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Carburetor tuning

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wbdvt

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Ok, I've been reading up on tuning my carb now that I've got it rebuilt and piston is moving and correct needle installed. I believe the mixture is rich as the plugs are black and sooty, not oily.

My question is what do you use for a CO analyzer? Is this something that can loaned/renter for auto parts place? I've looked online (ebay) and they all start at over $200. Is there another way???
 
On the side of my SU carbs is a small plunger. You will find it on the "dome" of the carb between the carb and the float bowl. It's all explained in the books. You take a tiny screwdriver and push up on the plunger which lifts the piston about 1/8" The engine speed should increase a few 100 RPM then drop back to where it was before. Sometimes it will drop lower in RPM but it should not stall. This should be ideal. If the speed increases and stays up there, then the carbs are too rich and you should then turn the brass hex nut below the carb a few flats of the hex at a time in the upward direction to lean out the mixture for that carb. Check the manuals.
 
warm it up and let it idle. Keep leaning them out until you get the highest idle speed. You will have to keep adjusting your idle down as you do this. When you get the highest smooth idle I usually richen them back up one flat for SU carbs and about an 1/4 of a turn for Stromburgs. You can then go and balance them as normal. Just make sure that your valves and timing are adjusted correctly before you start adjusting the carbs. You can also use a color tune but I never have and never had any complaints doing it the way I do. Good luck
 
WB- I am a non-Triumph mechanic but manage to keep my engine running and enjoy driving.

Do you have the Basic tuning tools?
A carb sync tool? (the Roadster Factory-cheap_
A carb mixture tool ( The Roadster Factory-cheap)
A basic timing light- pretty cheap at Sears.
Feeler gauges to gap spark plugs and dizzy points.
A flat head srew driver with long handle for idle..
The correct spark plugs,
Clean air filters,
clean gasoline filter- good high test gasoline?
A clean. no crud, gasolin tank?
An always functional, working fuel pump?
Decent ot rebuilt twin carbs.

I'm a non-mechanic and usually get things lop=sided-out;
but these tools and a few good comments from the triumph
experts here and you will be be zooming around town in your chick-magnet. Buy a Bentley's Blue Book.

My name is not important, best wishes.
 
wbdvt's profile shows he's driving an '80 Spitfire. Wouldn't that have just one Stromberg with a non adjustable jet and a somewhat adjustable needle?
 
3798j said:
wbdvt's profile shows he's driving an '80 Spitfire. Wouldn't that have just one Stromberg with a non adjustable jet and a somewhat adjustable needle?
Click to expand...
Yup, I think so.

If you are worried about emissions, then a CO meter is the only way. Either buy one or take it to a shop that has one.

If you just want it to run right, then I recommend the "lift the piston" test as Don mentioned. Your carbs won't have the pin on the side, so you'll have to remove the air cleaner and whatever else is in the way, then use a small screwdriver or pocket knife to lift the piston with the engine running. Lift it by 1/8" or so and listen to the engine rpm. If the engine speeds up and stays there, mixture is too rich. If the engine immediately slows down, mixture is too lean. Perfect is when the rpm rises slightly then falls back to about where it was before.

You can double-check that by doing "plug cuts" and reading the plugs, but usually it's not worth the effort.

You might also want to read through https://www.buckeyetriumphs.org/technical/Carbs/CarbsIII/CarbsIII.htm Although written for a TR6 (with dual carbs), the mixture stuff should be pertinent to your car.
 
OK, thanks Tim.

I've also read somewhere that those of us with chokes (that would be all of us, right?) should not place any emphasis on the areas of the plug that relate to idle speed.

Cheers!
 
Lifting the air valve or "piston" as some call it, is Ok once you get the hang of it.
The biggest pitfall that I've noticed when a person is just learning is that they leave the air valve raised up too long while trying to decide what they observed. So if that's the case, make your decision upon the immediate engine response.
Reading the plugs gives you a visual clue.
 
I like to read the plugs.
Make sure you are not idling the engine for more than a minute before shutting it down, wait for it to cool if possible, pull a couple plugs and adjust accordingly; Repeat till perfect; can take months!
 
Graham,

The next time you decide to read your plugs, would you make a video of it, so the rest of us can watch exactly how you do it? It sounds fascinating, especially the part about taking months to do it...... :lol: :lol:
 
Why not use a Colortune?

ColortuneBlueFlame.JPG
 
Brosky said:
Graham,

The next time you decide to read your plugs, would you make a video of it, so the rest of us can watch exactly how you do it? It sounds fascinating, especially the part about taking months to do it...... :lol: :lol:
Click to expand...
Iy involves quite a few beers, hence the extended timeframe!
 
I've never used one of those and always wondered what they looked in action. Thanks for posting that picture Tom.
 
Thanks all for the guidance and humor. I will be working on that as soon as I finish fixing a master cylinder leak. I do want to do at least one drive with it before snow flies here. Crossing my fingers for parts arriving this week and get a drive this weekend!!
 
A ColourTune is a good tool for less than an EGA, I've two of 'em with many years' service.

Depending on which Strommie (some earlier ones were non-adjustable) you can "cheat" the need for the mixture tool with a long 3mm Allen wrench and using your finger to pin the piston against its bore to prevent stressing the diaphragm. Minute (1/8 turns) make a big difference so don't get too 'enthusiastic' when making adjustments.
 
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