Author Topic: Suzuki RL250 lower fork offset  (Read 1340 times)

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Offline brent j

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Suzuki RL250 lower fork offset
« on: March 01, 2020, 11:37:36 AM »
I'm on the bludge again.
To try and work out if the forks on my RL are useable I need to try and find the offset from the centreline of the forks to the centre line of the axle. Just a couple of mm makes a very big difference in how the bike handles and turns. I figure I have a few options
1 If someone can measure the offset very accurately, and it's not easy
2 Someone can loan me a lower fork leg so I can measure it. Happy to pay post both ways (obviously) and even a cash deposit
3 I bite the bullet and buy a set of forks

Thanks
Brent
The older I get, the faster I was

Offline pokey

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Re: Suzuki RL250 lower fork offset
« Reply #1 on: March 01, 2020, 02:41:33 PM »
http://www.rl250.com/rl250_specifications.htm

teering

Steering Angle                                    60º                           60º (right and left)                                60º (right and left)                             60º (right and left)

Turning Radius                            64 in (1,630mm)                     53 ft (1.63 m)                                      5.3 ft (1.63 m)                                  5.3 ft (1.63 m)

Trail                                                   x                                 3.0 in (76mm)                                      3.0 in (76mm)                                   3.0 in (76mm)

Caster                                                x                                          63º                                                    63º                                                   63º

Offline djr

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Re: Suzuki RL250 lower fork offset
« Reply #2 on: March 03, 2020, 09:02:39 PM »
I'm on the bludge again.
To try and work out if the forks on my RL are useable I need to try and find the offset from the centreline of the forks to the centre line of the axle. Just a couple of mm makes a very big difference in how the bike handles and turns. I figure I have a few options
1 If someone can measure the offset very accurately, and it's not easy
2 Someone can loan me a lower fork leg so I can measure it. Happy to pay post both ways (obviously) and even a cash deposit
3 I bite the bullet and buy a set of forks

Thanks
Brent
I have a Beamish RL250, early silver engine type- so should have same forks
happy to try and measure offset , but haven't long assembled the forks , so would rather not dismantle again to measure
how would you recomend measuring offset of assembled fork ?

Offline brent j

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Re: Suzuki RL250 lower fork offset
« Reply #3 on: March 03, 2020, 10:47:22 PM »
http://www.rl250.com/rl250_specifications.htm

teering

Steering Angle                                    60º                           60º (right and left)                                60º (right and left)                             60º (right and left)

Turning Radius                            64 in (1,630mm)                     53 ft (1.63 m)                                      5.3 ft (1.63 m)                                  5.3 ft (1.63 m)

Trail                                                   x                                 3.0 in (76mm)                                      3.0 in (76mm)                                   3.0 in (76mm)

Caster                                                x                                          63º                                                    63º                                                   63º

Thanks for that Pokey, I can put the rake, trail and measured wheel diameter in the trail calculation program I have and that will give me the total offset.
Suzuki (and it seems most trials bikes) have the steering tube at a different angle to the fork legs so it's not really possible to measure the offset at the triple clamps.
BUT, Having the full offset figure (from the numbers you have supplied) means I think I can bolt the entire fork assembly onto the table on the mill at work and get an accurate offset measurement for what I have.
The older I get, the faster I was

Offline brent j

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Re: Suzuki RL250 lower fork offset
« Reply #4 on: March 03, 2020, 10:55:49 PM »
I'm on the bludge again.
To try and work out if the forks on my RL are useable I need to try and find the offset from the centreline of the forks to the centre line of the axle. Just a couple of mm makes a very big difference in how the bike handles and turns. I figure I have a few options
1 If someone can measure the offset very accurately, and it's not easy
2 Someone can loan me a lower fork leg so I can measure it. Happy to pay post both ways (obviously) and even a cash deposit
3 I bite the bullet and buy a set of forks

Thanks
Brent
I have a Beamish RL250, early silver engine type- so should have same forks
happy to try and measure offset , but haven't long assembled the forks , so would rather not dismantle again to measure
how would you recomend measuring offset of assembled fork ?

Thanks djr but getting a measurement usually means pulling at least one fork leg off.

My method is to put the forks on the bed of a milling machine (or accurate flat surface) and bolt them down on parallel spacers. This way I can get an accurate measurement from the fork leg to the table and axle centre to the table. I can also put the triple clamps on and measure from the steering tube to the table and/or fork leg. Plus there's a bit of adding and/subtracting tube/forkleg/axle diameters.
 
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Offline pokey

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Re: Suzuki RL250 lower fork offset
« Reply #5 on: March 04, 2020, 07:47:03 PM »
I figured seeing your doing so much to the frame you would be able to run a straight edge down the headstock and a find that magic mark in space of where to measure from.

From a little investigation it seams the tolerances or subsequent "usage modifications" on the frame change that head angle a bit.  Ive read one owner recording three different measurements from different machines. with variance of 3/4 " from axle to Fr engine mount. Good luck with the build.

Offline LWC82PE

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Re: Suzuki RL250 lower fork offset
« Reply #6 on: March 05, 2020, 01:34:08 PM »
In case its not clear to viewers, this is the measurement hes after between the lines

Wanted - 1978 TS185 frame or frame&motor. Frame # TS1852-24007 up to TS1852-39022

Offline brent j

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Re: Suzuki RL250 lower fork offset
« Reply #7 on: March 06, 2020, 04:06:27 PM »
I figured seeing your doing so much to the frame you would be able to run a straight edge down the headstock and a find that magic mark in space of where to measure from.

From a little investigation it seams the tolerances or subsequent "usage modifications" on the frame change that head angle a bit.  Ive read one owner recording three different measurements from different machines. with variance of 3/4 " from axle to Fr engine mount. Good luck with the build.

The way Suzuki put these frames together there's no accurate way of measuring the frame, there's a weld seam just where you'd normally measure. I think I read about the three different frame/steering head angles on the trials forum. A guy had and modified the head angle of three frames. I've kept the same steering head angle but shortened the frame to move the weight forward then lengthened the swingarm to get the wheelbase back. I am copying what someone else has done and apparently it is very successful. I'm looking forward to finding out!
The older I get, the faster I was