changing forks advice

[stirlinggaz]

hi all,
I fancy a wee challenge.
what pitfalls are there in changing forks/front ends from completely different bikes?
heres what I would like to do : nsr 125 has cheap, spindly rwu forks.
the cagiva mito has far better quality usd's.
i have both front ends off the bikes (im doing head bearings on honda anyway) & when i compare them, the stems are pretty much same length & diameter. (although the cagiva has a different thread arrangement)
would it simply be a case of getting the stems pressed out & swapping them over?
I realise I would have to look at the brake caliper & disc but I cant see anything too difficult, or am I missing something?
even the steering geometry would be relatively unchanged afaics.
anyone care to advise?
please avoid the usual "dont do it cos its not worth the hassle" as I think anyone who has ever ridden both bikes will testify the mito handles much better than the nsr & I think the forks fitted to the mito have a lot to do with this.

cheers,
GAZ

[Kickstart]

Hi

Steering stem might press out of one and in to the other, or with minimal machining. Be easiest to use the Mito front wheel, brakes, etc. Although you would need to check the speedo drive is right. Possible issue with lock stops, but should be easy enough to sort out. Also a possible issue with the thicker USD forks catching on the fairing bracket.

All the best

Katy
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[Vincent]

What about wheels on both bikes? Are they similar? If the Mito has a wider or bigger rear wheel, you may, (will), find problems getting the two different ends to match, handling wise.

I know you have them spare but not all upside-down forks are better or an improvement on stock RWU forks, there are some pretty cheap USD forks out there.
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[stirlinggaz]

hi,
thanks for the replies.
iirc the mito stock tyre size is 110/70 at the front, with 150/60 at the back.
the nsr uses 100/80 front & 130/70 at rear, though it's quite common to fit a slightly "wider" tyre at the back.
so there's a wee bit difference in tyre size....but would it make that much difference to the bikes handling?
as for the forks, the nsr uses showa rwu's which are just about adequate, if fitted with new springs & heavier oil but there's no getting away from the fact they are a budget item compared to the marzocchi usd's fitted to the mito, which imo, are much better quality forks.
there's certainly a huge difference in diameter of the legs
I hadnt thought about the lock stops...& not really bothered about the speedo tbh.

I agree, it would be easier to use the mito front wheel as well but it wouldnt look right as the nsr has 5 spokes whereas the mito uses 3 spokes

the brake disc on the mito is huge compared to the nsr's & the mito uses a decent brembo caliper compared to the crap grimeca fitted to the nsr.

if I could fit the brembo stuff to the nsr front wheel, it would be a massive improvement imo.

hmmm.. seems theres a fair bit more to think about than just getting the stems pressed in/out...& now im wondering if the mito swingarm would fit as well
I have a swingarm c/w rear shock sitting doing nothing...I could then use both wheels/tyres from the mito.
I reckon, if I could pull this off, it would make the nsr a "better" bike.
the Honda has good electrics, a reliable engine which doesnt need rebuilding as often as the mito, which handles better, has better brakes but has crap electrics & doesnt look as nice as the nsr foxeye (im talking about the mk2 mito, not the mini ducati mito evo)

opinions?

cheers,
GAZ

[Vincent]

Five major things I can think of to look at for the swingarm:-

Wheelbase; where possible, try to end up with the original Mito wheelbase, aim for replicating the Mitos geometry.

Pivot width. Relatively easy to sort out if not too differrent. If the Mito arm is too wide, you can usually get the ends shaved down to fit depending on how the bearings are seated. If slightly too narrow, you can shim them out.

Pivot pin size, if the Mito pin is too fat, you may be able to open up the holes on the NSR frame but you're then wrecking a decent frame for future use as an NSR. It's possible you could use the NSR pivot pin with a sleeve. If too thin, it's possible you can use bushes on the frame.

Shock mountings: This is what usually spoils the fun, shocks are mounted in different ways at differing angles and are of differing lengths. Some go through the swingarm, some sit in front and they can have different mountings at either end. There's usually a way round if they're completely different but it can take some head scratching to work out.

Chain run: I doubt this would be a problem for your swap, a lot of converisons are done to fit wider rims, with more tyre availability to older bikes that have larger, thinner wheels so the chain fitted at the original run can foul either the tyre or the swingarm. This can sometimes be remedied with an off-set front sprocket.

The easiest way to do any conversion like this is to use a "Tried & Trusted" set up. Maybe not very adventurous but that way, you let someone else discover the pitfalls and problems. Some snags you run up against can take quite a bit of working out and before you know it, the bike's been off the road for ages. Good fun if you like tinkling with bikes though
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[Kickstart]

[stirlinggaz]

[Vincent]