Newbie project 1973 CB250K4

K

KeithS

New Member
Just thought I'd drop by and say hi. Just picked up a new project: 1973 Honda CB250K4 which was built as a café racer back in the day, and then finally abandoned in the owner's father's workshop for 21 years... Has some typical period home-brewed detailing, such as crude gauge mounting plate, home-modded tank (from a CB550, maybe?) and flimsy generic front guard. Has other nice touches like Amal MkIII concentric carbs, starter motor delete and funky rear-sets. Aside from the inevitable rebuild plan on changing tank and seat to something more traditional Brit café racer look, and want to get some swept-back pipes made in the style of those used on Tritons etc. We'll see. Just spent four years building a hot-rod 'outlaw' Porsche, so needed some light relief after al that time!

Anyway, early days. And this is what I'm starting with – fresh out of the 'barn'...

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Started to investigate the bike a little more. Nice to see that it looks like it's never been thrown down the road as the cases are not scuffed, the foot pegs aren't bent and the mufflers are unmarked. There are no rounded-off nuts and bolts BUT the wiring is hilarious. The builder also didn't like to spend on new shorter cables to take into account the low-set clip-on bars. The headlamp looks to be an old Brit one, judging by the quaint old-style 'amperes' gauge. Engine fins are all good, so I'm keeping my fingers (and toes) crossed that nothing nasty shows up when I get round to lifting the top off it all.

Rear seat loop is non-existent, so that's one on the to-do list as soon as I get things stripped a little further. On the whole, though, I'm really pleased with what I've found so far. Nothing truly nasty. It cost me £700 (roughly $1100). I'm happy.

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Spaghetti, anyone?
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Not so well thought-out...
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Anyone have a new loom?
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The PO obviously liked making things at home...
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Engine dirty from storage (it was covered in sawdust!) but very good external condition
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Must have taken him hours to make such an ugly mounting plate!
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Steering damper bracket – wonder if it really needs a damper? Opinions?
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More wiring fun...
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Nest step is to continue strip down to bare frame and get it powder-coated...
 
Began the big strip down yesterday and only found one nasty surprise so far: a broken top yoke as a result of somebody over-tightening the pinch bolt on the left side fork leg. A nice surprise was seeing the amount of effort somebody had put into blending the inlet ports to match the Amals and generally smoothing them out. Looks like a pro job rather than a home-spun piece of tuning. Wonder if further stripping will reveal any other such work? Considering how much the Amals cost when new, somebody loved this bike...

So, I need a CB250 K4 (same as US CB350K, I believe) top yoke, or may have to go for a billet aluminium one. Can't find a stock one on eBay at present.
 
How far did you manage to strip the engine down? Are the carb internals and top end in good nick, considering the velocity stacks being uncovered in storage?
 
generalyen said:
I would have gave to po 300$ max for that basket case. It does have potential though.
Click to expand...

You can't get bikes in any condition for that much ($300 is about £200) in the UK.
 
The more I look at the pictures the more little details I see.
It is built very much like the Tritons of the time withe that CB500T tank and typical seat. I had one much like that on a Goldie back in 73.

Front fender appears to be aluminuium with Y brackets - like a Norton. Front brake is a CB77 (larger than stock) but the brake shoes are worn out judging by the angles of the levers.

The carb conversion is an expensive way to go - especially with those smoothbore stacks and the bath tub plugs to keep crap out is what we do on our race bikes. And that mount is a copy of what we used to do on cafe racers back then, but most of us used two small brackets.

Headlamp mounts are John Tickle style and there were lots of copies back then. I would raise the clip ons and modify the rear sets to move them forward a little and lower. Fit new tyres and other consumables and rewire it and ride it. There isn't much fitted that I would change.

I don't think anyone did sweptbacks for Hondas because the ports are not as splayed as most Brit bikes and the pipe run under the motor which is cleaner and slimmer anyway.

If you were to build a bike to look like one from the time, that would be it. Just as it is. Nice find.
 
generalyen said:
I would have gave to po 300$ max for that basket case. It does have potential though.
Click to expand...
Nice post... You clearly don't live in the UK... ::)

Green199 said:
How far did you manage to strip the engine down? Are the carb internals and top end in good nick, considering the velocity stacks being uncovered in storage?
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Not got into the engine yet, but the carbs are very good, with no scoring to the pistons at all. As it's been kept inside, and with the plugs in the carbs, there is no corrosion on the back side of the valves or seats.

teazer said:
The more I look at the pictures the more little details I see.
It is built very much like the Tritons of the time withe that CB500T tank and typical seat. I had one much like that on a Goldie back in 73.

Front fender appears to be aluminuium with Y brackets - like a Norton. Front brake is a CB77 (larger than stock) but the brake shoes are worn out judging by the angles of the levers.

The carb conversion is an expensive way to go - especially with those smoothbore stacks and the bath tub plugs to keep crap out is what we do on our race bikes. And that mount is a copy of what we used to do on cafe racers back then, but most of us used two small brackets.

Headlamp mounts are John Tickle style and there were lots of copies back then. I would raise the clip ons and modify the rear sets to move them forward a little and lower. Fit new tyres and other consumables and rewire it and ride it. There isn't much fitted that I would change.

I don't think anyone did sweptbacks for Hondas because the ports are not as splayed as most Brit bikes and the pipe run under the motor which is cleaner and slimmer anyway.

If you were to build a bike to look like one from the time, that would be it. Just as it is. Nice find.
Click to expand...
Thanks... The more I see, the more I like. After my Porsche rebuild, this is a gem.
 
Oh yeah, missed the plugs covering the stacks in the pictures! That's a relief!

Really is a nice bit of kit, especially with the 77 drum.
 
Also interesting are the footrest hangers which are very much like the RD500VPVS (RZ500) set that I modified to fit to an RD400E many years ago, but this set is steel. Can't wait to see what's inside the motor, Kent Cam perhaps or maybe and race kit cam. 2 ring kit pistons would be nice to find but not so likely. Maybe a 6 speed race kit cluster? One can but live in hope.

Merry Christmas - it came early for you.
 
Just a thought. You could get pipes made with tighter first radius then straight section before teh bend under the motor to look more angular and pick up on the style aspect of sweptbacks without going to a wide pipe that would reduce ground clearance.
 
teazer said:
Just a thought. You could get pipes made with tighter first radius then straight section before teh bend under the motor to look more angular and pick up on the style aspect of sweptbacks without going to a wide pipe that would reduce ground clearance.
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That was my plan. Been looking at various Tritons and working out best angle – follow the frame tube is an obvious one but looks too 'upright', so prefer more of a sweptback look. It may not work visually because of the engine sitting further forward in the frame compared to the Triton, but I like the traditional look of the bike below. Plenty of time to mull this one over...

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UK or not, when you are building a bike for yourself to keep and ride, the original purchase price (and every dollar after that) many times becomes negligible. I have a couple that have thousands into them and yet still not many parts are attached to the other parts. Time and Money. And Passion.

I love this project, looking forward to seeing you use whatever you can from the original find.
 
Green199 said:
Oh yeah, missed the plugs covering the stacks in the pictures! That's a relief!

Really is a nice bit of kit, especially with the 77 drum.
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Discovered it's a 40-spoke CB450 drum - the CB77s have 36 spokes (every day is a school day for me!).

EDIT: rear is also a 40-spoke with a larger drum, again from a CB450 I presume.
 
Just received (yesterday) the Benelli Mojave tank (yawn, I know, I know...) which is absolutely perfect for what I want. All the way from India, with fuel tap and Monza cap delivered to the door for £150 all in.. can't complain. Quality is very good, tank treated inside, well oiled outside to protect in transit. Delighted! Fits the bike a treat and lines up with my rear seat and subframe perfectly. I'll get a photo or two as soon as I can get off my backside to do it! Why change the tank? The CB500 one had been badly modified and looked a little too cumbersome for my aesthetic tastes.
 
Just balanced in position for the moment, but happy with the proportions and the way I can get the bottom of the tank to line up with the seat.

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