View original topic: 30 pict 1 (only) carb idle adjustment Page: 1, 2  Next
Brokenbus Fri Jul 01, 2011 7:22 pm

Ok so I replace my 30/31 pict carb on my 67 DC(was running fine) with a 30 pict 1 which was rebuilt by builder on flea bay with great feedback and now can't get an idle after choke opens. Runs fast but fine while choke is warming. Once fully opened no adjustment with volume control screw helps. This 30 pict 1 does not have an electrically controlled idle solenoid valve. Is it supposed to? If so does it insert in place of the pilot jet? I pulled the pilot jet to check but hole is way to small to allow for the 30/31 idle cutoff solenoid to fit. 1600 sp motor, mechanical fuel pump. All worked well before installing this supposed "bulletproof" carb 30 pict 1.

I did replace the aluminum spacer that allows fitting with a genny and put in a bus governor in it's place but doubt that's the problem. It sounds like the idle control solenoid is bad or not hooked up (it's not hooked up because no hole to insert one) but like I said this carb doesn't appear to have a place for 1.

I searched the forums but unless I missed something I didn't see anything address this solenoid/idle question specifically for a 30 pict 1 only.

Thanks for any help you can toss my way.

busdaddy Fri Jul 01, 2011 8:06 pm

Likely the idle jet has been overtorqued at some time, back it out 1/4 turn and see how it behaves, if it's better locktite it in that position or better yet drill the hole it butts up against in the bottom of it's bore with a #50 drill to attempt to restore it to the OG size (works sometimes).

So I'm guessing this guy doesn't test run these or offer any warranties?

EverettB Fri Jul 01, 2011 11:42 pm

The electronic jet replaces the non-electronic jet on the 30 PICT-1, meaning you can use one or the other.

The 30/31 carb. may have a different size electronic jet.

If it's all warmed up and you can turn the idle mixture screw all the way in without causing the Bus to stall, something is messed up. Either the carb. has an air leak or the idle jet is drilled super large or something.

Is the pilot jet a size 55?

bill may Sat Jul 02, 2011 5:23 am

what distributer are you using?
if idle adjustment screw was tightened excessively it causes a groove to be formed where it seats.
i have never used a electric idle cutoff solinoid on a 1967 only 30pict-1 carb,so i cannot help you except to say = unplug wire to it ,turn on ignition key and touch wire to terminal and listen for click.
i use the brass plug type setup = right side of carb.
i also do not use any govenor other than my right foot.

Brokenbus Sat Jul 02, 2011 8:18 am

To Busdaddy. When you say to idle jet do you mean volume control jet? Is that the hole you bore with a #50 drill bit?

To EverettB. Yes the pilot jet is a 55 and by idle mixture screw you also mean the volume control jet?

To Bill May. I am using a stock vacuum advance dizzy and do not have the electric idle cutoff jet. Carb has the brass #55 standard jet.

Thanks, Ken

EverettB Sat Jul 02, 2011 9:15 am

First, pilot jet = idle jet.
Mixture screw = Volume control screw
I was using those terms interchangeably.

Pilot/Idle jet = jet on right side of carburetor, by the generator.

Mixture/Volume control screw = screw on left side with spring. It's not a jet.

Mixture control screw is the screw here with a slotted head

Pilot jet is the jet seen here, below the choke and near the upper-left screw of the accelerator pump:

The above carburetor does not have an electro-magnetic shutoff pilot jet. This is ok.

I hope that helps clarify some things.

The mixture screw should be about 1 1/2 turns out to start. Warm up and adjust from there.

Brokenbus Sat Jul 02, 2011 9:58 am

EverettB, the pilot jet is a #55. Removed idle jet and put a #50 drill bit in the hole and fits and is sloppy meaning its drilled larger than a #50 so I guess your saying carb is shot because once engine is warm it wont idle at all regardless of idle jet setting-all the way in to all the way out. I contacted seller but wont hold my breath. BTW do you know why PO's would drill the idle jet hole larger than stock? Bigger engine is my guess.

Thanks for the imput and have a Happy 4th!

VolkzBitz Sat Jul 02, 2011 1:23 pm

Ok, we seem to have a LOT of confusion here.
I am the builder of this carb in question, and will work with the owner as much as I can, even though its been nearly a year since he purchased it.
Everett is correct with what he says, and with the diagrams.
The # 50 drill in the carb where the pilot jet is removed from is ridiculous, lol. This will only damage the carb. What about the idle screw on the arm? If this is screwed all the way in, the engine should be revving, if not, then its either a bad air leak, check with WD40 or similar on all joints, or the idle screw on the arm is not long enough, this can sometimes happen. Will it idle if you keep the arm open a little?

quartermilecamel Sat Jul 02, 2011 1:33 pm

Blow the idle jet or idle solenoid and carb idle passages out with air yet?

busdaddy Sat Jul 02, 2011 1:41 pm

SteelyTim wrote: The # 50 drill in the carb where the pilot jet is removed from is ridiculous, lol. This will only damage the carb.
The drill fix is only for an already damaged carb where someone has torqued the jet so tight it squished the hole the tip of the jet seats on almost shut, usually resulting in no idle circuit. The undamaged hole is actually larger than #50 but better to be a little undersize than screw it up worse, it doesn't work all the time but on a carb that will only idle with the pilot jet cracked open it often corrects the problem so you can still use the metered orfice instead of the wildly variable opening you create cracking the jet loose.

Good to see you're stepping up to resolve this for Brokenbus.

Brokenbus Tue Jul 05, 2011 6:47 pm

I have done considerable troubleshooting on this issue and these are my findings.

1st I removed the bus governor and installed the 1 piece spacer to remove any doubt of an air leak thru the governor.

2nd as suggested by the builder I had to remove the retaining spring on the idle adjustment screw which rides on the choke cam in order to get any idle. I was able to attain an idle while the bus was parked in the garage but seemed too hi of an RPM but at least it was idling and I wanted to road test it. As I drove about a 15 mile route the bus would stall when coming to a stop. I would get out and adjust the idle screw 1/2 a turn at a time increasing the over all idle to keep from stalling. The last 5 or so miles were stop and go traffic the engine did not die but I could tell it was revving higher than normal. Pulled into garage without shutting off engine and hooked a tach to it and engine was idling between 1350 and 1400 rpms. Way to high.

3rd I have an Oklahoma blueprint (another 67 bus with same engine configuration. Stock 1600, mechanical advance dizzy, etc.) So first I insure points and timing are correct on both busses. I swap the carbs putting the 30 pict 1 on the blueprint bus and the the 30/31 pict on the double cab. Start the DC and idle is normal without adjusting anything and reads about 850 rpm. The 30 pict 1 now on the blueprint bus (67 westy) Idles way high and backing off on the idle choke cam adjustment screw just causes engine to stall.

I am not an expert with the 30 pict 1 but it seems to me I checked everything I could think of and even swapped it to another almost identical bus and the problem moved with the 30 pict 1 carb so I can only deduce the 30 pict 1 carb is at fault somewhere but no idea where. I know the builder of this carb has joined the thread so hopefully he can provide some help.

Builder of carb is correct as I did purchase this item a while back but it was still in the box he sent and was never put on any engine since I bought it. I think everyone here buys parts for their busses as spares or whatever just to have in case you need it and that's the case here. I would sure hate to put a part on a bus that gas runs though only to pull it right off and put it back on the shelf as a "spare" with gas sitting in it.

Any other insight appreciated and thanks for everyone who chimed in to help me out over the holiday weekend.

Teeroy Tue Jul 05, 2011 10:15 pm

Did you try richening the mixture? Make sure its timed right for the distributor you have (oldvolks chart has all specs)

BarryL Wed Jul 06, 2011 9:55 am

Almost every time I had that syndrome it was the pilot jet: either the jet was clogged or the circuit was clogged. It has the same symptoms as a non operating solenoid.

Another thing is make sure the tiny pinholes are all clear where the throttle butterfly contacts the throat. There are three holes that are involved in the idle and transition to power.

Have you tried the Gypsy Tune-Up? Remove the air cleaner and rev the engine. While it's at a high rpm put your whole palm over the top until it almost dies. Do that a couple times and see if it doesn't get better. It may give you a hand hickey so beware.

Brokenbus Wed Jul 06, 2011 10:45 am


If you read the first post this a freshly rebuilt and rebushed carb sold on auction site. This carb is out of the box from builder so nothing should have to be done to it. If you read post by builder he says erratic idling is solved by turning in idle adjustment screw on choke shaft but will only idle at the point of 1400 rpms or so. This is basically a "new" carb right freshly rebuilt.

BarryL Wed Jul 06, 2011 10:54 am

Brokenbus wrote: BarryL,

If you read the first post this a freshly rebuilt and rebushed carb sold on auction site. This carb is out of the box from builder so nothing should have to be done to it. If you read post by builder he says erratic idling is solved by turning in idle adjustment screw on choke shaft but will only idle at the point of 1400 rpms or so. This is basically a "new" carb right freshly rebuilt.

Yes I read it but that doesn't necessarily mean that all the circuits are clean and all the orifices are operating. Rebuilders aren't perfect machines and aren't making a new carb. Even new carbs have defects sometimes. If it were working correctly and all your other parameters were correct so that the carb could do it's function then you should be able to turn the idle down to about a stalling idle and it would still idle.

VolkzBitz Wed Jul 06, 2011 11:18 am

It does seem there is something wrong with the carb if its been on 2 vehicles and had the same problem on both.
Even though its been nearly a year since the carb was purchased, send it back to me, and I will check it out or replace it free. Im not going to just leave you with a carb you cannot use. I rebuilt this carb and you should expect it to work for many years.
Sorry for the troubles.

Brokenbus Wed Jul 06, 2011 12:32 pm

Thanks Tim, I will contact you.

Teeroy Thu Jul 07, 2011 12:07 am

Rebuilt or new you still have to dial it in to your engine! You adjusted the idle speed but did you adjust the air fuel mixture?

BulliBill Thu Jul 07, 2011 7:19 am

I'm glad to hear that Tim is stepping up to continue to try to help you out.

In any rebuilders defense, a rebuilt carb is still a 40-50 year old carb body that is hopefully cleaned well and has new gaskets/diaphrams, etc. Most folks miss removing the the "check ball(s)" and cleaning out those passages. Mating surfaces can/will warp from overtightening over the years. Various carb metals wear with time, operation and vibration. Most parts in a rebuild are cleaned and reinstalled. Damage to parts can usually be spotted, but wear tolerances are harder to spot. Jet orifices can wear and enlarge as forty years of gasoline with contaninants pass through them. Unless you can locate a source of original NOS jets (and measure them too), we are all are probably dealing with used, worn jets in our rebuilds.

I hope that Tim can help you to sort it all out!

Bill Bowman

EverettB Thu Jul 07, 2011 11:24 am

If it makes you feel better, I have a couple carburetors that would never run right no matter what I did and I could never figure out what was wrong.

One wouldn't work at all, Bus would not even start even though it was squirting fuel when tested by hand.

I replaced them.

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