Author Topic: CB250 RS - Project "Phoenix"  (Read 5476 times)

Offline paddyshepherd

  • Posts: 59
Re: CB250 RS - Project "Phoenix"
« Reply #70 on: Jul 25, 2018, 04:30:36 »
Couple of bits and bobs done the last few days.

I was at Silverstone Classic weekend just gone and picked up an AntiGravity Lithium battery while I was there. This thing is tiny and weighs next to nothing! So as soon as I got home I immediately offered it up. I've decided to hold off on shocks until I get my rear wheel and tyre sorted, so for now I'm not moving the battery tray until I know if it's necessary or not.

I offered up most of the key electrical components to the bike. The coil and reg/rec sit underneath the tank like they used to & the CDI unit can sit next to the battery within the battery tray. I'd already cut out a cardboard template for the main electronics tray but it appears there'll be very little for it to house now as most of the items already have a home! I'm also slightly concerned about the risk of over-stiffening the frame if I put a big panel in there... is that a valid worry or do we not think it'll make much difference?

I've also now decided I'm going to reuse the standard 250RS switchgear and simply refurbish them. The housings are metal so I'll either rub them down and leave them with a raw finish or I'll re-paint them black. At the moment they're kind of a faded grey. I originally planned on replacing but they actually look pretty nice, and very period. I'll probably run a separate quick-action throttle housing and some stubby levers since the clutch is so light.

In other news, I've also purchased a Daytona Velona combined speedo/tacho, I've finally received my reworked camshaft and I've started removing more of the engine casings etc ready to get them blasted and painted. Progress is a nice feeling!

Offline paddyshepherd

  • Posts: 59
Re: CB250 RS - Project "Phoenix"
« Reply #71 on: Sep 17, 2018, 16:23:44 »
Well, this has been very slow.

Due to various personal goings on, along with currently raising a puppy, work in the garage has pretty much ground to a halt.
I got 10 minutes or so to have a mooch at stuff a while back so I started fiddling, and instantly spotted an issue. With the disc removed from the wheel so that I could centralise the wheel to my previous measurements, the caliper hits the spokes of the wheel. This is due to the fact the caliper is mounted inboard of the fork, since the yokes on the monster front end are spaced for a wider wheel than the aprilia ones are. The ducati forks and caliper simply will not work, not without machining either the caliper or the mount - neither of which I want to do. I kicked the tyre and went back in the house.

A few weeks of sulking later I finally had a bit of a rethink, and the solution is much more glaringly obvious than I ever imagined. When I first started looking at fork conversions I looked to All Balls Racing for a conversion set of bearings. They didn't do anything for a 250RS, it's simply not common enough. Today however, thanks to a conversion list on here I accidentally stumbled upon, I discovered there's a lot of much more common hondas using the same bearings as the RS. One of those happens to be a CB750, which All Balls do several (and I mean several) sets for. Scrolling down the list for some smaller bikes that the kits are available for, I came across a kit for the KTM RC 390/Duke 390. These run a similar width front wheel to the RS, and are less than 3kg different to one, dry. With this kit I can run the yokes and forks of the 390, a wheel bearing is available for the spindle, since it's the same size spindle as the RS125 one I previously fitted. To eBay we go, armed with my ducati forks and brembo caliper to try and buffer some of the cost!

Edit: Had some measurements through for the KTM. Forks are a bit longer at around 745mm, so approx 20mm or so longer than original.
The stem is also longer, including bearings and seals between yokes there is approx. 200mm, compared to approx 180 on mine. I think it may still be workable, just with the forks dropped through the yoke a little and having the stem machined down to suit, I suppose? What do we reckon?
« Last Edit: Sep 18, 2018, 08:11:41 by paddyshepherd »