Scooterotica

Thought I would screw my jetting up on another scooter and found this brass type dish on the base of the main jet tube. Now I knew it was there when I put this 2nd hand PHBH on around 12 months ago. But, is it necessary or is it doing more harm than good, because it isn't on my other PHBH carbs.

Reason for looking at this carb is that it bogs down at just over 1/8 throttle in 2 and 3rd gears. So my intention was to start by reducing my 55 pilot and raising the needle, as a first stab. But this brass type dish covers the pilot jet.

Thats an ANTI-SURGE WASHER according to the diagram, some one who knows will no doubt explain it as I havent a clue

i got told its to stop fuel frothing and i don't need it.....so i take them out....

doggbhoy wrote:.so i take them out....

+1 took mine out as well,no problems with it 2000+ miles

off the MB site

"This washers stops the fuel surging around your main jet and causing misfires."

paulnobodyimportant wrote:Thought I would screw my jetting up on another scooter and found this brass type dish on the base of the main jet tube. Now I knew it was there when I put this 2nd hand PHBH on around 12 months ago. But, is it necessary or is it doing more harm than good, because it isn't on my other PHBH carbs.

Reason for looking at this carb is that it bogs down at just over 1/8 throttle in 2 and 3rd gears. So my intention was to start by reducing my 55 pilot and raising the needle, as a first stab. But this brass type dish covers the pilot jet.

My advice would be to adjust one thing at a time.

djh66 wrote:

paulnobodyimportant wrote:Thought I would screw my jetting up on another scooter and found this brass type dish on the base of the main jet tube. Now I knew it was there when I put this 2nd hand PHBH on around 12 months ago. But, is it necessary or is it doing more harm than good, because it isn't on my other PHBH carbs.

Reason for looking at this carb is that it bogs down at just over 1/8 throttle in 2 and 3rd gears. So my intention was to start by reducing my 55 pilot and raising the needle, as a first stab. But this brass type dish covers the pilot jet.

My advice would be to adjust one thing at a time.

Seconded!

The brass 'anti-surge/frothing' thingjust prises off and pushes back on. It will not be causing your mis-carburation. I have also noticed no difference with it there or not. Remember the main use of these carbs is on Moto X and scramblers wheelying up 2 in 1 inclines.

Thanks for all your answers; it’s finally brought my memory back. About 18 months ago I put a classic 200 Rapido top end on this one with a LTH reed valve, all sorted for piston skirt etc and solid manifold fixing by Ben at AF Rayspeed. In addition, I went for a solid mounted 30PHBH carb and that’s the reason why I left the anti-foam ring on. But over that time, I had totally forgotten why I did it. Anyway, might leave it on for now and as others have suggested, do one thing at a time to find the culprit.

In that respect, 18 months ago I had set up this carb and had great plug chops right through from ¼ to WOT, but bogging down as suggested at 1/8, which has got worse over time. Last week I dropped the needle down a notch to see if it made a difference, but it didn’t. So what I meant in the above post, I will put the needle back to where it was last week and then change the pilot jet. Let you know if this was the problem.

But many thanks for your responses and jogging my memory for why the brass type dish was there.

Paul