Fork tube compatibility

[Thumper]

Can anybody tell me me if the fork inner tubes (the shiny chrome bits) from a model with leading axle will fit the 1979f model. Was looking at parts diagrams for different models and the part numbers are nearly all the same except for the first three digits. Example 1979f model #2H7-23110-00-00, 1979 79sf #3H3-23110-00-00.

[Jerry]

Best guess I have is that the fork tubes are not interchangeable.

This comes from the specs for the fork seals:

Early forks use a 36mm x 48mm seal
Leading fork - later models- uses a 37mm x 49mm seal.

To me this indicates both the outer and inner tubes are different sizes in the later forks. As I said, though, I've never actually tried this swap...late inner may work in early outer if you can find a 37mm by 48mm seal.....

BTW, Dennis Kirk and K&N both list the wrong applications for XS/XJ seals in their literature. My recollection is the seals are 36 x 48 for early forks, the literature says they will fit the late forks as well which is incorrect.

This is from memory, so anyone correct me if they have different numbers.

[Thumper]

My forks do use 37 x 49mm seals. That's another mystery solved, why every other time I order fork seals I end up with 36 x 48mm. Thanks!

[John]

I have found that every aftermarket seal that I have bought leaked after a short time. A couple of years ago I bought some OEM Yama seals, and have had no problems, and I am running 11 lbs. of air pressure also. Some items are just better if you break down and buy OEM. I know it can be expensive, but if you replace seals every year, that can add up to more tha the cost of OEM. I know some items are just no longer available from Yamaha anymore.

[rover]

Re: Fork tube compatibility

Originally posted by Thumper
Can anybody tell me me if the fork inner tubes (the shiny chrome bits) from a model with leading axle will fit the 1979f model. Was looking at parts diagrams for different models and the part numbers are nearly all the same except for the first three digits. Example 1979f model #2H7-23110-00-00, 1979 79sf #3H3-23110-00-00.

I just measured my 79f, 79sf, and 81lh. All three have 37mm fork tubes. I think the specials have longer tubes than the standards, cause my lower tree is about the same distance from the ground on both the special and standard.

[Dennyz]

They fork tubes are the same diameter, but different lenghts. The seals are different because the shock housing are different.

The answer to the original question is yes. I have been running my "F" with Special fork tube for a couple of years (15K miles).

The special tubes (shinny chrome pieces) are about 3" longer and will stick out of the triple clamp farther. Perfect for attaching clip-ons.

[Thumper]

I'll just have to wait until I can get a set of standard f model forks as I've noticed the specials all seem to be air assisted and mine have the preload adjustment instead. I'll also echo the advice of John from Dallas (^about three messages up^) always buy Yamaha fork seals aftermarket or pattern ones last no time at all and if you're a high miler like me you'll end up stripping your forks again in a couple of months.

[TopCatGr58]

Hey there THumper,

Since the uppers are the same diameter size, then you can just swap your upper spring "Preload" cap for the Air Cap. I think the Special uses a longer spring, so just swap it as well. I have a Special, and I'm using 4" over length uppers and so it came with a 4" plastic insert tube to take up the extra space, and I don't even put any air in mine! I also got after market seals with the Forks by Frank, and they've held up nicely so far, 3 years, but not as many miles as a daily commuter.
T.C.

[Thumper]

Tis okay I can wait on the right forks I'm sure the breakers will have another container from the states in soon. Besides due to my bad habit of heavy handed overtightening I've damaged one of my caps, it's one of the reasons I'm looking for new forks I'll use the bits I need and will always have the rest for spares.

[scoobes]

hey thumper there is a chap over here in the uk that might have a set if you want a contact email address let me know.

[malloryduck93]

forks

i need to know if the just the upper tubes of a 80-81 midnight special will fit a 1979xs 1100 sf spacial