CRF450 with MX-Tech Susp., worked great till now!

[seerf450]

Jeremey or anyone, my MX-Tech suspension worked perfectly. It has new heavier springs front and back, .50's and a 5.8 and revalve front and back. I used to be able to blitz through the whoops and maintain total control untill now. I just installed a set of RG3 20mm clamps, stock was 24mm; now when I go through the whoops the front end feels heavy and I don't have as much control. Alomost feels like the forks are a little stiffer through the whoops. Is this as simple as clicker adjustments or is it something I have to live with? The bike was setup for a 250lb(with gear) beginner level rider in January. I have not touched the clickers as the bike was perfect for me. Also, on some landings, the front end gets a little twitchy or bounces. Like maybe I need more rebound dampening. Please help. :ugg:

 

[CanadianRidr]

Did you replace the bottom clamp as well? I read in jermey's install tip's that a over tightened clamp can cause mid-stroke harshness.

This could be a long shot in the dark, but I figured I would mention it :D

 

[seerf450]

Yes, they're offset clamps. You need both top and bottom for them to work. As per RG3's instructions, I torqed the pinch bolts on the clamps to 16 foot pounds.

 

[RM_guy]

Isn't the reason people put the offset clamps on to make the bike steer quicker? This would also make it "twitchy" and load the front end more. I would assume the suspension would have to be readujsted (clickers only) to compensate for the new weight biasing that the offset clamp gives it.

Play with the clickers until it feels right again. I'd go stiffer on the compression for a start.

 

[seerf450]

Yes, I put them on to cure the steering problems on my bike, but the whoops is where I'm best on the track. I don't want to give that up. I'll try more comp., anyone have more ideas.

 

[Thump]

The front end is heavy because you have changed the ergonomics of the bike to allow it to turn sharper. Improvements on a technically drive industries product rarely have improvements across the board meaning if you want more of this you usually give up a little of that... In other words your bike used to be deficient in its turning abilities and stable through whoops and rough sections, now it has reversed. So if you want the best of both worlds you will need to compensate by shifing your weight differently than you are used to. ie: if the front feels heavy through the whoops get your but back farther.

At least that is how I think it works....

 

[Jeff Howe]

Experimentation is your only option. You have clicker adjustments, and rear sag adjustments as easy starting points. One thing at a time though or you may never know what solved your problem or made it worse. A little objective tuning will probably get you back on track.

 

[Jeremy Wilkey]

Serf,
You'll need to exsperiment for sure, however try some addtional compression.


Best Regards,
Jer

 

[Jaybird]

Shocknut may be on to your problem. With the change of clamps, a new dial-in of the sag (front & rear) is in order.

 

[MACE]

I wonder if there is a less than perfect tube alignment issue going on here??? :whiner:

Could be as simple as axle clamp alignment.
Could be the trips are not aligned (do hondas have a steerer stem pinch clamp?).
Worst case the new trips were not manufactured true or were damaged if you had to press in the stem.

Over tightened head bearings can make the steering notchy which can make the bike "hunt" in whoops.

I think I would look at these mechanical issues before changing the fork tuning.

BTW, it's been six months. Time for an oil change.

 

[tom sawyer]

mr seerf
just got in from testing all day with a set of 22 's. i used the line on the forks as a starting point ,but my rider was back in just one lap with similer complaints front end hanging down and to quik steering .
i atribute this to having the weight bias moved foward .
to cure the problem we dropped the forks down leaving 4mm between
the top of the tube and the top of the clamp and went from 14 to 11 on comp.
and stiffend shock comp. from 10-7.
after that it was way better than with the 24's no more popping up in corners and guicker more precise and stable handling .we are going to ride on this set up a while and then experiment with a longer shock..
i know your have the 20's but this may help get you started also this bike has mx-tech suspension valved for vet mx .47and 5.6springs
take care tom

 

[seerf450]

OK guys, I slid the tubes down 4mm, added more compression and it's too stiff now. I got worn out after a few laps. Instead, I opted to go softer on the compression. The clickers were set (set by MX-Tech) at 14 clicks out for comp. and 10 clicks out for rebound for the forks and 12 clicks out comp and 14 rebound for shock. I changed it to 16 clicks out for comp. and left the rebound alone. I also went 2 clicks softer on the shocks low speed compression. Seems to work better but I'm still not happy. I've not been able to bottom the suspension even at these settings. The forks will not use the last one inch of travel. They have 400cc of oil. Should I remove 5 or 10 cc of oil?? I'ld like to use all the travel, front and rear. I've also read about the twin chamber spring mod. Some people and suspension shops change the spring in the twin chamber to something lighter, like from a CR250R. I spoke to a guy who said it made his bike so plush on the small stuff, yet did not affect anything else. Jeremy, is there a reason MX-Tech does not consider this mod? Are there negative side affects? Any help would be greatly appreciated. Thanks...

 

[Jeremy Wilkey]

Seerf,
Good question..

The reason I don't consider it seriously is it a hype type mod.

The purpose of the airchamber spring is to insure that the cart valving is allways consistent and no internal presure rise is needed to have effective valving.

Now..
I've been entertaing working on a litte tech article that dispels the myth of the TC spring. You see since the fork moves at a one to one ratio with the wheel we have three types of spring effect.

in order of importance:
Main spring:
Air spring: (Works late in the stroke and progressive in nature due to volume change as fork compresses)
Pressure spring: The pressure sping is fairly stiff rate, and is prelaoded at least 5mm when the fork is fully exsteneded. Now its effective rate contribution inpacts the whole fork range in a linear fashion. However its not as simple as addtion.. The effective rate contribution is only the addtion of the PS rate devided by is mechanical relationship to the rod. So lets say 6:1 so the contribution is 1/6 the actually storred energy of the spring.. When you work the math out you have nothing other than a fork prelaod adjustment.

Now While I do believe that fork spring preload is important, I don't see the big deal with these things. Its far from a miricle cure, and far from what most people actually think it does. And furthermore, a very elaboreta exspenive prelaod adjustement. However! Reducing preload on CRF fork springs is not exactley easy.. So its a workable concept.
One last thing, I've noticed that alot of offroad guys are replacing them. Acoading to the lighter spring more preload concept that has become popular, the only guys really intrested in this mod would be hardcore MXer's who run a stiff fork spring rate.

I will work the math to ilistrate the point, and who knows once we deal with real numbers the prelaod may be higher than I exspected.

I've just Got Tony Foale's new book and I'll be getting to it right away.. I may have some more to comment on the clamp deal shortly. I've really got a mission to learn more abut Chassis influnces..

BR,
Jer..

PS if you have a "issue" please e-mail me directly.

 

[seerf450]

Jermey, you've got mail. :D

 

[seerf450]

Jeremy, did you get my e-mail?

 

[Jeff Howe]

I do not change this pressure spring in my modification process either. The guys have no problems with the bikes, well, I did have one guy that wasn't happy right off but we were just a tad too soft up front for him. A quick change took care of that though. Anyway... In this instance I'm currently in agreement with Jer on this being more of a hype thing based on the fact my customers have been happy without having to resort to this. Whatever the extra cost is I don't think it's needed. The other thing is they don't seem to complain of any ill handling manners requiring a $500 change in clamps either.