Dellorto PHBG replacement Jet

captainrichhill said:
I've tried an 81 size and moved my needle clip and the bike ran like crap on the low end and the high end was slower then stock for my HT 70cc. I don't think a bigger jet is the answer.
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On the stock HT carb I agree, largest I could run was a 70.... but with a larger carb and more airflow you need more fuel to keep the mixture from leaning out, and with the 85 it is still slighty lean, looking at the plug, maybe a 87 next...
 
Ah, I mssed the larger carb part. Have you guys worked with the Walbro carbs at all? If so which ones are the best? They seem cheep and you can get more adjustments (High end and Low end).
 
Good to see a lot of feedback with jet sizes.

I too tried a Dellorto replica SHA which didn't work, these carbs don't have the pin slider design so the fuel regulation cant be adjusted only delivery via the jet size.

Yes SHA jet won't fit the NT stock carby's but the PHBG jets will. PHBG or PHVA carby't have a similar pi-slider design but include and idle circuit and a choke circuit.

A bigger jet will only help if you have increased the airflow in the carby with some boring and muffler work.

Having said that I have moved back to the stock jet and slimmed the middle of the needle very slightly with steel wool. I think a larger jet is useful during break in however but once the rings have sealed up it becomes too rich
 
Indeed. The SHA carb is no panacea. I will know exactly in a few hours, but the stock jet on the thing is way large...something like .80mm+. My engine was spewing raw fuel.

If smaller jets don't help, it's back to stock with mods.
 
Whelp I finally got a few minutes to measure the jet. My knockoff SHA carburetor = Dude .90mm!!! HUGE
 
That is way huge! I tried everything from 65 to 80 and the SHA still didn't work, its the delivery at in between throttle's that doesn't work well without the tapered pin. Also the SHA is HEAVY it broke my manifold and bent the nuts!

I have a PHBG knock off but it is 19mm so I need a custom manifold which should be welded up in a couple of days. They are common and cheap if I have sucess I will let you know :)
 
Walbro's are vacuuum pump driven so for one of these to work you would have to drill a hole in the crank case, cut a thread and then make a sealed nipple to attatch hose which will drive the pump. Would be awesome if one could be bothered
 
RLorange said:
That is way huge! I tried everything from 65 to 80 and the SHA still didn't work, its the delivery at in between throttle's that doesn't work well without the tapered pin. Also the SHA is HEAVY it broke my manifold and bent the nuts!
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Yikes. I'm getting a .55 so we'll see - I'm afraid you may be correct about the design of the SHA.
 
RLorange said:
That is way huge! I tried everything from 65 to 80 and the SHA still didn't work, its the delivery at in between throttle's that doesn't work well without the tapered pin. Also the SHA is HEAVY it broke my manifold and bent the nuts!

I have a PHBG knock off but it is 19mm so I need a custom manifold which should be welded up in a couple of days. They are common and cheap if I have sucess I will let you know :)
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Ya dun cornfused me. .50 or .65 is the smallest you tried?
 
Sorry I tried a 65 and 80 but then I bogged one of them and progressed from 50 up once I found someone with a micro drill set
 
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