SOHC.co.uk Forums > CB650

1981 cb650z - carbs

(1/3) > >>

blackeagles:
I suspect I know the answer to this but I thought I would post my problem as there may be something I’m missing.

I have never had much luck with 4 cylinder carbs (3 too many) but I spotted a tatty 1981 cb650z so against my better judgement I thought “how hard could this one be?” so I have spent the last few months cleaning it up and now I have got to the carbs.

OK, the problem, it ran and ticked over well without any smoke/hunting or choking so I was going to leave it but being a meddler I had to check it and the carb sync showed 1 and 4 twice the value of the base carb and 3 just a little high but the real thing I could not live with was the slow running screws were set between 3 ½ and 4 ½ turns out ( the correct setting is, I think, 1 ½ out).

So anyway I re-synchronised them with the screws at still out and it ran hwhen hot so I reset the screws to 1 ½ and big surprise it no longer runs. It starts on full choke but if I touch the throttle it stops even when hot.

I’m going to guess they will have to come off but before I do that any other suggestions or things to check?

SteveW:
If it’s PD50 carbs like on my 1980 650 the accelerator pump jets are blocked.
That’s exactly the symptoms I had, open the throttle and the engine dies.

blackeagles:
It is the pd50 carb and I had forgotten the acc. pump.  I will have to drill out the screw in the clamps (rusted) and check.

SteveW:
I was on the point of giving up on my 650 and dumping it in the back of the shed.
My carbs must have been on and off a dozen times.
The only way I found to unblock the accelerator pump jet was to separate all 4 carbs. The hole left by the aluminium tubes between each carb, connect a piece of hose connected to a large syringe.
In the syringe caustic soda mixed with water.
Apply pressure, nothing will happen then it will suddenly start to flow as the blockage clears.
Immediately rinse with water as aluminium doesn’t like caustic soda.

If you do this method ALWAYS add the caustic soda to the water, never water to caustic soda.

blackeagles:
well, I'm not sure if its good or bad but I borrowed one of those cameras of a flexi connection and the acc. pump jets that point into the carb are clear as I can see a jet of petrol firing out of them into the carbs.

Its an odd thing but it was running well with the sync and pilot jet settings so far out originally - 1 and 4 were twice the reading of 2 and 3 AND the pilot screws had 1 and 2 set at 4 1/2 out  and 3 and 4 set at 3 1/2 out so you would have thought it was running very rich at tickover but it was not!!
 

Navigation

[0] Message Index

[#] Next page