Dellorto PHBG replacement Jet

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RLorange

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Jun 21, 2008
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Australia
Is everybody here aware that the jet in carby is replaceable? By chance I discovered that Dellorto PHBG main jets are a perfect fit! The 70cc's really need a bigger jet. I am using an 0.85mm jet which compares to 0.70-something for the stock. I raised the pin clip to the highest (leanest setting) and then dropped it back by a 1/2 using a tiny washer.

That is another great tip: To get an in-between clip setting simply use a tiny washer.

Bigger jet is a massive improvement with the leaner clip setting needed for compensation. Now my engine is very smooth during the mid range and no longer starves for fuel at full throttle. I feel that idle may be a little lean however because it idles very high now.

Dellorto PHBG jets are cheap mine cost $5.
 
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RLorange

New Member
Jun 21, 2008
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Australia
Lots of places sell them try a minimoto dealer 'cos they use Dellorto's for pocket bikes.

Next experiment is to try fitting a Dellorto PHBG 19mm Carby to my engine!!

19mm might be too big but I got it very cheap (its a replica) and they do use them on mini bikes with sucess.
 
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RLorange

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Jun 21, 2008
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Australia
Well I can tell you that the Throttle cable fits but you have to remove the cable guide at the carby.

The carby slips OVER the manifold snugly which is an amazing coincidence unfortunately this doesn't work for long because liquid fuel quickly gathers at the 'Step' down to the smaller diameter intake tube so it runs rich as ****.

I did get it going tho briefly. These PHBG's have THREE jets! an idle circuit, main jet pre-mix circuit and a choke circuit. There is an idle mixture screw but no main jet mix screw cos it doesn't need one being a pin/clip design like the stock NT's

All I need is my custom 19mm manifold made up.

I am drooling in anticipation
 
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RLorange

New Member
Jun 21, 2008
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Australia
Will do for sure. My Dellorto Repllica cost me $40 AU! Hope it is good working order.

I've got an expansion chamber muffler coming soon too, I'm going to get the same guy to make me up a header pipe. really wanted to get the one from Easy Rider but postage to Australia... I'm looking at $200+

Being lazy I'll have to post some pics soon
 
misteright1_99

misteright1_99

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Mar 21, 2008
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Treasure Coast, Florida
I have been drilling mine out. I have just bought a used mikuni carb for an 80cc yamaha dirt bike off Ebay. I believe it is 18mm but ill have to wait and see. I bought another carb a few weeks ago, but found it was for a four stroke, would be VERY hard to modify to mount, and the jetting for four strokes is consideably different, so I got it back up for sale...
 
Pablo

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
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Duvall, WA PNW
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Re: Dellorto PHBG/SHA replacement Jets

So check this out.

I have a $20 k-knockoff SHA carb, Xing Ding brand......it's been sitting on the shelf for awhile...this carb is essentially identical to this one:

SHA : Dellorto Carburetors, And parts for you.

I needed to get some parts (air cleaner side) to make it work. So I ordered the stuff from Delorto, and some 5mm jets in .60/.65/.75/.80 mm orifice size. All the stuff finally arrived.

I hooked up the carb this am, with the stock jet (no concept of size). Bike started right up. Idled great, but is running REALLY rich. So I remove the stock jet and guess what? None of the jets I ordered will work! This SHA knock off takes 6mm jets (AFAIK). Cornfusing.

Search Results : Dellorto Carburetors, And parts for you.

The good news is the 5mm jets fit the stock Chengine carb (.70 orifice). So I take the Xing Ding carb off, put a stock carb back on with a .65mm jet. With needle e-clip one down from the top. Runs pretty well, especially at higher rpm. Kinda flat at low rpm.

Need to move clip to top and try again....
 
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misteright1_99

misteright1_99

New Member
Mar 21, 2008
716
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Treasure Coast, Florida
Thats a shame. I ordered a bunch of mikuni jets, mains and pilots and NONE of them fit. I ordered some Kehin jets that are longer but work great. I am now running a 85 in my mikuni on my 48cc and it works good but I think I need a 90 now. I am going to stay with the 85 thru the summer and maybe do some tuning come fall. I did have to do some work on the slide for more airflow at low RPM's.
Pablo did you ever get the chamber to an acceptable noise level? I ended up making a silencer that was almost twice the diameter of the factory silencer and it helped alot!!!!!!!!
 

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misteright1_99

misteright1_99

New Member
Mar 21, 2008
716
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0
Treasure Coast, Florida
Pablo said:
Those sizes seem HUGE, but each carb type is different.

Yes my set-up is now nice and quiet. Check the pics in this thread:

http://motorbicycling.com/showthread.php?t=2577
Click to expand...
I talked with a guy in AU, someone posted a video he had, and he is running a 90 main in his 18mm Mikuni, on a Zbox 48cc with stock exhaust, and some porting. The video he posted the bike screamed...I figure if the airflow didnt justify the jet, the spark plug would tell me.

I posted a comment there about the steel wool. Doesnt the additional muffler restrict the flow?
 
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captainrichhill

New Member
May 31, 2008
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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.
 
Pablo

Pablo

Master Bike Builder & Forum Sponsor
Dec 28, 2007
3,696
33
48
Duvall, WA PNW
www.sickbikeparts.com
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.
Click to expand...
Quoted for truth.

Ghost0, Norman, I, and others have come to the conclusion that a smaller jet is the way to go. I went with a 65, but I was using a needle that I had not tried with this jet tube before......
 
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