CB250RS Rebuild/Tracker Build from Up Over!

Hi Guys,

picked up this a few months ago.

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Yeah, I know...why? Simple, light, chuckable and cheap. That plan is to build a (legal) bike that's lots of fun and very ridable on the local roads in Norfolk UK which are often narrow, bumpy, twisty with the odd bit of wildlife.

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I'll be sticking roughly to the tracker outline, but it's going to be more of a form follows function build. Just so happens the Norfolk is home to Lotus cars, so I'll be doing a Chapman and adding lightness.

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I have a decent sized garage at home and access to a well equipped workshop at work complete with a bike mad toolmaker. I'll be learning how to machine and turn parts as I go on so expect this to be a long build. No doubt I'll be making plenty of mistakes along the way.

I had originally planned on getting the basic bike on the road and riding it for a bit to assess what improvements I could make. But decided against this as much of the original components would fail the MOT thus i'd be wasting time and money.

and so it begins......

 

First off is to sort out the front end. The stanchions are badly pitted. Having priced up re-chroming or new stanchions I've decided to bite the bullet and do a front end swap to something better, lighter with better brakes. But something that will go on relatively easy and allow me to use the original wire wheel with alloy rim.

I've done a little bit of Googling and have just taken delivery of a pair of decent forks complete with yokes from a 90's ZZ-R250 for £60 and caliper, complete with master cylinder , usable pads and braided line for £30. Appropriate ALL BALLS RACING tapered head bearings have been ordered (3-4 week delivery) £40.

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I wanted to see what the bike weighs in it's original form, so with the aftermarket tat removed I pushed her on to the scales.

Front 57.3kg Rear 71.2kg Total 128.5kg (in old money that's Front 126.3lbs Rear 157.0lb Total 283.3lb)

Not bad wet weight (oil & brake fluid) no fuel. Which appears the manufacturers spec of 125kg (275.6lb) dry weight is pretty much spot on.

That's front 44.5% and rear 55.5%.

Be nice to get it sub 120kg (264.5lb) with closer to a 50/50 weight distribution, I doubt if I will, but I don't think it'll be a millions miles away either.

As for me, yeah there's some weight I can shed there too, but my mass is centralised

 

Roughed up some spacers today at work......had lots of help and guidance.

 

Little bit more turning.

spacer by Groovii D, on Flickr

spacer by Groovii D, on Flickr

I've ordered a cheap used CB750F disc to offer up. Plan is to do a rough build...then strip it down and rebuild and finish everything properly. I'll develop her as I go along.

 

Street tracker style




http://www.bikeexif.com/honda-cb250rs-tracker


something along these lines, built for me to ride on my local roads.

 

I am liking that tank.....can't seem to figure out what it's off.

 

Found a localish guys selling a CD175 tank it's cheap enough, but no chrome panels.

I'm playing with trying to use a brembo caliper and ditching the ZZR one....and looking at my disc options.

In my quest to shed weight, I've hollowed the front wheel spindle, it's gone from 320g to 230g.

 

Talking of weight........I realised that I'd taken off one of the shocks and had not included it in the weigh in. It comes in at 1.5kg (3.3lbs) So the revised starting stats are.

Weight 130kg (286.6lbs) Front 57.3kg (126.3lbs) and rear 72.7kg (160.3lbs) that's Fr 44% and Rr 56%.

 

Just a quick update. Got sidelined for a bit with a building project. But my bearings came yesterday from All Balls so I can get cracking on getting the forks and frame acquainted. Still messing about with the caliper disc conundrum.

 

Sorry for my absence guys......been busy (hiding from you Aussies whilst the Rugby World Cup Was on)

Back on this now. So far as my brake set up goes, I'm using a Brembo 2 pot from a CB500 and 276mm disc from a CB900 as it bolts straight on to the hub. I shall be making up a caliper bracket next week (also learning how to use a mill) and I'll be venting the disc too.

Also I know I promised myself not the buy anything until I am ready for it...........



I plan on slipping in this 6 speed box from a XL250R...goes straight in, looks immaculate and it was cheap on the bay of evil.

 

Please correct me if I'm wrong, but in the UK the standard XL250 had the same engine as my little CB RSA. The XL250R was again the same engine but Honda made it a bit more hardcore for off road use and abuse. That included fitting a six speed box. I understand that the final output is about the same but the ratios are now much closer together providing better acceleration (as long as I don't balls up my changes).

I'm hoping to maintain the RSA's 80ish MPH cruising speed. I don't plan to fit this anytime soon, but I saw it cheep and made an offer. Cannot see any noticeable wear/damage and they are very rare in the UK - bargain . I plan on doing a full engine rebuild as I'm building this as a keeper.

and if it doesn't fit......back to auction with it.

 

think I may need the single gear driven balancer shaft from the XL250R to replace the two chain driven ones inside the CB