My R1 fork conversion...

[Greg]

Ok - so I posted on the other bit of the forum about the plan to resurrect my TRX and finish the fork conversion I'd planned for last summer...

The story so far is that I've bought a load of bits on Ebay, 2 sets of R1 USDs, two sets of yokes (1x4XV and 1x5PW) and a Thunderarse wheel with discs.

Today I've bought another wheel spindle to suit the '03 forks, a set of spacers and a speedo drive so I think I have all the bits I need now.

I'd asked Honk and Phuk about the removal/re-pressing of steering stems into the R1 yoke, but my '03 (5PW) yoke definitely has a bigger hole than the OD of the TRX stem! So now the plan is to weld up the TRX stem and turn it down to size (now I'd wish I bought that bloody Myford...) to then press it into the R1 lower yoke. Hopefully I'll have it all back by the weekend so I can start to offer everything up to see how it will go.

Just in case anyone's interested, I have a set of mint '99 blue top USDs wheel spindle and bottom yoke up for grabs ...

Greg

[honkdawillydahonk]

Ok - so I posted on the other bit of the forum about the plan to resurrect my TRX and finish the fork conversion I'd planned for last summer...

The story so far is that I've bought a load of bits on Ebay, 2 sets of R1 USDs, two sets of yokes (1x4XV and 1x5PW) and a Thunderarse wheel with discs.

Today I've bought another wheel spindle to suit the '03 forks, a set of spacers and a speedo drive so I think I have all the bits I need now.

I'd asked Honk and Phuk about the removal/re-pressing of steering stems into the R1 yoke, but my '03 (5PW) yoke definitely has a bigger hole than the OD of the TRX stem! So now the plan is to weld up the TRX stem and turn it down to size (now I'd wish I bought that bloody Myford...) to then press it into the R1 lower yoke. Hopefully I'll have it all back by the weekend so I can start to offer everything up to see how it will go.

Just in case anyone's interested, I have a set of mint '99 blue top USDs wheel spindle and bottom yoke up for grabs ...

Greg

You have PM.

[Greg]

Ok - so I've offered everything up and done a "dry-fit", and at first sight the front end looks very low... Comparing the free lengths of the TRX and R1 forklegs, there's about 6cm difference (TRX longer of course), but more obviously the ride height is significantly different... The nose of the bellypan is 12cm off the deck, and there's 10cm of fork travel left. The top yoke is about 95cm from ground. When I jump on, the back end sinks as usual, but the forks hardly dip at all, which I guess can be sorted out with adjustment (see supplementary grovelling question below).

So, the big questions are:

Is the geometry going to make it too frisky or do I need to find a buyer for all these R1 bits and get the TRX forks re-worked instead...?

Does anyone know what / how to set up the R1 forks properly? (oil level, preloads etc...)

Slightly pissed off at the moment so I'm off to see Borat at the flicks..

Greg

[honkdawillydahonk]

I didn't think R1 forks were significantly shorter than standard Have you got the fork tops flush with the top yoke and the clip-ons under it?

BTW Just measured mine. My YZF750 top yoke is just under 1m off the ground (measuring parallel to the fork legs) How high is standard?

As far as adjustment goes; back compression and rebound adjusters to minimum (right out) and adjust the preload to suit your weight - should drop about 2" when you're sat on it (from fully extended) The spring rate can't be that far out.....

[meemo_meh]

I didn't think R1 forks were significantly shorter than standard Have you got the fork tops flush with the top yoke and the clip-ons under it?

Yeah my R1 forks are 80mm shorter than the original TRX ones. Can compensate geometry by lowering the rear end (risk losing some precious ground clearance though) depends how corner happy you are. I left the riser as it was, made the bike pretty twitchy on bumpy roads, but you can compensate by wacking in some large orifaces inside those forks, (allow lower restriction flow, prevents head shaking)

I had to get heavier springs in the front too (.85). Made an assumption based on the fact that the forks are designed for a bike that is 160kg, opposed to a bike that is 200kg.... I took some gas out of the rear shock to make it softer for me, eventually I should get a new spring for that one too. You do get used to the diff riding position. For me it was a bonus, shorter bike Thing you need to watch out for too is the position of the handlebars. Do you have raisers? Or leaving the normal ones on? Cos I have just normal bars on and unless you cut back your fairing these bars (due to reduction in height of those forks) will touch the fairing and catch your fingers up full lock either side... I got lazy and havent done anything about it but slow manouvers can become rather menacing...

[philk]

I was asking this a while ago, my reasoning was that the forks appeard to be 25-30mm shorter when installed.
bearing in mind im using an r1 wheel and the 120/70/17 tyre, and the fact that the r1 forks are stiffer, i recon the front end has dropped around 10-15mm.

Hence why i was asking about steering dampers!!!!

I was wondering. could someone with a standard front end measure from the ground to the bottom of the head stock (not bottom yoke as i think the r1 one is different) following the line of the forks when measuring.

[Greg]

Well, I can only agree with you Phil - and I guess you used pre-03 forks with the blue tops, cos the gold topped ones are even shorter (ask me how I know!) !!

The biggest problem I had was with the steering stem - Honk's experience was that the R1 stem was a direct press replacement for the TRX. Sadly not so for me (were there any significant chassis changes in the TRX over the years?) cos the stem was about 0.5mm smaller than the hole in the R1 bottom yoke. My guy had to build it up with weld and re-cut to size then press the whole thing back together. The other issue was that the TRX top yoke was thicker by about 10mm than the R1 top yoke. The net effect of all this was that the steering stem was too long by that 10mm. Now, if I'd known that then, of course I'd have had my guy press it that leetle bit further into the yoke.. hmmmm. But he didn't and I wasn;t about to go back and have him do it again. So...

This is what I ended up doing - I know it might appear to be a bodge job, but I thought about it a long time and couldn;t see any reasons why not to do it - what do you think?? So - I had a spare bottom steering head race from the R1 yoke, I inverted it and installed it onto the TRX stem This race is about 7mm (I can;t remember now), then installed a new race conventionally on top of that one. This in effect just drops the bottom yoke further down the fork-leg but as far as I could see wouldn;t stress or be loaded any more than it would be if mounted normally. Anyway, then we were pretty close to being right except that the stem was still just a snadge too long and the hole in the yoke was 3 or 4mm bigger than the stem. Now, I've been promising myself a lathe as a present for a while and this was all the excuse I needed, so I got one and turned myself a lovely stepped spacer out of some bar end stock I got from the local scrap metal yard. This centralised the stem in the yoke, and took into account the difference in thickness between the top bearing surface and the threaded section. I also turned a seat into the spacer to accommodate the chromed steel washer so that the headstock nut didn;t chew up the spacer...

The fork legs needed a little work to take the Thunderarse wheel - I've read that the left leg needed 8mm taken off the inside shoulder to accommodate the speedo drive - yup, that's about right but it took bleeding ages doing it by hand (and yes, before anyone asked it's flat and square too lol), then using the redundant R1 steering stem, I turned myself a new axle spacer (18mm long, 22mm ID, 28.5m OD) and the wheel's mounted lovely and central within the caliper castings too, which is a bit of a bonus !

Now all I have to do is to weld a new lock-stop post on the frame headstock (remember the bottom yoke is dropped - now it clears the stops - bugger!) and it's all ready...

This is all just at the 'dry-fit' stage as I want to do a quick re-build/re-oil of the forks just to be sure in my own mind that they're as fresh as they can be ...

This is starting to get interesting now - cant wait to get the FCRs... lol.!

G

[philk]

Greg, mine are the gold tops off a 02/03 model.
as far as i know the TRX stem fitted straight into the r1 bottom yoke (i will check as my friend fitted the front end)
we wound the pre load in as the 03 forks are quite softly sprung, but not as bad as the trx forks.

should be fun round the lanes lol

[Greg]

Hi Phil...

Thanks for the reply...

I can only guess that there are some differences between years cos there was no doubt a difference in size - sloppy sloppy sloppy!

I did notice though that the gold top forks were shorter than the blue top ones by a margin too - quick eyeing up guess at about 10mm, the gold tops have 120mm free travel while the blueies have 140mm... as far as I can measure the gold forksprings are stiffer too which might just mean that the previous owner was a bit on the lardy side lol...

Is yours rolling yet?? if it is how did you get over the difference in thickness of the R1 top yoke..? how do you find the handling now?

Cheers

Greg

[PhatVR6]

here's my blue tops.

can take any measurements you want (except to the clip ons, as I'm not using any)

[philk]

Phat,
could you measure from the ground to the bottom of the head stock (not bottom yoke as i think the r1 one is a different thickness) following the line of the forks when measuring.

As you have an R1 front end, have you jacked up the back end?
How does it handle?

Cheers phil

[philk]

Info compliments of Trixynut......with much thanks.

Measurement, as best as I can get it with the front wheel in, is 770mm from ground to underside (lowest part) of headstock, following the line of the forks.

However, my forks are dropped through the yokes with 30mm showing above the clip-on. Standard setting is with about 10mm showing above, so this would make the measurement 790mm or thereabouts.

My front end is standard, and I have a standard 120/60 17 front tyre on at the moment.

[PhatVR6]

Phat,
could you measure from the ground to the bottom of the head stock (not bottom yoke as i think the r1 one is a different thickness) following the line of the forks when measuring.

As you have an R1 front end, have you jacked up the back end?
How does it handle?

Cheers phil

Will take some measuments next time it's off the stand. got a standard TRX to compare it to too.

haven't touched the rear suspension,

haven't ridden it, it's still not finished.

[Greg]

Ok - the forks are in, everything lines up and looks ok. I've got about 7mm of stem poking above the top yoke, but I turned a spacer to accommodate that. The biggest problem now is that all my dry fits were done with an old crash damaged yoke that I'd cut the lock housing off. The new yoke I wanted to use still has the lock mechanism attached, but this now fouls the lock's bolt plate on the headstock!! On top of this the lock-stops on the yoke clear the limit plate on the headstock. It'th a bit of a Kerfuffle!!

So I'm leaning now towards using the first yoke, but milling the front faces properly so it looks decent, then just using the kill switch as the main switch with a remote key or secret squirrel switch somewhere else. I think I'll make the lock-stops adjustable with caps on top of the pegs on the bottom yoke.

The might be hope that it will be finished before the spring!

G

[honkdawillydahonk]

It'th a bit of a Kerfuffle!!

So I'm leaning now towards using the first yoke, but milling the front faces properly so it looks decent....

G

That's what I did originally, when I was running R1 yokes (I had a switch mounted next to the clocks) When I fitted YZF750 yokes I ended up angle grinding off the gubbins from the headstock completely and fabricating a new one so I could lock it both ways....