'02, CR80 Suspension

[leemiller]

I need some guidance on the correct set-up for my son on the rear suspension of his CR80. He weighs approx. 72-75 lbs. and the spring does not seem to have enough relief for the proper race sag. Is their another spring that I should consider to get the race sag correct?

 

[Mattski]

try www.racetech.com and do a valving search and this will bring up the recommended spring rates for your weight and bike.
Big wheel:.25kg/mm front and 4.4kg/mm rear but don't take my word for it check it out for yourself.
Big wheel and small wheel may differ also.
Does MX Tech have a simular service on the net?

 

[ewbish]

Sounds like my daughter. She's on a 99 CR80, same exact suspension as the 02. I have the forks set up with the rebound cranked one click of from hardest, compression is one click off from softest. The shock is basically the same, one click of from hardest on rebound and one click off from softest on compression, preload is backed all the way off as far as possible. She weighs about 72lbs. This gave her very close to 3 inches of sag. I would like to get it revalved and softer springs, but by the time it came back from the shop she will have grown another 2 inches and gained 10 more lbs. As it is now, the suspension works pretty good for her, soft enough to soak up the small stuff and corner well. More importantly she doesn't do the "pogo stick" on jumps, no back end kickup or front end kick up at all. One thing, make sure your chain is adjusted correctly. Measure the slack with the bike sitting OFF the stand. I just helped a kid out on a RM80 who couldn't get his suspension set up. I checked it out and it was hard as a rock at half compression. I sat on it (and I'm a big guy) and bike only sagged about 3 inches, I looked down and the chain was so tight, couldn't even move it. Kid said he followed the directions but who knows. I gave it another inch of slack and wallah! All the sudden he had full travel in back.

 

[dell30rb]

wait, so you measure the slack with the bike sagging under its own weight? not when the rear wheel is on the ground?

 

[ewbish]

That's what I do. The Honda manual that came with my daughters bike says to measure the chain slack with the rear wheel off the ground (on a stand), if I do that, then the chain is so tight at about 3/4 compression on the rear shock, that it won't compress any farther. So now I measure it with the bike standing straight up off the stand, I bounce it a couple of times, then measure. That seems to be right on the money for her bike. The bottom line is, the chain should be tight enough not to come off, but should be loose enough that there is some play at the point where the rear suspension breaks the center point when compressed. If your chain is too tight, you can play with the clickers and the pre-load all day long, but you will never get it dialed in.

Eric

 

[simimi]

Hey Eric, my son is on an '02 CR80, thanks for the suspension info. He is about 100 lbs, so I will experiment with the Sag. Did I see that 3" is the correct sag setting?

Also, with the chain, I seem to have problems getting it just right. We loosened it up, then went riding and after a couple of trails it was back to tight. I know it is worn out and I have a Renthal R1(?) on order, but is that typical of a worn out chain to tighten after a short ride?

Once we get the new chain and sprockets on I hope after the 1st day I do not have to adjust it anymore. With the cheap chains it seemed like adjustment was an every ride task.

Also, the bike came with an FMF Fatty and Turbine Core 2 with Spark Arrestor. I am running it with stock jetting and needle, but get a bit of spooge with Honda Synthetic oil at 32:1. I am considering changing the jetting a touch, seems that 122/52 seems to a common set up, also it was what FMF recomended with the fatty.

Finally, I ordered the spacer ring and moose torque spacer, and a taller rear sprocket. hoping to bring some of that power down to the low/mid range. Would do a port job but do not want to wait 3 weeks. I will post after the changes and let you all know how it goes,

Any other advice, please share,

Mike