Read thru that and you got me stumped [img]i/expressions/face-icon-small-smile.gif[/img]

I honestly dont know enough about that model to get into anything specific but it does seem that there may be a combination of things causing your problem. The torque of the engine and weight transfer SHOULD have an effect on the springs and compressing them is normal, but the fact that it does not recover is telling that there is another issue here.

Just thinking out loud etc but maybe the front is over powering the rear, and or there is also some mechanical problem with the rear suspension that is may be binding on a pivot point or hitting something that holds it in that position.

To start I would clean everything up real good and carefully inspect it all while having someone sit on the quad and moving the suspension up and down and see if anythying doesnt seem right.

A couple things that I was thinking, does it have a swing arm or ind rear? Shocks struts? Anything else you think could be causing it or affecting it etc?

I am prob not the right guy to diagnose that problem but am happy to try and go thru the motions with it etc.

 

Cro, The adjustment screws are in the normal locations on the shocks and rez etc.

The idea of selling a 400ex that beats yfz450's to get a trx450r that isnt supposed to beat that same quad is confusing me [img]i/expressions/face-icon-small-happy.gif[/img] LOL

Good luck with selling and enjoy the new one when you get it, but remember you will prob end up needing almost as many mods as the ex did except for some of the internal engine stuff.

**

On a side note, I finally dialed in the ride height on mine (never found the time to do most of the work I was intending to including fully measuring the suspsension, but I am still wanting to if I can find the time) and got the front to 8-3/4 and rear to 8-1/2 ride heights and the measurements are accurate now as I am using actual markings I put on the center of the frame rail etc. I think it was a total change of 2 turns down on the fronts and 1/2 on the rear (have records but not here)

The first obvious thing was increased traction, and I am thinking the front to rear bias was the major problem with poor traction, and not the tires like I had blamed in the past. The second obvious thing was that there was way too much feed back thru the bars, and I mean a whole lot more than before raising the front ride height. So now I have traded a plush ride for a better bias, so I think I got a problem here. In all fairness I tested at Tower City PA that has a large amount of really rocky terrain and was riding with much more advanced riders (two upper level a class, two c class riders) than myself and it was a rough ride. So some of the level of my evaluation could be contributed to this and the fact it was the first "real" ride of the year.

The second problem didnt appear untill later in the ride but it made its presence known loud and clear. When hitting certain trail obstacles (downed trees or a good square bump) at speed the rear was kicking like crazy and allmost put me over the bars three times and pushed me into the trees twice. The one time the rear had to be over three feet high and these were things that I used to just hit the throttle and hang on with no problems.

Originally I thought the problem was a need for a slower rebound on the rear to correct for the added preload, but after trying everything up to full slow it would still do it.

Not sure if mojaveadict is still following this or if anyone else may know but could this be either a result of too much preload, or a blown rear shock? Maybe I was just missing something due to being highly fatigued from trying to keep up with much more experienced and better conditioned riders, or maybe was just a little cautious from allmost being pushed off the side of the mountain the third time it happened. Just dont want to go messing with it and screwing it up more if I am missing something simple.

Thanks in advance for any info or advice.

 

440EX, thanx for the info, the adjusters were easier to spot than i thought. i have the quad now, and have only ridden it up and down my street, that thing is really fast in first gear! one thing i failed to mention in my signature is that when my buddy and i (the buddy has the yfz that i almost beat) switched quads, i beat him on my 400 by at least 15 quad lengths. lol. i'm not planning on modifying ne thing except for handlebars, grips, i wanna put a new tether kill switch on, and i'm adding nerfbars. plus the razrs that i got for the 400 arrived after we put it on consignment, so i have brand new razr rears on the 450. i'm heading up to gorman sat. hopefully, so i'll be able to do lots of adjustments on the suspension then. i do have one question tho, with everything in the stock setting, the back end sags about 3.5-4 inches when i sit on it, but the front doesn't sag at all. would adjusting the preload help this?

as for ur rear shock problem, push down on the rear of the quad and let go quickly, if it springs up faster than usual and makes a clunk and still has freeplay above where it stops, then u probly lost suspension fluid (what happened to me) and should check all the seals. if its not that, then good luck.

 

Yea I deff need to be checking out that rear shock, and just hope its nothing more than a simple preload or rebound adjustment.

I have seen enough of the trx450r's to know that what you describe is how they are setting them up stk, so I would think it would be a good idea to get some seat time on it and see what you find. Some of the guys I have talked with have claimed that the stiff feeling front end isnt as stiff when riding etc, but it did seem to have a much stiffer spring rate than the rear.

The way its set up stock should show excelent rear weight transfer and therefore excelent forward traction (something my EX has had problems with lol) but I also think that there may be some benefit to balancing it out a little in the front.

One thing I am finding from owners of both the new 450's is that the suspension is needing to be replaced almost as quickly or as much as the older models. So its an improvement over the older models shocks but you will still need to be making changes if your into any serious competition.

Another thing though not suspension related is the intake and exhaust, and replacing these on your new 450 will make a world of difference so think about these mods also.

Actually was impressed with the modified yfz I rode with over the weekend but the owner who is a a-class xc racer was not happy with the suspension and when comparing it to his lt axis/gibson set up on his 250r mentioned something about a cadilac and a yugo so it seems the normal suspension mods will be coming for many of the new machines.

 

what settings sould i use for my 2000 rm 250, it has fully adjustable everything, with a frount air fork system, and revalved shock in the rear for racing, i want the bike to ride smoothly, and i wont be doing to many bike air jumps, any suggestions?

 

Hi 026, Its me again, dont have much time but I have an idea that might be your rear kicking problem. It is common on the 400ex to have a kicking rear when you lower it. The rear linkage is designed to progressively get less leverage as the swing arm goes up to make the shock stronger against bottoming out. On the 400 this happens kind of early in the stoke so when you lower your quad you are now riding in or close to this zone and when you hit a bump the shock does not compress as easy as it did because the swing arm is at a different ratio. To combat this the shock needs to still have enough stoke in the tender spring before transfering to the main to soften it a little at first. You may want to raise your ride height back up without changing any shock settings and see if the problem goes away. Then you will know what to try with the shock if you lower it back down. You will need softer compression and a little slower rebound but make sure there is some tender spring travel available. if there is enough you may need a softer tender spring. I may be all wrong here but this is a good possibilty. Some of the new linkages like the one from Gt thunder are supposed to help with this problem. You may want to give them a call and question them about this situation and their linkage. I like the no link setups because all the tuning is done in the shock and there is no change because of the link to worry about. But with the 400 you will have to deal with the linkage. Of course you may find that you are better off just to run a little higher ride height.

I can see no reason for extra feed back in the steering from the changes you made. You did not change rims also did you?
2+3 offset rims will do this in rough terrain like you were riding when they might not have been noticable in other areas. may have just been the area you were in, if it continues in other areas keep us posted.

 

440EX it still seems like the front is too stiff, and the rear is saggin a lil too much, bit if that's how they set them up stock, then i guess it performs well like that. i'm definately gonna ride it before i start adjusting the suspension. as for the intake and exhaust, i know that the GYTR system for the yfz450 takes it from 49hp to 55hp or so. the honda stock has about 37 but i dont' have any numbers for it with the HRC kit. a guy i talked to said that with the HRC kit on his 450r he was smoking stock yfz with paddles at the drags at pismo. apparently the kit come with a new cam, you take out the insides of the silencer, and just put on a dif. end cap that has a screen in it for a spark arrester, and you get an airbox lid with a big hole in it. plus it comes with a new jet (one size up). the downside to all this is that my mom wont let me mod. the quad yet, and i dont' have the money for it anyway. would opening up the airbox without modifying the exhaust have anybenefits? i'm headin up to a higher elevation (3,000 ft.///i live at 50ft.) and i don't wanna worry about jetting, so could i jus take the lid off the airbox and it'll run the same as it does here?

 

mojaveaddict good to see you back etc.

I have the new linkage but from Elka not GTT, but I have a gut feeling there not any or much different.

Originally I did try slowing the rebound, but it was close to max to start off so I only added a couple clicks. I had also tried reducing or speeding up the rebound just to be sure I wasnt packing, but the results were not anything special.

The feedback I am describing or attempting to may not be from the wheels since I run a 4:1 offset, and this is what I find everytime I have gone past a certain point adding preload to the fronts in an attempt to raise the ride height. I added 1-1/2 turns the day before this ride, and 1 turn to the rear but backed off a 1/2 turn on the rear before the ride due to the results of a short run being really stiff in the rear.

So net change for this ride was +1-1/2 F and +1/2 R turns on preload.

I am starting to give cro's idea of a blown out rear shock a little more thought as I remember the return being slower with this much rebound damping when lifted by hand.

I should have some time to mess with it some more tomorrow and hope to get more info if not somehow fix the problem.

Just a thought but one of the selling points of that linkage was it reduced the kick considerably and also lowered the ride height without have any ill effect on the ratio etc.

*****

Cro, one guy I know went from a 118 stk main jet to a 190 just from doing the hrc exhaust mod and a intake filter, so this one is pretty "plugged up" for sure.

Was at a multi line dealer earlier today and the front to rear on the 450R was still the same as the others so I am believing this is how there setting them up stock, but I wouldnt be afraid to make small documented changes if it still doesnt feel right when riding it etc.

 

ya, i've been messing around with the dif. adjustments. if i were to turn the rebound all the way up (fastest) and simply push down should i be able to tell a difference versus the stock settings? this is jus sittin in my garage, not riding it. after this weekend i should have a whole bunch of comments/questions about the suspension. til then, good luck with ur rear shock 440ex. i'll still be checkin the thread, but i'm out of questions for now.

 

Sorry bud but totally missed your post before.

A dirt bike is very different than a quad thats for sure. I had learned basic suspension tuning on bikes in the past, and when I tried to apply it to quads only some things crossed over etc.

Compression and rebound work about the same but you need to giv emuch more and paticular attention to sag, and the fork settings are very important as they have a large effect on handling as well as ride quality etc.

Check out MX tech (web addy listed earlier) as they have some excelent tuning guides for bikes, and one of the best features is there written in a very easy to understand way.

Let us know what you find or fix etc.