Fork Springs?

[Kiwi Dannyo]

Hi all,
I've been a member for a few months or more but this is the first question I've posted.
Owned several bikes over the years. Currently a '79 XS1100F and a '83 XJ550RJ "project".

So, I currently have the forks off the '79 XS in order to replace the leaking seals. Everything is going well (so far, ) but here's the thing.
When I removed the cap bolt I expected it to be under spring pressure from the fork spring but there was none. So I checked maintenance manual (Clymer) for the correct spring length and measured my springs.
The manual says 503.5mm (19.82 in) for regular forks or 612.2mm (24.1 in) for air/oil forks.
I have air/oil forks and my springs are just 480mm! This seems like a massive (XSive, some would say) discrepancy.

Could my springs have compressed that much or has a PO altered them for some reason? (and if so, why?)
I wouldn't think that they would be more than 130mm shorter with normal use?

What are issues involved with having much shorter springs? (i.e. why would a PO change them for shorter)

The bike seemed to ride and perform well until the seals started leaking. Could the air pressure have been increased to compensate for the shorter springs?

[jkorn]

I wish I could remember if mine were under pressure when I pulled them. It’s been awhile. But my 79F does not have air front forks. There is a “srew” in the fork caps that changes the preload. Do them maybe there was some need to compress the springs as I put them back together. Nice looking 79 though. Jeff

[cajun31]

Hi all,
I've been a member for a few months or more but this is the first question I've posted.
Owned several bikes over the years. Currently a '79 XS1100F and a '83 XJ550RJ "project".

So, I currently have the forks off the '79 XS in order to replace the leaking seals. Everything is going well (so far, ) but here's the thing.
When I removed the cap bolt I expected it to be under spring pressure from the fork spring but there was none. So I checked maintenance manual (Clymer) for the correct spring length and measured my springs.
The manual says 503.5mm (19.82 in) for regular forks or 612.2mm (24.1 in) for air/oil forks.
I have air/oil forks and my springs are just 480mm! This seems like a massive (XSive, some would say) discrepancy.

Could my springs have compressed that much or has a PO altered them for some reason? (and if so, why?)
I wouldn't think that they would be more than 130mm shorter with normal use?

What are issues involved with having much shorter springs? (i.e. why would a PO change them for shorter)

The bike seemed to ride and perform well until the seals started leaking. Could the air pressure have been increased to compensate for the shorter springs?

Sounds to me like someone prior to you modified the fork setup. Genuine Yamaha Bolt Cap PN 2H7-23111-00-00 | eBay .... these are the original caps for the xs1100F. There was no air valve on them. The springs are also not correct. Seems whoever modified it replaced the fork caps and either shortened the springs or had some other setup. Hopefully someone else will chime in that might know more of what he or she may have done. Adding the air caps did provide to ability to apply some pressure which accounts for the ride still being ok. There is an aftermarket company that provides some modifications for the forks. I believe JetMechMarty may be able to provide more information on that because if I remember correctly he modified his forks.

[red bandit]

Hi all,

The manual says 503.5mm (19.82 in) for regular forks or 612.2mm (24.1 in) for air/oil forks.
I have air/oil forks and my springs are just 480mm! This seems like a massive (XSive, some would say) discrepancy.

I think they are the original springs. They are only compressed 23mm, not bad for 42 years old. OEM for an F has progressive springs. IIRC. They are F forks so no air cap. OEM: when screwing in the top cap there is spring pressure. Can be difficult to get it started because of spring pressure.

[jkorn]

Waaaay back when, I kind of remember ordering different fork springs from Yamaha. Now I can’t remember if they were harder or softer. But Yamaha parts. I also remember modifying the part at the bottom with holes is it that fluid goes thru. Slightly bigger holes?? This was all documented in a bike magazines when my 79 was only a year or so old. Back then new bikes were the subject of “recommended” performance upgrades in the magazines.

I also remember removing one of the weights or springs on the timing advance. Changing the main jet from 137 to 140. Moving the carb needle up one notch.

I owned the fastest production motorcycle on the street for several months until the 4 valve Suzuki came out. ☹️

I still love to ride it….. jeff

[Kiwi Dannyo]

Thanks for the replies so far. It seems that my forks have definitely been changed. 2H7 030407. Definitely a US (originally) '79 F model, that came out with no air cap.
I think Red Bandit's reply has helped me understand it best in that you think that the compression is not unusual for the original springs. With that in mind I am a little less anxious about the whole thing.

I think that the previous owner has just changed the caps in order to use air pressure as the absorber dampening adjustment while retaining the original springs, i.e. of course the fork tube remains the same length which means the same length spring (503.5mm) and the same fork oil level (212cc). It also means that the new fork seals that I have will fit!

SO! I'm thinking that I will order new springs but in the meantime I'll put it all back together with PVC spacers (23-25mm) to make up the difference. Can't wait to be back on the road!

Also, thanks very much to Rasputin for the Parts Fiche and workshop manual. Very helpful.

[red bandit]

When I had my old springs in it was easy to put the cap on using a socket, extension & ratchet standing along side the bike. With the new OEM springs I couldn't hardly put the cap on. I had to get on the bike and really lay into the ratchet. If you buy OEM from ebay pay close attention. Just because the box says Original doesn't mean the springs are. A lot them are not progressive. Don't know if that's important but be aware.

[Schming]

HTH - When I rebuild forks I use a piece of sheet rubber in the vise as a pad for the fork cap then carefully thread the fork tube onto the cap. Way easier than pushing and trying to turn the cap.

[jetmechmarty]

You can not swap the fork caps between a standard XS1100F and an air cap from an XS1100 Special. They are not threaded the same. The standard has KYB forks and the Special has Showa forks. Parts don't interchange. Looking at them, the Special has a leading axle. The axle is mounted in front of the fork. On the standard the axle is mounted on the bottom of the fork. Triple clamps are different because of this. Installing the air caps is a challenge in fighting against the spring. My XS650 has forks very similar to your XS1100F. Springs aren't a fight, but mine were sacked and I just replaced them last week. Right now, I don't know what you have. Post some pictures.

Somewhere on XS11.com I posted pictures of an air cap install tool I made from PVC.