32mm fork problems 125cc 6-day

[garrettccovington]

When I went racing at CE, the front Forks were horrible.  I'm trying to get this bike ready for the Jan 10th Race and I rather solve the Fork issue than the Shifting issue.  The back end has a set of Boge-mulholands and they were great.  
This is what I did before the race, Changed fork seals, cleaned out the caps and put a new little spring and ball in each. Filled each tube with 150 cc of maxum 5 weight oil.  The manual says 135cc, but, I read somewhere that a little more oil will stiffen things up.
Off of the jumps the front end would hit so hard I thought the bike would break in 2. I am 60lbs heavier now, but, nobody could tell me if the forks were bottoming out.  It almost felt like they were locking up in mid-stroke.  Thankfully the rear shocks worked fantastic.

Note: My wife used the bike as a shelf for 15 + years. She threw the original seat away, cause, She couldn't store her Lead, 1 ft sq blocks, level on top of it.  So maybe the springs are shot.

G

72 six-day

[gooddirt]

Your springs could be sacked out. If you are over 200lbs the 35 mm forks would work out better for you. LG

[joe novak]

Hello,  What I suggest is that you work at the front forks in a methodical manner.  What I would do first is to place a zip-tie snuggly around a fork tube nearest the leg.  As you ride, the zip-tie will slide up the fork tube indicating how much fork travel is being used.  I believe the 32 mm Cerianni forks have 6" of travel.  Be sure that you tighten the front axle the correct way.  I believe the axle nut needs to be tightened first, then the fork leg clamp closest to the nut.  Next, the other fork leg needs to be centered over the axle.  I do this visually, first, then with locking the front brake, compress the forks as far as I can (I just push hard on the handlebars).  I would remove the fork caps and springs (leave the tubes right in the triple clamps).  Be sure that the springs are not broken.  Check to be sure the legs slides easily to full compression without binding.   I know you did not make this mistake, but I have heard of people filling the forks to the top with oil, then wondering why the ride is so harsh.  Fluids tend to be incompressible.   5 wt. fork oil sounds light to me.  Did you say you were about 190# with riding gear?   Keep us informed with your progress with the forks and suspension.   joe

[Dwight Rudder]

150cc will not help as it will just blow the oil out the vent.  You would have to plug the vent to make more oil help.
135cc will be fine.  I use 7.5wt and it works great.  I found 5wt way too soft.  10wt works good if you weigh over 200lbs.
Dwight[8D]

[garrettccovington]

I'm right around 195 lbs with gear  Those are a couple of good Ideas. You know, I was in a hurry the night before changing the front tire and maybee I didn't tighten the front axle correctly.  I also like the one about the zip tie and checking travel.  I'm gonna check it out on Tuesday.

I went to the bike show today in Long Beach and Race Tech can rebuild mine for around a Million Dollars.  I was sold, my wife said no.
Thanks for the Ideas.

G


72 six-day

[garrettccovington]

Changing the Oil weight to 7.5 sounds like another thing I will do Tuesday.  I hate to do it, But I was thinking of adding a little spacer too to stiffen up the springs a tad.  I can live with the overshifting into 2nd, but the fork has got to get better.

G

72 six-day

[Larry Perkins]

You need 20-30wt fork oil in my opinion.

Larry P

[joe novak]

I agree with Larry.  5 wt. is way to thin.  I think 20 wt. would be better.  Thinner oil will help if your springs are weak.  Not a bad idea to add a shim on top if the springs sag.  Do the springs need to be lightly compressed when you install the fork caps, or do they sag into the fork tubes?   joe

[garrettccovington]

You can put the caps on with out pushing on the springs at all they sit about 1 inch below the top of the fork.

G






72 six-day

[garrettccovington]

I ordered the Penton repair handbook from Al B. this morning and suggested trying the 20 to 30 weight oil, checking wheel alignment and adding a little peice of spring to take up sag.  Thats what i will do tommorrow.

G

72 six-day

[socalmx]

I have always heard that if you add a piece of spring it actually softens up the overall spring rate. I live in Anaheim Hills and have a '72 with 32mm forks if you want to compare your forks to another set.

quote:Originally posted by garrettccovington

I ordered the Penton repair handbook from Al B. this morning and suggested trying the 20 to 30 weight oil, checking wheel alignment and adding a little peice of spring to take up sag.  Thats what i will do tommorrow.

G

72 six-day

[brian kirby]

Adding spring will soften the rate, all other things being equal a longer spring is softer. If you want to preload the spring cut some PVC pipe the length you want. I set up my Berkshire's fork with some preload spacers (about 3/4 inch long I think, its been a while) and I use ATF which is somewhere around 7.5W at a relatively high level, I think I set it at 5" from the top springs out and collapsed. This gives good static sag (bare minimum) and the high oil level with relatively thin oil gives good small bump performance and good bottoming resistance too. I only weigh 140lbs though so a more "normal" size person might need heavier weight oil.

Brian

'72 Berkshire

[Lloyd Boland]

Garrett, if I remember, there was a topic on oil height many months ago, maybe a couple years ago.  I typically measure my the height the same way Brian does.  Springs out and the forks completely compressed.  I then measure from the top of the tube to the oil height.(Make sure the forks are vertical.)  That way you are sure both legs have equal height, and can adjust up or down from there.  I am not sure what the height would be for your forks since I don't have the same type of forks.  I also use a pre-load on my springs using PVC.  Check the search feature and see if you can locate the height that most of these guys recommend, Brian may be correct.
Lloyd

[garrettccovington]

I did a search on the topic before CE and that is where I got the 150cc and 5 weight oil.  Looks like tommorrow I will have a full day of testing in front of me.  PVC tubing, different weights of oil and spring additions.  Good thing about tommorrow, All the whoops, dust and deep sand should be gone.  Thats if it rained in Barstow today. I'm in Chino Hills today and it is pooring.
 Thanks for the invite Socalmx, but, I think this is just going to take some testing.  

G

72 six-day

[joe novak]

ERROR ABOVE.   What I meant to say is that THICKER oil will help if your fork springs are weak (not thinner).   I would say your springs are sagging about 1", and you need to take up that space.  I base this on four sets of Cerianni forks sitting in front of me: steel tank 35's, 32's, 35's, and ribbed 35's.  I like Brian and Lloyd's suggestion of using PVC spacers.   It seems to be unanimous that you need to slow down the fork action by going to a thicker oil.  I agree with Al and Larry; you need to switch to at least 20 wt. to make the difference you want.