Setting up a PHBG carb for the first time, any tips?

Spare_Parts

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Standard plug is ngk b6hs. You should probably get the b7hs because of your mods. If you are in a very hot climate b8hs.
 


extremeodd

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Thanks for the info, I went ahead and ordered a 4 pack of the b7hs plugs. Along with that I also ordered a micro drill bit set #61-80 wire gauge and some solder to downjet the idle jet, f*** paying $5/jet when for about $10 I can have the supplies to make any jet 36-100. Also nabbed 10ft of #41 chain, a cnc adapter 44t sprocket (started drilling out my dished 44t 9 hole but I'm not confident in getting the chain to align, my adapter is set for flat sprockets) and some locking forceps to do jet work (damn broken petcock). Also grabbed a set of main jets 70-80, $12 for 5x beats the hell out of soldering/drilling when possible.
 

gary55

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Thanks for the info, I went ahead and ordered a 4 pack of the b7hs plugs. Along with that I also ordered a micro drill bit set #61-80 wire gauge and some solder to downjet the idle jet, f*** paying $5/jet when for about $10 I can have the supplies to make any jet 36-100. Also nabbed 10ft of #41 chain, a cnc adapter 44t sprocket (started drilling out my dished 44t 9 hole but I'm not confident in getting the chain to align, my adapter is set for flat sprockets) and some locking forceps to do jet work (damn broken petcock). Also grabbed a set of main jets 70-80, $12 for 5x beats the hell out of soldering/drilling when possible.
You probably already know this, but if not just be aware that the numbers on the micro bits do not coincide with the numbered call out of the jets. The bit # is just a indexing # indicating a measurement that it's number does not equal i/e a #72 bit is .0250" or .64mm. where as a #72 jet is .72mm. So if they don't call out the equivalant in mm you'll have to mic the bit to get the correct jet size. You should mic them anyways as the cheap sets may have the bit in the wrong place in the holder.
 

extremeodd

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I appreciate the heads up. When I was trying to find the appropriate bits I came across a wonderful little document on a near abandoned site that had a reference chart for drill bit # vs jet size vs mm size vs imperial size. With how cheap the bits were, I'm not really holding my breath on their accuracy. Only hoping that they can make a smaller hole than the one I soldered.
 

JerboaJohn

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i got some tiny bits, not the cheapest but what i thought were mid-level, Shars. nice case but when i grabbed one, it was not straight. try next one up same,,, out of 10 only half were usable. I was drilling plastic, ended up just melting a hole with a pin
 

extremeodd

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I'm starting to see why the VM18 is such a desired carburetor, this PBGH is a mystifying little so and so.

After getting my 70s range of jets, an intake from zeda motor sports (super wide open compared to stock) and a super free flowing foam filter; I'm finding that I'm having to upjet the hell out of the carb rather than downjet like I had planned.
I tried initially going from 80 to a 78 but it was running super lean and hot, swapped in a 85, 87, 88 all to the same effect. Tried plug chopping but either it's running on the really far end of lean or my little 1/4 mile loop isn't long enough.
The porcelain stays white almost all the way to the very base, the lowest maybe mm gets the faintest hint of the tan color that is supposed to mark the perfect mix. The ground electrode has been basically white after each test, the metal walls going down to the porcelain get a light golden coating but that's not really covered in the guides/charts.
Tomorrow I'm going to jump from 88 to 92 or 94 to see if I blast past the sweet spot.
Never would have guessed changing the intake and filter would increase my jetting needs this much, but thinking about it, it makes sense as so much more air can flow now with the stock intake swapped out.
 

extremeodd

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Apologies for the double post. So I tested out the 94 jet and that seems to still be running somewhat lean. Then I tried the 96 followed by the 98 and I'm thinking the 98 might be what I needed. I wasn't able to discern any color just looking at the spark plug porcelain however after taking pictures I think I was able to see the tell-tale color I was looking for.

These pictures aren't the greatest but does any of this look right to you guys?

The motor seems to be running far cooler then it was after doing these tests, smoke no longer comes out of the spark plug hole when I take it out, and my RPMs seem to climb a bit higher than they were. It's hard to say if the sputtering when it revs out is 4 stroking or leaning, the one video with audio sounds basically the same between running lean vs rich.

EDIT: The plug in the picture is a touch dirty because I was running out of plugs to chop with and this one wasn't getting anything on the porcelain. I do a 1/2-3/4 mile run with each chop, .3 miles one way then turn around (while keeping the revs around 8k) then head back the other way for .4 miles then I pedal back to the house. I've been getting approx (sh*t tach) 8600-8800 rpm during the first .3 mile then 8400-8600 rpm on the way back, bouncing off the "rev limiter" that these motors seem to have. Still wont idle below 3k but thats mostly due to a too fat pilot jet.
 

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Frogslayer

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Judging by your pictures of your plug chops you are still lean as hell. With this and your idle problems i would guess you have an air leak some where and are chasing it around with carb jets. I have the same spark plug in my China girl A80. When i get home later I'll post a pic of my plug so you can see what a legit fuel mixture burning with no air leaks looks like.
 

extremeodd

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I'm not sure if there is an air leak, I sprayed some carb cleaner all around the intake and there was no signs of it revving up.
After playing around I can get it to idle fairly smoothly at about 1800 RPM.
Went for a 4 mile ride and it seems to be good, if not a touch rich when on the needle (need to move the clip back up a notch). Here's what the plug looks like after 4 miles of about 5k rpm. First picture is with flash, the other 2 are without. It's looking like it got the 'too rich' ring at the base of the porcelain which isn't too surprising as the pilot/idle jet seems to be way fat for my needs as it seems to idle best with the screw almost bottomed out. The guides indicate this means I need to downjet the pilot, especially since I cannot achieve a quick and smooth transition from idle to 1/8th throttle short of turning the air screw most of the way in and having it run at 3k rpm (basically on the needle).

Found this refrence that goes from "extremely rich" to "slightly lean"
87739


My plug after the ride at 5k rpm looks to be about perfect, but I might try drilling out one of my duplicate jets to a 100-105 to see if I can get a viewable line with only 1/2 mile of running distance.
Can a person plug chop while the bike is on a stand or does it need to be under load?
I'm guessing it's probably prudent to do it while riding so you don't overheat the motor and you're replicating it's real world use. I might be worrying about this too much as I am not a fan of riding the bleeding edge of where the motor will run. In the last 2 days of plug chopping this motor has seen far more time at WOT than it has in its life. Usually I only got WOT to get to the speed I want to be cruising at and ride 5-7k rpm most of the time. This is to avoid getting clocked at more than 20-25 mph by the local PD, the moment I'm clocked over 20-25 mph this bike goes from being an assisted bicycle to an unregistered moped. It's part of the reason I swapped from a 36 to a 44, I don't like the feeling of the motor at past 8k so this has effectively chopped damn near 10 mph off my top speed (that I'm willing to ride at, went from 42ish to 35ish full balls out)

Motorized Bicycle (hereafter referred to as MB): No operating license is required, nor is title, registration or insurance. MBs may use bicycle lanes per 2516(6). However, MBs may not use paths because these are generally not “designated for the exclusive use of bicycles” [upon reflection, that struck-through phrase is a misinterpretation of 2516(6). It seems to me that that section *allows* something; and to say it prohibits other things may be logically incorrect. Many cities do prohibit MBs from shared use paths]. The motor is limited to 48cc’s (which begs the question about an electric motor, was that an oversight? Tuscon’s ordinance DOES include the 1HP electric limit). In other words it is treated just like a bicycle would it not be for the following phrase: “operated at speeds of less than twenty miles per hour”. No Insurance is required per 28-2516(7), because Chapter 9 is the insurance chapter of Title 28.

Moped: A motor vehicle operator’s license is required, but it can be any class — unlike more powerful cycles where a class M is specified. Title requirements are waived, required license and registration are inexpensive and fixed by statute. The power requirement is more specific: < 50cc’s AND < 1.5HP AND < 25 mph at 1% or less grade. Mopeds may NOT be operated in bicycle lane or path. ADOT says that insurance is required for mopeds (but not for motorized bicycles); I cannot find any statutory basis for that conclusion — see the analysis here, which revolves around the fact that both motorized bicycles and mopeds are both defined by statute as types of bicycles.

Motor Driven Cycle: IS a motorcycle, but the motor is limited to 5HP. As such, a class M operators license, and title/insurance/registration would be required. There are a bunch of equipment differences, seems to mainly revolve around headlight requirements. They may be restricted from controlled access highways.

Motorcycle: No motor power limit. Class M operators license, and title/insurance/registration required.
Technically speaking, no matter what I do I'm in violation as this is 66cc and more than triple the 1hp limit. Hell, I'm probably not too far off of the limits of a motor driven cycle with how much power this zeda motorsports engine has once kitted with an alright mz65, a 19mm PHBG carb and a massive intake manifold. Once I get this carb fully dialed in, I want to grab a high compression head then eventually grab a windowed piston/reed.
 

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