Quick jetting question... Surprise surpirse!

[Hughieboy]

Hi All

With help from the good folks on here I've been setting my 30 PHBH carb up. I have a quick (?) question about lean/rich running beyond half throttle.

Scooter is Li150 with Harry Barlow 190/Suzuki Ts piston that I have matched and polished the ports running with a TSR Evo expansion and a Varitronic. Timing as per Cam Lam recommendation is 19 degrees at fast tickover and retards to about 15 for anyone who hasn't read my previous ramblings

45 slide (came with carb, I know most seem to have a 40)
55 pilot
AV264 with X13 needle set on second clip
70 Choke
120 main

Air screw 1.5 turns out.

As above it runs well but seemed to hold back slightly on full throttle and almost speed up a bit when let off slightly. Choke test made it initially splutter for a second and then run normally. ETG said the head temperature was 110 degrees centigrade, I wonder if this is a bit hot? Plug colour looked good to possibly lean.

Thinking this to be the case I changed the main jet to a 122, this made it splutter at three quarters to full throttle intermittently although it still seemed hot. I took this to mean the main was too big and went back to the 120 but dropped the clip on the needle to the third clip to richen up the mid range and now it's boggy and spluttery in the mid range.

I have limited experience but it feels like it's either too rich and too lean at the same time almost. The first set up (120 main, second clip) ran well but I felt it needed to be a bit richer for safety but 122 is too much. Third clip on the needle is also too much either way.

Anyone recognise this and could tell me where to go with it?

Thanks,

Hugh.

[Norrie Bodge]

Hi All

With help from the good folks on here I've been setting my 30 PHBH carb up. I have a quick (?) question about lean/rich running beyond half throttle.

Scooter is Li150 with Harry Barlow 190/Suzuki Ts piston that I have matched and polished the ports running with a TSR Evo expansion and a Varitronic. Timing as per Cam Lam recommendation is 19 degrees at fast tickover and retards to about 15 for anyone who hasn't read my previous ramblings

45 slide (came with carb, I know most seem to have a 40)
55 pilot
AV264 with X13 needle set on second clip
70 Choke
120 main

Air screw 1.5 turns out.

As above it runs well but seemed to hold back slightly on full throttle and almost speed up a bit when let off slightly. Choke test made it initially splutter for a second and then run normally. ETG said the head temperature was 110 degrees centigrade, I wonder if this is a bit hot? Plug colour looked good to possibly lean.

Thinking this to be the case I changed the main jet to a 122, this made it splutter at three quarters to full throttle intermittently although it still seemed hot. I took this to mean the main was too big and went back to the 120 but dropped the clip on the needle to the third clip to richen up the mid range and now it's boggy and spluttery in the mid range.

I have limited experience but it feels like it's either too rich and too lean at the same time almost. The first set up (120 main, second clip) ran well but I felt it needed to be a bit richer for safety but 122 is too much. Third clip on the needle is also too much either way.

Anyone recognise this and could tell me where to go with it?

Thanks,

Hugh.

Id go one step at a time m8
a tip a mate gave me regarding setting needle was, if a position of the needle clip was too boggy as you say, lift clip back up one
& then put a thin washer under the clip so you have it at say position 2.5 & then try that
hope this helps

& good luck

[Hughieboy]

That's a good idea, cheers!