.
Don
Absolutely worth taking dampers out to use phenolic LP Williams damper rings. Spread them gently, don't wind them on, but spread with thumb nails. Lube them well. They will fit damper very loose. You'd think they'd not work good, but they are fantastic.
You can just unscrew allen bolt in slider & push damper rod out the top. Keep track of dowty washer in slider, but it generally stays put. Very careful visual inspection through bolt hole & you can see if washer is in place. I just did the through the top on a set I installed recently. Hold slider full up. Push long screwdriver or piece of rod/dowel up bolt hole. Engage rod into bolt hole of damper rod. Guide rod down to slider. I often use a 3/8 drive spark plug socket & extension from top to help push down damper rod. If handle bars are in place restricting access Just use a long rod or screwdriver. This method you don't have to unscrew the retainer nut on stanchion or remove slider & have to work seal over fork end.
Sealant on allen bolt head is always a good plan. I've seen so many leak even with new dowty washer. Sealant on spring nut threads also or they will leak.
Gaiters are a good thing. Keeps water, dirt, bugs at bay. I don't use them because my bike didn't have from new. I want to keep it visually stock.
Don
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I got the 97-4001 I’m going to swap them out . At least I put them in the correct way but I’d rather have a better seal . Thanks for the info . Any recommendations on where to purchase these seals. The place I was getting parts from sent me these I’d rather buy my parts from somebody that is selling a higher quality item or at least gives me the option
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102 Posts
Thanks Don I already went through the process of putting the new seals and the O-ring in just having second thoughts about the ones that I did use I am going to swap them out for the better product. I haven’t put the fork oil in yet and my bike is 100% apart so it won’t be a big deal to swap them out. Thanks again . Cheers
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Hi 76barnfind, These are the seals I purchased. At the time was best price incl shipping, tx etc. Leak Proof sells direct. Shop around.
71 and Up Triumph Leak Proof Classic Fork Seals 34.6mm 7216 | eBay
Be very careful you buy correct kit for early fork with press in retainers. The later kits are for snap ring retained seal. They cost less so beware. To be clear the rubber seal itself is identical in both kits. The difference is the retainer. The later kit includes thin NOT pressed in washers. So will similar in package. That's why such caution is needed.
There are other makers of these kits. I've noticed 2 versions of pressed in rings. A poorly made square ring that is not machined smoothly. I don't know brand. The rings with Leak Proof have always been nicely machined & have gone it nicely for me. Warming fork leg with head gun to just very warm, not hot to touch eases assembly. In every case lube the bore in leg & press in ring well to assist in assembly.
LP Williams damper rings. Note: the online store for LP Williams is "Triumph-Spares" so search will show that.
Damper valve seal conversion 1971 on (pair) (triumph-spares.co.uk)
The photo on web page shows grey rings. They can come in grey, brown, green color that I know of. All have worked equally as well for me.
I use paypal. They do the dollar/pound conversion + small exchange fee for you. Final total will depend on exchange rate at moment of transaction.
Neither is cheap. However they work & work well.
Actually Triumph itself had so much leaking with the normal 97-4001 they finally started using the pressed in retainer version, then later machined snap ring groove to ease assembly & service. Again the snap ring version washer is thin & loose fitting. I just recently had to purchase new slider for '73 Bonnie. Was able to get genuine NOS Triumph. Was snap ring version. Came with seal. Removing seal as it was as old & the fork had same seal part number/font etc. As the Leak Proof was. The old original seal probably would have been fine, but I elected to put new one in from the early kit. As Peg stated & the instructions state, the seal must have correct end float. The bore in slider where seal rides must be smooth without gouges. You put these seals in, you think this is not right. However they actually don't leak & last a long time. Both pressed in retainer & snap ring/thin washer version will give enough end float.
Removing pressed in ring is not too hard. I always warm leg very warm. I have a small slide hammer with a flat pulling hook. Hook the hook inside ring & slide hammer it out a little at a time going around the circle. Comes right out. You pry them as well, again go around the circle. Leak Proof recommends removing ring to replace seal, not wadding them up & wiggling them in. I really don't know if it's bad for seal or not. Again I don't know difference between soft & hard seals.
The very best way to install slider is wrap upper with a piece of binder page plastic.Overlap plastic about 1/4". Feed seal /into plastic just enough to cover seal. Then push slider/plastic up as a unit. Guarantees no damage to seal lip. Lube all well with fork oil. The excess lube will seep out in 50 miles or so. Wipe as needed. Then will be good, don't see that as a failure.
Here is photo of how far to press in retaining ring. Also what the snap ring one looks like.
Don
71 and Up Triumph Leak Proof Classic Fork Seals 34.6mm 7216 | eBay
Be very careful you buy correct kit for early fork with press in retainers. The later kits are for snap ring retained seal. They cost less so beware. To be clear the rubber seal itself is identical in both kits. The difference is the retainer. The later kit includes thin NOT pressed in washers. So will similar in package. That's why such caution is needed.
There are other makers of these kits. I've noticed 2 versions of pressed in rings. A poorly made square ring that is not machined smoothly. I don't know brand. The rings with Leak Proof have always been nicely machined & have gone it nicely for me. Warming fork leg with head gun to just very warm, not hot to touch eases assembly. In every case lube the bore in leg & press in ring well to assist in assembly.
LP Williams damper rings. Note: the online store for LP Williams is "Triumph-Spares" so search will show that.
Damper valve seal conversion 1971 on (pair) (triumph-spares.co.uk)
The photo on web page shows grey rings. They can come in grey, brown, green color that I know of. All have worked equally as well for me.
I use paypal. They do the dollar/pound conversion + small exchange fee for you. Final total will depend on exchange rate at moment of transaction.
Neither is cheap. However they work & work well.
Actually Triumph itself had so much leaking with the normal 97-4001 they finally started using the pressed in retainer version, then later machined snap ring groove to ease assembly & service. Again the snap ring version washer is thin & loose fitting. I just recently had to purchase new slider for '73 Bonnie. Was able to get genuine NOS Triumph. Was snap ring version. Came with seal. Removing seal as it was as old & the fork had same seal part number/font etc. As the Leak Proof was. The old original seal probably would have been fine, but I elected to put new one in from the early kit. As Peg stated & the instructions state, the seal must have correct end float. The bore in slider where seal rides must be smooth without gouges. You put these seals in, you think this is not right. However they actually don't leak & last a long time. Both pressed in retainer & snap ring/thin washer version will give enough end float.
Removing pressed in ring is not too hard. I always warm leg very warm. I have a small slide hammer with a flat pulling hook. Hook the hook inside ring & slide hammer it out a little at a time going around the circle. Comes right out. You pry them as well, again go around the circle. Leak Proof recommends removing ring to replace seal, not wadding them up & wiggling them in. I really don't know if it's bad for seal or not. Again I don't know difference between soft & hard seals.
The very best way to install slider is wrap upper with a piece of binder page plastic.Overlap plastic about 1/4". Feed seal /into plastic just enough to cover seal. Then push slider/plastic up as a unit. Guarantees no damage to seal lip. Lube all well with fork oil. The excess lube will seep out in 50 miles or so. Wipe as needed. Then will be good, don't see that as a failure.
Here is photo of how far to press in retaining ring. Also what the snap ring one looks like.
Don
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