fork spring length

jayel

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changing fork oil on my 74 TX650A decided to check spring length Mikes lists the progressive springs for my year/model at 495mm (19.5) my stock springs measure 390mm (15.4 inch) couldn't find a stock spring length... think they're shot? don't have to push down the caps when re-installing them how much harder is it going to be to push another 4 inches of spring? :banghead:
 
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The parts diagram shows what appears to be a rather long preload spacer. Do you have that? If so, you probably need to leave it out if you switch springs. If you don't think you have it, maybe the P.O. stuck it in 1st, under your spring. You know how those P.O.s are, lol.
 
yeah it's got the spacers forgot I had made a couple about a inch longer to get more pre-load... edited fisrt post no pre-load on springs when using stock spacers
 
The best tool for installing fork caps is a T handle. You can push and turn at the same time, push quite a bit too. Motion Pro makes them, about $10 from your local dealer .....

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yeah got one, think you hit the nail on the head about leaving the spacers out with the longer springs tho'.... that's about the make up length.... anyone else running a 74/76 that has used the progressive springs?
 
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For my 74TX, I'm in the process of changing fork seals and installing new progressive springs with your same questions (I have the "T"handle). What about oil quantities with the new spring setup. Should we be putting in more or less oil or amounts that the manual says?
 
The later 35mm forks benefit from a bit more oil (about an ounce) so I don't see why the earlier forks wouldn't too, but you'll probably need to do some experimenting. I would put the speced amount in one leg then measure the level (spring removed, fork fully compressed). A general "rule of thumb" for many forks is to set the oil level 6" from the top. See what the stock amount of oil gives you. On the later forks, adding that extra ounce actually raises the level higher than that 6" mark, closer to about 5" (or just under that). But this seems to work well and not be too much.
 
Before you start to try to wrestle the fork cap and spring to start to catch a thread, without the spring in the fork take the cap and start to thread in and note where it starts to catch. Draw a matchline on the cap and fork. This will make it easier to know when you need to push and turn to start it to catch a thread. Good luck. JC
 
Okee Dokee Mr 5twins and Superjet I'll give that a whirl. I do have another question on the process. I'm now in the process of installing fork seals and new progressive springs. The new springs measure 495mm(19-9/16), old ones are 392mm(15-7/16) also in the tube is a 90mm(3-9/16) spacer. Shall I assume that this original spacer can be tossed and assemble each leg without?
 
Yes, leave the original spacers out. If the new springs prove too soft, you could probably add a much smaller spacer to preload them a little more, say maybe one an inch long or so.
 
Great thread! Just picking up on this as I am about to take the forks off of my '74 TX. Not sure what the PO had done, and starting to squeak a bit.
I was curious about the stock spring length.
 
Before you start to try to wrestle the fork cap and spring to start to catch a thread, without the spring in the fork take the cap and start to thread in and note where it starts to catch. Draw a matchline on the cap and fork. This will make it easier to know when you need to push and turn to start it to catch a thread. Good luck. JC
My 78 special has fork cap nuts that are 3 inches from bottom of thread to top of nut, and have a air valve in the top. They also seat on top of the top triple and have a 1 inch spacer on top of the springs under the nut. It has severe spring dive so I am looking at new springs and top nuts and oil so I can get rid of the air valve rubbish. I have previously replaced the seals and I used a f clamp to compress the nut down to the thread while I turned the nut with a inch and a half spanner and it worked well. Never seen the air valve cap on a xs before.
 
My 78 special has fork cap nuts that are 3 inches from bottom of thread to top of nut, and have a air valve in the top. They also seat on top of the top triple and have a 1 inch spacer on top of the springs under the nut. It has severe spring dive so I am looking at new springs and top nuts and oil so I can get rid of the air valve rubbish. I have previously replaced the seals and I used a f clamp to compress the nut down to the thread while I turned the nut with a inch and a half spanner and it worked well. Never seen the air valve cap on a xs before.

Hi Oldfart,
my XS11 had air valves on it's forks and Yamaha parts swap like LEGO, Gawd knows what your bike's dreaded POs had to do to keep it running.
Note that us Canadians are legally supposed to be bi-dimensional as well as bi-lingual and 1.5" = 38mm to within the usual wrench tolerance.
 
Hi Oldfart,
my XS11 had air valves on it's forks and Yamaha parts swap like LEGO, Gawd knows what your bike's dreaded POs had to do to keep it running.
Note that us Canadians are legally supposed to be bi-dimensional as well as bi-lingual and 1.5" = 38mm to within the usual wrench tolerance.
Thanks Fred, yes it has parts from many different years, it's not a 78 wiring harness, it's got the early round tail light and I've replaced the small 10litre special tank with a 15litre off an earlier model. When I replaced the fork seals the sliders were pitted so I got them re-chromed at a hard chrome shop here in brisbane and they had to straighten them as they were bent 3mm!! . When I mentioned the air caps he was mystified and said that when rebuilding forks the needs to be bled out of them.? I will be removing springs today to check length and order new cap nuts .
 
Thanks Fred, yes it has parts from many different years, it's not a 78 wiring harness, it's got the early round tail light and I've replaced the small 10litre special tank with a 15litre off an earlier model. When I replaced the fork seals the sliders were pitted so I got them re-chromed at a hard chrome shop here in Brisbane and they had to straighten them as they were bent 3mm!! . When I mentioned the air caps he was mystified and said that when rebuilding forks the needs to be bled out of them.? I will be removing springs today to check length and order new cap nuts .

Hi Oldfart,
unless you really hate the way the air caps look, just don't pump 'em up. The money saved can be better spent elsewhere.
 
G'day Fred, I've had it over 40years and never liked em they are butt ugly. The original nuts will be a lot easier to install with a tbar. I can always sell the air caps or trade em. Ride safe.
 
Not sure about your Aussie models but our U.S. models had a top cap that was adjustable. Each step added 10mm more pre-load to the springs. Although I don't change the setting on mine much, it is nice to have the option .....

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You can't buy these adjustable caps new anymore so if you wanted some, your only option would be to scrounge up some used ones. There is also a rubber cap that covers them and you really need and want that, it keeps water out .....

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Running without the protection cap and allowing water to get in can rust up the insides of the cap to the point where it seizes up and is basically ruined. Also, you need to fit a solid washer (no hole) on top of the spring between it and the cap .....

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Those preload caps would be ideal 5twins but I can't find any here. Z1 enterprises in Tampa has some about the same size without the preload but the cost to get them here defies logic. I can get 77-84 caps which are about 35mm in length and I can add a spacer , just need to work out the size as the air caps were about 75mm and had a 30mm spacer under them but with new springs and more oil as you recommend it may take more than one try to get it right. Way back when I replaced the seals I only put the amount of oil stated in the manual and I don't think I pumped them to bleed the air out. So the lack of oil could be why they were so soggy all these years and a bit hairy at sudden stops. The new springs are 484mm and my originals are 482mm so I could try them with a 70mm spacer and 15w fork oil to six inch from the top of tube.
 
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Just got the lower leg off. Being an old fart I was following the instructions from Hugh's handbuilt thread on the forum and my Haynes manual but I forgot there is a stepped nylon bush that fit's tightly into the top of the damper rod which stops any tools from locking it while the Allen bolt is removed. The nylon bush is not mentioned in any threads or any of the manuals that I have seen or heard of and I had totally forgotten about it from 20 odd years ago when I replaced the seals . Turning the forks upside down they still did not move so I used a long bar with a coarse thread screw on the end to jam into the 8mm hole in the centre of the bush and pull it out so I could stop the damper from turning after I got the Allen bolt loose with the rattle gun. Anyone seen this type of forks.? At least reassembly will be easier.
 
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