Ceriani fork set up

[skiracer]

Hi guys.  I have a question pertaining to the set up of Ceriani forks.  I have an extensive background in motocross from many years ago.  In rebuilding my MC 5 this winter, I set the forks as my past experience has taught me.  They have been fine up until an enduro I went to a couple of weeks ago.  The course was a typical Northeast course; tight, lots of rocks, roots, and very slippery slimmy mud.  My bike would not hold a fine all day.  I fought all day long.  In the beginning I thought maybe my air pressure was too high, so I dropped it down to around 9 or 10, but that didn't change anything.  

SO, my question to all of you is, there any way to set up the forks to better handle the slower speeds of an enduro, and help keep the wheel where I point it?  

Thanks, James
Original owner 1976 250 MC 5  

[john durrill]

James,
 I am far from an expert but i can pass on what we have learned from the Pentons we have owned and ridden ,this last one in particular .
 Your MC5 are they the leading axle forks or ones with the axle center of the lower leg?
 The stock springs that came in the non leading axle forks were pretty good for enduro's and trail riding. I think they were 23 lb springs.
 Sag the front out about 1/4 the travel and the rear at 1/3. If you weigh more than 185lbs or ride aggressively use ATF for fork oil.
 Don't run much preload on the springs. The reason I say this is when we first put the 35 mm forks on my 73 Sachs Penton, we bought new springs. The old one were twisted and distorted. They were supposed to be 23 LB springs but were at least 25lbs or higher. We had the same problem you did . The front would not work right , it would kick on small bumps and not hold unless were were really hauling the freight. Not a good idea on Trails you dont know or could meet someone coming the other way on.
 I found some old 23 lb, 35 mm ceri. springs and cut them down to just contact the top nut about 1/4 inch from tight and the they worked great. ( about 1/4 inch of preload ). That got my sag at just about 1/4 of the forks travel. We used 10 Weight fork oil at 5.5 inches from the top.
With my 200 lb bike it worked well. We rode a 2 day Dual Sport this spring with the bike set up like that and it worked good. Bottomed out some in the whoops but it tracked good in the corners. We changed to ATF this fall , measured the level out at 5.5 inches from the top  of the fork tube for a 2 day dual sport ride with Rick Grant and the bike handle great , did not bottom out in the whoops at the speed I was running and handled good in the corners. It was the right combo for my 200 lb bike , my weight and my riding speeds.
 I think your setup while good for MX may be similar to what we had at the start on my bike.
 If I'm on the right track you should be able to check the sag on your front forks and it will be different than the 1/4 we have on ours now. We did the rear shocks  at 1/3 the travel per the Works engineer and they do the job very well. If you can do the sag at that % and play with the oil level and weight, you should see the same results we did.
Your bike is a little heavier But the principle should be the same.
 We ended up with about 6.25 inches travel in the rear and 7 inches in the front. That was what the Works guy recommended on front travel to have balance between front and rear suspension . We went with more rear travel to allow me some more years to ride. Had to give my neck vertebra a little help because some are fused together now chuckle chuckle!!!
 I hope others will jump in here and add more. This did work for me on my bike but like i said I am no way an expert on this.
 Hope this did help some.
John D.

[tomale]

John is quite right. In the old daze we use air pressure to stiffen our forks to elimate the bottoming out. but it is a poor trade off.If you are having trouble with bottoming out, adding preload or air to your forks will only get you what you already have a bike that does not turn well.. and It does not work for Motocross either. Doing as John suggested works very well on my MC 5.  Also, make sure that the rear shocks are set up with the right amount of sag. Too much and it will make the bike wallow in the corners. Not enough sag and the bike will corner well but the rear wheel will not hook up well... Most people do not spend enough time setting up their bike for their current weight and your riding skills... again as John has suggested, having the bike balanced will give your bike the best chance of handling as well as it was desgined.... Once you have the right weight springs and they are the right length and if you still have trouble with the bike bottoming out the thing to do is to 1/4 inch of oil to each  fork leg...(add even more if it is still not enough) notice John and I did not say a specific amount of oil.... the reality is that each fork leg is not exactly alike. The reason for using a measurement is because it equalizes the forklegs. by doing so you allow the forks to act as a air shock... but this time balanced. the adding of oil now allows you to elimate the bottoming out with out changing the fork action within the first few inches of travel.....I hope this helps. if need be email me and I will send you my phone number and we can talk...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)
72'sixday (project bike)

[skiracer]

John and Tom,

Thanks for the detailed info!  WOW!!!  I too have air on the forks.  I don't know what the pressure was during the event.  Are you saying to eliminate the air all together?  I wasn't having problems with bottoming out, just not holding any lines on the trail.  Question: On measuring the height of the oil in the tubes, is the tube extended to full length, or compressed all the way to the bottom.  When I redid the forks last winter, I used the measurement method as listed shop manual.  I am a little reluctant to loose any travel on the bike....   But I guess six inches of great suspension is better than nine inches of suspension that doesn't work for the application.  I'll give it a try, and see what happens!  Thanks again for your help.  Motor On!!!!

Thanks, James
Original owner 1976 250 MC 5  

[john durrill]

James ,
 It sounds like if you are not bottoming out you are not useing all the travel now. I dont add air and keep the vent's in the caps working. They are springloaded on my bike and use a ball bearing to seal unless the air presure rises enough to over come the spring tension.
 We measure the oil level with forks compressed and the springs out.
 You will not loose any travel like that. It should make the forks track the ground  smoother. If you can call Thom. He will save you a lot of time and hair pulling chuckle chuckle!
 John D.

[skiracer]

Thanks John, I will call him!

[Gavin Housh]

It might not be a bad time to check the condition of your steering head bearings. Bad bearings can also cause funny steering. Gavin

[Lew Mayer]

John, what type ATF, Dexron? Type F? or doesn't it matter?

Lew Mayer

[brian kirby]

Never run air pressure in your forks, it is a band-aid gimick. The valves should only be used to bleed excess pressure. Set up the forks as John said with springs of a rate so that you can run very little preload to get your proper sag. Too much preload means your springs are too soft and preloading only helps static sag, once you get under way they will be too soft. I think in your situation, I bet zero air pressure would probably be perfect for enduro/trail use.

Lew, for fork use it does not matter what type, they are all the same viscosity, but if you are using it in a transmission only use Type-F for old Ford transmissions, everything else has friction modifiers to make the auto trans shift smooth that will cause a wet clutch in a motorcycle to slip.

Brian

[wfopete]

Along with steering bearings, be mindful of your fork alignment and triple clamps.  Check your forks action for sticking/binding both on and off the bike.  An old "back in the day" technique I used and still use today is upon reassembling the front end, the last thing i do is; I loosen the front axle, get the front wheel off the ground and give it a good spin (in direction of travel).  While the front wheel is spinning apply the front brake HARD and hold it on while you tighten the front axle.  This works best with a helper. The theory is at this technique will help "center" the hub/wheel & backing plate for best brake performance & accurate steering.  When you spoke of air pressure you were referring to tyre air pressure or air pressure in the forks?  Your tyre pressure & type of tyre can have a big impact on woods VS MX performance. You wouldn't be the first person to roll out of the garage with 35+ psi in the tyres!

Good luck.


Pete Petrick
175 Jackpiner
Slow but Good

[john durrill]

Lew,
 We have always used Type F . It worked in the Sachs tranny and the 32/35 mm forks well for us.
john d.