PHBG question

I'm working on tuning my garelli and had a quick question that i couldn't find an answer for searching, or am confused about some aspect of tuning these carbs.

So i'm trying to tune my lowend and what i'm running into is on the stand everything sounds good but under load i bog from 1/8 to 1/2 throttle. If i drop the needle one notch leaner i get a better lowend but get a bog in the progression closer to 1/2 throttle. What i'm wondering is if i drop the needle and use the mixture screw to richen the mixture should this even my mid throttle bog?

I've spent the last couple of days trying to get this lowend sorted out and keep hitting a wall. Please keep in mind this is my first PHBG so any help would be greatly appreciated.

The setup is

1977 garelli ssxl noi

70cc polini

19.5 phbg

starter 60

idle 42

main 90 (for now, haven't chopped it yet)

Needle 3

Re: PHBG question

Sorry estoril exhaust

Re: PHBG question

I.R.E. Mike Pee /

I'd bet your idle is too lean. I run a 45 idle jet in my 65 metrakit on an e50. I know we're talking different engines, but you need to lube 5cc more than me, and you've got a smaller idle jet. I'm thinking bringing that up to at least a 45, if not 48 and tune from there.

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I run a 38 slow 106 main

Airsal 70cc

HC head

Technigas Next

20mm PHBG

A lil rich up top, but nice down low.

Re: PHBG question

I would not listen to mijunkin about the idle jet, its totally different situation and nothing can be inferred from his setup related to yours. Plus the idle jet has very little effect on half throttle.

I would question your 3 needle, that is a weird needle. The tuning guide recommends using a 7, 8, or maybe 9 needle unless you know what your doing in regard to the needle. The needle will definitely effect your progression around half throttle.

Re: PHBG question

I wonder if the # three needle came in the carb . I think everyone I ever met with a moped and a phbg is running a #7 needle . With the exception of maybe just a few . I struggled with a w16 ,w11 , w10 , w9 ad then the 7 came in the mail and it worked like magic . 100% better then any other . It may be worth a try . Just record your data.

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i assumed needle three was 3rd from the top. i dunno

Just fyi

a W3 needle is near identical to a W9 exept the main needle width is 2.45 versus the W9's 2.5. If anything a richer needle than the w9 or w7.

If i were you id start at the richest setting on yr needle. Put the clip at the bottom notch so you are richest and work down from there.

Also, you need to be sure that the 90 is the right main jet. As that can affect your needle tuning. If you haven't plug chopped then that is the first thing you should do, as its pointless to tune your needle if your main isn't figured out first.

good luck dude.

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Mark you're totally right, needle set third from the top.

I'll plug chop the 90 today and see what i come up with. This thing is totally screwing me up one day to the next. The top end tuning isn't a problem, i get that, but the whole lowend/idle thing... Am i right in assuming that the rear tire should be spinning just a little but not out of control or should the idle on there be somewhat higher than a SHA?

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Alright, so i've got it pretty close. Up jet to 96, 45 idle, w9 needle 3rd notch, lowend is still lacking a little. I checked the spreadsheet and it seems most are running w7's , so i've got one in the mail. Hopefully that will help out some. What do you think?

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what needle did you actually have. you might not need another one.

just remember to do things orderly. main jet first then needle then idle/mixture. the first one affects the next. so it makes sense to go in that order.

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I have a w9 in there, clip on the 3rd notch, i have the top end a little rich, 96 main. 3 down from 4-stroke , and a 45 idle, 2 turns out. It's running pretty good on the top end but i feel like there is more mid/low end to be had.

I figured a w7, leaned out, might give me what i'm looking for in the low end. The only reason i'm thinking of trying a w7 is that there seems to be a sweet spot that i can't get to with the w9, you know? Hell maybe i'm totally wrong and this is just the way it runs. Reading the spreadsheet and posts where people are saying they have "great" low end makes me think there is more tuning that can be done to wake it up.

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Maybe your low end is a clutch or timing problem.

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Checking those tomorrow. I don't think it's a timing issue, everything seems fine there. I did consider the clutch but thought if i got the carb close enough to what others were using i could rule it out then move to the clutch.

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Checked the timing and clutch this morning, timing was good, clutch needed the small rubbers replaced. Filled it with 10/30 which helped some but there's still more low end to be had. Now my 96 is running way richer than yesterday which leads me to believe the clutch was part of the problem and fine tuning the carb should even out the rest of it.

Thanks for the help guys and if you have any other suggestions or if i've overlooked something, please let me know.

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