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I have a 1980 TR7 with standard dual Stromberg carbs. The engine runs very well, but I can't seem to adjust the idle down to anything below about 2000-2500 rpms. I thought maybe the auto choke was sticking, so I disconnected it, but that has not helped. Any thoughts? Thanks. /ubbthreads/images/graemlins/hammer.gif
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Wedge TR7 High Idle problem
- Thread starter Dilbert
- Start date
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Chances are that one or both of your Stromberg deceleration bypass valves are floating.
The deceleration bypass valves on the Strombergs have adjustments -- essentially, when you screw them in, the valves float, causing the idle to go to 2500ish.
Disconnect and plug the vacuum advance from the distributor.
On the right side of each carb is a little screw with a thumb adjustment. On one of the carbs, spin the screw counter-clockwise (loosen) until it is all the way out. Then on the other carb, turn it in (clockwise) until the RPMS are at 2500 at warm idle. Then turn it out until the RPMS dip down to normal range. Turn the adjustment screw on the other carb just to the point where the idle rises. Reconnect your vacuum advance.
The deceleration bypass valves on the Strombergs have adjustments -- essentially, when you screw them in, the valves float, causing the idle to go to 2500ish.
Disconnect and plug the vacuum advance from the distributor.
On the right side of each carb is a little screw with a thumb adjustment. On one of the carbs, spin the screw counter-clockwise (loosen) until it is all the way out. Then on the other carb, turn it in (clockwise) until the RPMS are at 2500 at warm idle. Then turn it out until the RPMS dip down to normal range. Turn the adjustment screw on the other carb just to the point where the idle rises. Reconnect your vacuum advance.
KLUTZ
Luke Skywalker
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It is amazing how these posts come up when you need it the most, Sammy.
I have been trying for a year to get my idle down below 1300, but to no avail. I read this post, looked on a couple spare ZS's I have in the garage, and located this deceleration bypass valve. The ones on the spares had a small clip on them, to hold them in position I presume, so I looked at mine on the 7, and the rear was fine, but on the front carb, the adjustment screw was broken off, and I could feel some air being sucked in. Well, off came one from the spares and I replaced the broken one. The small gasket was also well worn.
Well, I now have a steady idle of 800. What a differance it made.
Thanks to this post, and your super description, one more step made in the learning curve.
This is what makes this forum the best./ubbthreads/images/graemlins/thumbsup.gif
Paul
I have been trying for a year to get my idle down below 1300, but to no avail. I read this post, looked on a couple spare ZS's I have in the garage, and located this deceleration bypass valve. The ones on the spares had a small clip on them, to hold them in position I presume, so I looked at mine on the 7, and the rear was fine, but on the front carb, the adjustment screw was broken off, and I could feel some air being sucked in. Well, off came one from the spares and I replaced the broken one. The small gasket was also well worn.
Well, I now have a steady idle of 800. What a differance it made.
Thanks to this post, and your super description, one more step made in the learning curve.
This is what makes this forum the best./ubbthreads/images/graemlins/thumbsup.gif
Paul
KLUTZ
Luke Skywalker
Offline
Re: Uh... Sammy or others
Well, the idle held nicely around 800 to 1000 for a few days. It is now back up to around 1600 after a run.
Now, to follow the stated precedure, it says to disconnect the vacuum advance. I don't have a vacuum advance from the Dizzy. How do I do the adjustment without this step?
Thanks
Paul
Well, the idle held nicely around 800 to 1000 for a few days. It is now back up to around 1600 after a run.
Now, to follow the stated precedure, it says to disconnect the vacuum advance. I don't have a vacuum advance from the Dizzy. How do I do the adjustment without this step?
Thanks
Paul
Re: Uh... Sammy or others
You should be able to do it w/o plugging the vacuum advance. In fact, you might try to simply rotate one of the adjustment screws out and see if it brings the idle down. It might not be truly "floating."
It's also possible that the bypass valve rubber is disintegrating on one or both of your carbs. Take a look at a Moss or Vicky Brit Catalog and you can see the little diaphram for the bypass valve. I actually took mine off to check them -- not that difficult (if I can do it, I know you can, because I'm just slightly less dense than a coconut.)
I know some people have permanently blocked-off their bypass valves, as well. You might search in the forum for "deceleration bypass" and see if that post describing this process comes up.
You should be able to do it w/o plugging the vacuum advance. In fact, you might try to simply rotate one of the adjustment screws out and see if it brings the idle down. It might not be truly "floating."
It's also possible that the bypass valve rubber is disintegrating on one or both of your carbs. Take a look at a Moss or Vicky Brit Catalog and you can see the little diaphram for the bypass valve. I actually took mine off to check them -- not that difficult (if I can do it, I know you can, because I'm just slightly less dense than a coconut.)
I know some people have permanently blocked-off their bypass valves, as well. You might search in the forum for "deceleration bypass" and see if that post describing this process comes up.
Offline
Re: Uh... Sammy or others
I blocked the bypass on the Z on my 79 Spit, when I had idle problems. That was two years ago, and I haven't had a problem since. I just made a plate and a gasket, and screwed those down over the bypass on the carb body. The carb works much better all around this way.
I blocked the bypass on the Z on my 79 Spit, when I had idle problems. That was two years ago, and I haven't had a problem since. I just made a plate and a gasket, and screwed those down over the bypass on the carb body. The carb works much better all around this way.