CB250 RS - Project "Phoenix"

ex119x

Been Around the Block
I have built more than a few of the Honda FT/XL motors and I am not a fan of the 540 piston. I thought it felt a little lazier than the stock bore and a little slower revving. However, that was on the track and not the street. The extra torque might make it a fine street motor. If you go with one of the higher compression Wiseco pistons, you will have to run some high octane fuel to avoid detonation, which will break a piston. ( I know from experience).
I have a 38mm VM carb on my current Ascot racebike and it works fine with the basically stock motor. When I build my next XL it will have the Wiseco 1.5:1 1st over piston, megacycle 4140 cam, which requires shortened guides with hd valve springs and hardwelded reshaped rockers. With that I will run at least a 38 flatslide and a a ported head.
That doesn't look like a stock header on your ascot, which is a good thing. Good exhaust systems are hard to find for the FT. Jemco makes a flat track pipe that makes great power, but it really is a race only item as it is pretty loud and not that good looking.
Let me know if you have any questions, as I have been racing these since 1981. I currently have 1 Ascot ( leaving tomorrow for the WERA GNF at Barber) and 2 XL500S.
 

paddyshepherd

Active Member
ex119x said:
I have built more than a few of the Honda FT/XL motors and I am not a fan of the 540 piston. I thought it felt a little lazier than the stock bore and a little slower revving. However, that was on the track and not the street. The extra torque might make it a fine street motor. If you go with one of the higher compression Wiseco pistons, you will have to run some high octane fuel to avoid detonation, which will break a piston. ( I know from experience).
I have a 38mm VM carb on my current Ascot racebike and it works fine with the basically stock motor. When I build my next XL it will have the Wiseco 1.5:1 1st over piston, megacycle 4140 cam, which requires shortened guides with hd valve springs and hardwelded reshaped rockers. With that I will run at least a 38 flatslide and a a ported head.
That doesn't look like a stock header on your ascot, which is a good thing. Good exhaust systems are hard to find for the FT. Jemco makes a flat track pipe that makes great power, but it really is a race only item as it is pretty loud and not that good looking.
Let me know if you have any questions, as I have been racing these since 1981. I currently have 1 Ascot ( leaving tomorrow for the WERA GNF at Barber) and 2 XL500S.

Funnily enough, you're not the first poster I've seen to say that about the 540 - unless it was your post I was reading on another forum (possibly ThumperTalk?) I can run 99 RON fuel over here no problem so it's pretty good stuff. Our lowest here is 95. Now that you mention it, I think you're right about the header. I've had a quick look and it could be either a White Brothers or Kerker header. All just from a first glance and a google search however so I could be wrong. Sounds like it'll be worth keeping if I can get it cleaned up well - it's pretty worse for wear at the moment but feels fairly solid so may clean up. It does make me wonder if I might find anything nice inside the motor - since it's also had an oil cooler on it at some point. No cooler there now but the fittings are there in the right hand casing. I'm going to pull the valve cover off tonight and see what condition the camshaft is in.
 

paddyshepherd

Active Member
Pete12 said:
This will be a trick bike with a 500 in it now Paddy. Looking forward to the updates and glad to see you're back.
Thanks Pete. It's nice to be getting on with it again. Yours is looking well!
I've got a lot in mind but it's just nice to be making some progress at last.
 

paddyshepherd

Active Member
So I've pulled the top end apart tonight to see what it's like. Also properly checked the headers and they're definitely aftermarket, but there's no markings. The bad news is they have a few holes - repairable but we'll see. I'll hang onto them, if for nothing else but to use as a template for some custom made ones.

The top end though looks pretty good. I'd say it's stock. Maybe a possibility of some cam/rocker work but I'm not sure. There's some slight pitting on the cam lobe and rocker arm but the journals are good.





I did notice these blue/green marks on the valve springs, I'm not sure if that's standard?



It does look like it's been ran a little lean. But other than that no complaints.


Last but not least, the bore is good. No scratches or marks. Appears to be standard bore. Piston is a little coked but nothing major!

 

paddyshepherd

Active Member
So today I decided I'd try to get the engine into the frame.
In order to do this I needed to chop the top mount (head steady) off. The engine would still have 4 mounting points so not an issue, and the head steady mounts have also been rumoured to be the cause of cracking heads.

First of all, I installed the 250 side casings. However, I got stuck with the left hand one, since the flywheel is in the way. The 500 flywheel has the starter ring where the 250 one doesn't, so the casing isn't deep enough to clear the starter ring when you swap it over. Once I get my hands on a flywheel puller, it'll all be fine. Saves a little weight too. I then compared the 250 and 500 valve covers, since the 250 has the decompression where the 500 doesn't. I knew the XL250 and XL500 covers were the same (thanks, CMSNL part numbers) so I assumed that the 250 and 500 ones would be interchangeable when it comes to the road versions. Thankfully, that's the case. The only changes I'll need to make is one or two of the bolt holes are slightly small (I assume they must use slightly bigger bolts on the later 500.

So, knowing I had two valve covers that would work, I started to cut the head steady off the 500 cover. Took a few goes of taking a bit off, dropping it onto the engine, realising it needed more, and repeating the process. I eventually took off as much as I was happy with doing and got enough clearance to get the two rear bolts into the engine. I'm still about half an inch away at the front bolts so the frame might need some work instead.



As you can see, it's pretty tight. I'm thinking I'll trim the seam back and then run a reinforcing weld around it. that should then give me enough room. The holes in front (to the right in the photo) are for the coil and reg/rectifier - be nice if I can keep them untouched so it's less stuff to hide elsewhere. I might need to make a little bracket to move the reg-rec up a little away from the valve cover and into the void under the tank, but it's pretty close to fitting straight off.

But most importantly, I get my first look at roughly how everything will line up on the bike; I have to say, I'm bloody happy. The engine looks well with the bulkier tank, and the back end (once shortened and fitted properly) should be absolutely perfect. No headlight for now as I'm waiting on bigger clamps to arrive to get it into the position I'd like.



 

paddyshepherd

Active Member
I need to get a shifty on with this...

Engine spec is now pretty much decided. I've ordered a 92mm piston with a 10.5:1 comp ratio. This negates the need to resleeve, just bore and hone, and also negates the need to use really high octane fuel. I'll also be using a Dellorto 40mm round slide carb off a Husaberg 550. There'll be bigger valves installed by my machinist with new seats cut. The exhaust I'll probably get a copy of my White Bros header made with a reverse cone end-can. Intake will be via a velocity stack with a filter sock. I'll also be installing decompression to the 500 engine, either by using the 250 valve cover (if the rockers will work) or by adapting the 500 one to accept it. I am getting conflicting information regarding using the 250 rocker arms, so I am going to have to measure it myself. That will have to wait though, as the engine is currently upside down on the bench awaiting kick start installation.

I've also had a quote to get my forks re-done in anodised silver, so one of the next jobs is to get those stripped down and sent off. I've got a replacement seat arriving tomorrow, since this one is, well, wonky... The new one has a central ridge that will match that of the 400/4 tank, and should fit a little nicer too, but only time will tell when it comes to fibreglass parts. It's also got less up-sweep so it should look a bit more period-correct. I think colour wise I am going to go for a Dick Mann inspired scheme, finished in Topaz Candy Orange, replacing the white graphics with a dark metallic silver.

My first local show is the 2nd week of May and I have around a year's worth of work to do by then... Let's get moving!
 

unclerob

Been Around the Block
I've recently done an FT kickstart conversion on a friends bike, he sent me some info about machining the cam cover, part numbers etc ....if you want to pm me your add I can send it on to you?
 

paddyshepherd

Active Member
I've recently done an FT kickstart conversion on a friends bike, he sent me some info about machining the cam cover, part numbers etc ....if you want to pm me your add I can send it on to you?
That'd be fantastic - PM incoming. From what I gather it's a case of just machining the case out to accept the decomp arm then installing the bits. I know the head covers match from bike to bike (part number wise) but that doesn't mean the valves themselves do, or the rocker arms.



So I got my new seat today. I have to say it looks 10x better than the other. With a little trimming it lines up beautifully and really matches the tank. I've got a little more fettling to do at some point but as far as tonight goes I'm very happy. Apologies for the multiple pic orientations but it was too dark to pull the bike out and get proper pics tonight.





 

paddyshepherd

Active Member
So on saturday I dropped the engine back in as a final trial fit. I wanted to mock up carb fitment, and it's a good job I did, we're gonna need a bit more work.





There's enough room under my tank to run the throttle cable like that, thankfully, but the bracket needs cutting a bit back, because the carb isn't fully inserted into the boot yet. I've got a new carb mount coming from Dellorto as well, since the honda one is angled weird and it makes the carb hit the frame on the left side.

Also managed to mock up the kickstart assembly, since the only thing you actually need to split the cases for is the return spring mechanism. The kick arm is going to need a little manipulation, but nothing too excessive...



Next was a quick test at making some fender brackets, using 10mm x 2mm aluminium flat. It went better than I expected so I'm looking forward to getting my fender and make some properly.



Last but not least, a quick wheel out of the garage for a proper photo of the side profile with the engine in. I have to admit, I'm bloody liking that...

 

paddyshepherd

Active Member
So I got home from work today and there was two parcels waiting for me, so it was straight into the garage.

First up, my new carb manifold and boot arrived from Dellorto. The hole centres weren't quite right, so I got the Dremel out and started boring the holes out to get the hole centres right. In the end the wee thing was bored out to within a fraction of its life, but it worked in the end. It's a good job I have a lot of dead space under my tank....



Believe it or not that does actually fit. There's enough space to at least get a meshed velocity stack on there, and hopefully a small filter as well. The tank void comes to around about where the black Sharpie line is on the top tubes.

The second parcel that arrived was this little Honda Owners Club pin badge. I got it to slot into the recess left by the original factory footpeg. My thoughts were either fill the recess, or make a feature of it. Once centralised and secured, and with the hangers painted up, that might just work nicely.



However with every step forward there's another back. My original plan for the rear brake was to use the original mechanism, actuated by a cable from the new rearset lever. That's simply not going to work - due to the longer shocks increasing the swing arm angle, the swingarm now hits the brake mechanism. The rearset lever is also much too close to the brake spline, so that again wouldn't work anyway. This one's gonna take a bit of thinking about - I may be able to convert the brake to cable actuated rather than rod actuated. Suggestions would be more than welcome!

 

paddyshepherd

Active Member
Here is a pic on how WM (JDM accessory maker) do the honda GB rod to cable conversion. maybe it will give you some ideas ....
Thanks mate. I think I've actually sussed it now though.

So....

It turns out, with my natural riding position, it's comfy for the rearset arm to actually be below the existing spindle. It looks extreme, but that's where my foot was when I sat onto the bike and got myself comfy...



So that then makes everything much simpler. I can cut the arm down at the back and move the mounting point closer to the spline, giving clearance around the swingarm..... i.e.: move the pin to where my fingertip is in the next pic. This might then mean I can use the existing brake rod. However how well this will work with the dropped swing arm is yet to be seen, I may have to convert to cable, but even that would be much simpler if I do it this way. So all I need to do now is cut the original brake pedal arm down, drill a hole in it, and make a linkage between that and the new rearset arm. Might mean that my exhaust needs a rethink...

 
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paddyshepherd

Active Member
So I got the motor back out and stripped it down on Sunday afternoon. There's really not a lot to taking these things apart. I've got the cases split now to do the kick start conversion. There's some slight differences in the FT motor than the XR and some of them caused some head scratching. First of all the kick start stop plate needs modifying, the 250 has a 6mm hole for the retaining bolt (not the spring hook bolt) where the 500 engines use an 8mm. Not only that but the FT500 has an oil banjo which has a steady bracket on it, which mounts to where this plate should. This is completely exclusive to the FT motor and isn't present on the XRs, from what we can see the banjo squirts oil into the selector shaft, which then squirts it back out onto the oil pump drive. Thankfully the banjo bracket is pretty thin, so we can still use the stop plate. Just might need a washer at the other end, and will need to check it still engages the stop properly. From memory, if anything it will mean it stops ever so slightly sooner, since the stop works by pulling the ratchet away from the starter gear.

Easier to modify this one than pay £40 ish for a 500 plate. So we pulled the plate and took it over to our bench drill to bore it to take an 8mm bolt. Now, this drill ain't the best but it's normally enough for most stuff we find in the garage. Not this. Nothing we had would even leave a scratch on that plate, what the hell are they made of!? So I've had to drop that at a machine shop. I'm also getting him to drill my crankcase to accept a new breather, since he's probably got better kit to get it accurate than I do, and the pipe is supposed to be a press fit. Not the end of the world if its a little slack, but better to be right. I should also have my Wiseco piston arriving this week, so as soon as that gets here the head and barrel will be off to my engine machinist to be mated up with the new slug.

So in the meantime I was at a bit of a loss on what to do. Thankfully my front fender arrived yesterday so that filled the gap. I've bent up some brackets out of 10mm x 2mm aluminium bar. They still need a bit of work but I'm really happy with the overall fit. I'll either get the brackets tig welded to the guard or I'll use those aluminium brazing sticks. I've not used them before as I didn't trust them but a mate has and reckons they'll be fine for a fender. I'm swayed by doing that since it'll mean I can have a crack at it myself rather than pass it off to my mate to Tig it. If I cock it up, it's not the end of the world, those fenders are only £35 delivered!



I'll probably either polish the brackets to match the guard or I'll paint them black so they don't draw in attention.
 

Pete12

Been Around the Block
Hey Paddy, the plate you have is hardened steel and the best way to drill that is with a masonary bit (preferably new). The bike is looking really good, that seat unit looks perfect, matches the tank lines exactly.
Not too sure about the mauve nail polish though....
 

paddyshepherd

Active Member
Hey Paddy, the plate you have is hardened steel and the best way to drill that is with a masonary bit (preferably new). The bike is looking really good, that seat unit looks perfect, matches the tank lines exactly.
Not too sure about the mauve nail polish though....
Yeah, once I realised the way it all goes back together I realised why the bugger was so tough. I had cobalt bits on it and it just wouldn't touch it. I've probably got a masonry bit somewhere but it's already at the shop now - since he's doing the case for me it was easier just to get him to do that as well. Thanks for the kind words about the bike overall. I agree on the seat, I'm really happy with it. My next decision to make is whether or not to make the hump into a stash box - I was planning on putting a plate across underneath then have a hole in the front of the hump, which would be covered by the seat pad. But I don't know if the resultant pocket would actually be usable enough to be worth the effort.

Hopefully still get the piston this week so my machinist can have it over the holidays, and in the meantime.... I'll start on wiring loom and get the tank/seat mounts done!
 

paddyshepherd

Active Member
Finally, something worth updating about.
So since I dropped the new piston etc at my machinist before christmas, not a lot really happened; I'm halfway through buying a house and spare time is hard to come by.

However, time is marching on and with a house move coming up I needed to get the engine back in one piece, else you can guarantee I'd lose something small but important.

So I got the machining work back from Jim at Flowtech/Milwaukee Muscle. He mainly specialises in harleys but does older jap stuff too. His work is spot on. He's bored and honed the barrel, tidied the piston up a little, ported the head and port matched the carb mount and cut a multi-angled valve seat.






So then I had a pile of parts that needed cleaning and reassembling. I wanted to paint the casings so I started to clean them up first. I originally planned on black engine with polished side casings. I very quickly realised that they were a bit far gone for hand cleaning, so opted to get them blasted. So the valves all came back out and the rest of the casings fully stripped of any left over seals and parts, and off they went to the local vapour blasters.

They came back looking bloody fantastic.



I was desperate to see how it looked in the frame as I'd warmed to the idea of leaving the engine raw, so I threw the cases together empty and mounted it up. That'll do nicely!



The cases still had a bit of blast media floating around in them so I wanted to make sure I got out, so I got up early for work, stuck them in the dishwasher and made sure I was out the house before my mother woke up and found them...!




Another coat of degreaser and a good wipe down and they were about there, time to reassemble.

First off put the valves back into the head and placed the head and barrel in a box out the way.



Then it's time to rebuild the bottom end and gearbox, install the kick start mechanism and the gear selector drum.



All relatively simple but I was using an XR/XL manual, where the FT has a number of upgrades to the oil system in the bottom end, extra pipework, banjos etc which aren't documented in the XR/XL manuals, and an FT manual is like hens teeth... So it took a little figuring out - we had to backtrack a few times after installing bits only to find there was an oil pipe in the way of the next bit; things had to be done in a slightly different order. But we got there in the end.

The next big task was to assemble the top and bottom crank cases together. Should be an easy job, other than the rear balancer is in the bottom crankcase and the front balancer is in the top - they need to be timed up with the crank as the cases go together. Once they're together there's too much tension on the chain to reposition it if you end up a tooth or two out. This took a few attempts, especially as the bearing carrier for the front shaft likes to fall out as you move the case; add in the fact you're conscious of doing it with enough pace that the gasket paste doesn't go off in the meantime...

All's well that ends well though, and the cases are finally back together with the bottom end all reinstalled.



New stainless hardware throughout.




Next up is to rebuild the top end, check piston clearance and cam profile etc as it all goes together. I'm ordering a new cam chain (despite thinking this one is fine) but it's worth having the safety while I've got it all stripped anyway. Once it's all rebuilt it'll get put in a dry box until it's actually ready to be installed and commissioned.
 

paddyshepherd

Active Member
A little more work done recently.

As the UK went into COVID-19 Lockdown, I got my house move through. We just got in in time, meaning I've had a load of time at work stuck at home. However before I could start working on the bike, the garage at the new house needed serious work. It was a bare brick building with a bare concrete floor, loads of junk and full of dust. So I've spent the last couple of weeks completely renovating it and here's where it stands now:





With that done and the bike round I could start prioritising what needs doing. First of all I want to get the engine finished off, then do wiring, then controls/brakes etc and finally paint.

So I've got a bulk order in of parts and seals etc to finish the engine off. In the meantime, I've filled the deep pit marks in the clutch cover, and painted that, the generator cover and the sprocket cover. The main casings, cylinder and head will remain raw aluminium. The casings should give a lovely contrast. I've done them Toyota Decuma Grey Metallic, with a gold infill on the lettering. The lettering turned out lovely on the generator cover, but less so on the clutch cover - so I need to have another look at that tomorrow once the paint has hardened. Then they need a final clear coat to finish them off.







Once that's all done, I should hopefully be able to box the engine up properly with the new batch of parts. I've got a new cam chain coming too as when I've re-installed this one it's not far off the wear limit. (7mm of the wear indicator showing, maximum is 9mm). I also need to get a filter for that crankcase breather, or a breather pipe/catch can.
 
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paddyshepherd

Active Member
Long time no update! The last few months have been pretty hectic with just about everything BUT the build, unfortunately!

I have got a few updates though. I got the engine just about complete, save for fixing side cases on as there's some wiring to do, and back in the bike (I've also realised I completely forgot to update on the rest of the engine rebuild, top end etc!)

So here's the complete engine...



And then back in the bike...



But before long, one step forward, two steps back... As I went to take the engine back out I spotted an area that looked a bit suspicious. Low and behold I could put my screwdriver through the frame. How I didn't spot this before I'll never know! The lower portion of one of the main tubes was completely rotten through.



At this point I was panicking and looking for a new frame. However thankfully a local bike fabricator was able to cut it out and weld it up for me! Time to get the whole thing blasted I think.



In amongst all that I bought a 1992 ZXR750 and got a few jobs done to put it on the roads, rode it for a while and decided it was too much work to be distracting me from the Honda, so I've sold that on and bought a 2003 SV650 to run around on and have been practicing Moto Gymkhana too. I even squeezed in a mountain biking trip to the french alps, a campervan trip to Scotland and got my driveway redone. So it's been pretty busy!
 
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