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View Full Version : Wedge TR7 Carburetor losing dashpot oil



GeoffreyK
03-09-2014, 11:00 AM
The previous owner installed manual choke carburetors on my US market 1980 TR7. It has a pair of ZS CD175's. The car runs resonably well and starts fine. Idle and acceleration are a bit sputtery, but the biggest problem is that the forward carb loses its dashpot oil over 3 days even if it is not used, and 150 km if it is. The rear carb needs a dashpot top up every 60 days or 500 km. I tried different fluids but that is just avoiding the repair. I had a mechanic replace the needle "o" rings with no change.

The previous owned cannot tell me what the carburettors came off. He says they are original TR7 carbs but i don't think there was a North American TR7 with factory manual choke. In addition to this, one carb had a vented plunger knob and the the other didn't. The mechanic drilled a hole in the non-vented knob(?). They are black in colour.

What is going on? Could it be the wrong needles? Could the diaphragm be leaking? Could it be the wrong "o" rings? There is no good local service for Triumph or Zenith Stromberg carburetors. The little brass ID tag is missing off both carbs. I am reluctant to take the carbs off the car and send them away because the car is in paid storage only until May. If i don't get the carbs back on the car and get it out of the garage it will cost me $125 per month.

Does anyone have a solution, suggestion or a set of carburettors?
Geoff

tdskip
03-09-2014, 11:33 AM
Good morning, and welcome to the forum. Good people here who are happy to help.

You are very unlikely to need new carbs, the oil disappears due to perished o-rings that are fairly easily replaced without having to take the carbs apart. Here is a good overview:


https://www.bowtie6.com/other/zenith-stromberg-carburetter-repair/

DNK
03-09-2014, 11:49 AM
The manual choke kit can be bought after market so the carbs could be correct

dklawson
03-09-2014, 12:29 PM
+1 on Tdskip's post. However, "not having to take the carbs apart" depends on your definition of the task. Since replacing the needle o-rings involves taking the piston out and disturbing the needle location (fuel/air mix) I consider this a task that not everyone is up to. However, it is not beyond the scope for a confident DIYer using the instructions in the article linked above. Just remember if you do this task yourself you will need to tune the carbs after you are done.

poolboy
03-09-2014, 12:47 PM
You may want to read this although may be what tdskip posted.
Following the steps and doing one at a time using a kit such as Moss 365-955 and 2 of 365-745, you should be able to tackle the job yourself.
Basically the same carbs..close enough.
https://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm

TR3driver
03-09-2014, 02:28 PM
In addition to this, one carb had a vented plunger knob and the the other didn't. The mechanic drilled a hole in the non-vented knob(?). They are black in colour.

Very likely, the vent hole was not required and the vented knob is from some other carb. The space under the knob does need to be vented, but all of the CD175s that I've seen have an internal vent for that space.

However, since you say your mechanic has already replaced the O-rings once and you're still losing oil; I wonder if perhaps you are overfilling. As long as you can feel resistance for the last 1/4" or so of travel when you insert the plunger, there is "enough" oil. If you put in too much, it leaks out through the vent and through the sliding joint.

George_H
03-09-2014, 03:20 PM
Didn't 75-76 tr7s have manual chokes?? Also, I put new o-rings in last year and one carb still uses twice the oil of the other.

poolboy
03-09-2014, 07:31 PM
Some of the O-rings that seal the damper well might be a bit loose on the adjuster and that may be why they leak.
I've noticed that on several carbs that had their O-rings recently replaced, yet leak. I didn't ask where they came from. I get mine from Joe Curto.

NeilRogers
03-10-2014, 12:22 AM
Canadian TR7s all had manual chokes unless, of course, they were fuel injected.