125-200cc 125 Powervalve Spring--How do I get to it?

I'm following in Wallybean's footsteps and am trying out a lighter power valve spring. I looked at the parts diagram in my manual, and it looks like it's accessed through the small circular cover at the two o'clock position beside the clutch cover. I pulled that cover off, but could get no further. It looks like the centrifugal governor is the next thing to come out, but I couldn't get it to wiggle out. What's the trick?

Dfeckel,

Pull the cover off the pv linkage, unsrew the 8 mm head bolt on the bottom end that is connected to the shaft that is turned by the govenor, I used a small screw driver to pop the linkage off the shaft. It will always be a little sticky because the govenor is always pre-loaded a little. Now pull the round cover off that covers the govenor. While gently wiggling the end of the shaft of the govenor turn the shaft to the linkage about a 1/4 turn clockwise. The Govenor will pop out, keep the linkage shaft at this point and it will go right back to the correct place when you slip the govenor back in.

Now when you have the govenor in your hand depress the entire ball containing round end towards the gear end. This will allow the retaining pin to slip out. Now holding onto the gear end pull the entire round end off in one piece. This keeps the balls in the cup and avoids having to chase them around the shop table. You will now have the spring open to be slipped off. Make sure you note the placement of the shim cup that the spring rides on between the spring and ball cup. Slip in the new spring and reassemble in the order it came apart. Now is a good time to lube the ball ends of the linkage that the plastic link fits over. Use the same oil you are using in your tranny. The plastic doesn't work as well with any of the dry lubes. Make sure that the pv is operating easily and returns to closed with no sticking. I now have 4 different springs that I can use. I have settled on a music wire spring that is 1.25" long by .975" od with a .072 wire diameter. This is just a refinement of the spring I liked best which was 1.0" long and had a .074 wire diameter. With that spring I had to shim the spring an additional 60 thousand's washer to provide enough pre-load. These springs are ~$8 each at Century spring. I ordered 6 different springs so I could exceed their $40 minimum. I have one extra of each of the 4 different springs. 2 stiffer and 1 softer. The softest one opens the pv at about 5500 rpm and is a bit tougher to ride in tight single track unless you can ride like Antoine Meo. It feels like you are just above idle when Katy bar the door we are flying now.

Some figures for initial opening pressures for each of the springs I have used:

.064 wire dia ~ 12 lbs opens @ ~5000 rpm
.072 " " ~ 18 lbs ~6200 rpm this is the spring I like
.074 ~ 20 lbs ~6200 rpm this is a .25" shorter spring
.082 ~ 28 lbs ~6800 rpm
.097 ~ 40 lbs ~7200 rpm
.105 ~ 50 lbs ~8000 rpm stock spring

The opening rpm to spring dia. graph is definitely not a straight line. The spring I am using gives you a solid 5000 rpm pipe. It really pulls hard the entire time and yet it still leaves you just about the right amount of low end/mid for negotiating tight stuff or putting.

Hope all this drivel helps,
Walt

If you want to try some of these springs just send me a pm and I will get them to you and you can send me back what you don't use and of course the spring is $8

That sounds a little more involved then I was hoping. Now I hope when I send my stuff off to EG he puts all that together and I don't have to mess with it. Great detail Walt but I sure hope I don't need to do what I just read. Thanks for the great write up. dfeckel you got all that?

Sir! Yes, sir!

I ain't skeered!

Thanks Wallybean for the info. You should really be talking with Kelly about marketing the springs that work best so all us 125 nutjobs can buy a nice $65 set of three PV springs to tailor the power to our liking. If the springs really cost only $8 each, then you buy a hundred, bundle them into three packs, take a few pictures the next time you swap out a spring, add the pics to the text in your reply above, print 'em up, and you got a product!


I would absolutely buy that product. Well, maybe not now that I already have a new spring to put in, because the recommended spring (the .072" x 1.25") ended up costing $45 after shipping from the supplier you mentioned a while back (not the new supplier you just mentioned). $65 for three springs with clear printed instructions would be awesome.

Yes pics are my friend. Hey please give us your ride impressions once you haveit all back together.

Guys,

It really is far easier than it sounds. If I didn't have to remove the pipe the whole operation takes maybe 2 minutes, 5 with the pipe removal. It took me all of 15 minutes the first time when I had to chase 4 little ball bearings all over the bench.

I have now done it so many times I could literally do it with a blind fold on. I will put together a pictorial instruction of the process and post it. I will give all this stuff and part numbers to Kelly and maybe he can make a few bucks.

Walt

That will be greatly appreciated Walt, thanks.

I took pictures while changing my PV spring.



First you need to take these two covers off.



You can see here that the centrifugal governor is retained on the shaft with a pin. Pushing the governor in will cause the PV linkage to raise. The spring we're changing resists this pushing and closes the powervalves.



Push the governor in so you can slip the retaining pin out.



When you take out the two bolts which hold the linkage arm onto the shaft, the shaft will rotate and allow the governor to slide past where the retaining pin was. The best way to take this apart is to keep a hand on the governor as you remove the linkage bolts. When the linkage separates, the PV spring will try to shoot the governor parts across the garage. You can see the PV spring under the "dish" part of the governor. Just substitute the replacement spring for the stocker, make sure it is properly seated as you push the governor assembly into place, put the pin back in, and reattach the linkage.

Check to make sure the linkage moves freely when you push it up and that it snaps back under the pressure of the new spring. The new spring wasn't strong enough to return the linkage after I pushed it up, but the plastic link was binding on the lower ball--a little grease fixed that right up.

I haven't had the chance to actually ride the bike since replacing the spring, so I'll have to report back when I get a little saddle time.

Thanks again, Wallybean!

Glad you got it done. You did it the way I did the first time. After doing this many times to try all the different springs, I have stream lined the process a little. I don't remove the retaining pin until I have the whole assembly on the bench. To pull it out I just take the bolt off that holds the linkage on. You can just see the bolt in the right side of two of your pictures and it is removed in the one shot of the the linkage. I just then gently pry the linkage off the shaft and while wiggling the end of the govenor I rotate that shaft clockwise. Out pops the govenor and you can make all the changes at the bench. This way you don't have to take the cup and balls off in a tough place to control them. If you have the 1" spring and start to have problems with the linkage returning to closed, either place a shim on the back side of the spring cup against the bearing(.0625" was what I used) to preload the spring or I can get you the 1.25" spring that I am now using.

Next week I am going to pursue a conical compression spring that offers a much more progressive opening of the Power Valve. Currently I think Drew Smith from WER will be helping me sell enough of these springs to defray the cost of the engineering and manufacture. The spring we need will more than likely not be an off the shelf spring like the single rate springs we are now using. While the spring I am now using is a large improvement over stock, I think it can still be improved on for tight single track use. If I was an MX'er I wouldn't touch anything about my current setup. It will always be on the pipe and will at least eliminate a number of shifts every lap. It pulls really hard from 6000-11000 rpm, almost 4 stroke like except it revs so fast. For tight woods riding it transitions quickly from the mid-range to wfo. It still has tons of room to ride below the pv opening and this motor really runs well down there for a 144. What I would like is a govenor action that starts to open at about 5000 rpm but doesn't fully open until about 8000 rpm(~stock). This would make the bike more predictable in the transition from mid to top end. Kind of Gas Gas like if you know what I am talking about.

I will have it all apart either tomorrow or Tuesday and I will take further pics and PV comparison picks.

Walt

Thanks for the pics and info I appreciate your help defeckel and Walt. When I get around to sending mine off for the EG144 kit this will help me big time.

PS, Nice pics and well done.

Walt

Man Walt, where were you when I had a 125!! I think you were on a 250. Thanks for taking the time in doing this. I used to spend hours trying to shim these things up to change the Characteristic of the motor. I have a buddy I ride with who is going to be contacting you about these. At least that way I can get my fix of tinkering with the power valve again. The 125 is so much easier to access than the WR 250 on this but I think it needs a little tweaking as well. Great Job!!

I am going to have to try some tinkering. I will buy a spring from Walt if it will help cover the cost of manufacturing. But a kit with several springs would be awesome.

JS

That is so much easier than getting at the spring in a ktm 125/200. From memory, not all guaranteed right, That set up uses two springs one inside the other both shimmed the first one is soft and opens real soon then it bumps against the stiffer one. I just removed balls on this model. Probably going the opposite way from most folks. They are back in now. Any idea where you could get balls of that size made of different materials with different densities? IF the balls get loose all they do is crack that little cover which is not real expensive.

Fran

Fran

Hi guys, I'm Italian and I've got a new WR 125 2010 in my garage!
I've got a question for you. Do you have to setting/adjust the position of power valve after every spring change ?
Many thanks

No, Thank you Kelly for all you do I like doing this stuff and the object is not to make money but to offer a service. I will put together several options for you guys, several springs in a kit or individual springs, etc. and charge only enough to cover the costs. This really isn't a money maker anyway the volume is too low. What I will do is put the options out there and when I have enough orders from you guys and Drew's guys I will make the order and send the springs out. I will do a flat rate shipping using USPS(cheapest). Winter is the time when I have lots of time so this should happen quickly.

If you want to order now for the 3 spring, single rate spring kit just pm me and I will start the list and place an order before Christmas. These springs will be in $8 each neighborhood.

Walt

Fran,

I tried some tungsten carbide balls. I had no idea that this metal is slightly magnetic and wants to stay close to the center shaft and maintain its place in the cup. This force seems to counter act the added centrifugal force of the heavier weight of the balls. These are fairly small balls and surrounded on all sides by steel and this contact area just overrides the extra outward force. In other words I experienced no change in action between the steel balls and the TC balls that are twice as heavy.

Walt

Thanks Walt for taking the time and being willing to do the experimenting for us and then be willing to locate and sell us the springs we need. Once I get my EG 144 kit installed I may want to change things up so I will give you a call. Thanks for going outside the box for us; this 125/144 rider really appreciates it!