Forks get stuck

[Quinn]

79 forks (35mm)
I just went for my first test ride and noticed that the ride was pretty rough, upon further investigation I noticed that the forks had compressed but did not return. *I though I had maybe done something wrong when I took them apart and then reassembled so I thought I'd tear them down again.

After removing the forks from the bike, and then removing the top caps & springs I moved on to the lower bolt that holds the dampening rod - all of this went ok. *But now I found that the fork tube was stuck to the lower fork. *I actually had to put the lower fork into a large vice and then use a long rod to tap out the fork. *Btw: both forks were like this. *I didn't think much of it at the time but is this typical? *Shouldn't the fork tube be able to travel the whole distance of the lower fork without getting stuck?

Anyway I did the Minton mods (enlarged all the wholes - 4 lower and 2 upper), reassembled and started adding oil (10w, 169 ml). *I read on some other posts that you are supposed to compress and decompress the forks to purge any air bubbles and before adding the springs and capping off. *I did this or at least I tried to... When compressing the tubes I found that they would get stuck again. *I managed to get them decompressed after a lot of pulling but it wasn't easy. *Because I only had two hands I decided to put them back in the triple trees and then added the springs and the caps.

The bikes not running (waiting for some parts) so I couldn't go for a test ride so I decide to try to use body weight to see if I had any suspension movement (I weigh 170)... No movement. *I then decide to get a running start and clamp on the from brake - the forks compressed about an inch and then stayed there (no rebound). *I put the bike on a lift and then hit the tire with a rubber mallet - the forks returned to full length. *I then decided to anchor the front wheel and then use ratcheting tie downs to pull the front down (like when it's being transported on a truck). The front was hard to compress and then when I released the tie downs the front stated compressed. *Again with the lift and rubber mallet and the forks returned. *I even cracked open the fork caps when compressed thinking that I might have some sort of air lock but this seemed to have no effect one way or the other.

Thanks for your time and Help!

Quinn

 

[jd750ace]

If they hang up like that as individuals it is usually due to bent tubes. Worn bushings and seals usually work just fine, but maybe leak under dynamic load. Sometimes you can get the axle spacers mixed up on some bikes, and they will do it on the bike but not off. Put your upper tubes in the clamp. Rotate the upper part of the tube in the clamp. It should turn 360 degrees freely. If it does, move it up 2 inches in the triple clamp and do it a again. Keep sliding it up until you have to room to work with. If the tube binds and releases, or will not slide up with hand force at any point, it is bent.
Other things could be wrong, but this is a quick check to point you in the right direction.

 

[5twins]

Something's definitely wrong with your forks. The lower should slide up and down the tube with very little resistance and should come right off when you remove the bottom bolt. Maybe your tubes are bent? Maybe someone swapped some parts and they're not compatible (lowers, damper rods, tubes)? Post some pics of all your components and maybe we can see something that's not right.

 

[Quinn]

Hey thanks guys. Now that you mention it, it makes perfect sense that these tubes are most likely bent. If they are bent can they be fixed? Maybe i could rob the tubes from my 74 that's still in pieces (also 35mm I believe.)? Or is it better just to buy new ones from Mikes?

I'll post some pics in the next few days.

Thanks again.

 

[irristeve]

I have straitend tubes but at the price Mikes sells them at thats where Id be,also on those dampners that you drilled youl notice a small plastic seal,very cheap from Yamaha if they still have some,that seal makes the dampner work right & suports the bottom of the tube,possibly a bit of wear ring also good luck

 

[gggGary]

pre 77 are 34mm tubes.

 

[Quinn]

I have straitend tubes but at the price Mikes sells them at thats where Id be,also on those dampners that you drilled youl notice a small plastic seal,very cheap from Yamaha if they still have some,that seal makes the dampner work right & suports the bottom of the tube,possibly a bit of wear ring also good luck

Mikes is out of stock right now, but I agree a fair price. The dampener did still have the orange plastic seals and they looked pretty good.

Thanks!

 

[Quinn]

pre 77 are 34mm tubes.

Yeah Gary, that's what i've been told too. However i think that somewhere in this bikes past life it may have had a front end upgrade. Stock photos show the brake caliper to the front but this bike came with the caliper to the rear. I also triple checked the diameter with a calibrating tool and it measures exactly the same as the one on the 79 - 35mm.

 

[CDNTX650]

if it has the newer style brake caliper on it then they are 35mm forks....easy tell.

 

[Quinn]

OK good to know!

 

[gggGary]

I think I am confused The first picture appears in all ways I can tell to be a 72 with 34mm forks, the second picture looks like a 77 to me but that is mainly from the gas tank paint and decals, that bike does look like it has 35mm forks.

 

[Quinn]

Your probably right about the first photo - i just posted the first image that i could find when i google'd 1974 XS650. Anyway thanks for confirming my forks in the second photo..

 

[Dusty]

You can straighten your tubes yourself. I've done it a few times. make 3 wooden v-blocks,and a big c-clamp. i think you have a tolerance of .009 of run out. Bridge the tube over 2 blocks,and set the 3rd on top of the tube with the bend up. Use the c-clamp to draw it down. If the tubes are in good shape,and only out a little, I would try this before buying new ones. Mikes is out of stock on em anyway. Try it???

 

[Quinn]

Hey Dusty, Thanks for the tip - I'll give it a shot and post my results later in the week.

 

[gggGary]

Quinn I have a set of forks I am working on apart. (Don't ask me about old seal removal right now, grr) Without the springs to prevent bottoming the tubes will "stick" in the bottom of the lowers. It is the spring and the rest of the parts that keep the tube from going too far down and getting stuck. They need the rest of the insides to prevent them from "bottoming" and getting stuck. Check that you have all of the parts in the picture installed? Especially part #10 the "rebound spring"

 

[5twins]

#10 is a top out spring and appeared in '78. '77 forks don't use it but it can be added.

 

[gggGary]

You beat me to the correction, thanks 5 twins. I'm putting a set of the mikesxs cartridge emulators in a set of forks I'm doing for the 79 One side done Except for the oil.
Seems straight forward, drilling the bigger holes in the damper tubes really removes some metal from the tubes. He recommends using 77 caps to help compensate for the extra length of the emulator under the spring. I had a set so that's what I'll use. The springs were still at original length. The bike will get a set of tapered steering bearings which it REALLY needs, it don't want to turn. I am going to bolt a MikesXS rotor on it too. Brakes are overhauled with new piston and master cylinder kit so the front should be good to go.

 

[jd750ace]

What springs are you using Gary, and do Mikes emulators come with reccomended starting settings for the pop-off spring? I've only done Race Tech, so I'm Curious before I get asked to do a set!

 

[gggGary]

Staying with the stock springs, yes he gives recomended settings, 2 turns in from touching for street 4 turns in for race or uh beefy riders. range of 1/2 to 7 turns.
15 weight 6" down from the top with no springs, tubes contracted IIRC Ride report to follow. It's getting a new front tire but haven't got a back one yet so no cornering heroics from me not that I push that hard anyways.

Oh I messed around with pushing the tube all the way into the lower and the tube would "stick" at some twists but not if I rotated it in other directions.

 

[jd750ace]

That seems odd with the twists. So, if you have the extra Minton Mod holes, you just blow them out to the point of ineffectivity, right? I think on my SV it went from 2 3/16 holes to 4 5/16 holes for the emulators. I did the front and back at the same time and installed a GSX-R750 rear shock with the same straight rate (.9kg/MM, I'm a good sized fella) and the bike was just incredible. I didn't realize it until about the 4th run after the mods, since I had installed new Conti Motion tires as well, but I had replaced my worn out footpegs with pegs with no feelers. I was accustomed to scraping one on certain curves, and I went thru them 4 or 5 times thinking I was pussy-footing it since I hadn't touched a peg, until I did, in a left hander, and I thought I was going to dump it! That's when I realized that I had built about 5-7 degrees more lean into it before touchdown, as I had no feelers on the pegs, and the GSX-R shock raised the rear close to 3/4 of an inch. I really love the way it feels, but I ride the front wheel hard on anything, so my front end has to be happy. I'm sure it will be well ahead of stock. Looking forward to your report.