3AJ starter plunger o-ring

[Doubleyoupee]

Hi guys,

I've bought a revision set for my XT600Z 3AJ carb.
When checking on the starter plunger, I noticed something weird.
I read on the forums the o-ring on the plunger could be damaged and cause the starter-circuit to not work properly (mine is very inconstant starting).

However, my plunger doesn't have an o-ring at all:



I look online for more images and found this on here:



Weirdly enough, mine is different and has a pointy bit at the end, unlike his.

Also on CSMNL the OEM seems to have an o-ring.


Can anyone confirm?

[N67]

not an expert opinion since it's the first time i'm seeing the choke plunger like yours, but suppose that you're right - there should be that pointy bit, seems that it works as a guide.
and the shape of your plunger says quite loudly that it needs to have some rubber on it )

it's interesting that "straight" plungers (left one on the upper pic) seem to have same diameter "jamming cylinder", but normally they do work without any o-ring.
who knows, maybe different materials and/or more snug fit of the working surfaces...

[Doubleyoupee]

Originally Posted by N67

not an expert opinion since it's the first time i'm seeing the choke plunger like yours, but suppose that you're right - there should be that pointy bit, seems that it works as a guide.
and the shape of your plunger says quite loudly that it needs to have some rubber on it )

it's interesting that "straight" plungers (left one on the upper pic) seem to have same diameter "jamming cylinder", but normally they do work without any o-ring.
who knows, maybe different materials and/or more snug fit of the working surfaces...

I just installed the o-ring from the kit. It seems to fit.
The plunger is much tighter fit with the o-ring, the plunger didn't want to go into the carb bore until I screwed in the bolt and the spring forced it in. Plunger moves with more resistance but still smoothly. I think its good, no time to ride yet though.

Still interested if somebody has some concluding info. Even on XT600.de they have 20 pictures of the 3AJ carb disassembled but for some reason never took out the starter plunger...