Planet Minis

MAZZ77X · 06-02-2009, 06:16 PM

Can some one give me a little tutorial on shortening XR 70 forks? I need to drop the front of the kids bike 2" and cant with the stock top triple and I also feel that with the shorter amount of travel it would be like killing 2 birds with one stone. Maybe I'm wrong though.

This is a Road race bike only by the way.

doopsx3 · 06-02-2009, 06:22 PM

you can cut the springs to reduce the travel but the best way is to get a BBR top clamp and then you can just raise the forks up in the clamp..like this

Paxracing · 06-02-2009, 06:25 PM

You can make a spacer for the top of the damping rod.

THOSE GUYS RACING · 06-02-2009, 06:37 PM

change the top clamp so you can keep the little travel you have .but find one that will let you slide the tubes up where you want them

doopsx3 · 06-02-2009, 06:40 PM

this is what ya need

firepower354 · 06-02-2009, 06:51 PM

#5 can be replaced with a longer spring, or like Uncle Don says, add a spacer to go along with it.

Supermoto594 · 06-03-2009, 08:06 AM

Quote:

Originally Posted by firepower354

#5 can be replaced with a longer spring, or like Uncle Don says, add a spacer to go along with it.

Watch out for your rebound holes in the dampening rod though, I added a spacer and it covered the holes, making the rebound crazy slow. You might have to fill them in with a weld and re-drill the holes lower down the rod.

firepower354 · 06-03-2009, 10:20 AM

Good call. I got a bucket of valve springs. Those shouldn't cover the holes.

MAZZ77X · 06-03-2009, 03:23 PM

I appreciate the help but can some one tell me if I need to replace #5 with a spacer or add a spacer? If so how big and of what material? I want to shorten them 1"-2".
Also I thought of the triple clamp but the next move is a custom set of clubman style bars and the forks would get in the way. Plus I don't want to spend anymore money on this bike.

Thanks

firepower354 · 06-03-2009, 07:46 PM

You won't want to remove the spring, or at top-out it will clunk like mad. You'd add an additional stock top-out spring, or a spacer to go with the stocker, or a longer single spring.

stik__boy · 06-04-2009, 08:10 AM

i.e.----- want it 1" shorter...... put in a 1" spacer.....keeping in mind, this affectively "preloads" the fork spring, from the bottom, by giving you 1" less fork tube to stuff the same fork spring into....... so remember that this process will also stiffen the forks. DO NOT shorten them with a spacer, then CUT the excess spring off, as a shortened spring is a stiffer spring..... then it'll be WAY stiff.

stik__boy · 06-05-2009, 01:08 AM

I'm not sure.... You'd have to know the end spring rate.... But I know that if you did BOTH it would be stiffened up both ways.

s_10onbagz · 06-07-2009, 11:32 PM

I would cut the springs just a tiny bit less than the height of the added spacer to even things out. Add a little bit of preload to the forks, but don't add the height of the spacer in preload if that makes sense. adjustable top clamp is your best bet. I hear you can run an XR80/100 top clamp for added adjustability, but you can only slide the fork tubes up like 0.5" before they hit the bars. I would dish out the cash for the BBR clamp.

2bamp · 06-08-2009, 04:27 PM

How much difference would 1" make to the stiffness of the fork? Is a 1" spacer/spring going to give much the same result as heavier springs?

I am thinking of applying the same concept to a budget KLX for parking lot fun. I assume the same idea would work for that application?

06-02-2009, 06:16 PM	#1 (permalink)
MAZZ77X 3rd Gear Member Join Date: Oct 2006 Location: Right down the road from NJMP Posts: 2,428 My Mood:	How to Shorten 70 forks??? Can some one give me a little tutorial on shortening XR 70 forks? I need to drop the front of the kids bike 2" and cant with the stock top triple and I also feel that with the shorter amount of travel it would be like killing 2 birds with one stone. Maybe I'm wrong though. This is a Road race bike only by the way.

06-02-2009, 06:22 PM	#2 (permalink)
doopsx3 3rd Gear Member Join Date: Aug 2008 Location: San Diego Posts: 5,018 My Mood:	Re: How to Shorten 70 forks??? you can cut the springs to reduce the travel but the best way is to get a BBR top clamp and then you can just raise the forks up in the clamp..like this

06-02-2009, 06:25 PM	#3 (permalink)
Paxracing 3rd Gear Member Join Date: Mar 2004 Location: ca Posts: 5,754 My Mood:	Re: How to Shorten 70 forks??? You can make a spacer for the top of the damping rod.

06-02-2009, 06:37 PM	#4 (permalink)
THOSE GUYS RACING 3rd Gear Member Join Date: Oct 2006 Location: costa mesa ca. Posts: 1,283 My Mood:	Re: How to Shorten 70 forks??? change the top clamp so you can keep the little travel you have .but find one that will let you slide the tubes up where you want them

06-02-2009, 06:40 PM	#5 (permalink)
doopsx3 3rd Gear Member Join Date: Aug 2008 Location: San Diego Posts: 5,018 My Mood:	Re: How to Shorten 70 forks??? this is what ya need

06-02-2009, 06:51 PM	#6 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 12,345 My Mood:	Re: How to Shorten 70 forks??? #5 can be replaced with a longer spring, or like Uncle Don says, add a spacer to go along with it. __________________ If it has my name on it I did it;) FirepowerMinis.com 810-237-9537 M-F 9-6 Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Piranha/Medina/Thumpstar bikes, parts, engines and accessories.

06-03-2009, 10:20 AM	#8 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 12,345 My Mood:	Re: How to Shorten 70 forks??? Good call. I got a bucket of valve springs. Those shouldn't cover the holes. __________________ If it has my name on it I did it;) FirepowerMinis.com 810-237-9537 M-F 9-6 Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Piranha/Medina/Thumpstar bikes, parts, engines and accessories.

06-03-2009, 03:23 PM	#9 (permalink)
MAZZ77X 3rd Gear Member Join Date: Oct 2006 Location: Right down the road from NJMP Posts: 2,428 My Mood:	Re: How to Shorten 70 forks??? I appreciate the help but can some one tell me if I need to replace #5 with a spacer or add a spacer? If so how big and of what material? I want to shorten them 1"-2". Also I thought of the triple clamp but the next move is a custom set of clubman style bars and the forks would get in the way. Plus I don't want to spend anymore money on this bike. Thanks

06-03-2009, 07:46 PM	#10 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 12,345 My Mood:	Re: How to Shorten 70 forks??? You won't want to remove the spring, or at top-out it will clunk like mad. You'd add an additional stock top-out spring, or a spacer to go with the stocker, or a longer single spring. __________________ If it has my name on it I did it;) FirepowerMinis.com 810-237-9537 M-F 9-6 Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Piranha/Medina/Thumpstar bikes, parts, engines and accessories.

06-04-2009, 08:10 AM	#11 (permalink)
stik__boy 3rd Gear Member Join Date: Apr 2005 Location: wisconsin Posts: 1,227	Re: How to Shorten 70 forks??? i.e.----- want it 1" shorter...... put in a 1" spacer.....keeping in mind, this affectively "preloads" the fork spring, from the bottom, by giving you 1" less fork tube to stuff the same fork spring into....... so remember that this process will also stiffen the forks. DO NOT shorten them with a spacer, then CUT the excess spring off, as a shortened spring is a stiffer spring..... then it'll be WAY stiff.

06-05-2009, 01:08 AM	#12 (permalink)
stik__boy 3rd Gear Member Join Date: Apr 2005 Location: wisconsin Posts: 1,227	Re: How to Shorten 70 forks??? I'm not sure.... You'd have to know the end spring rate.... But I know that if you did BOTH it would be stiffened up both ways.

06-07-2009, 11:32 PM	#13 (permalink)
s_10onbagz 3rd Gear Member Join Date: Sep 2007 Location: Connecticut. Posts: 1,742	Re: How to Shorten 70 forks??? I would cut the springs just a tiny bit less than the height of the added spacer to even things out. Add a little bit of preload to the forks, but don't add the height of the spacer in preload if that makes sense. adjustable top clamp is your best bet. I hear you can run an XR80/100 top clamp for added adjustability, but you can only slide the fork tubes up like 0.5" before they hit the bars. I would dish out the cash for the BBR clamp.

06-08-2009, 04:27 PM	#14 (permalink)
2bamp PM Newbie Join Date: Dec 2006 Posts: 44	Re: How to Shorten 70 forks??? How much difference would 1" make to the stiffness of the fork? Is a 1" spacer/spring going to give much the same result as heavier springs? I am thinking of applying the same concept to a budget KLX for parking lot fun. I assume the same idea would work for that application?

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