PHBG Peugeot polini tuning question...

Sorry if anything in this post screams of "do your fucking research"... but I have read the tuner spreadsheet, both articles in the wiki and the dellorto manual so cut me a _little_ slack.

Peugeot 103, old-school 2 port cast-iron Polini 70cc, "Top One" exhaust, larger reeds, 16mm phbg w/ foam rubber-banned over the filterside.

I was running a 15.15 SHA w/ high-flow, but I had to jet up to 94 to four-stroke and drop down to 90 to run safely..... as a result I had shitty low-end, and it would hardly even idle. So I bought a 16mm phbg and I'm learning to tune it.

currently jetting is 60 choke, 50 Pilot, w7 needle at setting #2 (that's all pretty much stock, and going with what the tuner spreadsheet indicates others have done, although that's with 19-21mm carbs). My main jet currently is 76, coming down all the way from 90.

I followed the "how to (made easy)" wiki article and adjusted my mixture screw and idle screw accordingly so it idles well and has good response at 1/8 revs. I left my W7 needle at setting #2 because it seems to accelerate fine and that's where everyone has theirs' in the moped tuners spreadsheet.

I started main jetting at 90, where I had it before.... WAY rich, 4-stroked at WOT (but not at 1/2. I got down to 78 jet and it still four-stroked at WOT, so I dropped down to 76 and it doesn't four-stroke anymore, AT ALL. Maybe I just stumbled upon the magic safe spot (since I didn't have many jets b/w 78 and 84 to test the threshold), but I'm still paranoid about being too lean.

I'm also a little confused why a 15sha would require a 90 jet whereas a 16 phbg would be in the high 70s-- possibly because the needle is also delivering fuel in a phbg? but I dunno.

When I pull the choke at WOT above 30mph the ignition seems to cut, slow down and then it four-strokes really bad, that's a good sign that I'm not too lean, right?

Just looking for a little advice on whether that jetting, needle setting, etc. sounds about right, although I know every bike is different, so I appreciate any advice you have.

Re: PHBG Peugeot polini tuning question...

you have to run a smaller jet because your idle jet is always running, which in turn affects the main, you are totally on the right track.

Re: PHBG Peugeot polini tuning question...

Siiiick! That's Lee.

Re: PHBG Peugeot polini tuning question...


Re: PHBG Peugeot polini tuning question...

OK.... So idle to 1/2 throttle is all dialed, feels great, not tooo rich b/c the choke makes it 4-stroke immediately.

78 for main was too rich so I dropped to a 76, it four strokes a bit warming up but works out okay after that. When I go WOT for a block or so it makes a lean noise and sometimes bogs out for a second, but at 78 it did it worse so this must be some kind of new rich symptom I never had with an SHA. When I use the choke at WOT it doesn't 4-stroke, it just dies, slows down, then starts 4-stroking at like 20mph.

3/4 throttle (isn't it called "riding the needle") feels too lean, and sometimes when I pull the choke when I'm going fast at 3/4 throttle it has NO effect. I dropped the W7 needle down to position #3 (first before the richest) and it had little effect. Obviously I ought to try #4 but everyone else has theirs' set to #2 so I'm confused.

the plug however gets dark pretty fast, and with 76 jet and W7 at #2 it was BLACK after a few miles of riding, even with those weird sucking, lean feeling symptoms.

Any suggestions? thanks.

Re: PHBG Peugeot polini tuning question...

Tim Sandberg /

hahaha. Like the end of a sitcom:

_That's Lee!_

Andy: most people run a 50 or 55 idle jet. 60 might be way to big of a starting point, esp. considering its a 16mm.. I dont even know if it works that way..

smaller carb, smaller jets to get the right ratio?

Re: PHBG Peugeot polini tuning question...

I meant to say thanks!

I don't know the carb mm to jetting ratio but everyone with a 19-21mm carb (and huge exhausts) seem to run in the 90s.

60 is my starter/coke jet, the idle/pilot jet is 50.. anyways the low end is fine and fully tunable... my mix screw is on the lean side and it's still rich enough.

I usually tune so it 4-strokes when warming up and as the engine gets hot, starts running normally.

I just put the W7 needle on the richest setting and it 4-strokes at the needle now too, and at the main jet when warming up. So I think I've got the right needle, since I could get it to 4-stroke it seems tunable enough.

When it warms up and breaks from the 4-stroking if I hold at WOT it feels really lean, sounds weird and sometimes it cuts out in a way that makes me REALLY nervous--- like a soft seize or as if I just just pulled the choke. could that be from a fouled plug? My plugs are very dark.

to compound things, my left-side pedal just SNAPPED right off, so I gotta find a replacement with metric threads, ugh.

Re: PHBG Peugeot polini tuning question...

Benji explained to me tuning would be hard without a proper high-flow filter (can't just rubber-band on some foam I guess). After that I upjetted crrrazy, from 76 to 90 which is fine. Sucking more air + upjetting = more power, no?

I've got the main jet tuned rich so it four strokes because my only remaining question is about needle tuning...

The W7 needle is too rich at the richest setting, but too lean at the next one... such that 1/2 to 5/8 throttle BLASTS and pulling my choke does NOT make it 4-stroke in the slightest. I don't rely on plug chops for something so specific, and I wouldn't want to run 1/2 mile if it's too lean, I'll seize my polini.

Soooo. Is there anything else I can adjust to richen-up my 1/2 to 5/8 throttle a bit or do I need a different need needle or something?

Re: PHBG Peugeot polini tuning question...

try a 9 needle in the second leanest position.

sounds like ur on the right track now, and yeah a proper filter is always required for max performance and durability

Re: PHBG Peugeot polini tuning question...

also don't take the spreadsheet to literally its a guide and what worked for others might not work for you at all. not to take into account location, possible air leaks, different port work, parts, etc.

Re: PHBG Peugeot polini tuning question...

Thanks Elliot, W9 FTW!

Mid range feels good, a bit rich warming up but pretty healthy after that.

WOT w/ 90 jet 4-strokes for the first 10 minutes or so, after that it really blasts at WOT but feels lean like it has an air leak, but I've checked with carb cleaner... do air leaks pop up suddenly when you're going 40mph? Cause I can't find any leaks at idle. Honestly, it could be that I don't know what a 70cc engine feels like at full rpms, cuz this is my first kitted bike. But yeah, seems like if it 4-strokes for the first 10 minutes, and there isn't an air leak, it shouldn't be lean at WOT.

almost done, siiick.

Re: PHBG Peugeot polini tuning question...


I am totally stuck again. Last Friday the 90 jet and W9 needle seemed a little rich but close to perfect. Today I started it for the first time since the rainy weekend and it stutters and misfires at WOT--- like minor, intermittent 4-stroking, it won't break into full rpm-land. Uhhhh, did a coil or condenser start to die? It still idles great and doesn't start stuttering until I'm in the upper circuit. !!!!!!!!!!! so frustrating.

I figured... well maybe it's cuz my plugs are black. So I downjetted a ton, down to 76 and it still stutters and misfires even though my new plug looks good. what the fuck?

I've been trying to tune this thing for a fucking week and I'm totally stuck. I haven't a clue what to do, I have no wheels.

Re: PHBG Peugeot polini tuning question...

you're still to rich. You shouldn't 4 stroke, at all. The fact that it cleared up as the motor warmed, indicates you're just barely on the edge of running. Go leaner.

Re: PHBG Peugeot polini tuning question...

Not too rich. Too stupid.

I was running out of gas from dumping the carb so many times re-jetting. I had to switch over to reserve to get a solid fuel flow...ddduuuuuhhhh.

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