20mm PHBG tuning problem

Just installed a 20mm Dell on my Maxi. Kitted Polini 64cc. Having trouble with the idle.Bike will not start without the choke on.Will run with choke on.If I close the choke while riding,the bike dies if I stop. Idle mixture screw does nothing.

Re: 20mm PHBG tuning problem

Also only hits 30mph. Went faster with a basicly stock bing and 14mm intake.What the f@#k?

Re: 20mm PHBG tuning problem

what setting is your needle on and what jet do you have. you need to tune that bitch and do some plug chops.

Re: 20mm PHBG tuning problem

Just for the hell of it I tried the jet it came with.A frickin 90! Went WAY down to a 75. Didn't change much.See pic.I did check the plug with the 75 and it's still wet.

1215926106_100_5031.jpg

Re: 20mm PHBG tuning problem

my phbg on a athena reed kit runs a 75 main jet. If your idle screw does nothing its probably a bit lean. I have a 65 in my idle and thats a bit rich.

Re: 20mm PHBG tuning problem

Needle is set at 3rd from top.

Re: 20mm PHBG tuning problem

Ped is faster with stock bing. Can't figure out what's wrong with Dell. Anyone in the IE (So Cal) that can help??? Thanks

Re: 20mm PHBG tuning problem

Sounds like the reason i went with the SHA instead of PHBG:

Too much tuning, too much tuning.

Re: 20mm PHBG tuning problem

I think it's just too much carb.Maybe?Case is not port matched.Most likely the problem. Square peg, round hole thoery.

Re: 20mm PHBG tuning problem

Make sure you dont have an air leak with that rigged intake. Kind of a weird setup isn't it? Stock intake with a rubber hose but your using a female clamp on carb rather than a male rubber mount carb?

Re: 20mm PHBG tuning problem

You need to case match it before you burn up your piston, especially with 4 petal intake, you will really be pulling all kinds of power if you can ever get it jetted correctly.

Re: 20mm PHBG tuning problem

It's not a stock intake. Had it pressure tested. No leaks. Even with the bike running I sprayed carb cleaner around all joint.No reving.

Re: 20mm PHBG tuning problem

Help me understand what I"m looking at. A flat plate over your reeds with a metal spigot to attach a radiator hose to it, that then curves up to another spigot which then is attached to your clamp style PHBG? Do you have any pictures of this with the hose off?

Re: 20mm PHBG tuning problem

Here you go.

1215996568_carb_and_intake.jpg

Re: 20mm PHBG tuning problem

My guess would be your Idle jet is to small and your main jets to big.

Re: 20mm PHBG tuning problem

Idle is 60 and main is 75.

Re: 20mm PHBG tuning problem

Most guys with 20phbg on Polini run in the 100's for a main jet, and if you can't get it to run w/o the choke, then you are obviously too lean.

Re: 20mm PHBG tuning problem

The jet that came in the carb was a 90. Tried that. Plug was really wet. Went to an 80.Better but still wet.Ended up at 70.Plug is still a little wet but not as bad as the other two.The only thing I can figure is the port matching. Now looking for someone to port match.

Re: 20mm PHBG tuning problem

i dont know where you live, but out here in LA, pollini's are running with 105 to 110 jets, the fact that you have to run it with the choke on .. well thats fattening it up, sounds like you need to go bigger with your jet. sorry this post was long.. im sure its been said

Re: 20mm PHBG tuning problem

If you haven't read it yet. Here's a link to the dello manual( at the bottom)

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

Re: 20mm PHBG tuning problem

i think those 20mm carbs come with wierd needles and diffusers and idle jets in them.

check you needle, if you have one of those x09 needles, or any needle with an x throw it away and buy a w6 through 9. check your diffuser. 260 and 262 should be in the range. also check you idle jet. 45-55 should do you right!

good luck

Re: 20mm PHBG tuning problem

whoa whoa whoa... backup....

that pic is essentially this:

forgive the crude sketch.

I can see a host of problems with that, mainly a carb that's way too big for the intake, tuning that is not gonna be like tuning a 4 pedal setup with a phbg at all, there are gonna be eddys and air pockets all over the place. who knows what jets u need.

what I would guess is happening is that since the carb is too big for the intake and at low rpms the intake charge is not strong enough to move air fast enough thru the carb to get the idle or pilot circuits working properly, thus you need to open up the choke a small side passage to get it to idle, but its then idling off a jet that way too big, and also causing your extra rich looking plugs (depending on how u ride when u are testing this all out).

just a theory, what do u think?

Re: 20mm PHBG tuning problem

Heres another pic. Osprey, where in LA? I'm in Corona (no not Del Mar). Just the other side of OC.About 50 mile south east of LA.

1216080546_blown_carb.jpg

Re: 20mm PHBG tuning problem

osprey of Dee'z loinz /

henry, aren't you looking for shaw to port your cases... you might want to go ahead and have him do you up an intake... I was looking at this last night on my 13" macbook, didn't even see that intake... what elliott is saying is making alot of sense..

when we run rubber mounts, it's as a bridge... between carb and manifold,,, but they are butted up against eachother...not the bend...plus I know when dustin went from a 19 dellorto with a 16 mani, it was nothing but trouble... everytime we stopped to pee he was trying another jet...

I get down in ktown. probably seen eachother at myrons a hundred times.

Re: 20mm PHBG tuning problem

Completely understand.The whole setup was just trying to get a little more mph. I'm going to the drags this weekend with the bike and was going to see if they would let me run it.Just for shits and giggles.Do you have a 4 petal? How can I get a hold of Shaw?Or have him mail me.

Re: 20mm PHBG tuning problem

Ok went to a 100 main. Gained top end but had to feather the throttle to get there. Just mashing the throttle caused the bike to bog. Let up a little and it would pick up then mash it.Need a new pipe too. Any sugestions? Want all around good power or mid to top end.

Re: 20mm PHBG tuning problem

does the bogging sound like is gasping for air? if so its too lean in the mid throttle range.

if it sounds like a 4 stroke or close to 4 stroke, then its too rich in the mid throttle range.

adjust the needle, and forget that setup, ur better off with a bing on the stock intake, u gain nothing (or very little top end) with a huge carb on the end of a small intake but tuning issues

Re: 20mm PHBG tuning problem

No disrespect elliot. The intake on the 20mm is custom fabed.It has, let's say a 20mm bore versus the stock 13 or 14mm bore. The bog just sounds like it runs out of power. Backing off a little it picks up rpm's.

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