SOHC.co.uk Forums > CB350/400

fueling problems

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470four:

--- Quote from: Boggieman on August 17, 2011, 08:41:03 PM ---470four

Thanks for that, will look into getting some D8EA's. Exhaust on No.1 gets warm but the others get so hot you cannot bear your hand on them.
Plenty of fuel is going to the carb, and the plug is wet when we removed it, but when we blocked off the air intake to the carb' there was no appreciable difference. Possible air leak on inlet manifold???

Appreciate all your help
Ian

--- End quote ---

Ian
400/4 manifolds will go hard after all these years and then suffer an Epic bond failure between the alloy insert and the rubber itself:



 :o



The screws holding them on are an absolute arse to get to - forget getting an impact driver in their, no room.... I settled for chiseling off the top of the alloy insert then twisting the manifolds out, with the pressure released the screws came out easy enough with mole grips on them?

The manifolds & O-rings are still available from David Silver, use allen bolts to refix   ;)

The middle two will get cooked first, directly behind the block & running v.warm - wouldnt hurt to replace them anyway...

Boggieman:
470four

Thanks for that. I am hoping to get new plugs today and will try them first before attempting to get the bank of carb's off. It does look like the manifold rubbers have been off before as they are held in with Allen headed bolts ???.
As I said before, really appreciate all the help.

Ian

K2-K6:
Assuming you've got sparks at the right time and fuel on the plug then you'd have to consider the compression.

What do the cylinders measure when tested?

Have you swapped #1 plug with one of the others to see if the problem switches over?

The pipe will heat up just a little even if not firing, but after about 1 minute they would usually be too hot to touch.

Boggieman:
K2-K6

Checked the compression last night, starting at No1 pot it goes 80psi, 75psi, 75psi, 80psi across the engine. Yes have swapped the plugs from 1 and 4, problem stays on No1 pot. Dismantled the carb' for No1 last night and apart from a tiny constriction in the main jet it was really quite clean, haven't had chance to get them back on the bike to try them again yet. All inlet rubbers were in a good condition, all still quite flexible, not gone hard and broken ( I think they were newish when I picked the bike up).

Was wondering though whether the plug lead could be breaking down, and only manifests itself when connected to the plug, ie; when disconnected all appears well ??? Realise this sounds like I'm grasping at straws, but I am getting to that stage.

Thanks for all the suggestions.
Ian

K2-K6:
You can also switch the leads of 1+4 over to check that as they are fired from one coil (may have to unbolt the coil to do this but make sure you still have a good earth).

Make sure carbs are full then take tank off and start the bike in as near dark conditions as you can manage, you'll be able to see if the the leads are leaking and sparking across to any metal parts near them.

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