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Author Topic: CB250 RS - Project "Phoenix"  (Read 5109 times)

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #40 on: Mar 28, 2018, 04:12:14 »
No visual progress as of late. The bike is currently a unicycle in the garage.

I've dropped my fork yokes off at my local fab shop to have the stems pressed out and swapped over. I've also gave them the front wheel, after deciding I wasn't happy with the inner shoulder - it effectively made one of the bearings defunct as the inner race would end up spinning with the outer race. They're gonna machine off the shoulder to match the opposite side, I'll then pop the bearings back in with a new, longer spacer.

I'm also looking at a re-bore kit with a slightly oversize piston to get a bit more power out of it combined with some carb work and a decent exhaust. I've also started deciding on what electrics will go in, a Daytona Velona speedometer and hopefully a P700 style headlight. I plan on using LED lights to reduce current draw as I'm still considering using a battery eliminator, but may end up with a small lawnmower style battery yet.

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #41 on: Mar 30, 2018, 08:15:07 »
So Last night I was itching to get something done on the bike. My wheel and yokes are still with the fab shop so there's nothing I can really do on that side of things, so instead I decided to have a look at the motor.

It's renowned for these engines to strip the threads on the rocker cover bolts, so I decided to crack them off and see how likely it was going to be for this engine to need rethreading.

I vaguely remembered that honda hid two of the rocker bolts under the valve adjustment caps, so first these had to come off:




They came off nice and easy, so we started trying each bolt on the cover itself. The alloy is in pretty bad shape so I wasn't expecting much good to come of this!



Before we could think about removing them, the tachometer drive needs removing from the end of the camshaft. This came out nice and easy and looks in good shape. I'll probably get a blank made up for this since it's unlikely it'll get reused (I'm not sure I'm gonna run a mechanical tach)



Following that, we were able to take the rocker cover bolts out. With a lot of finger crossing, some very gentle persuasion with a 3/8" ratchet, and to my amazement every one came out of the head without stripping anything. Some took a bit of force but thankfully not enough to damage anything. I didn't even need the plusgas!



The inside of it looks in fairly good shape. There's a small amount of pitting on the cam lobe, but I'm going to have to inspect that properly and see if it's reusable as it looks like getting a replacement would be nigh on impossible.

I also got this hub cover in the post for the MZ front hub, as a nice bit of finishing. I'm planning on boring the hole out to suit the aprilia axle shaft, I'm also tempted to get a second for the brake side - the MZ hub was originally drum, but an adapter bolted through the centre of the hub has now converted it to disc. You can't really see the remaining drum due to the size of the aprilia disc, but I'm half tempted to get it covered anyway simply because I know it's there. In order to do that, I'd need a hole boring in the middle of it to about 60mm! I'd maybe silicon bond it to the disc adapter though, such that it becomes one piece. Welding might be an option, but I feel it's probably a bit unnecessary for the purpose it'll serve. Should look nice all polished up.


Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #42 on: Apr 01, 2018, 07:51:01 »
Little bit of faffing about with the bike yesterday. I offered up the rear wheel to the swingarm and after about an hour of fettling I've decided I'll be better off just respoking the rear hub into the new rim. The MZ rear hub uses a right-hand drive, whereas the honda is left. As a result, the drum brake mounting is all over the place. If I line the actuator arm up, the brace mount is in the wrong place and vice versa. So I looked at the possibility of creating a new bracket for the brace. This would work, but the hub is approx 45mm slimmer than the honda one, so it would need spacing and centralising. FWIW, I'll just save the headaches and reuse the Honda hub on the 17" rim.

Offline Pete12

  • Posts: 221
Re: CB250 RS - Project "Phoenix"
« Reply #43 on: Apr 01, 2018, 08:35:51 »
Doing a nice job there Paddy, I'm following along for sure.

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #44 on: Apr 02, 2018, 08:13:00 »
Doing a nice job there Paddy, I'm following along for sure.

Thanks Pete, I'm getting itchy feet with it at the moment as there isn't a lot I can do until I either order stuff or get parts back from the fabricators!

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #45 on: Apr 10, 2018, 09:01:43 »
So!

A little more engine work done. I've got it stripped such that the head and barrel are off, piston out etc and it actually looks in incredible condition. I'm starting to feel guilty about wanting to overbore it it's in such good nick!





The piston needs a good de-coke but it looks good overall. Lots of parts that need cleaning up externally but the internals are looking good. Time to decide the extent I want to go to if I want to squeeze some power out of it.

In other news, I finally got my stem/yoke and front wheel back!

Here's the Aprilia yoke with the Honda stem machined and pressed in & the new bottom taper bearing installed (I need to do this again, as in my excitement I forgot to put the dust seal on... >:( )



Here's the new top bearing installed - the taper race doesn't sit flush with the frame at the top, but the protruding part is covered by the cupped top nut.



& here it is all fitted up. There's still some finishing work to do on the top yoke, as well as replacing the top yoke nut with a better looking one and a smaller washer. I test fitted the bearings back into the wheel so I could mount it up. I still need to make a new bearing spacer for it.

I may see about getting the tank front mounts dropped a little so that the front of the tank sits a bit higher. What do we think? I think it sits a little low at present. The mounts need work anyway as one is slightly bent, so this may be an option. I've also been in touch with Maxton Suspension to see about having the fork internals replaced with some of their race cartridges.




Finally, I dummy mounted the aprilia brake to see how misaligned things were. Thankfully, it doesn't look like there'll be too much work in getting it centred!



Offline kagraves

  • Posts: 150
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Re: CB250 RS - Project "Phoenix"
« Reply #46 on: Apr 12, 2018, 23:27:48 »
Awesome project so far! If you ever want some photoshop rendering done to get some of your styling on point hit me up I'm a designer and fabricator over in California. I don't have a bike at the moment as a sold my last one and need to be working on something! I will definitely be following along.

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #47 on: Apr 14, 2018, 11:57:17 »
So the bike has just gone over to my mates workshop to get the welding work done. It's getting the rear triangle levelled up, braced and boxed at the back end. It's also getting some tabs welded on for me to fit a splash guard, lock stops welding on, and the tank alignment sorting out.

In the meantime, I'm figuring out the suspension at the front. I got a quote back from Maxton and lets just say their internals won't be happening. Instead, I'm going to kill two birds with one stone. I'm going to swap out the fork legs entirely. To put into context how bad these aprilia legs are, when they're on the bike I can just about bottom them out just by pushing down on them, and I only weigh 75kg... I don't want the bike to be bone shattering, but that's way too soft for my liking.

Thankfully, the aprilia stuff uses a fairly standard 50-54mm top/bottom clamp diameter, meaning I can mount up any fork legs that fit that, and are of similar length. My theory is that I want the forks silver, and to do that it would cost me 150 in anodising. Since I've not done wheel or brake alignment on the aprilia fork legs yet, I'm not losing anything if I swap out the legs, other than a 10 pair of wheel bearings. Therefore, I've got a budget of about 150 for some silver forks in decent condition. In the UK it's easy to pick up a set of ducati monster or older SRAD 750 forks for that price. Finding a caliper for one is slightly harder, but I'll cross that bridge when I come to it!


Awesome project so far! If you ever want some photoshop rendering done to get some of your styling on point hit me up I'm a designer and fabricator over in California. I don't have a bike at the moment as a sold my last one and need to be working on something! I will definitely be following along.

That would be awesome mate, drop me a PM  ;D

Offline teazer

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Re: CB250 RS - Project "Phoenix"
« Reply #48 on: Apr 14, 2018, 15:37:54 »
Maxton do make some awesome stuff, but maybe there's a more cost effective solution for this project. Rather than getting GSXR forks and opening another can of worms, what about a set of stiffer springs to fit in those forks? You may need a slightly stiffer damping setting to work with stronger springs but you could save a bunch of that cash for fine tuning once you get it up and running.

And you still need good rear shocks...

Offline paddyshepherd

  • Posts: 58
Re: CB250 RS - Project "Phoenix"
« Reply #49 on: Apr 15, 2018, 09:09:49 »
Maxton do make some awesome stuff, but maybe there's a more cost effective solution for this project. Rather than getting GSXR forks and opening another can of worms, what about a set of stiffer springs to fit in those forks? You may need a slightly stiffer damping setting to work with stronger springs but you could save a bunch of that cash for fine tuning once you get it up and running.

And you still need good rear shocks...

Hey Teazer. The issue we have is that Aprilia RS125 forks use a rather unconventional system. They only have a spring in 1 leg, and a damper in the other. Each leg on its own is utterly useless, until you put a wheel in and bolt them together. Because of the funny set up, no one does a spring kit, so the only way to really make them good, is to machine the legs and put Maxton or Matris cartridges in them. The Monster 695 suspension was noticeably soft for a big bike, so should be about right on a 250 with a bit of fettling.

Plus there's the aspect of getting the anodising done on the aprilia ones... If I can get forks and axle less than the cost of re-anodising, I'm quids in really.
« Last Edit: Apr 15, 2018, 09:31:46 by paddyshepherd »