SOHC.co.uk Forums > CB350/400

CB400F Frustrations - Not firing, low compression (Cyl Block now off)

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ManicGTI:
EDITED title to current status.
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Ok apologies for the lengthy post!  I'm having difficulty coaxing any kind of life out of my CB400F.  Not a massive surprise as it was last taxed on the road in the mid-90's!

I'm really looking for a bit of guidance on an order of attack...what to check next and in what order, all advice welcome!

Intro thread and background to the bike: http://www.sohc.co.uk/index.php/topic,7399.msg44632.html#msg44632

I understand that there's a ton of things that need checking over before the bike will likely run 'well', but as a starter for ten I was expecting for it at least to attempt to fire up...It's turning over but it's not even trying to splutter into life :/

Status so far:

FUEL SYSTEM:
- Carbs were gummed and locked up.  Following advice on here I left them in hot water to loosen, then stripped and cleaned them with carb cleaner, including jets etc. Replaced all O-Rings along the way.
-  On reassembly the bowls leaked badly.  I've bought a rebuild kit (non-genuine) and replaced the Float Valves and pins, but left all the other parts as the OEM ones at the moment.  On reassembly (3rd/4th time lucky!) now only one of them leaks.
- Tank cleaned, new petcock, fuel hose, in-line mini filter and some fresh fuel.
- The carbs are roughly synced on the bench, but not balanced properly, just rebuilt as they were.  I have not put the airbox or filter back on.

ELECTRICAL:
- Checked Continuity across the starter circuit.  Clutch switch is duff so I have bypassed it with a jumper in the headlamp for the time being, now cranks on the electric starter perfectly fine.
- Checked continuity of Ground side of Coils and Engine Stop Switch circuit.
- Both Coils input sides appear to have a resistance of ~ 5.2 Ohms.  A couple of the HT leads havd kneckered ends so I trimmed them a little and refitted the Caps.
- Battery is new but admittedly undersized as I was planning on relocating it.  Its an AGM Fireblade battery, I have it sat on an optimate so it has full charge.
- Brand new spark plugs fitted.  All four are getting a visible spark when I crank with teh plugs lying on the head. 

My feeling at the moment is that no fuel is getting into the engine, I can't see any fuel on the plugs.  However, I've tried cranking it with some easystart into the carbs and not even a splutter.


TO DO:
- A 'proper' compression check, adaptor for my compression tester is ordered.
- Check static timing, although I cant see why this would be out.

Other things to check?
- Valve clearances, will this make a difference at this stage of things?
- Pull the carbs, clean again and replace idle jets etc with those from the rebuild kit?
- Anything else to check on the ignition system?

Dave

Bryanj:
Have you checked that the points are actually connecting and opening as corrosion would stop the former and age the latter

mike the bike:
I would have thought the points were ok since the plugs are sparking.
Two things have caught me our in the past...
Make sure the points cam is not 180 degrees out and
Check that enough air is getting through.
Since it won't start, the plugs should be covered in petrol.  If they're not then why not.

ManicGTI:
Thanks for the replies guys,  I started this thread to re-inject some enthusiasm as I got thoroughly pissed off with the whole thing at the weekend.

I've had the cover off and the points look in great condition, no corrosion and they open/close aif I slowly crank it on the kick starter with cover off.  I haven't adjusted them as I am getting spark to the plugs.  It's the NipponDenso setup, I'll dig out a photo.

- Points Cam, thanks I'll have a look at this.  Any way to check visually?

- Enough Air getting through - I haven't refitted the filter or airbox so there's no restriction other than the throttle sliders.

Dave

ManicGTI:

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