Fork dampers - early and late style on one bike?

[Stefw]

Hello,

I’m rebuilding my ‘78 standard and I’ve just come to sorting out the forks.

For reference I’m in the UK but this is a US import. Single disc on the right hand side, late style caliper etc.

Now I’m a bit dumbfounded as I have everything correct for late style 35mm forks on my left leg, but the right leg (with the caliper etc) I’ve found the early style damper inside.

Both top preload caps are late style adjustable, but everything from there down is different on the right leg - slightly shorter spring as well.

My question is does this matter? I assume both forks use the same fork seals that I’ve got for reassembly? Is this a potential factory issue or I suppose more likely someone’s changed it in the past? I guess damping/spring rate is largely similar - handled fine before other than diving horribly under braking which I intend to fix with more oil - I’ve turned up some additional preload spacers which you can see in one of the pictures.

And can I still do the Minton mods to both dampers without messing anything up?

Thankfully I managed to get the old style out without too much trouble but I’ll need to make a tool to get it back in, is a ground up 17mm socket the best option for this?

I could really do without trying to find another used set of forks if this will cause issues but I want it to be correct.

Cheers,
Stef

 

[5twins]

OK, it appears you have one '78 and later damper rod, and one from a '77 model. I suppose you could use them but personally, I'd look for a used matching damper rod. You probably also noticed the '77 rod had no top out spring. You can add one if you like .....

Yes, you can "Minton Mod" both rods. If you examine the '77 rod, you'll see that Yamaha beveled the oil holes. An engineer buddy of mine told me this makes them flow better, so you can bevel the ones in the '78 rod as well. You'll also notice that the '77 rod is more polished. Using some 600 paper, you can polish up the '78 rod as well. I think this makes the rod move more smoothly through the bushing in the bottom of the tube.

It seems Yamaha put a bit more time and effort into making the '77 rods nicer, what with beveling the holes and polishing the rods up.

For a holder to keep the '77 rod from spinning while installing or removing the bottom bolt, I simply hammered the end of some 1/4" steel rod flat. Then I just jam it into the top of the rod, between the outer wall and the roll pin .....

 

[Stefw]

Thanks 5twins. Worst part about this is I had a pair of forks spare that I let go not too long back.

I saw there was no spring, I assumed it was inside the fork tube - I’m sure the fork tubes themselves looked different at the bottom or are they the same?

I guess if the same I’ll need a damper assembly and the correct length fork spring - probably easiest for me to rebuild these and then wait out a spare set of forks or one fork leg.

Assume the legs are the same both sides?

Nice one on the damper holding tool - I knew there had to be a simpler way.

Thanks,
Stef

 

[5twins]

I think the tubes are the same internally but on a '77 tube, you can pull the parts out of the bottom (not that you'd need or want to), while on the '78 and later tubes, they're crimped in .....

Yes, the '77 springs are shorter as well. They were run with just a short plain cap and a tube preload spacer, but the longer later adjustable top cap you're using should be about the same length as those two parts .....

Here's some specs on the two forks .....

 

[650Skull]

Your problem is your in Europe. The models are different to the States.
A caution when buying parts.
If the Euro Standard front forks are the same as the Japanese counter part internals then they may have a combination of a US 77D and 78-83 with the cap bolt and a spacer, (same as US 77D), instead of an adjustable cap bolt with a spring, (US 78-83), but have the same 78-83 Damper.

Euro Standard model fork leg lower is different. They had twin disk brakes with a smaller 260mm front disk brake rotors so the caliper mount is lower on the fork than US models.

NOTE;
On the Japanese Standard model 80-82, (parts fich), have the same internal Damper, (US 78-83), but have the cap and spacer same as the US 77D. This may also b true for the Euro 78-83 Standard. On all pics and brochure I have seen they seem to confirm this with a flat profile where the top of the fork is on the triple crown. US models a rubber cap protrudes where it sits on the nut part of the bolt that sits above the crown.

Euro US custom has a single front brake rotor, (same size as the US), and all pics and brochures I have seen, the fork bolt cap looks to have the adjustable preload and spring the same as US models.

 

[Stefw]

Thanks for the replies guys - hadn’t even occurred to me that the lowers would be different so that’s a great spot!

I’ve managed to find a set of 79 forks with the correct preload tops etc not too far away, unfortunately the stanchions are bent so I’ll probably pick those forks up and get new stanchions for them, that way I’ll have some spares then as well.

Thanks for all the help!

 

[Wingedwheel]

For a holder to keep the '77 rod from spinning while installing or removing the bottom bolt, I simply hammered the end of some 1/4" steel rod flat. Then I just jam it into the top of the rod, between the outer wall and the roll pin ....

I’ve had good luck with a large flat-head screwdriver or a wooden dowel.

 

[Stefw]

So I picked up another set of forks today and got them apart. All looks to be pretty correct which is good, only weird thing is someone’s installed almost 2 inch ally spacers and long bolts that sat at the bottom of the dampers. I did think the stroke of the legs seemed short.

I assume I’m good to just remove these and use my original damper bolts?

 

[5twins]

Yes, just remove and discard those spacers, although I'm not sure how they shortened things. Seems to me they would extend the forks. Measure the spring lengths as well to make sure they weren't shortened.

I added short preload spacers to my '83 forks. I always liked the stock springs but they were always too soft. They are a nice dual rate spring and gave a nice ride, but even with the pre-load caps cranked all the way in, they were still too soft. The caps have two stiffer steps, each adding 10mm of pre-load for a total of 20mm that can be added ......

So, I figured spacers a little longer than that, maybe about 1" (about 25mm), would be good. That would put me about a half step stiffer than what I could get with the caps. But they proved to be too stiff. What I failed to do was take into account the thicknesses of the two washers needed (one above and one below the spacer). They brought my total spacer length up near 30mm, or like going another full step on the adjuster cap. So I shortened the spacer to around 13/16" (about 20mm). Combined with the washers, this put me right where I originally wanted to be (in the mid 20's) and it works well.

 

[Stefw]

Just measured - stock length thankfully!

Yes I can’t see how those spacers did anything other than limit the actual travel of the fork - seems pointless. They also used the incorrect pitch bolts in the bottom but somehow the threads appear to be intact in the dampers and the fine thread bolts I have seem to fit OK - I’ll probably loctite them to be sure.

I’ve got some 1 inch preload spacers I had turned up, they fit the preload caps well - bit of an effort getting the caps to seat but these spacers with a click of preload on the caps seems to work well.

 

[5twins]

Pretty fancy there, lol. I just cut mine from some pipe. However, I did manage to source some of the original top hat shaped spring washers that fit down into the spring top and stay centered. You can't buy them anymore from Yamaha and eBay prices were pretty steep, so I scrounged some from old junk forks, lol.

I'm glad I was able to "fix" the forks with these little spacers. Saved me the cost of new aftermarket springs.

 

[Stefw]

That would have been my solution but I sent a spare brake disc I had to be drilled so got them to make up the spacers at the same time - cost me the equivalent of about 50 bucks for the disc drilling and the spacers so can’t complain. He has the file on the CNC now, I may get some more made up in the future.

Interestingly the ‘78 damper on my original forks has the bevelling on the holes like the ‘77 damper on the other side. These new forks, no bevelling. I find that strange as the damper bolts had the stock ‘glue’ on the bolts and were super tight to get out, which leads me to believe that the holes were bevelled from factory. Perhaps there was some crossover.

I’ll get these dampers modded and bevelled and get the forks buttoned up, really looking forward to having the bike back on the road, I’ve never ridden an XS that wasn’t completely shagged so it’s going to be a nice moment.

 

[5twins]

Yes, the XS can be made into a pretty competent running and riding bike. Granted, it will never be as good as a modern bike, but it will be fine for most of the riding we do. I run mostly on back roads between like 40 and 60mph, with occasional bursts up to 70 or 80. The XS is perfect for this.

Beveling the oil holes is pretty simple, just drill into them a little with a larger drill bit. I think I used a 3/16" on the small top holes and a 3/8" on the larger bottom holes. For the oil amount, put about 7 ounces in, or you can set the level by measuring (springs out, forks fully compressed). Setting the level at the old stand-by, 6" from the top of the tube, works well. And I just use the recommended 10wt., I don't feel the need for anything heavier.