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 Posted: Sep 3, 2017 12:25PM
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US
I am feeling very special at the moment
I pulled the carbs this morning and disassembled and discovered that neither has the sealing crush washer under the needle vale. I would have bet my last 50c that they did but once I got them apart they did not - I took the recess in the cover fr the edge of the crush washer.
Ill either make a couple of aluminium ones or copper ones and try again - the bowl that was higher was oozing past the needle valve seat under pressure - not enough to run out of the overflow hole but enough to keep the level in the jet higher.
Thanks for all of the suggestions - I'll report back once I have them sealed just to confirm that is the problem.
cheers
Barri

some new cars, 99 disco II, 88 jag xj40, 76 cadilac de ville 500c.i. (8.2l), 74 450sl, 69 lotus 7, 61 countryman (restoration)

the best view is always from the point of no return

 Posted: Aug 31, 2017 05:46AM
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Quote:
Originally Posted by gurunutkins
Thanks for the thoughts - the carbs were balanced with a unisynch (they may be unbalance now since I have been playing with them), the needle valve is the viton tip type and the floats in both are the plastic ones with the metal bendable tang to set the float height. I have swapped floats and needles between carb bowls just in case - but no difference.
I do have an airtex aftermarket 1066 (I think) fuel pump that delivers a max of 3 psi.
The fact that i cant get the fuel level down in the jet worries me too - its something that should be simple to see so I'm obviously missing something especially as its not weeping from the overflow hole under the tag. When I remove the float the level seems to be similar to that in the other bowl.
I believe both springs are the same - I cant see a colour strip on them but they came in the carbs on the car.
I have the rear carb adjuster all of the way screwed in so the jet is high in the bearing and I can see gas oozing out of it if I kill the engine and pull the piston - the other one is just fine with the gas not visible in the jet and the adjuster down about just over 13 flats.
thanks again
Barri
That is the part that i don't understand. Surely if the float or needle and seat were not functioning correctly there should be a difference in the fuel levels. Are the overflow holes on the float lids unobstructed?
While you have the carbs back off make sure there is no wear on the throttle spindles.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Aug 30, 2017 08:13PM
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Member since:Jul 29, 2008
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US
Thanks for all of the helpful thoughts - I can only try some of the suggestions over the weekend so wont get back to you before then.

The things that I do know is that the copper crush washer is below the metering valve body on both carbs and the location ring are in the head and aligning the manifold.
I have no idea if the carbs were working as its the first time the motor has run since I rebuilt it. It sat for many years before that. I have sealed the tank and replaced the fuel lines from the tank to the front. I used the electric pump because I couldn't get the original SU pump to run properly (thats my problem I have never had luck in setting up the rocker points since I first tried as a student in the 70's with my mini). The jet tubes look fine but I will pull the carbs this weekend and check everything again and possibly replace the metering valve and body. The jets move freely with the choke operation there seems to be very little play in the shafts.
Once I have checked and cleaned and reset them to spec (after all of my adjustments) i'll try the moving the lids between carbs with the fuel supply attached to just the problem lid and let you know - when I was trouble shooting I just exchanged the needle valves and floats.
Thanks for all of the help and suggestions.
cheers
Barri

some new cars, 99 disco II, 88 jag xj40, 76 cadilac de ville 500c.i. (8.2l), 74 450sl, 69 lotus 7, 61 countryman (restoration)

the best view is always from the point of no return

 Posted: Aug 30, 2017 07:12PM
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If the level will not change after adjusting the float I would suspect the float valve is no good? The only way the level can raise or lower is the float height, excessive pressure or bad valve.  the viton tips are supposed to be good for up to 10PSI fuel pressure. Check if your valves require the washer under them or not..

Mini's are like buses they come along in a bunch

 Posted: Aug 30, 2017 01:21PM
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Possible air leak with worn throttle spindles and/or the head that is installed maybe not having the locating rings for the twin HS2 inlet manifold, although the higher than normal fuel height in the jet is unusual. Are the jet tubes kinked?

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Aug 30, 2017 09:13AM
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US
Was anything done to the carbs or are they as removed before rebuild of engine? Steve (CTR)

 Posted: Aug 30, 2017 06:52AM
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US
Quote:
Originally Posted by gurunutkins
I have swapped floats and needles between carb bowls just in case - but no difference.

I have the rear carb adjuster all of the way screwed in so the jet is high in the bearing and I can see gas oozing out of it if I kill the engine and pull the piston - the other one is just fine with the gas not visible in the jet and the adjuster down about just over 13 flats.

So the high fuel level stays with the carb even when you swap all the metering bits?  Do you have the sealing crush washers between the float valves and the bowl lids on both carbs? 

Since you are running an electric pump, try an inconvenient experiment.  Run a decent length of clean, new fuel hose from the main fuel pipe to just the problem carb.  Turn the key on but do not try to start the engine.  Observe the level of fuel in the jet.

Now leave the fuel hose attached to the float bowl lid and move the lid to the OTHER carburetor.   Repeat the test where you cut the ignition on.  Does the level of fuel in the "good" carb rise to an unacceptable and/or higher level in the jet?  How does the level of fuel look compared to when the lid was on the problem carb?

Doug L.
 Posted: Aug 30, 2017 05:12AM
Total posts: 397
Last post: Sep 27, 2018
Member since:Jul 29, 2008
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US
Thanks for the thoughts - the carbs were balanced with a unisynch (they may be unbalance now since I have been playing with them), the needle valve is the viton tip type and the floats in both are the plastic ones with the metal bendable tang to set the float height. I have swapped floats and needles between carb bowls just in case - but no difference.
I do have an airtex aftermarket 1066 (I think) fuel pump that delivers a max of 3 psi.
The fact that i cant get the fuel level down in the jet worries me too - its something that should be simple to see so I'm obviously missing something especially as its not weeping from the overflow hole under the tag. When I remove the float the level seems to be similar to that in the other bowl.
I believe both springs are the same - I cant see a colour strip on them but they came in the carbs on the car.
I have the rear carb adjuster all of the way screwed in so the jet is high in the bearing and I can see gas oozing out of it if I kill the engine and pull the piston - the other one is just fine with the gas not visible in the jet and the adjuster down about just over 13 flats.
thanks again
Barri

some new cars, 99 disco II, 88 jag xj40, 76 cadilac de ville 500c.i. (8.2l), 74 450sl, 69 lotus 7, 61 countryman (restoration)

the best view is always from the point of no return

 Posted: Aug 30, 2017 03:58AM
Total posts: 9241
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Member since:Jun 5, 2000
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US
You have made a lot of good observations and logical checks.  I am focused on your comments about the fuel level in the jet not changing.

When you reset the float adjustment on the one carb, you should have seen a slight change in the level of fuel in its jet.  Since you didn't, you need to confirm that the float is moving freely, does not have any fuel inside of it, and then possibly replace the float valve itself.  Why did you say "not the fuel inlet needle and seat, not the float"?  Are your float valves the traditional solid metal tip, the Viton tipped metal ones, or ball bearing Grose Jet types?

You did not mention if the car has a factory fuel pump or something aftermarket.  If aftermarket, make sure its output pressure is not exceeding 3 to 3.5 PSI MAX.

Since you have a pair of carbs, make sure the springs are the same and that the pistons drop at the same rate (YouTube video by John Twist shows the method well).  

Doug L.
 Posted: Aug 29, 2017 11:49PM
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GB
Have you balanced them ?

 Posted: Aug 29, 2017 08:30PM
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Last post: Sep 27, 2018
Member since:Jul 29, 2008
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US
I need some help again on my 1098 engine in my MG1100.
rebuilt engine with a 20 thou over bore and a reground cam (back to original grind nothing fancy) running twin HS2's with fixed M needles. The car is pretty gutless when it runs and misfires horribly. Running an allison XR700 electronic ignition and timing is spot on at 10deg BTDC with a good spark.
The compression is 180 all around but the car is running a very rich AF ratio in the pipe and the plugs are showing a lot of fouling. The front carb (left) is running just about perfectly and the colortune is showing a nice blue flash. Change the colortune to cylinder 4 and the flash is yellow and running very rich. I pulled the piston on the rear carb and can see fuel at the top of the jet. Checked the float and even reset the float to 2/8 (1/4 inch) gap and the fuel is still at the top of the jet (not overflowing though from the overflow hole on the bowl lid) I have the adjuster all of the way up and its still rich I cant figure out why its running so rich, not the fuel inlet needle and seat, not the float, same needle in both carbs etc etc.
any thoughts appreciated
cheers
Barri

some new cars, 99 disco II, 88 jag xj40, 76 cadilac de ville 500c.i. (8.2l), 74 450sl, 69 lotus 7, 61 countryman (restoration)

the best view is always from the point of no return