Rode at a local spot this weekend, and there was a guy with a brand new yamaha 450. I know that his bike is way better than mine. One stretch of this place consists of natural whoops where water sits in puddles after it rains. It was totally dry and when I tried to keep up with him thru this section his bike just skipped over them all, and the back of my bike seemed to bounce side to side when I tried keeping up with him. Now, I have counquered many of whoop sections and this was the first time I ever had any problems. Was it just that with alot of speed the 400ex is unstable, or is the 450's suspension that badass?

 

What you experienced is shock "packing", the stock shock could not handle the rapid compression/rebound cycles over the whoops, so it basically became solid, causing you to bounce the back end. The only cure is to replace the back shock with a good aftermarket one, or see if the stocker can be rebuilt for better adjustment/travel. Some factory sport quads have very good shocks from the factory, see if a 450R shock fits, or measure up one from other good riding quads,like a Raptor, or even the Yamaha 450, or the Z400, etc. I was able to swap in a 2001 Raptor shock into my son's 300ex, and it made a world of difference, but now that I think of it, the 400ex used a rear link system, so the Raptor shock won't bolt in, but a lot of the others might, just look aroud, and do a little measuring. Or break out the check book and get some Works, Ohlins, or other good aftermarket shocks.

 

Thanks for the explanation wolv. I have put on about 20 or so pounds since I could fly straight ove bumps like this, and I have read that you can get the stocker re valved or whatever for the riders weight, but I think I would rather just get an aftermarket one since I think it would be alot better, but probably more expensive!

Anybody put a shock from a different quad on a 400ex like the ones that wolv suggested?

 

I am the king of desert whoops! When we hit the whoops, I leave absolutely everybody behind, because I can bash through at full throtle...and they have to back off. What it takes if good shocks, but just as important they need to be properly adjusted:

http://atv.off-road.com/atv/ar...eDetail.jsp?id=192286


The stock EX shocks aren't superb, but they aren't terrible either. Sounds to me like your rebound damping is to fast, so your back end is bucking you. For some reason, the stock rebound settings are always set to fast...so you will get bucked in the big whoops.

Get your ride height (preload) set properly, then go back to your owner's manual and set the rebound and compression back to the stock settings. Go out to the whoops, and run through them. Then turn the rebound screw in a bit (screw at teh bottom of the shock) and run through the whoops again. Do this for the rebound and compression until you like the ride. I generally like my rebound screw turned in a little, and, my compression turned out a little from stock.

My 450R has the stock socks, and I find them to be absolutely supreb...if properly adjusted! My 400EX has WorksPerformance (Steelers with cans in front and Ultracross in back), and these have to be the best shocks I have ever seen on any EX!

 

UPDATE.........

Checking over everything before my ride on sunday, and I think I may have found my problem.

BOTH rear hubs were loose! Now I dont see how because the cotter pins were still in. Took them out and put anywhere from a quarter to a half a turn on both of them and reinstalled the pins.

I didn't remove the hubs to see if there was any damage to the axles, but figured they must be a little f'd up. Wanted to ride so I figured I would just take the chance.

Rode about 80 miles, about 20 of it was at WOT in 5th gear, (along train tracks). Got home and washed her down and everything was still tight with no play at all!

Should I disassemble everything and check for damage, or just ride it and keep checking?

 

Hubs can work loose a little....it's just something that happens. Tightening them is just part of normal maintenance.

How is the suspension. What your quad is trying to do is called "swapping".

 

Never knew that, thanks recon! Going to throw some parts at it, once I am decided on a different shock, would like to get some new fronts too, but have to save up for a little bit, girlfriend said to just keep it drivable for now and put some money into the truck because I have been neglecting it! That will give me time to research parts and get some more opinions. In the mean time I will set it up like recon said and try to make it a little better for the time being.