Modify steering, NOT 250r-related...

[wilkin250r]

So I just recently acquired a Yamaha Grizzly 600.  It needed a bit of work, but I finally got the last of the parts in and fired it up a few days ago, and took it for a test drive.  I'm really surprised!  It's got a solid axle, and when you start getting up up to speed, it kinda handles like a sport quad.


I don't want a 600lb sport quad.


Mostly it's in the steering, it's really responsive.  TOO responsive.   I'll try some of the easy adjustments first, like tire pressure and toe-on, but I might get more in depth.  I'm not even sure what to call the piece I'm looking at, but the steering stem is in two pieces and this piece that attaches the tie-rods to the steering stem.  If this was a car, this would be the pitman arm, but most ATV steering stems are one-piece so I'm not sure this piece has a dedicated name.

Basic physics says if this part is longer (meaning the tie rods are mounted FURTHER from the steering stem) then small changes in turning the handlebars equals big changes in turning the wheels.  The steering would be very responsive and the vehicle would oversteer.  The opposite is also true, if this part is shorter, with no other changes, then the steering becomes less responsive, and the vehicle understeers.

I'm thinking about cutting it and welding it shorter.  I want the steering to be less responsive, but I'm worried about unintended consequences.  I don't know if this quad is designed with a full Ackerman steer angle, but I would certainly throw that kind of stuff out of whack.  Or the steering might bind up because one part is moving more than another, or other undesirable effects.

Thoughts?  Anybody have any experience modifying or designing aspects like this?

[wilkin250r]

It's also really thick, like 3/8 inch thick steel.  Do you really think it needs to be THAT strong, do you think there is that much stress on it?  Maybe if/when I do try to modify it, I bring an extra along (they're about $7 on ebay) and the tools to change it, in case the weld doesn't hold.

[ytman]

I had an R stem that had 2 sets of holes in for that very adjustment. It doesn't sound like you have much to lose trying it. If it does break you're pretty much guaranteed a wipe out. Make it strong.

[pinned250r]

Kinda hard to test this, but make sure if youmove your tie rods forward an inch, they arent going to hit anything throughout the entire steer radius. Also ensure the stock tie rods are long enough to compensate this extra length, or else your cheap fix turns into a little more.

Other than that, sounds like a fun little project(even though i hate dealing with tie rod ends on the stem because tehre is no easy way to get a tthem with a hold lol) and the replacement part is very cheap.

[Dezsled]

Might increase the turning radius also.

Yeah don't wanna experience that part failing. I would weld in plate to strengthen it ... Piece of mind when your way out there

[wilkin250r]

Yes, it will increase the turning radius.  I'm not worried about that.

I'll have to draw it up in Autocad so I can see how dramatic the changes are.  Making the pitman arm shorter definitely will make the steering less responsive, that I'm 100% sure about.  But what about moving the tie-rod ends closer or further apart?  I think moving them further apart will make the inner wheel turn a tighter radius than the outer wheel, which is actually a good thing to a small degree because the inner wheel is traveling a smaller radius circle than the outer wheel (this is exactly what the Ackerman steering angle is), but it might be at the perfect distance already.  I might need to move them closer together to preserve the same ratio when I shorten the pitman arm.

I've got some research to do.

[wretched73]

I had an R stem that had 2 sets of holes in for that very adjustment. It doesn't sound like you have much to lose trying it. If it does break you're pretty much guaranteed a wipe out. Make it strong.

This sounds like the easiest/cheapest way to achieve your desired effect. If you just drill a new set of holes, then you don't have to worry about welds holding up or if you're wrong all together then it is an easy fix of just putting the tie rods back in their original holes.

[wilkin250r]

If you look at the part, I don't think I have enough width to drill two more holes.  The tie rod ends are too large to fit two holes together in the skinny part.  And I'm not sure I want to change the length by a full inch, I'm thinking only about half an inch or so.  I can't have two overlapping holes.

[rk88r]

You could make the handle bars longer . Raising the ride height in front and lowering the rear would give it a little more caster.

[fearlessfred]

If it has caster adjustment ,try increasing the caster before opening this can of worms.If there are no steering stops at the flag (center piece your wanting to mod)than the bars will turn much farther and the the tierods will become over center causing the steering to lock at full turns.If there is stops on the frame that limit the distance the flag can move ,you will be hating life when you need to make a slow tight turn but you wont have to worry about going over center.moving the pivots closer to the center of stem most likely will change the height of the balljoint causing more bumpsteer,that might be corrected.I wouldn't worry about ackerman to much.,to make much of a change to that ,you would have to move the location of the outer balljoint at the spindle.,True ackerman is created when you can draw a line from upper and lower a arm balljoint centers and then from that centerline draw a line thu it  and the outside tierod center to the center of the rear axle. I think atvs have modified ackerman,I could be wrong

[ytman]

cut it, weld it, cycle the suspension and steering, ride it. then scrap it, keep it, or modify it......oh yeah,then write about it.

[wilkin250r]

If it has caster adjustment ,try increasing the caster before opening this can of worms.

The front suspension on this thing is a single a-arm and a strut, I don't see any way to adjust the caster. If it was a duel A-arm I would do exactly that, just shim the arms to lean the caster way back and that would probably solve everything.

I'm not looking for a dramatic change. It's only noticeable when I'm up over 30mph, a half inch change in the location of those mounting holes is probably too much. It will obviously affect the turning radius, but I think that's a small price. With the CVT transmission, this is going to be the quad most of my novice friends will ride because they don't know how to use a hand clutch. If I had to choose between the hassle of slow-speed turns and the hassle of packing out my buddy with a broken arm because the steering is too responsive and he over-corrected when he got into a little bit of trouble at speed, I'll take the hassle of slow-speed turning radius any day.

And that's really the driving force. Under-steering is much more forgiving for a novice rider when they get into trouble. I want to make this quad safer for my friends and my daughter to ride.

And this is going to be a slow project, I'm not going to have results two days from now.  I'm just starting here to see if anybody has any experience adjusting aspects like this.

[fearlessfred]

Im guessing from the looks of the flag that it has steering stops at the frame that stop the flag .if it does you don't have to worry about going over center

[rk88r]

Can you shim the knuckle back in the strut brackets?

[fearlessfred]

Can you shim the knuckle back in the strut brackets?

Im thinking on the same lines as you rk88r anything that might make more caster ,raise front end lower back,shim top of strut back a arm forward,taller front tires