PHBH slides, 40 and 50, which is leaner and richer?

[Davidsquaredson]

Sorry,
I have a 40, 45, and 50 slide. Scooter seems jetted just fine except if I am under load going up a hill with throttle between 1/4 and 1/2 it bogs down, like a whaaah sound and power just dies, unless I grab a handful of throttle and get it up onto the needle and it takes off. I assumed I was too rich in the slide area. I had it on a 50 slide, have dropped down to 40. Still have the effect but some what less. My idle jet is a 52, thinking I would drop to a 50 and try it again.

My set up is 200 GT kit, BGM clubman, 28mm delly. Starts first kick with choke. Will settle down to around 1100 RPM idle.

Just want to confirm that 40 is leaner than a 50 slide.

Tx
David

[tonydevon]

40 is smaller cutaway, so less air than the 50 in the same throttle position

its the size in mm from bottom to the top of the cutaway

[Burnside]

50 is leaner than 40, the larger the number the higher the height of the front cutaway which allows more air in, therefore leaner

[Adam_Winstone]

40 is richer than 50

[warts]

You can file, or better, machine a small amount off to give an incremental change, or if you are poor/mean like me to spend the £40x2 for new ones.
On the big big PHF's you can take a bit of the bottom too, if you go too far.
AFAIK, the number is the height of the cutaway in mm, without the decimal.

[olliewtf]

Take a deep breath.

Not common to find 50 slide, its quite lean.

You have richened up this portion of jetting by fitting the 40.

What you thought was bogging down due to too much fuel was infact quite the opposite; not enough. Admittedly, the two can sometimes feel similar, though plug colour and the sound you describe are good indications of lean running.

So to cap off. Keep the 40 slide in, it seems to be doing a world of good. If it's still lean, try richening the pilot. The pilot has somewhat of an impact throughout, particularly when off the throttle after a run, so it is important that this is set with this in mind, not just for everlasting tickover.

You could also try lifting the needle one slot.

It can be tricky to scientifically work out what throttle position your definitively at and what jet is responsible; marks do help, but around this area I would try all 3 parts (pilot slide and clip position) to see what works best overall.

[Adam_Winstone]

If we're getting into jetting issues, rather than just answering the rich/weak slide question, what needle and atomiser are you running, what float weight/height, etc?

The more info we have, the more likely we can make informed suggestions.

Adam

[a.lo.v2]

i thought a smaller cut out richens up due to increased velocity over atomiser pulling more fuel rather than less air entering.

[Adam_Winstone]

^... I don't bother trying to get my head around it, especially when you consider that some slides have cutaways in the front (PHBH, etc.), whilst others have cutaways in the back (standard SH range). I stick to knowing the way that slides work for a range, e.g. the higher the number for a PHBH slide, the weaker it is, e.g. 50 is weaker than a 40.

[Davidsquaredson]

many many thanks.

we never ride alone as long as there are people like this