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Original Stromburg Carb Setting 72 Spitfire

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RobBB Rob H
Burbank, CA, USA   USA
Carb Setting.

Hello And Good Day everyone!
Thanks to all of you and your advice, I had a successful startup on Saturday! It is the first time the Spitfire has been running in approximately 26 years.
She didn't want to idle at first, with out the choke on. As I set the screws on the carb, I realized I did not know the initial setting for the air/fuel screw. The instructions just mention to adjust in small increments. I am running the original Stromburg single carb, which I rebuilt. After some adjustment on the two idle screws I have achieved idle.

Is there a initial start-up setting for the Air/fuel screw?

On my Amals, on my Norton, for example, the air screw setting is 1.5 turns out from all the way in, for initial start up.

On this carb, I turned it all the way in, they backed out 1/2 turn. I am guessing as you back it out, your leaning out the idle. But I don't know.

Thanks
Rob
1972 Spitfire, 1300cc, with Single Stromburg carb

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CarbInstalled.JPG

Growe58 Avatar
Growe58 Greg Rowe
Hatfield, PA, USA   USA
Been a while since I had a Z-S, but if I recall correctly it is 3 ½ turns from full lean to full rich and a good starting point is in the middle (roughly 1 ¾ turns from either extreme). A few things to bear in mind

-CW lifts the needle and enrichs the carb. CCW lowers and leans it
-If you lower it too much, it can come off the threads and further turning will have no effect. Fix is simply to push upwards gently while turning to re-engage threads.
-You can just use an Allen wrench in lieu of the special tool to adjust but only if the needle is very free to move. Without the tool, the torque of turning is transferred to the rubber diaphragm. Too much resistance and it rips and you have all sorts of drivability issues.
-I notice your “PCV” is unhooked. You can’t leave it that way or you will have a vacuum leak.
-The fine tuning screw right under the PCV port should be screwed all the way in and left that way. This was an air bleed that leaned the mixture for emissions reasons. Has very little real world effect and is better off an eliminated variable.

RobBB Rob H
Burbank, CA, USA   USA
Greg,
Thank you for the reply. I will if time permits, go over all this tonight after work.
Thanks for the screw setting, it is a real help. I will set it there, 1 3/4 turns out from full (in) stop.
The PVC hose was attached at time of start up. I include the pic in case I wasn't clear which carb I was describing. First British car, and I'm still getting familiar with name of parts and the like.

thanks for the allen wrench tip as well.

Looking back at the carb rebuild, I don't remember putting a new o-ring on the needle when I was cleaning and re assembling carb. I may have over looked swapping the old o-ring out, and put the needle back in on the bench with on old o-ring still on it. Thanks for jarring my memory!

sincerely,
Rob

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Falkon Avatar
Falkon Al Martin
Appleton, WI, USA   USA
I believe there is no real idle mixture on a '72 car. that screw is for fine tuning emissions settings only.

RobBB Rob H
Burbank, CA, USA   USA
Al,
Thanks for that. I have no idea about these cars, so all this is new to me. I take notes and it all goes into my notebook for the Spitfire.

Rob

Outfect Avatar
Outfect Dave B
La Sal, UT, USA   USA
1940 Ford N Series Tractors "Henry"
1951 Other Not Listed "SnowMan"
1979 Triumph Spitfire 1500 "White October"
1980 Triumph Spitfire 1500 "Tangerine Dream"
Robb,

Are you adjusting the mixture with the brass screw on the right side?


DaveInUtah

jimgt6 Jim E
Seekonk, MA, USA   USA
The brass screw is for break-in only Screw in until it bottoms.
There is a little adjustment on the needle about a turn and a half from lean to rich. you will need the stromberg tool to adjust without twisting and breaking diaphram

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Growe58 Avatar
Growe58 Greg Rowe
Hatfield, PA, USA   USA
Good point Al and Dave. The main mixture adjustment is thru the top of the carb. I assumed that was what you meant but if I jumped the gun, then what I said doesn't apply. I should have made sure of the question before trying to provide an answer. Sorry!

RobBB Rob H
Burbank, CA, USA   USA
Greg, Jim, and Dave,
Good morning Gentlemen,
Thanks again for all the advice. I was referring to the brass screw on the side, (front facing) of carb. Since I didn't get a chance to touch the carb last night, as the winds are a blowing here, nothing got touched, and therefore, I ruined nothing! lol.
I was wondering about the special tool you mentioned, now it makes sense. smiling smiley

My next chance to really get to the car may be Saturday, as after work doesn't allow enough sunlight. But If I get to carb , I will set the brass screw about midway in it's range.

After fiddling with that screw, which didn't seem to have much input response, and the mechanical idle set screw on the left or rear side, I now have the car idling with out the choke one once warmed up. I believe I'm on the right path.

Next is checking the new tank sender unit. As the gas tank was the first thing i did on the Spit, it was boiled out and installed empty and clean as a whistle, along with a new Moss Motors sender unit. The gauge, on start up read 3/4 full. I had only added 2.5 gal for start up. Moss Technical advised me what to do, how to trouble shoot the sender and how to get it working. Thats exciting, as any working gauge after 27 years being dormant is a little victory.

Attached is a tank pic...one of the tank removed, and one after it came back from the shop, freshly painted, and with it's new sender installed.

Sincerely,
Rob

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Attachments:
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gastankSenderNew.JPG

gastankNeck.JPG    51.7 KB
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J.P.Rap Avatar
J.P.Rap J.P. Rap
Mount Hope, ON, Canada   CAN
1976 Triumph 1500 "Donna"
2007 Ford Ranger
Since you can't get to the carb until the weekend, here's a good read for ya. Read it through a few times and you'll know just how everything on that carb works. There some experiments with adjustments the guy did at the end of the article. Worth reading even if just to see what he did.
Just ignor the parts that don't match up to your carb. Everything else is identical.

Page one...
http://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm

Links to the rest of the pages are at the bottom.



"In this world, you must be oh so smart, or oh so pleasant. Well, for years I was smart. I recommend pleasant." Elwood P. Dowd

RobBB Rob H
Burbank, CA, USA   USA
J.P.,
Thank you so much for the article. I printed it out, and started reading. More motor stuff to read at night, the wife will be thrilled!

I really appreciate this, and your effort,

Sincerely,
Rob

J.P.Rap Avatar
J.P.Rap J.P. Rap
Mount Hope, ON, Canada   CAN
1976 Triumph 1500 "Donna"
2007 Ford Ranger
No problem at all Rob. I'm pretty new to this stuff too and that article was a gem to find. Ive turned to it a few times while troubleshooting problems.



"In this world, you must be oh so smart, or oh so pleasant. Well, for years I was smart. I recommend pleasant." Elwood P. Dowd

RobBB Rob H
Burbank, CA, USA   USA
Thanks J.P., I am new to Triumphs as well.
I acquired the car last October.
It took a while, and some intense trouble shooting to get just a layman's grasp of a simple Amal carb. As this is my first British car, all is new to me, (yet some things strangely familiar due to Nortons...).

I'm sure I will be utilizing this article more than once.

Rob

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