erratic idle and low rev misfire after carb overhaul

[luke906uk]

Hi, after overhauling my carbs on my 96 xj600n and refitting them, I've now got an erratic idle making it difficult to sync. The engine idles at around 1200rpm then fluctuates from 800-2500 on its own accord! Has anyone else had this issue or have any remedies? Thanks in advance. Luke.

[luke906uk]

Another thing I've noticed is the vacuum pipe from no1 inlet manifold to petcock has a small amount of fuel going through it (currently is a clear pipe). Shouldn't this be dry? Maybe this small amount of fuel going into no1 cylinder could be causing the erratic idle. When I say small amount I mean more like a mist.

[showaddydadito]

Leak in the fuel tap diaphragm?

I've never taken one apart but there must be some sort of diaphragm for the vacuum in the inlet manifold to pull the tap open.

Wemoto do this: www.wemoto.com/bikes/yamaha/xj_600_n_diversion/96/picture/fuel_tap_repair_kit/

They're good - whenever I order from them I get the parts next day.

[luke906uk]

It must be a leak there, do you think that is related to the idle issue? Thanks for the link.

[luke906uk]

I was thinking of blanking the vacuum pipe on the inlet and running the engine with the fuel on prime with the lid cracked open. That will rule out whether the fuel tap is the issue.

[showaddydadito]

Gotta be worth a try.

[pilgrim]

Carb rubbers! They might be split or not fitted correctly. I had loads of problems with idle speed last year, twas just that.

Must check it out!

Good luck.

[luke906uk]

Thanks for the advice, will have a good look at them. I must admit, the upper rubbers (airbox connection) dont look like a great fit.

[pilgrim]

May 31, 2014 19:47:43 GMT luke906uk said:

Thanks for the advice, will have a good look at them. I must admit, the upper rubbers (airbox connection) dont look like a great fit.

It's the lower rubbers between carbs and engine. Splits around the screw clips often hidden before you take them off. Anyway you can only see the two outer carbs.

Good luck.

[CD]

Put new seals in the fuel tap. I got caught out when mine ran dry on normal setting. There was enough leaking through to use the reserve fuel. Also replace the various hoses including the main breather. Posh silicone are not silly money.


Sent from a widget that can't spell.

[palmydays]

Luke,
Did you sort the misfire, if so what was the fix? I am having similar issues but cannot pin down the cause.
Regards,
Dave.

[luke906uk]

Sept 5, 2015 17:41:01 GMT palmydays said:

Luke,
Did you sort the misfire, if so what was the fix? I am having similar issues but cannot pin down the cause.
Regards,
Dave.

Hi palmydays, the issue turned out to be a vacuum leak caused by one of the airbox to carb rubbers. After replacing this it ran smooth and still was when I sold her on last month ?! The fuel tap was fine. Hopefully yours is a similar issue.

[palmydays]

Thanks Luke, I will have to pull mine apart & have a good look at the rubbers etc.
Regards,
Dave.