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Stromberg CD150 Rich Mixture


Richard C
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Not so much a question as an observation. My 13/60 has been running a bit rich for a few years, and I've not been able to weaken the mixture sufficiently with the adjustment screw. The carb has been apart many times, minor issues rectified, but still too rich. Today I took the needle out to check its straightness and wear, and saw that the shoulder was recessed slightly into its socket. Recessed not more than 1/32, probably more like 1/64. Reset the needle just like it says in the manuals (Doh!) EXACTLY flush with the air valve, and the problem is fixed.  Can now set the mixture rich, lean, and just right. The problem must have arisen a few years ago when the need for a new float valve led me to renew the O rings and gaskets as well.

As a second thought, exactly HOW critical is the needle seating to the carbs performance. If I had to move it 1/64, ie 15 thou to correct it, what tolerance is there?

Third thought, if it works don't mess with it.

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One of life`s factors that we all tend not to consider, thinking that the needle was positively seated when hard home is one of them I suspect?. The taper is critical, as is wear in the Jet, I have known guys use piano wire or even a small drill to clear a blocked jet and then complain they cannot get a decent a mixture!. Too much "slack" in spindles, is another cause of frustration!, with irregular fluctation of air flow causing issues. Little wonder the world went to fuel injection as one of the ways to better control "emisions".

BTW, One trick I learned, If you suspect the Throttle spinde of leaking to much air, Putting some "putty" around the spindle as a temporary seal, (blue tack?) can show if your right.

With my 13/60, still some way from "completion" I have all this to come, I guess?

Pete

 

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on a stroms and SU the needle should be level with the base of the air piston ( thats  on biased and fixed  and on cdse the delrin washer on the needle 

is all flush )

i would have expected the std bottom adjuster to compensate for a small error 

have you centred  the jet ????  

and 13/60 does not have a piston spring   if one is fitted it will be rich when running 

Pete

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some other thoughts   the alloy sealing washer under the jet top bush is important as is the 0 ring the jet slides through

as for the float height its easy if the float has twin valve arms to clip the float in upside down as t will fit both ways up 

for good pictorial clues use            https://www.buckeyetriumphs.org/carburetors  ignore the car model the basics are ok for all CD models 

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Hi, Thanks Pete, for that link.

I am impressed with the prospect of fitting ball bearings to the Spindles as a way of also eliminating wear leaks?.

Anyone here ever done it or attempted it?. I`ve more that once considered over the years Sleeving/oversizing the spindles or re-bushing. But converting to sealed bearings just never occured.

Pete

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the problems with any spindle re boring is keeping it concentric with the throttle bore  if it goes off centre you will never 

get the idle under control as the butterfly doesnt seal the throat correctly   it generally needs to be  linebored/reamed  on a fixed jig 

but ...needs must.......... a bit of careful alignment and it will work ...or not   

Pete

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I didn’t change the bush, just the seals. The aperture in the new bushes in the rebuild kit were actually a fraction bigger than original and as original wasn’t worn no need. I would be a bit apprehensive if i had to change the bushes!

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Hi Pete. Thanks for listing all the other factors that need checking, but the point of my post was that all of those having been dealt with, it was the incorrect needle seating that was critical to solving the issue. As you say, one might expect the adjustment screw to deal with this, but the fact is that it did not. Thus my point is that flush fitting of the needle to the air valve is crucial to correct operation, within an unknown few thou tolerance.

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With the risk of upsetting Richard with the thread drift, re discussion re reaming the spindle seats/bearing, has anyone tried the aftermarket replacement spindles incorporating O ring seals, which don't require any new bush's or reaming, and is this a long term fix or just a get out of jail job, also is there any increased resistance to the rotating shaft?

Any thoughts or experiences.

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14 hours ago, daverclasper said:

Have you a price for that work Iain please?

Dave, the price is £114 each plus vat. This is for a complete recon including bushing/seal. As a recon kit including spindles from Burlen is over £100 for the pair I thought the price very reasonable. I hope they do a good job, if not I'll blame Pete! 

Iain 

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1 hour ago, Pete Lewis said:

Ok so  Ive left the country with a covid pass and hiding for a while 

I'll see you at Duxford.........! 

I'm asked nicely if I can have the carbs back to go in the Vitesse, if not its the boring modern

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16 hours ago, Peter Truman said:

With the risk of upsetting Richard with the thread drift, re discussion re reaming the spindle seats/bearing, has anyone tried the aftermarket replacement spindles incorporating O ring seals, which don't require any new bush's or reaming, and is this a long term fix or just a get out of jail job, also is there any increased resistance to the rotating shaft?

Any thoughts or experiences.

No personal experience. But any slight increase in resistance would not be felt as the return springs would/should compensate anyway?. I doubt if there would be any noticable difference in pedal action?. Sometimes a slight increase in pedal "weight" can help with fuel economy if you have a tendancy towards a "lead foot".

Pete

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