XS650 to XL250 front end conversion

[Hudson]

Hi guys,

I have recently picked up a 78' Honda XL250 front wheel, forks, yokes/trees/clamps for my chopper project.

The steering stem is 25mm shorter than the XS650 stem as pictured just for reference, XL stem on right

This will be my first time fitting a different front end to a bike so im looking for advice -

Whats going to be the best way to fit the XL250 stem to the XS headstock? Seeing as the XL stem is shorter, ive had a few ideas of how I 'might' be able to do it:

- Cut the original headstock off and replace it with XL headstock
- Cut the XL steering stem in the middle and extend it 25mm
- Find a way to remove the stems from the clamps and weld the XS one to the XL clamp
- Trim the original headstock top and bottom to try and achieve the correct length (not sure how bearings would fit.

Any tips? Those ideas might sound dumb and im quite possibly missing something simple, just need guidance!

Be great if anyone who's already done this conversion could offer advice, i've seen it can be done but theres next to no info on it. I want to make it work and i'll document it/make a proper post once ive figured out what to do

Cheers!

Rich

 

[figure8]

Weld the stem from the xs into the xl tree. My buddy did one for me pretty easily.

 

[Hudson]

Ok cool! So the XS stem fits the XL tree once theyre machined out, same diameters or?

Thanks

 

[650Skull]

Caliper's..........measure the stems or turn the trees upside down and measure the hole

 

[gentlemanjim]

WHY?

 

[Hudson]

Caliper's..........measure the stems or turn the trees upside down and measure the hole

Yeah i will measure them when im next st the workshop, just wondered if anyone knew!

WHY?

Why what? Do the conversion? Because i want an in-expensive 21” drum wheel and a narrow front end. Hope that covers it

 

[CBJamie]

I'd be worried that a XL250 tree's and forks are to light for a machine as heavy as a XS650. I get the reasoning but i personnaly would look for a XL 450 or 650 system. Think safety your life depends on it.

 

[Hudson]

Really? Taken from an enduro/off road bike and you think they’ll be at risk of failing on a street bike?

The forks are 35mm and i’ll be fitting the XS stem, i cant imagine theres an issue personally.

 

[figure8]

Wasn't able to finish my initial post, but you said something I was gonna say. As you said, the xl forks are 35mm. Why not use the xs trees and swap in the xl forks, make spacers, brake stay etc? Or keep stock xs front end and make spacers etc to fit xl wheel. What I actually did was fit a 35mm front end to a shorter 72 xs neck. My buddy turned out the the weld on the stem, pulled it down a 1/4 or so and reweld it back up. You sound fairly capable so you've got options.

 

[CBJamie]

Tube strenghth may not be an issue but valving could cause problems, the xl 250 is a very light bike and the off road suspesion is designed to give a lot of compression during jumps. You wont need that kind of compression but you will need more controlled compression and fork rebound during hard front wheel braking and cornering. If your forks compress during hard cornering and rebound to fast you'll go down fast. That is all contolled by valving. I'm building a XS chop with KTM super moto 450 inverted fork front end and raking it to 42 deg. I've done the research and found I need to dampin my rate of drop by 20% to decrease the amount the forks will compress and how fast they will rebound . Fortunetly I can achieve that with a heavier viscosty fork oil. Being your using dirtbike suspension valving is avalible for heavier riders. Just saying we need to keep our builds safe.

 

[Hudson]

Wasn't able to finish my initial post, but you said something I was gonna say. As you said, the xl forks are 35mm. Why not use the xs trees and swap in the xl forks, make spacers, brake stay etc? Or keep stock xs front end and make spacers etc to fit xl wheel. What I actually did was fit a 35mm front end to a shorter 72 xs neck. My buddy turned out the the weld on the stem, pulled it down a 1/4 or so and reweld it back up. You sound fairly capable so you've got options.

I originally bought the wheel and forks in the home that it will need minimal spacing to get it to work without spacing and messing about. In reality the XS fork width is much bigger than the XL fork width, it could easily be done like you say, with spacers and an extention on the brake stay of the fork lower, i just really wanted to go with the skinny XL yokes and make hard work for myself haha.

Tube strenghth may not be an issue but valving could cause problems, the xl 250 is a very light bike and the off road suspesion is designed to give a lot of compression during jumps. You wont need that kind of compression but you will need more controlled compression and fork rebound during hard front wheel braking and cornering. If your forks compress during hard cornering and rebound to fast you'll go down fast. That is all contolled by valving. I'm building a XS chop with KTM super moto 450 inverted fork front end and raking it to 42 deg. I've done the research and found I need to dampin my rate of drop by 20% to decrease the amount the forks will compress and how fast they will rebound . Fortunetly I can achieve that with a heavier viscosty fork oil. Being your using dirtbike suspension valving is avalible for heavier riders. Just saying we need to keep our builds safe.

I just re-read my last reply to your message, i sounded pretty blunt i didnt intend that. I see what you mean about the rebound of the XL forks as it did cross my mind, I plan to lower them however and hopefully leave the spring stock length/add pre-load as I do to make it a bit stiffer in the process. If it turns out dodgy I will have to look into other oils/springs to make it work.


-----------------------------

SO, i measured the stems today, the XS650 is 30mm in diameter, the XL250 is 26mm in diameter, bummer. So i was thinking about my options around this:

- Press the stems out, turn the XS stem down 2mm (to retain as much wall thickness/strength), and bore out the XL lower by 2mm to achieve the 4mm difference, press XS stem in, weld up

or

- Cut the XL250 stem across the middle, make a solid insert to press into the inside of the now two-piece stem, refit the top half the required 25mm higher up, weld the two halves to the insert in the middle. This will effectively extend the XL stem enough and in theory the insert will keep the stem straight. Use the correct conversion bearings to suit the skinnier stem to the XS headstock.


orrrrr drink loads of beers to clear my head and forget about bikes.

 

[XSLeo]

I think the XS stem turned down the XL tree then welded in would be stronger than the XL stem cut and welded. Probably easier too.
Leo

 

[fredintoon]

Hi guys,

I have recently picked up a 78' Honda XL250 front wheel, forks, yokes/trees/clamps for my chopper project.

The steering stem is 25mm shorter than the XS650 stem as pictured just for reference, XL stem on right

This will be my first time fitting a different front end to a bike so im looking for advice -

Whats going to be the best way to fit the XL250 stem to the XS headstock? Seeing as the XL stem is shorter, ive had a few ideas of how I 'might' be able to do it:

- Cut the original headstock off and replace it with XL headstock
- Cut the XL steering stem in the middle and extend it 25mm
- Find a way to remove the stems from the clamps and weld the XS one to the XL clamp
- Trim the original headstock top and bottom to try and achieve the correct length (not sure how bearings would fit.

Any tips? Those ideas might sound dumb and im quite possibly missing something simple, just need guidance!

Be great if anyone who's already done this conversion could offer advice, i've seen it can be done but theres next to no info on it. I want to make it work and i'll document it/make a proper post once ive figured out what to do

Cheers!

Rich

Hi Rich,
most likely a stem swap would work
BUT
you will have scrapped the XS650 'tree so you can't easily swap back.
I'd advise you extend the XL250 stem so it's long enough to fit the XS650 steering head tube.
BTW a mere cut'n'weld won't do it. I'd use a turned slug with long pilot diameters to keep the stem straight
and full Vee-welds ground off flush so the new headrace bearings will go on.

 

[XSLeo]

XS650 tree are not hard to find.
Leo