can you mail drawings to me too? cyberzar at hotmail dot com

Thnx!

Hei everybody,

I am back again with some fresh info and questions :) About the rear now. Because swaping the forks might be problematic for several reason, out of which one is the length of the new forks (I have a pair of KTM 640 enduro forks in my garage and they are about 4,5 cm longer than the XT's). You can slide them a little through the triple clamps, but they will hit the handlebar, so that's not enough play there. However, I found a device that raises the rear of the bike and this, together with raising the front a little, would mean somewhat the same geometry, isn't it? And also more ground clearance!

So, what do you guys think about this? Is it risky, does it look ok to you? I found it on ebay.de for 35 EUR.

http://ekkemu.tla.ro/Pics/xt_rear01.JPG

http://ekkemu.tla.ro/Pics/xt_rear02.JPG


http://ekkemu.tla.ro/Pics/xt_rear03.JPG

raising the rear to match the front may give you the same rake but the ktm forks woud give a different trail, plus raising the rear with that spacer will alter the way the swingarm linkage works and jacking the rear that way will shorten the distance between axle and pivot points.

if you read what i wrote erlia you will see that i had to extend the rear. even though my bike is supermoto'd and is fitted with 17" wheels i've had to do a lot of work to make the bike handle correctly.

Yes, I read what you wrote ... so you are suggesting that instead of that spacer I'd better use a longer rear shock? What if I change the spring on mine, will this make the situation better, i.e. raise the rear of the bike? I would love to also raise the bike a little with this mod if possible as it does not really have a big ground clearance (compared to the ktm 640 Adv for instance).

What are the essentials that need to be kept regarding the geometry in order not to screw up the bike handling?

Hey, I've got that higher-thingy from ebay.

It raises the ass pretty much, I'll guess 6-8cm.

Im about 2 meters tall, and it's allmost to high for me. I can stand on the ground fine, but when im riding on a path og generally offroad, I want to be able to push away with my feet, and i can barely do that.

My buddy has got som picturesof my xt, comparede to a stock one.

I'll upload them as soon as i get them.

i'm using a longer swing arm, my rear ttr shock is the same length as the xt600.
any shock change will alter the properties and geometry of the suspension.

it all depends on the intended use of the bike which way you want to go mine is set up for road use only so the ground clearance is not an issue.

if you want a lot more ground clearance buy a different bike the xt600 is not a motocross or dirt bike its a trail bike

altering the rake and trail will have a major difference in how it steers, in simple terms rake alters how quick it turns and trail alters stability.

Everyone told me that it would handle and steer very poor, when it was raised.

I cant feel anything different.

i'm only guessing here but if you're 2m tall you will be heavier than somebody thats 1.85m so you would actually compress the suspension more keeping it nearer to the factory set up so not compromising the geometry.

it also depends on the usage dirt gives tarmac doesn't.

Thanks for your reply wolfzero. I am intending to use my XT for trail riding, but I compared it side by side with a 640 KTM Adv and the difference in ground clearance is pretty big, both being bikes for the same purpose.

Anyway, I got the point and I understood what you explained, I think I'll hold on that riser thingy for now.

@Jens: Can you upload some photos, please? Did you change the rear shock? What other mods did you do to the bike? How much do you weigh?


I did some more measurements and I have a new question. The USD fork from a KTM that I have in my garage, would almost fit (with a changed 18 inch back rim, I think it will balance just fine), but there is one thing that I am concerned about. To make it fit to the XT frame, the distance between the 2 triple clamps has to be reduced by aprox 5cm. Would this impact the overall performance of the fork? Is there any danger of a serious mistake here? I am thinking that the forks being 43mm (i.e. thicker than the XT's) they might indeed need a longer distance between the triple clamps to hold them right, but ... again, I might be wrong. What's your opinion on this? The horizontal distance between the centers of the clamps (XT vs KTM) is the same.

the xt design is 20yrs old and the ktm is 5yrs old so the improved ground clearance over the xt is only to be expected.

the headstock depth is the least of your worries when swapping that front end the wheel spacing is different, brakes and caliper too and the upper headrace bearing is not going to work with those yokes.

Yes, I know that caliper, brakes and bearing fittings (I can take the low triple clamp to a machinist that has a lathe and will make it to fit inside the bearing - it has been done by others, so it's possible) will be a pain too, but all of them can be handled, they are doable jobs (even if in the end I am going to use a KTM caliper, wheel, disk brake).

Regarding your earlier remark with the trail that will be changed. Can you please clarify a bit on this part? I read an article here:

Motorcycle Rake and Trail Basics

And from what I imagine, if the angle of the new fork will be the same with the angle of the old one, the trail will be the same (having the same angle can be done by raising the rear of the bike). Am I wrong about this?


Thanks,
Adrian

ktm axle position is diff than the xt affecting trail and the yokes are also diff affecting rake angles maybe fitting taller risers and lower profile bars will allow more adjustment through dropping the forks through more.

Aham, good point with the axle position, indeed. Hmm, ok, I'll have to sleep on it for a while.

Have you seen this?

XT-660 'Rally Raid'

My 2pennies!!

I've put the whole front suspension,wheel,brakes,everything off a 2002 YZ250 and I just have to make some steering stoppers and weld them to the frame.

I don't know yet how it will handle because I haven't had a chance to change my leaking the fork seals/wipers but when I do, I will put a heavier fork oil.

If you want to compare the height of the forks with the XT's you'll have to measure from the lower triple clamp BEARING to the middle of the wheel axle and not the whole fork lenght (if you notice the top triple clamp is alot thicker than the stock top tripple clamp!)
And don't forget about the wheel size, if you stick with the 21" or change it to another such as 17"..
If you don't like it with the 21" wheel you can always change to a 20" or even a 19".. it's your choice!

BTW, I'm going to make some extra changes on my 90 XT600E so I'll start a new thread, I don't want to hijack this one :)


Have fun riding!

Vando :innocent:

Hei Vando, by all means, feel free to contribute to this one, or if you chose to open a new thread, at list post the link here too.

Good point there with the lenght measurement!