Hp2 Sport telelerver A-arm mod

[Joe the Viking]

Today feels like the first real day of spring in Stockholm: Sun is out, a few degrees above freezing, dry(ish) roads and bikers beginning to wake up from their winter slumber. A perfect day to try out any new, yet to be started dream bikes you happen to have waiting in the garage.



























This is what i did instead:






The plan is to cut the tapered part of the hole down flat, elongate the untapered part by 12-15mm and make an insert with a taper to fit in the slot. I haven't decided on how much i want to move the hole yet but i will be moving it 3-5mm MORE than the approx 9mm change that the tried and tested RT arm would make.

Tomorrow i will try to find cutter heads of the right sizes for the mill, I don't have access to CNC equipment so making a nice, clean radius cut requires a head of the right size. Machining is scheduled for Wednesday and/or Friday, If everything goes smoothly i could be riding this weekend. But how likely is that?

[Broop]

Is the thought behind the mod to adjust the wheel angle? To make it steeper for sharper turning?

God Bless you brave souls that are always looking to "make it better"

[shreddr]

Coolness!! I knew you and I were going to get along!! When you get yours squared away, do mine next! There is a stock a-arm for sale in the Parts section in case you want to experiment with a sacrificial piece.

R1200S OEM shocks/A-arm/exhuast

[Joe the Viking]

Originally Posted by Broop

Is the thought behind the mod to adjust the wheel angle? To make it steeper for sharper turning?

Rake, trail, wheelbase, ride height and the angle between A-arm/fork tubes will all be affected.
Results should be:

Quicker steering
Less change of the rake with suspension travel
Smaller turning circle
Better ground clearance
Less stability
More diving up front while on the brakes and in a turn
More tendency to endo on the brakes

All these things aren't on the positive side but if you want quicker steering the other option is to jack the rear way up and/or lower the front, this will produce different side effects that are a lot worse imo.

I'm sure i've overlooked something here, anyone feel free to fill in the gaps or question my theories.


Shreddr: are you sure you want to have your A-arm hacked to pieces by a guy who can't even spell "Telelever" in the title of a new thread?

[J!Rka]

And what about just lengthen rear shock? My R12S Öhlins shock can elevate rear end without changing sag.

[anotheroldrider]

http://www.tonyfoale.com has pretty nice software to analyze funny front end geometry for anti-dive percentage, rake and trail throughout the travel, etc. No relation to him or the site, but it's interesting software - I'm using it on my airhead Hossak front end & frame project.

[JonyRR]

Hey!
AOR is back...you do some neat stuff.
How about that giant oil field smack-dab in the middle of the US that dwarfs the saudi fields....

BTW, I now have the ultimate supermoto (an XR750 replica hardley-ableson)

[Joe the Viking]

Originally Posted by J!Rka

And what about just lengthen rear shock? My R12S Öhlins shock can elevate rear end without changing sag.

To get the same change in rake i would have to jack the rear up a lot, this would lead to a much higher center of gravity than the A-arm mod (bad). It would however not produce less change of the rake with suspension travel. This is a big deal for me as i don't like the fact that our bikes gain rake when decelerating and therefore when turning in. (More rake leads to slower steering).

Playing with shock length will be used as a way to fine tune stability/steering rate after the mod. Hopefully the mod will land me somewhere near the desired characteristics.

[Joe the Viking]

Originally Posted by anotheroldrider

http://www.tonyfoale.com has pretty nice software to analyze funny front end geometry for anti-dive percentage, rake and trail throughout the travel, etc. No relation to him or the site, but it's interesting software - I'm using it on my airhead Hossak front end & frame project.

I actually have used that software before and it's great but it can't handle the sliding fork tubes of the telelever I'm afraid.
I would love to have a Hossak front end, then it could really be tuned to what I want!

[anotheroldrider]

"...[the Foale software] can't handle the sliding fork tubes of the telelever"


Right, sorry - I forgot about that. You could always build a complete new front end.



"AOR is back"

Hi Jony - I've been here, I was just sort of watching and living vicariously through the dandy projects I see here. Since my 12S is a daily driver, I've resisted the temptation to do anything to it - it's gone almost 50,000 miles now with zero problems. A couple vacations to see my daughter and here family in PA, and trips from Port Arthur, TX to Claremore, OK every couple weekends seem to add up.

The XR sounds like fun - a buddy has an XR1000 that gets flogged pretty regularly.

[BMathison]

Art - I still need to get you out on one of our rides. I have yet to see another R12S in Oklahoma.
I'm still healing, but should be back on the bike within a couple weeks.

Good to see that you're back in town.

[anotheroldrider]

<...I still need to get you out on one of our rides.>

Thanks for the invitation - I'd love to join you. I'm supposed to start a boiler project in Choteau next October, and will actually get to live in my own house for a year.

[shreddr]

Joe, just so we are all clear here, you did ride the bike in stock form first, correct? I am looking at your bike pics and that exhaust looks pretty unused.

I may be a bit over the top when it comes to modding, but I do like to have a starting point from which to guage my success, even if it is my butt dyno/elbow potentiometers.

[Joe the Viking]

Originally Posted by shreddr

Joe, just so we are all clear here, you did ride the bike in stock form first, correct? I am looking at your bike pics and that exhaust looks pretty unused.

I may be a bit over the top when it comes to modding, but I do like to have a starting point from which to guage my success, even if it is my butt dyno/elbow potentiometers.

No, I haven't even started her up yet.

There's no real use in trying to get a feel for the steering and stability on cold, salty roads. If I wait for the first chance to test it on track the season will have started and it will be too late for major mods.
I'll be very happy if i can dial in the bike to be just stable enough to ride quite fast on track with my Öhlins steering damper set to 0. If i can't get it unstable at all well then I've gone in the right direction anyway. Knowing what the bike did in stock form isn't THAT important with this particular mod.
And the feeling of stripping and grinding on a 25000$ bike before even turning the key is something else.


That being said I will of course be curious as to what my mods have achieved and later this summer I'll be meeting up with Jonas the Swede for at least a full day of track riding. My plan is to get him to switch rides with me for some on track testing (just don't tell him about it yet).

The mill I'm going to use was unavailable tonight so I'll try again tomorrow, beggars can't be choosers.

[Joe the Viking]

Ok, I've had some change of plans: Instead of machining the A-arm to take an insert i came to the conclusion that it would be better to make a plug for the old hole and then machine a new hole 13mm further back. This leaves more of the original aluminium and is easier to machine without CNC equipment. The drawback is that i won't be able to switch between stock and steep rake but if i need to I can always make an insert later.



Step one: turning out a round plug with a tapered end from a square piece of billet Au.


The laith is at least 70 years old and is working well with good precision but the leather primary belt needed a little extra tension so i had a friend hold the wheel of a paddock stand against it.




It turned out pretty well and was a tight enough fit that i had to give it a few whacks with a rubber mallet to seat it properly.

[shreddr]

Joe. I was thinking the same thing, but I thought perhaps that welding up the old hole might be better. How will you keep your plug from spinning when you start cutting into it?

[Joe the Viking]

Sorry about the poor quality of the pics from here on, they're courtesy of my Sony Ericsson...

Step 2: leveling off the plug and the bottom side of the arm.



Fixing the arm to the table of the mill proved difficult but after a few tries i was sort of sure it would be ok.




Milling the night away.




Smooth as an islay single malt.

[Joe the Viking]

Step 3: Machining the hole 13mm further back than stock.



Making a pilot hole with a small drill.




Taking out the hole to 18,2mm. The hole is cut partly in the plug so it needs to be clamped in order to keep it from rotating or lifting.




Cutting the taper with a drill bit sharpened to the correct angle.

[Joe the Viking]

Step 4: Leveling off the plug and arm on the top side.



Similar problems with securing the arm to the mill.




The plug was difficult to secure so i just took care not to push it to hard, the fit was good enough that it actually didn't move at all.




Milling the night away.

[Guest24]

I guess all this makes sense if you live in a short riding season ice world. I'd have to be winning money with my HP2S before I'd ever consider altering a limited edition bike. Oh well, at least shreddr has a playmate. Making a street bike unstable is questionable IMUO. Come to think of it, I want everyone to whack away at those HP2S's-it'll make mine more valuable.