ADVrider

Go Back   ADVrider > Bikes > Some Assembly Required
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-31-2014, 09:40 AM   #1
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423
Slight TeDiuM

How many fork upgrades require taking a hole saw and a rats tail file to the front wheel I wonder



I blame the ducati for this you know, if the suspension wasn't so bloody good then perhaps I'd have left the other bike well enough alone, but no, the duke has spoiled me with its plushiness

So, which bike is under the knife today, its my 1998 TDM 850,


It's good for motorway work but the suspension department is shocking, and not in a good sense when it comes to city streets, where it crashes from one pot hole to the next. It's saying something when a ST4S is better in town than a longish travel bike!. Up front we have a set of basic 43mm forks with rebound damping and pre-load adjustment, coupled to 0.64kg springs.

Perusing ebay for a set of 43mm forks to fit and forget found me these absolute beauty's



A set of slightly bent forks from a 2000 Yamaha R6, the uppers are trash but the lowers and internals were good, and after a good think that's all I needed Well apart from a new axle, wheel bearings, spacers. the usual bits

The plan at this point was simple, a forced marriage of tdm uppers and r6 lowers / internals. That should net me proper compression / rebound adjustment along with pre-load and 0.74kg springs. A good starting point I figured. I feel that the stock forks were under-damped on the compression side of things so having some adjustability is a good thing.

So the forks duly arrive and I start the process of ripping things apart to see where I stand, good news is that that I have all the bits I need, bad news is that there may be some coercion needed to make things work.

And at that point a Sunday lunch is calling my name
__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Old 08-31-2014, 03:40 PM   #2
Navin
Beastly Adventurer
 
Navin's Avatar
 
Joined: Sep 2009
Oddometer: 7,171
How do I bookmark this thread to remind myself to never buy a used motorcycle...

Navin is offline   Reply With Quote
Old 09-01-2014, 12:06 PM   #3
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423
You've just done it

Also, I've been here before












Similar mod to a sv650, stock sv lowers with different uppers and internals, can't remember which bike but it gave me rebound damping and pre-load adjustment, a big step up from the standard forks. Forks were longer than stock but had 10mm less travel. Also shoved a 2000 era r6 shock in the back, had to move the battery tray to fit it in. Changed the handling of that bike for the better.

Also did a couple fo bits to my dakar, before it was written off



yamaha yz forks, wilbers rear shock with custom dog bones, bike was a good inch taller than stock and was a blast in the twisty stuff




The tdm was an absolute steal when I got it, 1998 with just over 6800 miles on it, owned by an army bod.

Where was i, oh yes, Coercion of parts to make them fit

The idea is to make the R6 internals (top) fit where the tdm bits (bottom) used to go and not lose too much fork length in the process, the length of the tdm fork from axle centre to top is 825mm, stock r6 is around 35mm shy of that. The r6 internals do have a bit of give in that department so I'm hoping to end up somewhere between the two figures. It's an experiment so I'll not know for sure until it's all back together.



a quick check fit revealed some minor stuff but thhe main issue is that the tdm and the r6 fork caps have different threads, tdm on the left, r6 on the right.



that meant that this whole thing wasn't going to be a straight forward swap, even the pre-load / rebound adjusters have different threads.



I thought that was the end of it, I did think about rethreading the tdm cap to take the r6 internals but there wasn;t enough material to do so, and the tap required is a m23 x 1 tap, those aren't cheap as they aren't a standard size. Couldn't swap over the rebound damping between the two as they are different setups.

The solution I came up with was quite simple, and involved high strength locktite and a vise





Whadda you know, perfect press fit I know some people my think that's about the worst idea possible, believe me I thought long and hard about doing that as its a little brutal and there was no going back if it didn't work out. I figure that part won't see much if any force trying to pull it apart, 99% of the force is trying to push the centre section through the fork cap. Of course this means i have to go old school and add washers between the spring and the cap to alter the pre-load, I'm fine with that.

In the end I figured I've got nothing to lose if it doesn't work, apart from having to fit an entire new front end of course, which would't be a bad thing I ensured the o-ring was good before I did this as it'll never get replaced now, also did the other side and checked the lengths out to make sure they were good.



I also cleaned up and re-sprayed the lowers too, went with bedliner with a laquer coat to see how it holds up. Also cleaned up all the parts ready for final assembly in the next coupe of days. The fork lowers came out great

__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Old 09-01-2014, 05:09 PM   #4
Navin
Beastly Adventurer
 
Navin's Avatar
 
Joined: Sep 2009
Oddometer: 7,171
What did you do with the hole saw???


Navin is offline   Reply With Quote
Old 09-01-2014, 05:50 PM   #5
bluestar
misfit
 
bluestar's Avatar
 
Joined: Mar 2014
Location: N.E. Louisiana
Oddometer: 746
__________________
2008 Yamaha Road Star
2008 Kawasaki KLR 650

Two lane blacktop isn't a highway, it's an attitude.
bluestar is online now   Reply With Quote
Old 09-01-2014, 06:27 PM   #6
cleatusj
Dirt floor engineer
 
cleatusj's Avatar
 
Joined: Dec 2010
Location: Granbury, TX
Oddometer: 1,021
My guess would be bore center of wheel for larger diameter axle.
__________________
In the stable now. '76 Moto Guzzi Convert Hack
'93 Moto Guzzi Calli 3 with Leaner turned rigid

Hack build: http://www.advrider.com/forums/showt...rt+floor+build
cleatusj is online now   Reply With Quote
Old 09-01-2014, 06:47 PM   #7
Navin
Beastly Adventurer
 
Navin's Avatar
 
Joined: Sep 2009
Oddometer: 7,171
Quote:
Originally Posted by cleatusj View Post
My guess would be bore center of wheel for larger diameter axle.

That was my first guess and greatest fear!
Navin is offline   Reply With Quote
Old 09-01-2014, 07:09 PM   #8
k-moe
Beastly Adventurer
 
Joined: Jun 2012
Oddometer: 2,394
Quote:
Originally Posted by Navin View Post
That was my first guess and greatest fear!


Yer s'posed ta use a 1/4 round bastard file for that sort of fine work.
__________________
Mixing metaphors is like killing two birds with a dog that won't hunt.
k-moe is offline   Reply With Quote
Old 09-04-2014, 01:05 PM   #9
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423
Quote:
Originally Posted by Navin View Post
That was my first guess and greatest fear!
yup, needed to make some material in the hub disappear, the internal hole on the front wheel is tapered. it's larger on one side than the other, that holesaw just happened to have the right outside diameter to just fit the narrow end (drilling from the opposite side of the wheel) where i needed to remove the excess material, not accurate by any means but now the wheel spacer fits just fine and nothing rubs

More progress to report anyway, got the forks together, pretty straightforward actually, no dramas there, until i came to fit the wheel, the wheel fit without to many issues but the calipers were another story
Lining up one disk and caliper



put the other disc into the fork leg



Not a good start, figured it was down to the tdm triples being narrower than the r6 triples, but they are identical. I was starting to look at alternative discs so i was outside getting measurements when my neighbour suggested turning the discs around. You ever had one of those Doh! moments

Quick cobble together later and it fits.



so now the disk is offset towards the centre of the wheel




I need 7mm spacers to get the discs where I need them, quick peruse of ebay and I have a set of 6mm spacers for 20 Yamaha used the same bolt pattern on most of their bikes from the 70's and most dukes use the same bolt patern, how bloody lucky was that Figure i can get away with spacing the caliper inbord by 1mm without any dramas.

Last issue to deal with is the caliper mounting bolts hitting the fork leg



currently pondering counter boring or countersinking the holes to gain clearance.
__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Old 09-04-2014, 01:09 PM   #10
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423
Also, i only have a flat bastard file, not a 1/4 round bastard file
__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Old 09-04-2014, 05:28 PM   #11
Navin
Beastly Adventurer
 
Navin's Avatar
 
Joined: Sep 2009
Oddometer: 7,171
Quote:
Originally Posted by rc mad View Post
Also, i only have a flat bastard file, not a 1/4 round bastard file

Perfect to make a rat bastard hole!

I'm just kidding around (). Cool stuff your doing!
Navin is offline   Reply With Quote
Old 09-08-2014, 11:32 AM   #12
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423


You know a fork conversion isn't going to plan when you have to break out the CAD software


Current fork travel is at 85mm, not a good length seeing as the standard r6 forks have 120mm or so and the tdm has 135mm.

The bottom of the TDM uppers are hitting the base of the lowers preventing further travel, However the actual problem is that the top out spring is hitting the internals of the TDM uppers which is preventing the forks from being extended enough, along with the damper rod being to short to allow further travel. Will update more when I get the parts in.

I'm learning a crap load here about motorcycle forks and their design, its good fun
__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Old 09-08-2014, 07:45 PM   #13
Navin
Beastly Adventurer
 
Navin's Avatar
 
Joined: Sep 2009
Oddometer: 7,171
Sawzall time!
Navin is offline   Reply With Quote
Old 09-11-2014, 04:05 AM   #14
Scudman
Gnarly Adventurer
 
Joined: Apr 2009
Oddometer: 220
My recommendation is to first center the front wheel. Then make spacers that will keep the front wheel centered. This will get rid of the issue with the brake disk bolt. The brake calipers need to be spaced to be centered on the disks. This may involve either shimming or cutting the calipers. All of this requires a machine shop or equivalent. Since the spring preload adjuster is threaded to the damper rod it is the only way to prevent the lower front end from detaching from the forks. Locktight may not be the best way to accomplish this task. You could top out the front suspension and the front wheel with brakes could detach from the fork tubes. Not a desirable result.
This illustrates the trials and tribulations of making Franken bikes. Never easy but very rewarding when finished.
Scudman is offline   Reply With Quote
Old 09-23-2014, 11:16 AM   #15
rc mad OP
Physycotic gecko
 
rc mad's Avatar
 
Joined: May 2006
Location: Deeping About
Oddometer: 1,423


__________________
"Mad Science" means never stopping to ask "what's the worst thing that could happen?
rc mad is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 11:38 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014