Topic: swopping Cb500 triple T for an NSR125 one

[Ewan 500K1]

so...in building my cafe racer I increased the rear forks by 46mm (nearly 2 inches) ... On a test ride today I was getting a front end side to side twitch at 90mph, despite having a steering damper on and with it set at full damping. So, I need Triple T set with less offset to compensaet for the reduced trail caused by raising the rear end. I understand that the NSR125 triple T would do the the job ... can anyone offer any advice on what is involved in this modification ?

[bwaller]

I'm in the process of organizing a set of these for another forum member. Because the NSR top clamp is flat & not "dropped" like the original the forks need to slide through the lower clamp enough to sit flush with the top of the upper. This ultimately brings the top of the fork leg closer to the bottom of the lower clamp reducing available travel. I need to play some more but may mean longer tubes or else the front of the frame will be lower. This might be ok except if there is already a change to an 18" wheel as well as longer rear shocks. If this is the case longer forks or tubes may be the answer, otherwise too great a change in rake & loss of trail will result even with 10mm less offset.

The OD of the steering stem where the lower bearing sits is smaller than the original so in order to use tapered roller bearings for a Honda it will be necessary to machine a sleeve for that lower brg.

I've just started looking at this so I have no final advice yet. Otherwise the fork spacing & diameter of these triples is correct.

[Ewan 500K1]

Bwaller ....  ta for that really thorough response mucho apprecio ... but god ma head's spinning now .  Pretty far from a straight swop and/or simple change to the stem then  .  Be really great to hear how you get on.  Plan B might be to go back to a standard frame and shocks, but I'm loathe to go there.

[bwaller]

Actually the swap shouldn't be that painful, the steering stops are nearly in a perfect spot. I tried with a tank in place and no issues with that. Another tidbit though is there are no h-bar clamps on the upper clamp so it's either clip-ons or source a set of bar clamps to bolt to the clamp. I'll try to make some time this week to figure out the fork length deal.

[Ewan 500K1]

Hi Bwaller, would an alternative be just to use longer fork tubes with the original 500 triple to increase trail ?

[Retro Rocket]

Ewan, if you aren't racing why not use the correct length shocks on the rear ? or even 1 inch longer..?  Offset is only part of the equation up front mate, you have steepened your rake quite a bit, you will get more trail with less offset on the triple tree's but it may still steer weird due to the decreased rake, also by going up in height at both ends you are raising your center of gravity which is not ideal either....... Racing suspension style mods rarely work well in the real world of street riding, Just saying..

[Ewan 500K1]

Ewan, if you aren't racing why not use the correct length shocks on the rear ? or even 1 inch longer..?  Offset is only part of the equation up front mate, you have steepened your rake quite a bit, you will get more trail with less offset on the triple tree's but it may still steer weird due to the decreased rake, also by going up in height at both ends you are raising your center of gravity which is not ideal either....... Racing suspension style mods rarely work well in the real world of street riding, Just saying..

Hi Retro ... I get what you're saying and sometimes I wish I'd just gone for a standard resoration... but need the longer rear shocks to give enough clearnane between the rear tyre and the the electrics tray that is welded in place on the lower side of the rear frame hoop.

[turboguzzi]

ewan, most people do add rear shock length to quicken the steering in race applications (but not rising the front), and in that case triples with lesser offset are needed.

if your are just in need of more overall height, would simply fit longer fork tubes. tarozzi has a full catalog of fork tubes that are also better made (top part chromed too), i think that someone imports them to the states too. 

[754]

Brent , if you carefully machine new fork caps, that fit closely into the fork leg, inner bore, you can gain some length that way. If the inner bore of tube is not concentric to the od, then the new cap may have to be turned to fork diameter, while installed in fork tube....should be perfectly straight then.