Fork Spring Length

BigGeorge · Full Member Joined: Apr 13, 2008 Posts: 267

I removed the fork springs on my 79xs and noticed they looked like progressively wound springs. I measured the free length which is 19" but the Clymer manual says stock springs should be 24''. I bought this bike from the original owner who swears that the front end has never been apart or had the springs changed. Anyone else run into this? Does anyone know for sure what the stock length should be? Thanks.............BG

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

According to the factory shop manual, the length should be 482mm or 18.98", so that 19" sounds about right. The Clymer may be referring to pre '78 springs, the type used before the 3-way spring pre-load top cap was installed.

Retiredgentleman · Posted: December 8, 2008, 2:21 am Post subject: Re: Fork Spring Length

The Haynes manual lists fork springs as 18.98" for 78 to 83 years. When I put in new fork seals on my 78SE, the springs were close to this measurement. The springs have tighter winding at one end. The tighter windings are installed at the top end of the spring.

BigGeorge · Full Member Joined: Apr 13, 2008 Posts: 267

Thanks 5 twins. I re read the Clymer and that length 24.0" or 610mm was for 1978 and later models but its not the first mistake I've found in the Clymer manual. But thanks for looking up the stock length for me.

Thanks also Retired Gentleman. You are correct in that the springs are tighter wound at one end giving the impression they are progressive and yes the tighter windings were at the top as you said.

Looks like everything is within specs and not leaking so I'll change the fork oil and leave well enough alone for now. Thanks again for both your help........BG

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Put about 7 ounces in each leg instead of the specified near 6. These 35mm forks just plain work better with a bit more oil than stock.

BigGeorge · Full Member Joined: Apr 13, 2008 Posts: 267

Yep I read alot of your posts 5twins and will go with 7 oz. I measured the amount I took out of eack leg and got exactly 5.5 ounces from each. One quick question. There is alot of black resedue in the fork oil I removed. Can I just flush out the forks with ATF and drain well then add fresh fork oil without disassembling the entire fork?...............BG

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Yes, you can flush them. I would recommend kerosene, then let them drip dry for a few days. Put 5 or 6 oz. in, pump them up and down a bunch of times, then drain. If it comes out really dirty, you might want to repeat the procedure.

Retiredgentleman · Posted: December 8, 2008, 1:42 pm Post subject: Re: Fork Spring Length

BigGeorge; When I got my bike the forks were mushy and had more front end dive than I wanted. Drained the old black oil and put in 7 oz. of 10W oil, but it was still to soft. After changing the fork seals, I put in 7 oz. of 15W40, and forks work much better; I like the firmer damping. Others will have different opinions, but I found 10W to thin.

metalredneck · Full Member Joined: Aug 04, 2008 Posts: 308

After replacing the seals on mine, I flushed 'em out with Brake parts cleaner, and filled 'em with Chrysler ATF+4. It is synthetic, and has the most magic seal-swelling additives possible, because Chrysler knows their trannies suck. Holds the road against my buddy's ol' Ducati 750. Very Happy

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

If you plan on installing aftermarket progressive springs, I suggest you go with the real Progressive Suspension ones. I have the ones from Mike's and while they work fine, since he recently raised his price nearly $25, they're not a good deal anymore. You can get the real original Progressive Suspension ones now for the same price, sometimes less if you shop around.

BigGeorge · Full Member Joined: Apr 13, 2008 Posts: 267

Thanks for all the info guys....
5twins, I stopped by that cycle shop in Springville today and picked up some 15w fork oil. The guy behind the counter said some people are using ATF with good results but he recommended the 15w Belray.... As for the springs I'll know better once I'm able to ride this bike if I want to go to the progressives or not. I see Mikes prices are the same as real progressives
Thanks again all good info..............BG

oldskoolcool · Full Member Joined: Sep 08, 2007 Posts: 372

i filled mine with 20-50 as it had waay to much dive when braking. all gud now.

yamaman · Posted: December 11, 2008, 12:36 pm Post subject: Re: Fork Spring Length

I had a bottle of 10W & one of 15W in the shed, so I mixed them up together and made some 12.5W (at least thats what I think I made) - love it!

xsleo · Posted: December 12, 2008, 5:38 am Post subject: Re: Fork Spring Length

the tx 650a and the xs650b and c the spring free length is 15.57 inches, 395.5 mm. the d model free length18.52 inches, 470.5 mm. i used kero to flush my 79 forks that i have on my 75. drained the oil, pulled the springs. put about 8 oz's kero in each fork. pumped the forks up and down a dozen times or so . drained out the kero. did it a second time. let drain . put in some 10w30 motor oil, pumped the forks 6 or 8 times. drained the oil. filled with 7 oz's of the 10w30 oil. pumped them a few times, with the forks compressed i measured down to the oil and added a little to the low tube to get the same measure ment in both tubes. put springs back in and got both adjusters in the caps working then put them back together. works fine so far only rode a little bit before tearing engine down for rebuild

What Happened to 650rider.com?

Yamaha xs650