TR6 low speed stall

[charleyf]

Just a guess, but often when you make a turn, you let up on the gas pedal.

Does the "stall" occur if you don't let up on the pedal during a turn?

Good question--- I'll try it and find out.
Charley

 

[Brinkerhoff]

You've never said what your float level is. You are still "guessing" aren't you?

 

[malbaby]

With the PO fitting "new" carbs, can you be sure that they are correctly set up. I would check that the main jets and needles are exactly the same size on both carbs and fitted correctly....
Cannot understand why anyone would fit those SU carbs to a TR6 anyway....IMHO, I would replace them with Strombergs which are simpler in construction and look much better.

 

[Brinkerhoff]

That low speed stall is a classic symptom of low fuel level in the float bowl / jet. Even though it sounds like you have the solid bodied floats ( without the metal tang) , if the needle and seat valves aren't stock ( Grose Jets for ex. ) you need to correct for that. Your mixture adjustment depends on the fuel level in the jet.

 

[charleyf]

With the PO fitting "new" carbs, can you be sure that they are correctly set up. I would check that the main jets and needles are exactly the same size on both carbs and fitted correctly....
Cannot understand why anyone would fit those SU carbs to a TR6 anyway....IMHO, I would replace them with Strombergs which are simpler in construction and look much better.

When I said "new"carbs , that is exactly what they are. Never been used, out of the box "new". I have the invoice from Moss Motors. I believe that either stromberg, SU or Webers should work.
Charley

 

[charleyf]

You've never said what your float level is. You are still "guessing" aren't you?

we have lowered the float level--no help... We have raised it with a second gasket that helped some but did not do the trick. Added a third gasket and that made the situation worse, so pulled the third one out.
Charley

 

[charleyf]

You've never said what your float level is. You are still "guessing" aren't you?

I checked the fuel level today and it is 1/2" below the floor of the carb. That does seem low. But I do not recall ever seeing what that fuel level should be. The books only refer to the measurement between the lid and the float. Does anybody have a recommendation for what that fuel should be in the jet?
Charley

 

[Brinkerhoff]

Finally we are getting somewhere !

 

[Brinkerhoff]

Read my previous post . The fuel level should be just below the top of the "floor of the carb". When you blow down into the jet with your mouth fuel should bounce up and spill out.

 

[titanic]

G.R. Wade's book on SU carbs recommends that the fuel level should be 1/8"-1/4" below the top of the jet. Also, it is important that the float chambers are level. There are various adapters to match the angle of the carb flange face of the intake manifold. I would that that the Moss kit would include the correct adapter.
Berry

 

[charleyf]

The fuel level is low by all of the recommendations I see here. I as well looked at some older SU books and it showed 3/8". So we will work on getting the fuel level raised in the float chambers.
Both float chambers are level.

It sure makes sense that the fuel level should be very near the top. The needle is large enough to virtually shut off the jet orifice then the fuel would be stopped by the needle. If the needle is all of the way down. Only lowering the jet would provide the space for fuel to come out of the jet.
Charley

 

[NutmegCT]

Charley - thanks for keeping us posted on all this.

Question: have you tried the "keep foot on the gas while going around a corner" test?

Also, your first post said the car had been completely rebuilt. Did it have this stall problem when you first got it?

Tom M.

 

[charleyf]

Charley - thanks for keeping us posted on all this.

Question: have you tried the "keep foot on the gas while going around a corner" test?

Also, your first post said the car had been completely rebuilt. Did it have this stall problem when you first got it?

Tom M.

This car came to us as a project. The engine had been rebuilt and it was a frame off restoration. It has been a long road, which has included a new paint job to replace the previous new paint job with a bad clear coat. Then a new engine rebuild after it developed a major problem during the initial start up of the PO engine rebuild. The car came with many upgraded parts. The SU carbs were one of those upgrades. To answer your question-- the car did not run when we got it.

when driving down the road with my foot on the accelerator it takes curves fine. It is the in town right angle corners or U-turns where one gets to low RPM's and then wants to accelerate to get going again that it stumbles. As we try different things we are getting varied symptoms and have to then try to get back to the BEST we have had . The float problem is now the focus.
Charley

 

[charleyf]

Update-- WE decided to try to more accurately measure the fuel level in the jet today. The one we were measuring was the rear and it was about 1/2 inch but then to our surprise the front one is about 5/16" down. So we tried to determine why the front and rear are different. When i pulled the rear carb off of the manifold I think I figured out why the difference. The float bowl of the rear carb is lower because of the slope of the engine. That means that the front float bowl is higher in regard to the front jet and the rear carb is lower in regard to the jet than the front carb. Hope that makes sense. It became very clear when I pulled the rear carb off the car and held it up to about level. I had gas running out of the jet.
I have another set of HS6 carbs that were included in a TR3 project. I went over and looked at the rear carb and there I found a 1/4" spacer between the float bowl lid and the float bowl. There is NO 1/4 " spacer on the front carb. It appears that the spacer would bring the fuel level in the jet of the rear carb up to closely match the fuel level in the jet of the front carb. I called Moss and ask them about the spacer and they have no idea or anything to show such a thing does or should come on these carbs.

So does anybody out there have any knowledge about needing such a spacer on the rear carb?
It is raining here so I don't know when I will be able to get the car back out for any test drive. But this is the first thing that we have found that makes sense and should be "fixable".

Charley

 

[NutmegCT]

Charley - take a look at this reference to shims, and to proper angle due to engine "tilt":

https://www.team.net/html/triumphs/2001-10/msg00983.html

TomM.

 

[charleyf]

Thanks Tom. It looks like they were dealing with the same problem. To bad nobody reported back the solution they came up with. I do have a set of HS6's on the shelf with a spacer under the rear float bowl lid. We will try that and see if we can get a "matching" fuel level in both carbs. I also received a set of needles from Joe Curto yesterday. They will richen up the low speed area. Moss must not be selling a lot of these carb sets for TR6's or there would be a lot more info on this problem. Laying a level on top of the carb body mounted on the manifold shows a good slope. The light really came on for me when I held the rear carb up and it had a full fuel bowl. On the car the fuel was low very in the jet, in my hands I held it about level and the fuel came pouring out of the jet.
Charley

 

[titanic]

Charley-I found it was necessary to fit the shorter float bowl (#2140) to the front carb to fix a flooding problem. I misidentified the float bowl as #2143 in a previous post.
Also,if the carbs came with BAG needles, I have found that they are lean in the cruise range, but not enough to cause misfiring or stalling.
Berry

 

[charleyf]

Charley-I found it was necessary to fit the shorter float bowl (#2140) to the front carb to fix a flooding problem. I misidentified the float bowl as #2143 in a previous post.
Also,if the carbs came with BAG needles, I have found that they are lean in the cruise range, but not enough to cause misfiring or stalling.
Berry

Berry,
What was the symptom of your flooding problem?
We worked on the fuel level today. We got the rear carb fuel level up closer to the front carb fuel level. We did this with a plastic 1/4" spacer under the rear float bowl lid. The two levels are much closer but not equal. Unfortunately the car ran pretty much the same as before. Then we put in a set of BAE needles that Joe Curto recommended. After leaning out both carbs the car improved a lot. The stumble and spitting out the carbs is only occurring now when I push on the accelerator fast while at low speed. If I gently push on the accelerator I can usually avoid the stalling and spitting.
Charley

 

[Brinkerhoff]

Its too lean not rich.

 

[charleyf]

Its too lean not rich.

Thanks. We pulled the spark plugs after driving it at the lower speeds and the front one showed lean and the rear one not as lean but lean. And the chase goes on.
Charley