Slightly Cafe CB250RS Project

[tychver]

Depends on how much power you want to put out. CR33mm smoothbores are generally considered to close to their limit on 1000cc inline fours from the 80s putting out 120ish hp, so I guess they're not going to be good for much above 30hp on a single. Infact they might even be worse because of the giant pulsing effect of singles. I'd go with the 35. Big is good right?

I'm going for the VM34s for $250 on my rebalanced wiseco 6 speed screamer

[tychver]

Carb rebuild kit arrived today. All looks in order, although I haven't compared it to what's actually in the carb yet. The weather is too horrible to go out and get it off the bike.

[tychver]

Got new bars. Cheapo ones off tardme. They'll do for a rat bike.

Also bidding on a VM34 on trademe.

[xwhatsit]

Nice, what sort of bars?

VM34... that's the top-pull version, right? No throttle `spindle'. You'll have to get a new cable made up. I'd like to see what you end up doing, there's a lot of those old-style roundslides around... you were right, I'll need a bigger carb with 350cc, and finding an XR500 carb is a little harder than I thought.

[tychver]

Yeah top pull old style roundslide. The throttle spindle is missing from the carb on my parts engine.

Current plan is to get the second engine running and move it onto the bike, but I didn't want to get stuck without a working carb so I bought a VM34 for $80.

Once I've got it all sorted, I'll put the rebuilt PD70 back on the newly rebuilt engine.

The stanard style exhausts are more restrictive than the standard carbs so there's not much point going bigger until I get my cycleworks.

[tychver]

Rebuilt the carb today. Couple of problems:

1) Someone has stripped the heads on one of the screws holding the throttle arm to the slide. Meant dismantling my second carb to get the one out of that. this turned out to kind of be a blessing because...

2) One threads for the float bowl screws broke as I was tightening it up. This meant moving all the nice stuff into the other carb body

Runs a treat now though, no refusing to idle and plenty strong up top. Needle in old carb was very worn, and the main jet was gunked up. No wonder it didn't idle properly and felt lean up top.

Not running the airbox at the moment, I'm planning to run with a pod and the battery (and all other electronics down there) under the seat.

[tychver]

Decided to ditch the airbox permanently and run a pod. Will rejet when I put the cycleworks exhaust on.

Still haven't done the bars and controls. Picked up a bit of a chest infection (hopefully not swine flu lol) which necessitates 6 cups of tea per hour when working outside.

I'm going to keep the standard seat minus the rails. Can't be fucked with messing around with the hassle of making a new seat unit.

Switching to a dual rectangle headlight and KOSO XR-SR digital dash is very tempting. Not sure I can justify the $450 though!

I might put off upgrading the headlight till I'm on my restricted license and can ride at night eh.

Pictures once I get the bars on.

[tychver]

CB250N front end and wheel conversion is officially beginning.

It's been spurred on by my completely fucked master cylinder. And my second completely fucked master cylinder.

If the reservoir screws strip their heads. Don't try to drill them out. It's impossible to do cleanly lol.

[murdercycle]

Sorry to bump this old thread but it seems like the place to ask-
I've got an 85 CB250RS, and fuel leaks from the carb when you put throttle on. I think it's an accelerator pump, but I went to honda to get a rebuild kit and they couldn't help, where are you guys getting them from? Is it worth it to just replace the carb with a "hotter" one? I'm 105 kilos so any more power is welcome lol.