TR4/4A Carbs too lean?

[Marla]

I did have a problem with the carbs being too rich...so I adjusted them and the black smoke stopped coming out of the exhaust and the spark plugs are not coated...but when I drove the car today there was a loss of power...had to hold my foot all the way down on the gas gas pedal to start the car after getting gas and driving it there was most assuredly a loss of power...took a bit of time to even hit 50 mph...so I should enrich the ZS carbs a bit...yes?...No?...Marla

 

[vette]

I was just surfing and this really isn't my forum but I'll give you my opinion anyway. Just turn each jet one flat and see how it runs.

 

[Marla]

OK...sounds good to me...can't hurt right?...Marla

 

[TR3driver]

Remove the air filters, and with the engine warmed up and idling, use a small screwdriver or similar to lift each carb piston in turn by about 1/8" to 3/16". The idle rpm should rise slightly, then fall back to where it was. If it goes up and stays up, that carb is too rich. If it immediately drops below the original rpm, that carb is too lean.

Note that you should feel some resistance when lifting the pistons. If not, the damper is low on oil. (Lack of oil will cause the mixture to go very lean when you open the throttle.)

If you've done that, and still have a lean bog (power loss while driving), the problem is something other than carb adjustment. Weak ignition can sometimes masquerade as carb problems.

 

[Geo Hahn]

...so I adjusted them...

How much did you adjust them by. As I recall ½ a turn moves the jet up or down 1/64". That is quite a bit so yeah, small moves are best.

...Just turn each jet one flat and see how it runs.

'One flat' = 1/6 of a turn (Strombergs' adjusters are not hex nuts, just serrated things with a big screwdriver slot). A two shilling coin works well in that slot. Okay, a quarter or a big washer would also work but a the two shilling seems more period correct.

 

[Marla]

Remove the air filters, and with the engine warmed up and idling, use a small screwdriver or similar to lift each carb piston in turn by about 1/8" to 3/16". The idle rpm should rise slightly, then fall back to where it was. If it goes up and stays up, that carb is too rich. If it immediately drops below the original rpm, that carb is too lean.

Note that you should feel some resistance when lifting the pistons. If not, the damper is low on oil. (Lack of oil will cause the mixture to go very lean when you open the throttle.)

If you've done that, and still have a lean bog (power loss while driving), the problem is something other than carb adjustment. Weak ignition can sometimes masquerade as carb problems.

Thank you...will test this

 

[Marla]

Thank's Geo...great advice...Marla

 

[bnw]

Make sure the linkage hasn't popped off one of the carbs.I can't imagine that radical a change simply from a mixture adjustment. Just realized you're dealing with Strombergs. "serrated things with a big screwdriver slot" ?? I remember an allen wrench tool passing through a slotted piece in order to keep the piston from turning as the jet needle is raised or lowered with the allen. Did you trash your rubber diaphragms ?

 

[glemon]

As I recall we are talking about a TR4 or 4a, which has the mixture nuts on the bottom of the carb just like an SU, the early 79s Strombergs had the Allen wrench from inside the carb method you describe, and you are correct, you can tear the diaphragm if done wrong. Given the symptoms described it might not be a bad idea to check the diaphragms regardless.

 

[poolboy]

Because you never know what a car that old might now have for carbs, a picture would help and if ZS carbs a shot of the bottom would reveal if they are the jet adjustable or possibly needle adjustable.
There are the "non-adjustable" ZS carbs that were found on a couple of later TR's but still mountable on TR4's...you just never know until you look.

 

[sp53]

Yes a Picture is good, and I would add that often it takes a while for an engine to totally warm up, perhaps 20 to 30 min. The gauge will read warm before the whole engine is completely warm by say 10 minutes.

 

[gbtr6]

Have ey been cleaned or rebuilt lately? When I got my TR out, with SU's, it ran as you described. I took the carbs off, and cleaned them both.Also, make sure the needle is clamped in. One of mine fell out, so it wasn't even raising to allow gas in.

Perry