Six-Days 125 Questions

[OUCWBOY]

Hey Shaun,
Someone has put your jackpiner into a 250 frame. The 54 means it was a 250.

Donny Smith

[Ron]

Hi Guys,

I was hoping someone would respond to my question about the different fork lengths. Is the difference in the damping rod length?

Also, do the bikes with longer forks have longer rear shocks?

Could someone advise the correct shock lengths used?

Looking down into the cylinders of the 5a and 6/b they aprear to have identical porting. Someone one has opened up the transfer at the base of the cylinder. I doubt this would make any difference.

socalmx, where are you located? I'm in Azusa.

Thanks again to everyone,
Ron

[socalmx]

Ron, I am located in Anaheim Hills....let me know if need any help with your Penton.

[firstturn]

Ron,
  I can't answer your question as to the difference in the parts for the two front ends.  I do have a set of each, but I have never compared the parts.  As far as the length of the rear shocks...I always dictate the length based on what rake angle I want on the frontend.
  Sorry that I don't have an original bike with the frontend you are talking about to give the lenght of the rear shocks.  Not much help except to how to selectthe length of your rear shocks.

Ron Carbaugh

[Ron]

Hi Guys,

I'll take the forks apart this weekend and post what I discover.
 
Ron, good point on using shock length to adjust rake. Hadn't thought about that.

I was mostly interested what Mr. Penton thought was the correct length shock to use.

What length rear shock do you use?

Socalmx, thanks for the tip on gearing, I may be carrying a few extra lb's to.

What are you using up front on the counter shaft sprocket?

Thanks for any info.
Ron

[firstturn]

Ron,
Subject:  Shock Length

Touchy subject, but here goes.  I run 13 to 13 1/2 and various spring weights.  If I need a quicker turning bike I use the longer set or for a cruser (Enduro) I use the shorter length.  As you made comment on the riders weight you need to figure how much compresstion you get when you sit on the bike.  I still think the old Curnutts and Koni were the best if you aren't riding on a modern MX track where they fade too quick[B)].  Just my take.

  Please don't start the same thread that we had on fuel mixture...this is just my opinion which Ron ask for and if it doesn't suit others, so be it[].

Ron Carbaugh

[socalmx]

I run the stock 14(?) tooth countershaft sprocket. Since it is a tapered fit, it is much easier to deal with changing out the rear sprocket. Alan B should have a 60 tooth if you want to gear down.

You can play a bit with the shock positions on the swing arm and of course, move the fork tubes up or down in the triple clamps. For Adelanto, you will want more high speed stability. Since the Penton has a long wheelbase, I leave everything set in the middle. I have never had any problems with head shake at speed doing this.

I agree with Ron's choice of shocks. I have ran a pair of vintage Konis for years and just recently installed a pair of Curnutt shocks. The Curnutts were unique for their time because they had no dampening at the top part of the travel. This was to allow the rear wheel to follow the dips as well as the bumps. These shocks are hard to come by but well worth trying to find. The only caution is that they were valved/springed for specific rider weight, riding style, and bike. I spoke with Charlie Curnutt Jr. a while back and unfortunately, he no longer has any parts for the shocks.

[Ron]

Hi Guys,

I took the two sets of forks apart last weekend and forgot to post what I found.

I was hoping the difference would be in the dampening rods, so one set would have more travel.

But the difference is in the fork tube lengths.[xx(]

The long ones are 24-3/8" and the short ones are 23-7/16".

The springs are also different lengths, but the dampening rods appear to be identical.

RonW

[jj]

Ron,

Here is what I know about the forks, maybe it will help. The shorter forks go with the single bolt narrow triple clamps and the longer forks go with the 2 bolt wider/heavier triple clamps. The top clamp on the 2 bolt version sits higher relative to the top of the frame head tube, plus the distance between it and the bottom clamp is greater, which is why it is used with the longer the fork. When you have the correct fork-clamp combination, the distance from the axle to the frame is identical (as close as I can measure ) with both sets.

From what I have observed, the narrow single bolt style came equiped on the first '72 CMF 125's, then they eventually switched to the 2 bolt design sometime before or during the '73 model run. All of the '72 175's that I have seen have the 2 bolt clamps.

So now you have a choice, weight or rigidity. I my case it usually ends up with a choice between light rust and rusted out or dented and bent.

John J Slivka

[Ron]

Hi John,

Thanks so much for the info.

I'm going to have to use the shorter set for the same reasons you mentioned, rusted and bent.

Only problem I have to spend another 4-5 hours polishing the single bolt clamps.[V]

Thanks again, RonW

[socalmx]

Ron, are you still targeting getting bike finished for Adelanto Grand Prix? Regarding the forks, since they are on 32mm the steadier the better. Using the two bolt version is best way to go.

[Ron]

socalmx,

Still have my sights on Adelanto GP. Got to get movng on my bike!

I'm still debating on buying new fork tubes to run the two bolt forks.

Do I have a limit on shocks I can use at Adelanto? I have a pair of Works Performance 4" shaft and a pair of old Koni's. Less travel with the Koni's.

Thanks, RonW