A bit of a breakdown...

[williredale]

I had a teensy bit of a breakdown yesterday morning on the way to work... She started fine but as I came off the choke there was some rough running, not quite enough cylinders firing and a bit of a backfire. Pulled over and it wouldn't start.

I checked under the bonnet and all looked well but it would not start. A lovely bloke in a BMW stopped, said I've had three of these and helped me push it into a handy parking space.

Now, all fuelling problems are usually ignition related aren't they? Rather embarrassingly though my tools were in my daily which has broken its heater...
Hello, AA, how can we help? I've broken down. Send someone with more of a clue than me!

Well, we checked / tested / replaced the rotor, points, condenser, leads and coil. Nothing.

Carbs look ok. Floats are working so off with the air filters and there it is. Jet on the rear carb has broken and is hosing petrol in like there's no tomorrow.

The man from the AA (Mark from Clevedon) who spent almost two hours getting me home was very good but now I need to replace the jets and needles. Can I do them in situ or do the carbs need to come off? Also, where's the best place to source replacements?


tl;dr MGB shat its carb jets. Do I need to remove the cards to replace the jets?

[williredale]

My breakdown was opposite the garage I use for my daily driver and one of the mechanics popped over just before the AA man arrived to check I was ok and he was singing the virtues of electronic ignition too.

Drowning in fuel certainly describes it! It was like an open tap pouring super unleaded into the engine. When we fixed / bodged the jet back together we ran the car up and treated the old peoples home to a smokey full throttle B series for a while

[williredale]

Geordie MGmike said:

I don´t understand this as I've never known a jet to break. Plus the float regulates the fuel level in the jet which "should" make this impossible. Please explain more with pictures.

But to answer the question:
HS carbs can be done in situ (but you'll need to be a bit of a contortionist ), HIF will need to be removed unless you are an expert contortionist

All the parts can be found here... www.burlen.co.uk

best of....
MGmike

I ordered the parts from the owners club so that's in hand. I've taken the air filters off to check for access but don't want to strip the jets until the new ones have arrived. That should give me a better chance of putting everything back where it belongs! pictures to follow.

I'm afraid I fell at the first hurdle of contortionism... I undid the four air filter (K&N) bolts with an arm either side of the bonnet arm... Which was tricky trying to balance everything! And then whilst trying not to drop anything on the wing my trousers fell down. All rather embarrassing!

What else could go wrong?!? I'll post pictures next time

[williredale]

nta16 said:

you might also want to look for a belt

there are a few John Twist videos on carbs that may be worth a look before you start

HS Carburetor Jet Repair - http://www.youtube.com/watch?v=Elgfc1xZkt8&fea...

44 Secrets of the SU Carburettor Part 1 of 2 - http://www.youtube.com/watch?v=7GRAcqDySog&fea...

43 Secrets of the SU Part 2 of 2 - http://www.youtube.com/watch?v=60Bj_2cZQnc&fea...

(MGA) 29 SU H-Type Carburetters - http://www.youtube.com/watch?v=GHNlT5yHDxk&fea...

41 Matching SU Air Pistons - http://www.youtube.com/watch?v=IfU47Oqq9wA

123 MG Carburetors & Doors (first part needles and seats, springs and carb oil) –
http://www.youtube.com/watch?v=v9QI3NlvwiY&fea...

147 MG Carburetter Tuning - http://www.youtube.com/watch?v=4nvGLgO6pj0&fea...

222 MG SU Carburetters: Setting the Float Height (needle & seat comparision) - http://www.youtube.com/watch?v=82YNx-RkGNI&lis...

232 MG Carburetter Needles and Seats (odd sizes) - http://www.youtube.com/watch?v=pVX_JClyeDQ&lis...

Edited by nta16 on Wednesday 17th September 10:30

+1 for the belt! I must have looked a right wierdo crouched over a car in semi darkness with my trousers down!

I've already watched most of the videos but i think they all show the carbs off the car whilst I'm going to attempt them in situ. I mentioned the John Twist ones to the AA man when we were talking about fixing them properly.

I don't know why I didn't order direct from Burlen. They were cheaper than the OC and I've used them before.

[williredale]

Pictures will follow which will help me understand what's broken as well as you. Shiny new bits arrived yesterday but I've not had a chance to fit them yet.

[williredale]

An update. The jet tube had split near its top so more fuel was flowing past the needle. Lots more from what I saw when it was broken. It was also a bit of a pig to remove as it was jammed into the jet bearing.

Next problem is that the rubber compression washer in the bottom of the float chamber has perished and stuck in there.
I've ordered a dentist's explorer tool as I think that should be perfect for prising it out.

I need to get everything back together for this Friday as that's when my daily driver is on for its service. Otherwise humble pie will need to be eaten as I ask my wife for a lift to work...

[williredale]

nta16 said:

a small pick set is useful for these types of jobs

Tell me about it! I've tried bent bits of wire, screwdrivers and a screw.


The right tool for the job!

[williredale]

Damn. That set is the same price for four tools as I paid for one!
I couldn't think what they might be called but knew that the dentist equivilant was an explorer. Oh well, it'll get used for this and then languish in the tool box for years until someone describes a small hooky type thing to pull a small rubbery do dah out of an inaccessible hole.