NC31 Carb repair / rebuild

[UncleBFester]

Hi Folks,

We have a CB400 SuperFour ( NC31) that has been sat for a bit too long and unsuprisingly, it now refuses to start. Prior to this it has been getting progressively worse at starting and has always ( for the 8 years we've been married ( wife not bike)) been a bit reluctant to sit at tickover until warm. I reckon it needs a decent thrash to clear its lungs but I can't do that until i get it running / MOT'd. Last time I had it running it took ages to come through on all four cylinders but once running it was fine. That was summer last year.

It's a 1993 K plate Jap import and has done about 30k miles, decent condition and no other issues.

It tries to start, clutch plates aren't stuck ... when it tries it'll huff and chuff and occasionally give a monumental backfire, sometimes with flame so it's clearly getting some fuel through. However it never quite catches enough to start.

Things checked .....

1. Fuel coming through fuel tap.
2. Drained some fuel out and run in the mower - starts and runs fine.
3. Opened the carb drains and fuel comes out.
4. Spark is good - but will remove tank and check plugs this weekend.
5. Battery was flat but good spare used - problem not fixed.
6. Nothing nesting in the airbox
7. CDI all looks neat and no frayed wires.

Which leads me to suspect what is in the tank and is now probably gumming up the carbs ....

Where are you getting your rebuild kits from - are those cheapo eBay kits ok for the gaskets / seals / carb to airbox rubbers? And what are these like to work on?

Part of me says just drop it to my local bike place and let them fix it but the other part of me knows that we're due another boring summer of no holidays so something to tinker with might be interesting.

Anyway interested to hear any thoughts.

[untonyto]

I purchased a carb repair kit off eBay for the same bike model. Seller called Cruzin Image based in Japan. Took a month to arrive but finally got it two weeks ago. Looks like a high quality kit; clean, shiny and all that . Now that I have it and the carbs sitting on my work table I'm stuck. To start with, there are a bunch of O-rings which I haven't identified where they go. And the usual brass jets and springs and float needles. I need to get the main carb body cleaned, but I don't want to go to a shop, and I'm uncertain about starting because I'll probably forget what goes where once it's all apart. Anyway, not to talk too much as I can't really answer your question, just found your post by googling how to tear down VP22 carbs. As you can tell I'm well lost. Anyway I'll give it a crack early in the morning and post here how it goes. Gotta say I'm still waiting for a million other parts so it propbably won't be tested on bike until two months later. Ok bye.

[MadMotoUK]

Take photos of everything as you take bits off.
Keep individual carb parts together, don't mix bits across the carbs if you can.