Topic: shorter offset yokes / triple T for 500K1

[Ewan 500K1]

Hi, anyone know if there are any yoke / steering stem sets from other bikes that would fit straight onto a 500K1. ?  Standard yokes are 45mm offest, looking for something with an offset of 30 to 35mm.  So far I have the attached list of bikes with the same steering stem diameters, headstock bearing seat diameters, stem bearing height  (ie they take the same steering stem bearings) and the same fork tube sizes. But cant find any info on steering stem length dimensions or yoke offsets

[calj737]

Ewan - I have a '74 550 that I know will fit. Further, I recently purchased a custom 750 Triple Tree that fit (offset, spread and tube dis.) with the small exception of the stem being too long. I pressed it back and shortened it by 0.760 and installed with tapered bearings. Like a glove and smooth as silk.

I have a '73 CB500 and have removed the triple and compared it to the '74. To my naked eye, they appear to be exactly the same. I can't test install the factory 550 stem into the 500 as the 500 bearings are wrecked and I must first complete disassembly, re-install of bearings after some other work. So that will be some time.

Hopefully, others will chime in with their experience and knowledge.

Can you post what your goal is? Perhaps others have met that objective with their 500 and can offer some guidance.

Cheers -

[754]

I am looking at an 83 ish GPZ fork..aluminum trees 38mm.stem is bigger longer..so can be cut down..remachined. Looks like 200mmcenters witharound40mm offset.

[Ewan 500K1]

Ewan - I have a '74 550 that I know will fit. Further, I recently purchased a custom 750 Triple Tree that fit (offset, spread and tube dis.) with the small exception of the stem being too long. I pressed it back and shortened it by 0.760 and installed with tapered bearings. Like a glove and smooth as silk.

I have a '73 CB500 and have removed the triple and compared it to the '74. To my naked eye, they appear to be exactly the same. I can't test install the factory 550 stem into the 500 as the 500 bearings are wrecked and I must first complete disassembly, re-install of bearings after some other work. So that will be some time.

Hopefully, others will chime in with their experience and knowledge.

Can you post what your goal is? Perhaps others have met that objective with their 500 and can offer some guidance.

Cheers -

Hi Cal the aim is to find a tripe T / yoke set that will be a straight fit and has a shorter offset that the standard 500 set up .... I've got longer rear shocks on. These are 361mm (or 14.4 inches)  between mounting hole centres, standard are 315mm (12.6 inches) ... so my rear end is raised by 46mm (1.8 inches). This done to allow enough rear end clearnce as like you I'v modified the rear end to put an electrics tray in. This means front end rake and trail are reduced. If possible I'd like to couteract that by fitting a tripe T with a shorter offset ... but dont have machining capability at home... so trying to find a Triple with same stem, spread and tube clamp daimeter but shorter offset. Maybe its too big an ask 
The 750 tripe T you mention is the same as the one on your build thread .. but they have the same offset as the 500 ? 
The 550 ones have the same offset as the 500 ?  Photo of bike attached, also attached a trail calculator which shows effect of longer shocks on rake and trail with standard Triple T offset

[Ewan 500K1]

got a quote for a one off CNC alloy set for £420 including taxes from D&M Engineering at http://www.d-mengineering.co.uk/   Probably a bit much for my (well okay , the wife's) budget.  Still keen to know if there are any straight bolt on swops from other bikes that would do the job

[Kemp]

How does it handle now? You have any issues? Should steer a little quicker than stock.

[Ewan 500K1]

How does it handle now? You have any issues? Should steer a little quicker than stock.

not been on the road since the new shocks have been put on ... still a few things to do like powder coat the frame, put rear sets on, get it tested etc.  Some comments on other threads are saying that I'll get tank slappers and raer end wobbles with the current rake and trail results from the new shocks .. so just exploring possibilities . I kno , I Know just get it on the roa and see how it feeels 

[754]

Modding a stem should be 50-90 bux..did a single race. Turn down for 25 on a Suzi stem a few weeks back.

[Ewan 500K1]

Modding a stem should be 50-90 bux..did a single race. Turn down for 25 on a Suzi stem a few weeks back.

bux = quids ??    .. yeah maybe I should get more adventurous ... how do you get the stem out of the lower yolk ?  .. or can it stay in the bottom yolk for machining ?  The 40mm offset on the GPZ would neraly get me where I want to be trail wise .. but not quite

[SOHC4 Cafe Racer Fan]

Modding a stem should be 50-90 bux..did a single race. Turn down for 25 on a Suzi stem a few weeks back.

bux = quids ??    .. yeah maybe I should get more adventurous ... how do you get the stem out of the lower yolk ?  .. or can it stay in the bottom yolk for machining ?  The 40mm offset on the GPZ would neraly get me where I want to be trail wise .. but not quite

US$1 currently equals 0.64 GBP, so that's not too many quid. 

[Ewan 500K1]

Modding a stem should be 50-90 bux..did a single race. Turn down for 25 on a Suzi stem a few weeks back.

bux = quids ??    .. yeah maybe I should get more adventurous ... how do you get the stem out of the lower yolk ?  .. or can it stay in the bottom yolk for machining ?  The 40mm offset on the GPZ would neraly get me where I want to be trail wise .. but not quite

US$1 currently equals 0.64 GBP, so that's not too many quid.

then it shouldnae cost mair than a pony (£50) ... I'd need tae fin a lathe man that I trusted. Maybe I'll just fling on a steering damper and take tae the road as is.. and get intae all this mair complicated business later ... bike needs back on the road soon ... runnin  oot o time the noo.

[754]

You need a lathe man that. Knows bikes, I leave stem in..

 You know they make blocks, for the rear that may help you, but I wont even mention them if you said you want your bike tohandlee well.

[Ewan 500K1]

You need a lathe man that. Knows bikes, I leave stem in..

 You know they make blocks, for the rear that may help you, but I wont even mention them if you said you want your bike tohandlee well.

handling well would be handy .. we've got some great wee twisty roads over here > i'm gona get a camper meantime ... and look at steering stem / yokes more seriously for the other 500 when the time comes

[Ewan 500K1]

Think I might have been on a wild goose chase . Recalculated the trail this morning using a different (hopefully better ) method and trail comes out at between 93 an 99mm (3.72 / 3.96 inches). This time I took some photos of the bike. First placing the bike on a plank of wood. Then printed out the photos and drew a centre line on the fork and using the plank as the horizontal drew a line along its edge. Then I  used a decent protractor to measure the castor angle (angle A in the attached photo). Out of four different photos (2 of each side) the castor angle was consistently between 65 and 66 degrees giving a rake angle (R on attcahed photo) of 24 to 25 degrees and a calculated trail of 93.2 to 99.5mm ...... a much more acceptable result that using the crude pole measuring methods above.  Just waiting for a mate to loan me an inclinometer to measure the angle of the forks to the horizontal now to see how that compares. .... but looks now as if I dont need to be so worried about the longer rear forks resulting in an unnacceptably low trail figure for the front end. So I currently think there's now no need to mess about with the front end geometry to compensate for the longer rear shocks. ust need to to put the old rear shocks on and use the photo/protractor method to see how the rake angle compared with the standard figure for the bike (26 degrees) and how the standard shock result compares with the longer rear  shock result .. and repeat using the inclinometer method.  later edit... realised that these measurements with the old shocks, so a bit a red herring of a wild goose chase

[Ewan 500K1]

First off, I've modified my last reply .... it wasn't the new shocks that were on when I did that first manual protractor / photo method at all.. it was the old shocks. I realised that when I went out to the shed today to take some more photos of the various combinations of rear shocks and Triple Ts to apply the manual protractor method to.  So ... I took photos with new shocks and bent Triple T, new shocks an straight Triple T , old shocks and new Triple T and old shocks with old bent Triple T. Four photos of each combination. Results were inconsistent with variations of up to one and a half degrees for the rake calculations for any one configuration.   

However the Digital Protractor ( A.K.A. the inclinometer ) arrived today (see first picture below) and this really has given consistent results (see third picture below),  ... it was absolutely consistent in the change effects that both the new shocks and changing the Triple T had on rake and trail and this gives me loads of confidence in the figures. So thats me done and dusted with rake and trail measuring. Its been an education for me at least  .

So, I now reckon (with confidence) that..

1. A one degree change in rake = a reduction in trail of more or less 6.5mm (quarter of an inch)

2. For every 10mm increase in rear shock length there is a 0.48 degree reduction in rake and a 3mm recuction in trail.

and with a bit of acceptable tolerance that..

3. With the new longer shocks I've got a rake of 23.5 degrees giving a calculated trail of 91mm (3.64 inches). Stock figures are 26 degrees rake and 102.5mm (4.1 inches trail)

Also got hold of a bargain basement GSXR steering damper today... might be a wee bit on the short side for a stock 500, but as I'm putting 10mm extra on the steering stop so that the ace handdlebars dont bang off the tank I reckon it should do the job. Just having trouble locating a suitable frame clamp (29mm) for the damper.