Help! with stromberg on a vitesse.

[Prince Brainier of Meccano]

Car Vitesse 2l mk2, was running well but front carb gasket was wet with fuel.  I took it apart and cleaned and tested the needle valve, replaced the tiny O ring under the jet as it looked rough.  Re assembled and it now is very poorly.  Seems the front carb (the one I over mended) is very lean.  No wet gasket though.  Will run with choke on but once off tickover drops to 400 and is clearly 1 good pop and then very little, that is back 3 cylinders OK front not so much.

Piston has oil and moves freely with the clonk when released.  Jet centred.  Diaphragm OK, Jet set 2 turns down from level with bridge, Black float in that seems OK, doesn't rattle and with 18-19mm before acting on the needle valve.  Partially covering the intake to strangle it (and I do feel like strangling it) brings the tickover up.  It all feels like low fuel level to me.  High, I could understand if the float had leaked but closing too soon doesn't seem right.

Any suggestions?  I'm missing my fun!

[johny]

well the 2 turns down is only a starting point so you can try winding the jet further down to enrichen the mixture. If you have to go a long way have you got an air leak somewhere?

[Prince Brainier of Meccano]

Just checking the float should have the wobbly shape to the bottom of the car, right?  That is when the float hangs down with the bowl off the flat side of the float faces to the right of the car???

[Prince Brainier of Meccano]

Thanks, Johnny.  I'm thinking not an air leak as nothing else has changed other than removing the float bowl and tinkering the needle.  There is one aluminium washer under the valve but that was there when dis assembled, that would make the valve shut sooner.

 

[Pete Lewis]

try 3 turns    2 is not enough try 3 then adjust from there to get best running dont think the float /setting is your problem 

and float  this is TR related   but the basics are the same 

https://static1.squarespace.com/static/5c6dec53b10f25d4edf0b3f7/t/5d0191191376fd00017521ed/1560383774528/TR250_TR6+Carbs+Part+II.pdf

 

[NonMember]

One aluminium washer under the valve is correct, I think. It does sound like low fuel level but try adjusting the jet a little first. It's a bit harder to assess the fuel level on a Stromberg than it is on an SU.

[Prince Brainier of Meccano]

When the float bowl fills how does the air get out?  Once the jet holder ports are covered it can't get out there and the choke dip tube won't let it out once the end is covered.  I'm wondering if there is a port or airway to atmosphere?  As to my own problem I'm wondering if this airway, should there be one is blocked.  That would mean that the petrol level  would be held down by back pressure.  Previously when there was a leak at the gasket the air could get out and let the bowl fill.  Thoughts? Advice?

[NonMember]

There is an airway for balancing the pressure in the float chamber. It emerges into the air filter as a small circular hole diagonally up from the main air inlet. There's also a D-shaped hole above the main one, which is the air feed to the bottom of the piston diaphragm. Fitting the air filter (or its gasket) upside down to block these holes will cause all sorts of problems.

I'm not sure what you mean by "the jet holder ports" or "the choke dip tube"

[Pete Lewis]

cds has a dip tube to feed the choke starter valve 

as Rob says gaskets or upside down air filters can cover the front face breather holes 

the buckeye site explains which is which 

but if you have not changed that any idea its low fuel levels seems a bit misguided 

have you dropped the jet the extra turn yet ??? 

are the dimples on the diaphragm located correctly in the casting relief   a quick look down the air piston the the two holes in its base must face the engine side 

if t worked before you worked on it  you must retrarce what youve done  

Pete

 

 

[Prince Brainier of Meccano]

Thanks for the continued advice.  No.  Not dropped the jet yet.  Diaphragm correctly seated. no filters or box on at present.

"Jet holder ports"  are the grillings through the large brass bit that screws into the bottom of the carb.  Inside is the jet adjuster/spring etc.

"Choke dip tube" is the short brass tube that goes into the fuel for the choke supply.

Started OK on 3/4 choke so I guess the choke  is getting the supply.  Will run at 2000 rpm (with applied throttle) when warm but is keen to die unless choke is pulled out when needed.   If left limps at a very low tick of 3-400 rpm.

 

I'll try dropping the jet and reply.  It does  look about where the other carb is at present?

 

Thanks again.

[Iain T]

As a starting point to get my carbs in sync I made sure the needles in both air pistons pertruded the same, from memory about 39mm.

Then again using a vernier caliper I measured the depth from the brass jet to the ali carb bridge body. Again from memory I started at about 1.2mm.

If you get both of these dimensions the same in both carbs it's at least a good starting point. 

Iain 

[Pete Lewis]

on a cd /cds  you should have the piston lifiting pins .

this gives a good clue but is a light fingered feely thing you dont give the thing a shove it will just stop

when up to temperature lift the pin quietly to just touchy feel it touch the piston then lift 1 to 2 mm only

if it falters its weak  if idle rises  its rich if no change its right

dont expect major rpm changes  more a hint of 50 rpm decrease or a 50rpm increase

these work well but its a careful feel and listen , not wam bang thankyou gorilla  tactics 

do it with the air filters off will get really upset when you refit them , this is obviously best done in a road running condition

setting by lifting air pistons with filters off is a right waste of time ,  no idea why this silly idea is shown in many manuals 

Pete

 

[Prince Brainier of Meccano]

FOUND IT!

It was the B+'@T£$7d throttle link.  The rod between the front and back carbs has flexi links and one has been bodged and has a brass sleeve inside that looks like the shaft from the back carb.  This had slid off the back carb shaft so the front carb was getting little movement.  The sleeve/shim was flared at one end and was probably just hanging on.   The front carb throttle stop screw was backed right off and so I think as bought by me, the tickover was set on the back carb stop.  So the front carb wasn't joining in much.  I'll still need to trim mixture and balance but it runs and ticks over OK.

Thanks to all who helped with advice and eliminating probables.  Once again it was found by looking not knowing.

In my early electronic days the old boys would say have a look first for anything that looks wrong.  And there would be the loose wire.  The overheated component.  The cracked diode. The blob of solder.  And here it is again.

Thanks again.

[Pete Lewis]

its not uncommon for the variety of connectors that diameters of shaft and clamp end up with a shim inserted to make a 'fit'

Pete

[NonMember]

2 hours ago, Prince Brainier of Meccano said:

It was the B+'@T£$7d throttle link

Last April we went on a tour of Scotland in my Vitesse. At one point, having overtaken some slow pokes uphill, we started to get overheating. That turned out to be because that pesky throttle link clamp had loosened and only the rear carb was opening. I've got some nice new UJs to build a replacement one with, which I'll get round to at some point, once I've finished all the welding that I decided needed to be done.