Usd front ends.

[Red Devil 777]

It seems this is a fairly popular mod for KR owners on here,
everyone has a different way ZXR 400 stem swap etc, RGV similarly.
Well looks like the easiest may be the ZXR250, never seen anything posted about it before, but I acquired one and it looks very promising

On a quick casual glance stem size looks exactly the same as a KR lockstops look to be in the right place so may well just bolt straight in.


Again not measured anything but looks like the front end of a ZXR250 shares caliper and discs with a KR1, whilst having a 5 spoke wheel. So would be a good match for 1S owners who fancy a set of usd forks without having to change thr rear wheel for a 3 spoke job.
Me, If it all goes in ok I'm going to have to swap my rear for a 1s, so how easy is that and what bits do I need

[Garry]

be interested to know how that works out

think the rears are a straight swap - i've got one but not tried
it yet - waiting for tyre to wear out first

[corky]

i have a zxr250 and a 400 usd front ends in my garage, gonna use the 250 stems and 400 forks as the kr1s calipers fit the 400 's not the 250...(45mm compared to 63mm mounting points)

[Red Devil 777]

Erm, just realised that this is in the 'engine forum', must have been reading a post and hit new topic

Anyway quick update, Yokes are in and with a bit of messing fit, fork legs are on and my original KR1 calipers are on, all bolts up quite nicely.

I've decided to stick with a three spoke KR1 wheel so I'm having the spindle machined down, dropping that off tomorrow so progressing pretty quickly

Think the zxr 250 front end used various parts, I'm not 100% but looks like KR1S discs with KR1 calipers and as corky said different fork legs to the zxr400

[sprocket stu]

i dont tend to like this approach couldnt you change the bearings to a different size, this has worked out for me many times.
i always think that the manufacturers specified that size for a reason
dont mind upping a size or 2 but down?

[Red Devil 777]

Yeah, suppose I could, might have a re think. Will do some more measuring.

[alimorg]

i dont tend to like this approach couldnt you change the bearings to a different size, this has worked out for me many times.

If it has a 17mm spindle and runs the same bearings as the KR-1s (6203-2RS = 17x40x12) you will need a 6003-2RS (17x35x10) in your KR-1 three spoke wheels however these are 2mm per side narrower (a coupe of washers could take up the slack!) and you will need to either have a new internal spacer made up (the one that sits between the bearings inside the wheel) or bore out the original.

Cheers
AL

P.S. THis has now been moved to steering and suspension

[sprocket stu]

if you need a new centre making do a drawing and i should be able to knock you one up on the lathe one night

[Red Devil 777]

Nice one chaps, going down the bearings route, just ordered them, Stu will be in touch if I need a spacer etc thanks very much for the offer.