Progress - She runs at last! (75 CB400F)

[mike the bike]

Take a few photos,  we may be able tp spot the problem.

[Bryanj]

If the tickover screw when screwed all the way in still has a gap to the lever it adjustes you definately have the slides not right

[Nurse Julie]

"Snigger, Snigger"

Sorry couldn't help myself. 

I'll write out "I shouldn't snigger in class" 50 times as a punishment.

I will stand in the corner for 10 mins, sorry Sir 

[ManicGTI]

So, 5 minutes after posting my 10PM message last night I took a long swig from the beer bottle sat on my workbench.  It was a big mouthful.

Sadly however, it turned out that the cool, refreshing (and undrunk!) Hop House 13 was in fact at the other end of the bench.  The bottle I had taken a swig from contained the petrol I had drained from the carb bowls.

Yuck. Luckily I don't 'think' I actually swallowed any, but I've gone through many litres of water to dilute and flush it through.  I can still taste petrol now.

At that point, my interest in continuing to work in the cold diminished rapidly.  So the only picture I have is this one:

If the tickover screw when screwed all the way in still has a gap to the lever it adjustes you definately have the slides not right

The lever does touch the idle screw when fully screwed in, but only just.  This is with the slides all bottomed out (ie the individual slide adjusters all screwed in as far as they will go), there's about 6mm gap.

[K2-K6]

At the risk of travelling too far along the axis of smut and double meaning, you may need to wear school uniform for that.

Back to the problem in hand  the first part of Bryan's setup of setting up on the bench is where I think you maybe going wrong. Perhaps thinking about it in reverse may get you going the right way.

Let the slides drop to bottom of carbs (closed throttle) then think how when you make slide adjustments you are trying to move the throttle mech towards the idle adjust screw. With the screw turned perhaps one turn in from nothing,  keep making adjustments to slides until mech meets stop screw,  at this point the operation should be within normal range and you can sync them on the bench.

It's harder to explain in writing than with them in front of you so hope this helps.

[ManicGTI]

It's exactly what a float chamber is for,  to break the head pressure ( no sniggering at the back there,  oddjob and Julie) and provide a reasonably constant fuel weight for the carb's vacuum to work on, which in turn gives you a chance of linear jetting response.

If it didn't do this then as the fuel tank volume varied then so would the jetting and the float height would be absolutely meaningless.

Thanks for the clarification, I have to admit I'm new to Carbs and this era of vehicles.  I'm used to working on Mk1 Golfs and MX5s!

Take a few photos, we may be able to spot the problem.

Thanks, I'll try and take some clearer images of the set up as it stands as soon as I can.

[ManicGTI]

Stealing a pic from ebay for reference, i'm confident that I assembled the adjusters correctly (although I could be proven wrong!):


So if I back all the adjusters out, the throttle will be returned towards the idle adjustment screw, and the slides towards closed?  I'll give it a poke tonight.

[mike the bike]

Now you're thinking it through logically.   Dont try starting the bike with Hophouse 13 (other beers are available)

[petermigreen]

There is another factor here.

I had the same issue when I stripped/rebuilt my carbs. Following all the set up dimensions in the Haynes manual, I could not get my Idle screw to operate in the normal range. After a lot of checking and re-checking I finally worked out that I had re-assembled the throttle assembly incorrectly.
Have you done anything to the spindle that the throttles pivot on? Mine was slightly out of position and affected the whole operation of the throttle. There is a flat on the top of the spindle that a fixing bolt locates on and it's fairly critical where it's positioned in my experience. Once I worked this out, I had my carbs dialled in sweet.

Where about in London are you?

Peter.

[ManicGTI]

This was pissing me off so I made haste home on the Street and got cracking. Backing all the adjusters off did bring the throttle Mech back round to about 2mm from the idle screw. Much better! I've now synced them with a 1.5mm drill bit.

Thanks for that tip Peter,  I'll take a look at the Mech position.

I was up near Dalston on the same road as Tom, but now in New Malden.

Sent from my ONEPLUS A3003 using Tapatalk

[K2-K6]

Looks like you're getting somewhere with them at least.

Take from your title that you're talking about the Bosch fuel injected golf's. As you say a bit different from these old bikes.

I'm just the other side of the A3 from you,  so if you need another pair of eyes to look at the carbs, give us a shout.

[ManicGTI]

Ah cool, thanks.  Yes indeed, I've had a couple of '83 GTIs on K-Jet.

It feels like I've progressed anyway!  Hopefully i'll get to refit at the weekend and try again...

[K2-K6]

There's a mk1 lives near me,  they look modern even now and very crisp design. We ran an 86yr Audi 5 cylinder some time ago a close relative in engine and fuel injection.

I don't think there's any mysteries in the bike carbs,  just a bit of time and careful setup and they're not much trouble when up and running. You can't be far from getting them sorted I think.

[ManicGTI]

There's a mk1 lives near me,  they look modern even now and very crisp design. We ran an 86yr Audi 5 cylinder some time ago a close relative in engine and fuel injection.

I don't think there's any mysteries in the bike carbs,  just a bit of time and careful setup and they're not much trouble when up and running. You can't be far from getting them sorted I think.

Indeed,  even the later engines weren't too far removed,  I fitted the 2.0 16V from a mid 90s Corrado, running a mix of 16v mk2 Golf and 8v Mk1 k-jet systems.

So carbs are back on and bike is started,  but appears to be running on only cylinder 1&4  now. Idle with choke on is laboured (Unsurprisingly).

Must have knocked something as all Four were firing beforehand. I have a feeling I'm going to be chasing my tale a little on this beasty before I get anywhere close to setting it up properly.

In the mean time I'm going to set up the brakes so at least I can run it up the road at some point!

Sent from my ONEPLUS A3003 using Tapatalk

[petermigreen]

Don't ignore other possibilities. Have you got a spark on 2 & 3? Gremlins have a way of diverting your attention while you're chasing something else.

Worth checking so you know for sure that it's fuel and not ignition.

Hope you get it resolved soon.