R1 front fork project

Please share your secrets! What mods have you made to your TRX?

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Vieze123
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Posts: 5
Joined: Tue Apr 30, 2019 10:58 pm

R1 front fork project

Post by Vieze123 » Thu Jan 16, 2020 11:15 pm

Hi guys,

Given the TRX on the homepage I reckon I won't be posting something totally new. But hey, everybody has his own way of modding and perhaps someone can be inspired by this.

After 100.000km + I decided to reduce the oil consumption of 1L every 1500km by replacing the valve stem seals and the piston rings. Ofcourse, when I was busy, another upgrade wasn't hard.
Decided to put in 91mm JE pistons as well. It has some more pull and it doesn't consume a drop of oil now. Very proud of this, since it was the first time I did this revision and just with the help of the Haynes Manual and some expert advice of co-owners ;)
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But, ofcourse, after all this hard work, the upgrade-addiction-hormone kicked in. After closely checking the front fork and my wheels after all this mileage, it was soon clear that an autumn-winter project was due.
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So I started collecting some stuff, knowing that it wouldn't fit without some effort. But hey, the shed had space and it's a long time before spring. Also: I have a friend with a lathe! \:D/
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My nephew welded a center stand, very thankful for that.
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Started with removing the old fork and replacing the bearings and outer races of the steering stem. Dear lord, what a chore. Clunking in the new ones wasn't that hard when using a freezer and a torch though.
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After that, transferring the TRX steering stem into the R1 lower yoke was up. Ofcourse these stems didn't have the same width in de lower part, so we milled the lower yoke and pressed in a stepped bushing and the stem after that.
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From here, I needed a bushing on top of the steering stem to seat the top yoke. The R1 yoke had a much wider centered gap.
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Also let the pro's powder coat the top yoke in matte black.

The ignition switch bolts werent plug and play with the R1 top yoke, so also made some bushings for that thing, to let it stick out exactly as much as the original TRX ignition. The steering lock had to be grinded off, but that's fine to me.
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From here it became a bit more challenging. I really wanted to preserve the TRX front wheel because it looks fine (after repair and coating) and my brake discs fit perfectly in the new fork, combined with the blue spot calipers.
But the thread of the R1 axle is M18, versus the M16 thread of the TRX axle. Discussed with co-owners, checked this topic, almost had a mental breakdown when pondering these options:
- R1 axle is 20mm. TRX bearing is 17mm inside diameter and 40mm outside. Let's see if there's a bearing with 40x20mm spec --> non existent and if so, perhaps not up to the load, deemed too unsafe
- Mill the TRX bearing notch to a larger diameter which will accept the R1 bearing --> impossible to do safely and reliably
- Insert a helicoil in the M18 thread of the R1 leg to accept M16 --> the TRX axle wouldn't sit flush inside the left leg and helicoils don't feel right to me ;)
- Use the solution of this topic, but chopping up an axle into two pieces also doesn't feel safe:
- Create a complete bushing inside of the R1 leg --> M18 bushing leaves to little space around the M16 thread of the TRX axle when inserted, even though not inserted fully.

So.... Eventually decided to do this:
- Tap M20 hole in the left leg
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- Cut M20 thread on a bushing
- Tap M16 hole in the bushing
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- Presto!
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Will use some thread locking to ensure the bushing in the left leg won't ever loosen. The bushing inside the right leg is pressed to the axle with a tiny headless bolt.

To do:
- Create bushings to space and center the front wheel
- Install the KOSO DS-03 digital speedometer, Didn't feel like preserving the analogue speedometer. That fat cable was always hurting my sight.
- Powder coat the original rear wheel and a new, used front wheel.
- Replace bearings etc.
- Fiddle with suspension settings
- See if it's spring
- Ride!

Hope it has been enjoyable up to now. Would love to hear your opinion on my actions.

Regards

spiritedride
TRX-Enthusiast
Posts: 88
Joined: Thu Feb 19, 2015 12:56 am

Re: R1 front fork project

Post by spiritedride » Sat Jan 18, 2020 8:11 am

Hi Vieze123, great to see a 100,000 km TRX getting some attention,too really wake up the motor, compliment those new pistons with a set of FCR41 flatslides.

Vieze123
TRX-Enthusiast
Posts: 5
Joined: Tue Apr 30, 2019 10:58 pm

Re: R1 front fork project

Post by Vieze123 » Sat Jan 18, 2020 10:56 pm

spiritedride wrote:Hi Vieze123, great to see a 100,000 km TRX getting some attention,too really wake up the motor, compliment those new pistons with a set of FCR41 flatslides.
Thanks! Yeah, for every extra 10.000km we became even better buddies.

Yeah, heard a lot about carb-upgrades. The sound alone makes my heart skip a beat. Are the Keihin's different from the Mikuni TMDR 40 flatslides? Either way they cost a fortune! :cry:

spiritedride
TRX-Enthusiast
Posts: 88
Joined: Thu Feb 19, 2015 12:56 am

Re: R1 front fork project

Post by spiritedride » Sun Jan 19, 2020 9:51 pm

Hi Vieze123, I've had nothing to do with the Mikuni's but the FCR's are brilliant.Had mine on for 3+ years and 15,000 km without an issue.They are still civilized and smooth crawling in traffic or highway cruising,but you get instant throttle response at any rpm ( thanks to their pumps ) and a much stronger pull all the way to redline.Exit drive out of corners will put a smile on your face.Only drawback is no choke function,but 2 pumps of the throttle before you hit the start button and it fires.

cobbadiggabuddyblooo
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Location: Brisbane,Australia

Re: R1 front fork project

Post by cobbadiggabuddyblooo » Mon Jan 20, 2020 1:05 am

Have both FCR-41 and TDMR-40.
Excellent midrange response from the Mikuni TDMR40’s with no real noticeable difference until into the redline. Little better velocity gains down low with the 40mm vs 41mm plus the emulsion tube design on the Mikuni atomises the fuel better down low.
I’ve seen Dyno results too between the 2 on a motor with similar build characteristics to mine with 10Nm gains in torque at 4000rpm and a loss of just over 1 hp at 8000rpm with the TDMR’s.
laughter is the best medicine

coxylaad
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Re: R1 front fork project

Post by coxylaad » Thu Jan 23, 2020 9:57 am

=D> =D>

nice!

Vieze123
TRX-Enthusiast
Posts: 5
Joined: Tue Apr 30, 2019 10:58 pm

Re: R1 front fork project

Post by Vieze123 » Mon Mar 16, 2020 9:17 pm

Well, it's done!

The spacers were a pain because of some perfect measurement errors of yours truly.

Eventually fixed that and properly pinched the bushings to prevent them from wobbling out of the legs in any way.

The levers touched the fairing when fully steered left or right, so there was some tweaking to be done.
A nice before and after
https://www.instagram.com/p/B9cFNOUpoJT ... hare_sheet

And the end result. Very proud of this project and can't wait for the trackdays to safely commence.
https://www.instagram.com/p/B9oz6-7nmVx ... hare_sheet

cobbadiggabuddyblooo
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Posts: 6809
Joined: Thu Aug 28, 2008 9:19 am
Location: Brisbane,Australia

Re: R1 front fork project

Post by cobbadiggabuddyblooo » Tue Mar 17, 2020 12:37 pm

Did a similar axle mod to run an original trx front wheel in an early R1 front end.
Fitted a Koso RX2-n dash to get around the speedo too.
But on the latest rebuild I kept the original dash and removed the speedo and replaced it with a GPS speedo ( $70 ) of the same size so fits all inside the original dash.
laughter is the best medicine

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