Poor idle and stumbling can be caused by many set up issues but also by leaking/ poor sealing after market dump valves.

 

However there is another issue we are seeing more and more commonly in the workshop and with the advent of inexpensive dump valves on ebay and similar looks set to continue.

 

Today in the workshop was a classic example of this very issue, a zed came in that has been off the road for around 2 years, the engine was struggling to run and had a huge flat spot when statically revved, with an MOT booked for the afternoon I had to act fast.

 

Whilst it would tick over sort of when warm the ConZult diagnostic was not revealling too much, which is ok, it just means getting a little more involved. A boost leak test soon revealed a massive air leak and not too far from the intake area, with the after market dump valves in sight I instinctively went directly to the rubber bungs that are supplied with the ebay units, these are essential and form part of the installation when fitting the valves.

 

So you can see in the pictures below the rubber boots look in reasonable condition when in place or held in you hand, however pinch them between your fingers and the boot opens up, the rubber material is just way to soft and the constant flexing cause by the increased negative vacuum when on the gas then swapping to equalised pressure when backing off just wears them out.

 

Shame really as they fit so well, they are just made out of the wrong material, the other concideration is the deteriation of the boot goes unoticed and the effects slowly get worse until any idle or hesitation problems are too bad to live with as more air is drawn through the rubber boot rather than the air flow meter.....if you have these fitted to your zed it would be worth a check now!!

 

Jeff TT

 

 

[ATTACH=CONFIG]69027[/ATTACH]

 

[ATTACH=CONFIG]69028[/ATTACH]

 

[ATTACH=CONFIG]69029[/ATTACH]

 

[ATTACH=CONFIG]69030[/ATTACH]

 

[ATTACH=CONFIG]69031[/ATTACH]

Edited February 28, 201313 yr by JeffTT

The evo boys use them all the time, apprantly they go a bit brittle after 12 months and need replacing but at the price nm.