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Discussion Starter · #1 ·
Picked up this 78 cb400 today for a whole $100 with a clean title. It needs a full engine rebuild and since I've been wanting to rebuild an engine for a long time I figured why not. It's going to be a cafe fighter for the wife. Well I called my buddy up and told him about it and he said what are your plans? I told him that I'm going to rebuild it for the wife but I'd much rather put a bigger motor in it and make it a fire breathing cafe fighter. He just happens a kz900 z1 motor with 1015 pistons and jugs and he'd sell it to me for a steal of a price.

So right now it's up in the air. The deciding factor is going to be when I open the bottom end up and see what the crank and tranny look like.


Top half of the motor side cases and all that good stuff


Plans that are definite are
Usd front end (05 zx6 or 99 r1)
Swingarm swap with 180 tire
Mono shock
Cafe tail
Different tank
And strip as much weight as I possibly can


Any idea tips or pointers are more than welcome as always.
 

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Remi's Dad
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You've got a single down tube stamped frame that you want to hold a pumped up 900cc? not a good idea or worth the effort. IMO

also a 180 tire would require a substantially offset counter shaft sprocket, not sold for the 400 twin. It would be at least a 3/4 offset sprocket.

swingarms would be limited as this motorcycle uses an outside boss swingarm not a sandwich pivot like other cb's
 

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Discussion Starter · #3 ·
Damn so maybe I'll just rebuild the engine and build a simple cheap cafe for the wife and build myself a fire breathing cafe later down the road.

Any way since the engine rebuild will take some time because I've never done one and I'm focusing more on the zx build this is just kinda a fun side project. It will be much easier to store her in mass of parts in pieces then try to find a home for her as a whole I broke her down completely except for the forks because I don't have the right size socket to get the fork caps loose to get it off.
How do I not have the right socket it kinda pisses me off but I'll buy it tomorrow.

What's she looks like now.



And the box O parts .


Going to build the motor it's own little table tomorrow so I can break her down and rebuild her at my own pace without having to move shit ( I really mean loose parts. ) when I need to my work bench for other projects.

And since my friend is offering that motor at such a deal I'm going to buy it and look for a titled kz frame that'll hold the weight and power to build my dream cafe.
 

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It's a CB400T - the generally unloved replacement for the 400/4. Frankly a stern chopping-up is probably the best thing for it! A swift image search shows two kinds of cafe racers from this bike: good ones, and ones which kept the drooping rear triangle.

As with all rust buckets / basket cases, get the motor working first before getting carried away! And set a strict budget, as buying OEM missing clips, rubbers, washers etc. will nickle and dime you to the poor house.

I'm in!
 

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Discussion Starter · #5 ·
O yea this is budget build the most expensive thing will be the motor rebuild. I'm ordering new pistons with rods for like $30 and a gasket kit for 65. I'm also throwing spiked wheels on it since this bike isn't going have enough power to push big usds and a 180 rear tire. I got a hook up the rims so those will be cheap.

EBay is my friend on this little guy



Edit: I've seen a cinch of people with little usds from a smaller cb anyone know which cb had usds on it?
 

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Remi's Dad
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as far as engine swaps. Another twin is still doable but just keep in mind an I4 is out.

The xs650, kz750 twin,2 stroke single (cr,kx,yz,rm), 4 stroke single (xr200/400/600, savage 650, crf,yzxxxF,rmz,kxf, dr,drz)

The price and end result of rebuilding the cb400 may let you down. It's a dog. Maybe find someone that has one and ride it before you rebuild.
 

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Discussion Starter · #9 ·
The motor had 1 piston stuck when they tore the head off and the bottom end spun freely. That was before they shoved some rags into it and let it sit outside without the head on it for 8 months or so. I already ordered a manual for it but I'm going to tear the bottom open and see what it looks like.

If I do it for my wife it is fine being dog but if I decide I want to ride it I'm going to put something bigger in it fit the fattest rear tire on it I can usds all the way. I guess it all comes down to how bad the bottom end is.
 

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Discussion Starter · #11 ·

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Remi's Dad
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the 250r.

I know that engine forwards and backwards. That is the best year for the frame. Awesome USD forks

My bike is a 280 wiseco and it hauls ass. The tmr carb i want will wake up the 280 kit and i'll be smashing 450s
 

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Discussion Starter · #13 ·
I just edited that post but look at the ad I neglected to paste in there.
 

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Hack in a barn
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Not a fucking clue where this thread is going, but hot damn I'm in for the long haul!...
 

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sickboy
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the 250r.

I know that engine forwards and backwards. That is the best year for the frame. Awesome USD forks

My bike is a 280 wiseco and it hauls ass. The tmr carb i want will wake up the 280 kit and i'll be smashing 450s
Agreed!!!, ive had two 2001 cr250's. Best cr250's ive ever had (which is a few)

never had a motor like that in a street bike though. How you think they would do on the road?
 

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Is my bike ok?
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Discussion Starter · #19 ·
I was thinking calling the guy with xs650 motors and serif he would part with just one. I don't have room for another truck load of parts. I already have 4 bikes and 2 truck loads of parts in a 1 car garage
 

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O yea this is budget build the most expensive thing will be the motor rebuild. I'm ordering new pistons with rods for like $30 and a gasket kit for 65. I'm also throwing spiked wheels on it since this bike isn't going have enough power to push big usds and a 180 rear tire. I got a hook up the rims so those will be cheap.

EBay is my friend on this little guy



Edit: I've seen a cinch of people with little usds from a smaller cb anyone know which cb had usds on it?
A swift google says the bike has a wet weight not far off a modern sport bike. Lighter wheels might help but in general I'd say kit from a 125/250 won't cut the mustard.

750 twins and big 2T motors? I think that qualifies under the heading 'getting carried away'. If you need a replacement motor, a later cb400/450 twin should work as they used the same basic design for ages.
 
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