Heavy duty fork springs?

[Deni]

Hi. Has anybody used the Yamaha heavy duty fork springs, and can you tell me what they do (or how they feel) compared to stock springs or Progressive springs?
If I were upgrading my fork springs, are Progressive the only ones to get, or are Yamaha heavy duty also a big improvement?
Thanks.

[dntemp_ca]

I won a set of heavy duty springs cheap on e-bay and will be installing them in the next couple weeks...together with new fork seals, oil, new tires. Figured I tackle it all at once. I have a fairing on my 78E and the front end is pretty mushy and dives on breaking with the standard fork springs. Will know more in a few weeks after riding a bit on them and will post my opinion of h.d. as compared to the standard fork springs.

[Jerry]

A couple of manufacturers sell progressive-rate springs. If you look at the spring, you will notice the coils are closer together at one end. A progressive-rate spring takes less force to compress it the first few inches, then more force to compress it the last few inches.

The advantage is that small bumps can be absorbed more eaily, giving a better ride, while the springs are still stong enough to keep the forks from bottoming over larger bumps. Generally this results in a better/smoother ride.

OEM fork springs are linear; that is they take the same force to compress the first couple inches as the last few inches. Very predictable, also cheaper to make. To help out, some forks are air adjustable, which sets the initial force required to get the springs to compress. Lower air, softer forks, and more air, harder forks. The forks can be adjusted for a variety of load conditions.

In practice, air has a tendency to leak out, and many of us don't change our bikes all that much for different riding conditions. Unless you have a balanced air system (1 filling handles both forks or both shocks) it can be difficult to get the forks properly balanced.

IMHO, for general riding the progressive-rate springs do a better job than OEM springs. I've not used the Yamaha heavy duty units, but believe they are of linear design. Anything new is probably better than the 23+ year old springs in those forks now!

The biggest factor in setting up progressive-rate springs is setting the initial suspension "sag", or the amount the bike settles when you get on it. The sag is generally set with lengths - a few inches - of PVC pipe at the top of the spring. There can be a few attempts made before you hit on the right pre-load, although the Progressive units come with some guidelines.

I went to Progressive brand progressive-rate springs back in 2001 and have been very pleased with them. Add a fork brace, decent tires, SS brake lines and your bike will handle a whole lot better than stock!

[dntemp_ca]

Actually, the h.d. Yammy springs I have are more tightly coiled at one end...albeit only for about 2 inches.

[Deni]

Jerry, thanks. I know about their theory, I just am hoping to find someone that has used both kinds and can tell some differences. Like your opinion, I think everybody seems to like the progressive springs.

dntemp_ca, I will be interested to see what you can say after you install them. There seem to be alot of the HD springs showing up and selling for reasonable prices. That 2 inches of tighter winding at one end might be enough to absorb alot of the smaller bumps.

I'm not really unhappy with my stock springs (I don't know for sure that they are stock, since I haven't taken the forks apart yet), but will eventually do so and probably rebuild them. I can feel the difference it makes by adjusting the preloading with the cam at the top.

[dntemp_ca]

When I install the h.d. springs, where do I put the tight coil ends....top or bottom?

[MartyA]

According to Progressive, up or down does not matter, as long as they are the same.

[Deni]

The Yamaha service manual says to install the stock springs with the "greater pitch" at the bottom. It's supposed to have a smaller coil diameter on one end, and this is supposed to be at the bottom. I don't know if the HD springs are like the stock springs in this respect.

[dntemp_ca]

UPDATE......long
Well, I have the h.d. Yamaha springs installed now. Along with new OEM fork seals and new fork oil. Man, those old seals are a bear to get out!
Lessons learned & observations so far:
1) The stock and the h.d. springs look identical. Both have 59 coils. Both have a couple inches of tight coils at one end. On removal, the stock springs had the tight coils at the top, so I put the h.d. ones in like that.
2) My bike is a 78E standard and the fork cap nuts have a pre-load device in them. Mine were set at softest of the three positions and the front end was pretty mushy. I will reset the preloads at soft again just to compare the ride h.d. vs stock springs, but I plan to experiment with the three preload settings. To increase preload, get a big flathead screwdriver, insert in the flathead screw in the top of the fork cap nut, then push down hard and turn clockwise to the next detent stop.
3) A 1" or 2" chunk of 1 7/8" o.d. pvc drain pipe makes an excellent seal driver! I zipped off a chunk of pipe with the power mitre saw for clean, straight edges. Oh, before driving the seal home, take the little spring collar out of the top of the fork seal so it doesn't get buggered up! DAMHIK Then put the spring collar back in there when the seal is seated.
4) The bottoms of the forks had sludge inside them...more than I expected, but its 27 years old and I bet I'm the first one to change the fork oil! I'd recommend changing fork oil for anyone that hasn't yet. I couldn't find any real fork oil locally, so I used hydraulic jack oil which, as I've read somewhere on this forum, is a good sub.
5) Yanking down on the fork tubes didn't unseat the old seals for me. Anyway, from looking at how it's put together, I can't see how that would work. Maybe I'm missing something.
6) Everyone should make the fork tool. See forum tech tips. Two feet of threaded rod, four 19mm hex bolts, under $5 bucks, works like a charm!
7) Contrary to Clymers, rather than clamping the fork tubes in a "soft vise" (huh?) I left them in the triple clamp to break loose the bottom allen bolt. Same with reinstalling. Just didn't feel comfortable with the vise advice.

I was a bit intimidated by all the above work, but with the Clymer manual, this forum, patience, a few beers and an occasional foreign word, it was a snap!

Next, the new tires go on, clean up and repack wheel bearings, and clean out the rear master cylinder cause my back break is dragging a bit. (not looking forward to those rear rim locks!@#) Any tips?

I thought I saw a thread about working on the rear m.c. It looks near impossible to remove it and get it out of there. Anyone see that thread? Can't find it.

Will post again when I get her on the road..or..when I get in trouble with remaining work!