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Tuning carbs conundrum.

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byakk0 Avatar
byakk0 Hazen Wardle
Boise, Idaho, USA   USA
Trying to get my carbs tuned and balanced.
I've got a unisyn and a color tune.
I've got them close to balanced, but one or both seem to be rich no matter what.
Plugs, even after a good spin around the block, are black. The rear are sooty and the front are a bit wet.
Idle is around 1000-1200 with the choke off
Using the color tune I couldn't get the color to change from yellow, even screwed the jet out all the way accidentally.
Question is, what could be wrong, thoughts, ect.
Thanks in advance

Dual ZS 150CDSE with bottom side adjustable jet and fixed needles. Manual choke.
They've been modified (not by me) such that the temp compensators are removed and bypass valve disabled.



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~Hazen.

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
The idle is too high and the (running) mixture too rich . This is not a syncronization problem, it is an idle speed and mixture problem.

brucejon Avatar
brucejon Bruce Jones
Santa Cruz, CA, USA   USA
1962 Triumph TR3B
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
Also make sure your ignition is completely sorted. Yellow = unburned fuel for any reason. When I first got a colortune I messed around a bit with it. You can change your color to yellow and back with timing alone, as bad timing results in incomplete burn. Anything else wrong in the ignition can do the same. You may be chasing multiple problems, and will chase your tail on adjusting the carbs if your ignition isn't sorted first.

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Rick in Miami Avatar
Rick in Miami Rick Z
Miami, Florida, USA   USA
1973 Triumph GT6 MkIII "Spit 6"
1974 Jensen Healey
Make sure your float height is set correctly.

Rick

kalombo Wilmer Sprunger
Berne, Indiana, USA   USA
I had a similar problem years ago with my '76 Spitfire (single carb). I also tried to adjust the internal mixture and screwed the jet out, all to no avail. It was still too rich!. So a mechanic friend of mine took the carb and soaked it in his carb-cleaning bucket overnight. That must have cleaned out some internal opening and now I can adjust the internal adjusting jet. Now the mixture can be adjusted accurately.
It was my assumption that if some internal opening was a bit plugged, it would restrict the gas and the mixture would be too lean. But obviously not. With the partially plugged orifice it blocked some air and so was always too rich. So make sure ALL the holes are open inside the carb[/u] and then you can make the proper adjustments. I learned this from past experience and want to share this with everyone!

Wilmer

Yellowhawk Valley Avatar
walla walla, washington, USA   USA
1969 Triumph Spitfire "Walla Walla"
1969 Triumph Spitfire "Portland"
1972 Triumph Spitfire MkIV "Spokane"
1975 Triumph Spitfire 1500 "Dayton"    & more
Ok, you guys might be confusing me... not that hard too do with these carb issues. You mention screwing the jet (s) out to adjust. By dropping the jet are you not making the mixture richer as you would be moving it down to the thinner section of the needle, same as lifting the needle out of the jet????? If it is already rich wouldn't you want to screw it up?
Dan

TheFlash300 Avatar
TheFlash300 Dave Gutknecht
Rochester Hills, Michigan, USA   USA
1979 Triumph Spitfire 1500 "Lil Spit"
Yes, it sounds like it needs to be leaned out, so raise the jet up to make the gap between needle and jet smaller for less fuel. Screwing the jets out allow a larger gap to the needle and more fuel.

In reply to # 1501568 by Yellowhawk Valley Ok, you guys might be confusing me... not that hard too do with these carb issues. You mention screwing the jet (s) out to adjust. By dropping the jet are you not making the mixture richer as you would be moving it down to the thinner section of the needle, same as lifting the needle out of the jet????? If it is already rich wouldn't you want to screw it up?
Dan

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kalombo Wilmer Sprunger
Berne, Indiana, USA   USA
OK, if that's your logic, try raising the jet (needle that goes down into the body) UP by turning the screw UP.
I turned it down because the needle is tapered, and I thought that pushing it down further it would block off more gasoline. To be sure, check in some instruction manual to see which way to turn it - so as to Reduce the fuel. I thought it was down (and ultimately out of the throttle piston)!
But now that all the orifices are open inside, I can adjust it. It's been a few years, so that's all I can remember!


Cheers. Let us know ultimately what the solution is!

Wilmer

byakk0 Avatar
byakk0 Hazen Wardle
Boise, Idaho, USA   USA
Up or down, didn't really matter. I ran it from all the way up too all the way down where it came out. Bear in mind these are the fixed non-adjustable needles, so the jet going up and down changes the fuel flow instead of the adjustment of the needle. (If I understand adjustable needles correctly)

I'll do a complete teardown... Again... If I need to. I'm getting good at removing them from my car. Be a few days before I can tackle it so any ideas at this point are welcome. Just more food for thought when I get round to it.



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~Hazen.

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65or66 Gold Member Jim B
Lake village, IN, USA   USA
1965 Triumph Spitfire MkII
1973 Triumph Spitfire 1500 "Jusanudda Munny Pit"
From your description, it almost sounds like someone has mixed/matched later CDSE carb bodies (with temp. comp. and bypass) with earlier adjustable jet assemblies. I have no idea what it takes to make that work. Not saying it's not possible, but I've never had each type in my hands at the same time.

If the CDSE piston/needles are still there, the needle is adjustable using the special ZS allen wrench adjusting tool.

Are you adjusting the correct portion of the jet (on the bottom of the bowl)? The smaller, center portion of the jet, and it should be slotted for a screwdriver. The larger portion of the main body portion will unscrew the entire jet assembly if you turn it too far, and will turn the adjustable portion out with it at the same time.

vancouver, washington, USA   USA
Hazen
I would agree with Rick in Miami that you probably have a float height issue or worn seats on the inlet jet. There could be a fuel pressure issue if you have replaced the fuel pump and not used the spacer between the pump and block. The worst that the temp compensator could do is introduce a lean condition. They are easily rebuilt , just a couple of o-rings. Start with the simple stuff before mortgaging the house.
Mike C

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, Nevada, USA   USA
The deep dark secret is these needles and jets wear out.

1964Spitfire Avatar
1964Spitfire Tim P
Santa Clara, CA, USA   USA
Check to see if the needles are worn. Easiest if you hold the needle horizontally under a bright overhead light. Rotate it slowly and look for flat spots.

Also remove the needles from the pistons and see if they are correct. Should be stamped on the side.

I haven't worked on the 150CDSE. But I've worked on the 175CDSE and they were fixed seat with adjustable needle. So seems strange that the 150 would be the opposite.

You could also try contacting - Joe Curto - Triumph GT6 - Zenith Stromberg 150 CDSE

byakk0 Avatar
byakk0 Hazen Wardle
Boise, Idaho, USA   USA
Joe might not be a bad idea. I bought the new butterfly shafts from him.

The needles are indeed fixed, not adjustable. Both are fairly new as far as I know, but worthy of an inspection again at this point.

The compensators are removed and the port blocked with a bolt. They effectively work like CD150, or so I've been told.

The jets are the adjustable ones with a screwdriver slot, which is the portion I have been turning.



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~Hazen.



Edited 1 time(s). Last edit at 2017-12-06 10:32 PM by byakk0.


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scardini1 Avatar
scardini1 Gold Member Jim Moscardini
Great Mills, MD, USA   USA
1968 Triumph GT6 "Rocinante"
2003 Jaguar XKR "Kitty"
Hazen. I'm sure you did this, but, ...

Did you completely disassemble and clean the entire jet assembly? I had experience (long ago) of the Jet being jammed in its carrier by accumulated gunk and dried fuel varnish. So it felt has if it couldn't get any leaner (because the jet wouldn't budge), and there was no response to richening (because the jet didn't drop as the adjuster was unscrewed).

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