Puch Polini WTF?

) Cupermcnewbster ( /

Yea, so my polini is pissing me off.

The setup is:

64 polini

malossi reed block (stock carbon reeds)

21 phbg racing (100 main, 55 pilot, 45? idle, stock needle 2nd highest setting)

Motomatic N8P

So heres the deal, this thing runs beautifully when it is colder, like 40-55 degrees out, so basically only at night around here right now. Its running just a tad all around, great power and is topping out probably about 58-60 (18x40 gearing)

A few weeks ago, and duing the day when its in the 70s, this thing sucks hard. It leans out really bad, runs super hot, no power or anything. It was mildly soft-seized once.

So WTF, isn't stuff supposed to lean out during lower temps? It seems to run well during the day at 1/2-2/3 throttle, but anything else and it bogs and sputters(not 4 stroking). It doesn't do too horrible at WOT, or at least once doing 35 or so, but its still super hot. So whats going on? There are no air leaks, exhaust leaks or anything like that. I just rotated the carbon reeds as there was a little flutter and thats it. Anyone else have issues like this with the phbg?

Is this a needle issue or what? I've tried raising the needle to richen it to no avail. Lowering (leaner) doesn't help either. Am I doing something totally wrong (very likely). In its current state I don't think its safe to run at stinko besides the night ride, but I'd rather not switch motors saturday morning. HELP ME!

Re: Puch Polini WTF?

my polini did the same thing at flock yea. ran like shit during the day. started kicking ass at night when the temp went down in the 50s

its probably a phbg thing.

Re: Puch Polini WTF?

) Cupermcnewbster ( /

yea, well I'll seize for sure if I run it like this during the day. I mean it is super hot, like even the entire stinker, all carbon burnt up everywhere, and the plug looking super white. Not safe on polini.

Damn. It ran so fast and strong tonite too.

Re: Puch Polini WTF?

🇮🇹💦 Of the Loin /

redo all your gaskets and make sure everything is sealed.

Re: Puch Polini WTF?

) Cupermcnewbster ( /

already did, much better than before. Like I said, ran great tonite (resealed), horrible the other day (during the day just after resealing). Retarded? YES

Re: Puch Polini WTF?

what plug are younrunning? Try a 9 when its hot?

Warmer air should make it run richer.

Re: Puch Polini WTF?

Advanced timing? That would make your engine run hotter. The cool night air could be keeping that in check when you're riding at night. Then during the day you're overheating.

Re: Puch Polini WTF?

thank you tim, thats more than likely my issue cause im advanced a degree or so.

Re: Puch Polini WTF?

How many mm's before TDC is your spark?

Re: Puch Polini WTF?

Just asking cuz I just finished a full rebuild (case matched, race crank, korado clutch, polini, 4 petal reed, 19 dellorto) and I set my points to open right at or a half a hair under 2mm BTDC. I saw in the puch service manual that they recommend 1.2 mm BTDC.

Re: Puch Polini WTF?

) Cupermcnewbster ( /

I am a bit advanced, not sure exactly how much, but that very well could be it. I'll check that out this afternoon.

I am running an 8 plug.

Anyone running this setup have timing specs? Tim I see you have yours at 2mm, but have you run that yet? I'm probably pretty close to that.

Re: Puch Polini WTF?

Nope. Haven't run it yet. I'm repacking my bearings at the moment. Hope to run it this weekend!

Re: Puch Polini WTF?

on my wheels that is...

Re: Puch Polini WTF?

i'm running a 16mm phbg with a 78 jet, and it's too rich. 100 seems a bit too high, even at 21mm. I know people run crazy high jets though, so maybe I don't know. what do your plug chops look like at wot?

Re: Puch Polini WTF?

) Cupermcnewbster ( /

100 is not too small. There are many determinants for jetting, and with my setup 100 main is fine (and I don't think the issue here). Either way, WOT chops are looking good, a tad rich.

I've always seen/heard polini's being high 80s-100+ jets in both bing and phbg.

Re: Puch Polini WTF?

in LA i ran an 88 and that was way rich.

Re: Puch Polini WTF?

I ran naked

Re: Puch Polini WTF?

Aaron McTaggart /

you got rid of that little brass baffle washer thingy that sits under the main jet, right? fuck that thing.

Re: Puch Polini WTF?

i heard that thing sucks. I have mine off.

Re: Puch Polini WTF?

100 jet is fine, i am running a 125 main (a bit rich trying a 122 soon) on a 19phbg.

What needle # are you using. also are you sure ur condenser is not beginning to fail you.

Follow this artical below to make sure ur jetting is correct, also hot weather will make the bike run richer

Words of Assurance: Jetting isn't hard and comes with practice. You're not going to mess your bike up unless you make huge changes. You WILL be able to tell if your bike is running lean enough to be in danger of seizing. So, don't worry.

Article by Spanky:

"Throttle Ranges:

Pilot Jet/air screw:0-1/4.

Needle Jet:1/4-3/4

Main Jet: 3/4-Full open

A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's power band. A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using. A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift.

The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent.

Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best.

It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving.

Before you start to rejet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing.

Before you start the jet testing, Install a fresh plug. Warm the bike completely, and shut it off.

As already stated, start with the pilot circuit. Turn the air screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idling. Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the air screw for the best response.

Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet.

Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the air screw slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn.

The air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day.

Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.

Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan.

Once you have a little bit of experience with jetting changes, and you start to learn the difference in feel between "rich" and "lean", you'll begin to learn, just from the sound of the exhaust and the feel of the power, not only if the bike is running rich or lean, but even which one of the carb circuits is the culprit.

Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit. Two-strokes have an air screw that you screw in to make the jetting richer, and screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer."

Re: Puch Polini WTF?

thanks so much for posting this! i have never tuned a carb with an air screw before, and i was extremely nervous about tuning my new phbg because jenning's procedure doesn't say anything about it. i'm going to follow this procedure to the letter.

ps though - he doesn't mention anything about throttle slide selection. do a lot of tuners not bother with that?

Re: Puch Polini WTF?

yeah i don't know much more about throttle slide selection than it is used to tune the 1st quarter of the throttle.

If anyone has an old bing on something that won't seize might be worth grinding and adding material on that bitch to figure out exactly what the throttle slide does.

Re: Puch Polini WTF?

) Cupermcnewbster ( /

based on that article, I think I need to play with my pilot jet, needle and air screw. Main is fine.

checked the timing and it was almost 2.5mm BTDC which I think is too far. I'll try to get it closer to 1.5mm.

Hey elliot, do you have any needles? I am going to mess with this friday mid-day before the night ride and hopefully dial it in, but it may be a needle issue. I guess I'll call you up if I have more problems.

Oh yea, I've run but with and without that brass thing in the carb and haven't seen/felt any differences. Feels the same at 50-55+. Dunno, maybe with a bigger jet it could be an issue?

Re: Puch Polini WTF?

Elliot, correct me if I'm wrong but the PHBG carbs have a mixture adjusting screw, not an air adjusting screw. Both of mine do. When I turn my screw in it leans the mix turning it out richens it. In the article you posted It talks about an air screw only.

Re: Puch Polini WTF?

its confusing, but this is what i've gathered so far about PHBG carbs. the mixture adjusting screw does lean it out when you turn it CW and enrichen it when you turn it CCW, but it does this in a way that you might not realize. when you turn the screw CCW to make the mix richer, it actually allow more air into the circuit, which makes more gas/oil bubble or foam up from the bowl. thats why the terminology can get confusing. I like to think of it as an idle circuit mixture screw instead of a air mixture screw or a fuel mixture screw.

someone please correct me if i'm wrong about any of that. i've been researching this a lot lately and thats what i've gathered so far.

thanks for posting that article elliot, it really breaks down the tuning procedure in a way that makes sense.

now to figure out a way to get my back tire off the ground for tuning. damn kickstandless ped.

Re: Puch Polini WTF?

Read pages 16 and 17 The idle air and mixture adjustment screws....

http://www.thisoldtractor.com/gtbender/mg_manuals/dellorto_manual.pdf

It states "As the idle screw adjusts only air, while the mixture adjustment acts on the fuel flow, we have to operate them in the opposite manner according to how the carburetor is equipped. To enrich we have to close the air screw(by closing the airflow) or open the mixture screw. To lean the mix, one has to open the air screw or close the mix screw."

Re: Puch Polini WTF?

thats what i said, i think.

"To enrich we have to... open the mixture screw. To lean the mix, one has to... close the mix screw."

Re: Puch Polini WTF?

Yes, that is what you said. It can get kind of confusing because air and mix screws operate opposit.

Re: Puch Polini WTF?

i think u guys are right but i haven't really found anything dellorto says in thier documents to support it. They just say:

"The adjusting screw meters the amount of mixture of a strength

predetermined by the metering effect of the idle jet and the air

corrector, and there fore on screwing in the mixture screw, idle

fuel delivery decreases and vice-versa."

Meh? not really what you guys are saying but just from personal experience I have noted that the bikes are much peppier when the screw is turned almost all the way in.

However all that being said, I find needle selection to be the #1 reason ppl can't get PHBG carbs running well. the idle and progression circuits really don't matter much at all on a moped. (or at least the stock settings and jet sizes seem to be close to appropriate) And I prefer they be rich so when u close the throttle on a hill at 50mph u don't seize.

Re: Puch Polini WTF?

what needles do you guys run? my dellorto 19 came with a W7 i think...

also, how did they run when you guys came to kalamazoo last year? did you have to make any adjustments?

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