Need PHBG tuning helps

I need to talk to someone who really knows what they are doing when tuning Dellorto PHBG carbs.

I am running 21 phbg, 96 jet (running a little rich). The needle is a W9 with the clip on second from top notch.

This setup was perfect up until I changed the pipe and removed the head gasket.

I have 2 problems.

1. If I accelerate just a hair past 1/8th throttle, it bogs and I have no take off. If I move the throttle back down a little bit it picks right back up and I have to wait for it to accelerate to 10 mph before I can give it anymore juice. I believe the fix for that would be dropping down the needle a notch to restrict fuel flow a bit more. But, here is my other problem:

2. When I am past 1/4th throttle, I am having problems with the fuel cutting off too quickly when I let off the throttle. This would be fixed by changing to a needle with a different taper, something higher than a W9.

So if I changed out needles, would I still move it down a notch? Do I need to switch out needles? I would like to get someones skilled opinion. I want to make sure I am understanding everything correctly.

-Commodore

Re: Need PHBG tuning helps

Overpriced Parts /

What bike ? What timing What kit? What pipe ?

Re: Need PHBG tuning helps

I didnt think it would matter what all that was since it was a carb tuning issue, so I didnt include it.

Pug 103, 70cc polini w-port, gianelli pipe, high comp head w/decomp (plugged), malossi 4 petal reedblock and intake, timing is 1.1 btdc, b10hs plug, max temp around 350-370.

Re: Need PHBG tuning helps

Commodore Perry Wrote:

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> I didnt think it would matter what all that was

> since it was a carb tuning issue

On which planet? Here on Earth, those are all factors when tuning a carb. (edited)

Re: Need PHBG tuning helps

I assumed the carb issues would determine what needs to be changed on the carb. So now that it is out there, any suggestions?

Re: Need PHBG tuning helps

Overpriced Parts /

Commodore Perry Wrote:

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> I didnt think it would matter what all that was

> since it was a carb tuning issue, so I didnt

> include it.

> Pug 103, 70cc polini w-port, gianelli pipe, high

> comp head w/decomp (plugged), malossi 4 petal

> reedblock and intake, timing is 1.1 btdc, b10hs

> plug, max temp around 350-370.

http://www.mopedarmy.com/wiki/How_To_Tune_PHBG_Carburetors

Since you went to a high rpm pipe and hi comp head the jetting may need

to be changed (if your pipe has a restrictor it I hope you removed it) over you other set up.

I'd start with 40-45 idle jet, AU 262 atomizer #7 needle and 40 slide in the carb

Re: Need PHBG tuning helps

well before you do a zillion things why not do one thing to your bike instead of two things and see which alone creates the problem. or at least keep this option open to consideration. if you are sooo rich does removing the air filter make an improvement?and before ya go crazy try a couple of new plugs and maybe a different heat range plug. how many degrees before tdc is 1.1 on a pug? is it way worse with the choke on. i would put the head gasket back on and tune to that and then if u want it off then take it off and figure that tuning condition.

Re: Need PHBG tuning helps

Tracy Meade /

In my opinion, changing needles is the LAST thing you should do when tuning a phbg. In fact, I have messed around with it a few times, but always went back to the good old w7 or w9.

Work out the highs first. It sounds like you are cutting out below 1/4. You can try to lower the clip (or raise the needle -- however you look at it ) and see if that helps. This will make the needle earlier & richer. If it fucked up things mid throttle and you get all rich, put the needle back and get a richer atomizer.

Your bog problem is a symptom of the same problem (I suspect a lean atomizer) and you are merely mistaking it to be rich. ( of course an assumption)

If imagined your scenario correctly, be ready to change your atomizer richer, and then modify your idle jet & possibly slide to accommodate the new atomizer.

Re: Need PHBG tuning helps

Tracy Meade /

or you have an air leak and a way to fat idle jet (edited)

Re: Need PHBG tuning helps

I know for a fact that I am not running lean. The plug color and temps confirm it. No airleaks whatsoever are present. I know I can down jet 1 or 2 sizes if I need. The take off issue has been present since I changed pipes. I have taken it on 3 rallies since then with no issues aside from that. The fuel "cut off" problem is not too bad, but I would rather not have it present. When I let off the throttle it doesnt quite give that pop pop noise like it normally would, but it shows back up at lower rpm. I had the fuel/throttle "cut off" problem when I first got the carb because it had a clone needle in it with barely any taper.

If you are referring to the bog on the take off as lean instead of rich, I suppose I could adjust the needle to find out

Re: Need PHBG tuning helps

Tracy Meade /

I'm saying that a lean atomizer would give you both symptoms.

Re: Need PHBG tuning helps

Move the clip in both directions and let up know. Don't keep us hanging!!

Re: Need PHBG tuning helps

George Warren /

Keep a diary of the changes you make and date it so you don't go BACKWARDS!! I started doing this and it is the most important step.If you write down the changes and whether it improved or got worse you will learn and achieve success.You can't see thru metal to see what you did yesterday! This is extremely important if you own more than one ped! I had a similar problem yesterday and raised the needle and or dropped the clip a notch and resolved a lot of my low end problem.

Re: Need PHBG tuning helps

Overpriced Parts /

George Warren Wrote:

-------------------------------------------------------

> Keep a diary of the changes you make and date it

> so you don't go BACKWARDS!! I started doing this

> and it is the most important step.If you write

> down the changes and whether it improved or got

> worse you will learn and achieve success.You can't

> see thru metal to see what you did yesterday! This

> is extremely important if you own more than one

> ped! I had a similar problem yesterday and raised

> the needle and or dropped the clip a notch and

> resolved a lot of my low end problem.

Good info. For a while I kept a tuning notebook of carbs common kits, pipes and engines for puch, tomos sachs and some Italian engines bikes. I don't know where it is now but I know for what I work on what's a close jet range and settings. I keep a set of Mikuni, bing jets/parts and both sizes of dellorto jets/parts on hand .

Re: Need PHBG tuning helps

As I did with a bigger idle jet for my flat slide on my e50. Keeping track of a bunch of bikes is impossible without some notes

Re: Need PHBG tuning helps

I have not been able to really do much carb tuning since I posted this. I ran into some other problem with my points going bad, replacing them (with breifly used one points (new ones on order), retiming my ignition, it wouldnt idle, then I adjusted the points some more, it then idled, so i then moved the needle up and upjetted as well (I should have done one at a time), I then found out that the head I was running had stripped sparkplug threading, so i replaced it only to have the bike temps sky rocket out of no where and my back wheel locked up on a brief ride with WOT. I am not sure Why the wheel locked up yet, I believe it possible expanded and hit the head and stopped the engine, or maybe a soft sieze, I havent had time to look into it yet. In retrospect, I am pretty certain that the stripped plug threads on the head had something to do with altering my timing from what I thought I set it since I use a bazzeti timing tool that threads into the head. So with inbetween all that chaos, I need to pull the cylinder, buy a new head (the current one was stock that was dremeled out to 46mm), check piston, ring and cylinder, replace my points and retime everything. Thank you guys for all of the suggestions and useful information. I will pick up back here soon.

Re: Need PHBG tuning helps

Overpriced Parts /

Ya when you messed with the points you advanced the timing and soft seized.

To control head temps @ WOT on a kit you need to have set to the Lower timing side of the specs

Re: Need PHBG tuning helps

Sounds like a totally normal moped experience!! I stripped a bunch of sparkplug head threads by not being able to feel the wiggle of the plug by hand starting the catching of the threads because the trail tech temp gauge restricted the movement of the plug. I now Dremel out the middle of the copper temp ring and slip it on OVER THE CRUSH WASHER as supplied with the plug. Yea this isn't the way it's supposed to be or u r supposed to remove the oem washer and use the trailtech and I say f that s..t I think my temps are pretty accurate and I am getting a very good seal...I hope.

So the helicoil can be done to fix your stripped threads with the right tool to keep the coil in place. But yea a new head makes it all simpler.

I would backtrack to a known set of parameters if possible.

A lot of bikes will lock up of they seize. And if u had a significant air leak at the spark plug that will account for most of the grief you have endured.

The pros on ma get the jetting and timing near perfect from the get go so they don't keep screwing with stuff enough to have parts fail from constantly taking them apart. So don't fret you are going to get it right. Just take a deep breath and get out your credit card.

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