Anyone versed in Curnutt?

[imported_n/a]

Fellow Penton owners,
I just purchased my first Penton a 74 Hare Scrambler and I am Lovingly trying to get her back to a ridable (Vintage) condition.
One of the issues I have is with the shocks on the bike. I am told they are Curnutt shocks. I have researched the internet and found an interesting rebuild procedure for them. It looks like they where made in California and the wearing parts are standard o-rings and oil is ATF type A. The artical is from 2002 and lists Chas Curnutt and a phone number, but not in service when I tried it?
My problem is the previous owner was not a mechanic, somehow one of the rubber eye bushing was lost. I think I can rebuild the shocks but I am in need of replacement bushing and probably stiffer springs.
Anyone versed in Curnutt?
Thanks
Cappy

[Big Mac]

I've rebuilt several Curnutt shocks sets and run them on a couple of vintage bikes. I think they work surprisingly well for low-cost (used to be anyway), period correct shocks. Charles Curnutt is no longer, but his son still makes quality shocks for mountain bikes, I hear.

If you look at the history of Works Performance on their website, it says Gil Vaillancourt started the company by making parts and improvements for Curnutt shocks when Curnutt lost interest, and the Works shock design evolved from Curnutts (http://www.worksperformance.com/html/customers/gil.html) your trivia info for the day.

No one, I've found, makes any parts or different weight springs. The seals and o-rings are SAE and found easy. Shafts are heavy 1/2" with good chrome, so usually fine. I've made my own bumpers out of 3/4" rubber material from the hardware store, cut out with a cheap holesaw in my drill. There were a few spring weights and several spring lengths when they were sold, so unless you find something different off another old set, you can only stiffen things up a bit by adding the 2" or so diameter bull-rings, usually available at any hardware store, for spacers under the spring.

Hard to make them stiff enough for laid-down setups or on PV bikes. The shaft travel exceeds AHRMA's 4" limits for vintage class on the 13" or so lengths, but I've run the 14-3/8" versions (about 4-3/4" shaft travel) on a '72 Husky, '73 Penton HS and a '74 CZ and added two rings, worked sufficiently fine for my 230lb+ girth. Some guys who set up with new Works shocks or shiny Ohlins still look down their nose at you though, until you beat 'em .

Jon McLean
Lake Grove, OR

[Merlin]

.............Curnutt used one spring rate,preload was the method used to suit the rider.The principal Charles used was "dashpot" speed sensetive,no bumpers were used,as for the bushes use some vinyl tubing of the appropriate size from Home Depot's plumbing dept. As for shaft travel and AHRMA,axle travel is what the limit of 4" is,shaft travel on an old standard type pre laydown multi mount Penton is 3.5".............

[Frenfroe]

Merlin, I could never explain to my seal parts house salesman the metal cased seal like my shocks have/had. He was clueless about an "Anchor-Packing" seal like is in my old instructions. I ended up using a standard rubber lipped seal, not metal cased, and ordered from McMaster-Carr. I'm not real confident it will stay in the shock. Do you have the modern CR part number for the shaft seal?

Thanks,
Frank

[socalmx]

I purchased my first set of Curnutts for my Honda SL100 in 1973 for $35. Charles Senior had a shop in Torrance and he built the shocks based on your weight and riding preference (in my case Desert). I also am running a pair on my current Penton that I rebuilt with parts purchased over the counter from a seal and bearing house. There are a couple of generations of Curnutts. The early ones used plastic tubing and machined metal for the bushings. Later versions used machined aluminum bushings that pivoted on O rings. The early shocks used harness rings (can purchase at a hardware store) while later versions used machined aluminum spacers for preloading. I cannot say too much about how well these shock perform when set up correctly. Sag is important because the shock is designed to drop down into holes to maintain traction. Early Curnutts were only oil dampned while the later versions were gas charged. Charles Curnutt is still around and I talked him into rebuilding a pair for me about two years ago. He does not have any parts left so not worth while to try and see if he can rebuild for you. My suggestion is to go on the web and find site (search Curnutt) that has rebuild instructions and go from there. Paint wise, gray primer the bodies and use Chevy engine red-orange for the springs. Long and rambling but hope this helps.

[Big Mac]

I've used the regular double-lipped, rubber coated seals, and haven't had any problems with them coming out. Size is 1/2" I.D. x 1" O.D. by 1/2" if memory serves right, any bearing and seal house in the yellow pages should carry them standard. I get mine from McGuire Bearing in Portland (or Seattle). Yes, 4-1/4" of shock travel is like 5"-5-1/2" wheel travel for most bikes with shocks run in the up-down, least travel position...so you're left with need for the 3-1/2" (or so) travel shocks for AHRMA, which unfortunately were only about 13" length, so not the best for steering dynamics. I don't take Curnutt-shocked vintage bikes to AHRMA events.

[brian kirby]

If you have too much shock shaft travel AHRMA tech inspectors can/will put in spacers to limit you to the needed amount so dont worry about that. Dont pass up a good set of Curnutts or other shock that has a tad bit too much travel.

Brian

'72 Six Day (on loan from Ernie P.)

[socalmx]

I ran my Curnutts at Mid-Ohio last year and never got a second look. I did however get into an arguement with Dick Mann at Sand Hill (Northern California) about a pair on my Honda Elsinore. I was lucky enough to get Charles Jr. to rebuild them and he put in internal travel stops. Mr. Mann was not willing to accept my explaination up to the point where I even offered to remove the springs so he could cycle thru the travel. Double standard because there was a 75 Penton running moved up shocks that raced which should have not been allowed.

[brian kirby]

I have not seen it myself, but your story of "someone didnt like it" during tech is not rare.

The final measure of travel is actual axle travel. If you did have internal stops, it would have been a pain, but as you said you could have removed the spring and shown actual travel. They can not dispute actual travel no matter how much they might not "like" it.

Brian

'72 Six Day (on loan from Ernie P.)

[socalmx]

It is those types of situations that have soured me on riding AHRMA events. What I don't understand about AHRMA is if the technology was available then (Curnutt had a 5" travel shock available in 1971)why isn't it allowable now?

[brian kirby]

I understand the 4" rule, you have to have the limit somewhere. But you are correct, there were many bikes with more than 4" travel before '74.

Brian

'72 Six Day (on loan from Ernie P.)

[sixdazed]

Being that a lot of us are old and probably have worn out backs,knees,etc. from the short travel era probably a few inches more travel would make more sense.Even before everyone started moving up/laying down shocks in the quest for better suspension lots of guys just ran longer shocks/forks.If they eased up on the rules a bit we might save what's left of our bodies and be able to ride further into our old age!Just my opinion,
                                         Ric


ric emmal

[socalmx]

I have compensated for limited travel by increasing the cushioning effect of my behind. I knew there was a logical reason why I gained weight!