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?

[Steffan]

williredale said:

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?

Not if they are SU's but it might be worth the effort to check float levels etc. and satisfy yourself there are no other carb issues. The misfiring and spluttering does sound like a fual problem. Is there fuel at the carbs and can you smell it on the exhaust?

I think you did well to find an AA man who can deal with cars and condensers. I would certainly recommend transistor ignition the decent kits really are effective and the spark produced is much more powerful and likely to fire the compression a lot more.

From your description it sounds like the engine was drowning in fuel. Once you have replaced the broken jet (unusual problem) IME I would hope the car fires up. I have often found a car is much more likely to fail when the spare wheel/spanners/other tools have been left in last nights crte. I tend to have minimal tools and a reay spare in every kit car and classic car I own because of that experience.

Sod's law of the inveterate cussedness of inanimate objects I think. Best of luck with the repairs it seems you are on the right tracks. Onward and upward!

[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

[Geordie MGmike]

williredale said:

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.

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

[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

[Steffan]

Geordie MGmike said:

williredale said:

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.

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

Excellent service from Burden. They took over where SU stopped. Absolutely brilliant on the SU gear. I suggested earlier in the thread that a broken jet s very rare. I have only seen a few where serious damage to the carbs has occurred. Best of luck with the repair.

[nta16]

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

[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.

[nta16]

always, always pays to review and research before even planning the job as it can throw up something you've missed, forgotten or misunderstood

the times I don't are when I make stupid mistakes or need new parts but fit the old because I've not ordered the new parts or can get them before the job needs completing which means I either have to repeat some of the work later or I've left on old parts when it'd been better to replace with new - which Sod's Law comes back to kick your arse later

the vids are off the car (except tune-up) but the principles remain the same and the warnings and advice

I'd say always check any new parts as soon as they arrive that they are the correct part and if possible that they will fit correctly

Burlen like all other catalogues and data lists has errors and omissions - don't think they can't make mistakes

obvious never assume that what's fitted to your car is original or correct or is fitted fully correctly, cross reference all information with at least two reliable sources (that includes part numbers)

the broken jet has already been questioned so also look for other faults whilst you're doing the work - which could entail waiting for more parts

good luck

[perdu]

shame about the trousers

shame about the jet if its true

Me, I have me doubts

Its not unknown for the feed tube to drop out of the thread in the base of the jet, it's on a kind of olive and nut arrangement with a very small nut holding it all together

Pipes split olives fail and petrol floods all over the place

You may only need the olive and if you have ordered one, a new pipe to cure the fault

Just be glad (ish) that you heve mentioned this problem here and not on the MGE Bulletin boards

We have an American chap over there who'd be convinced that it is all Obama and GW Bush's fault when an MG goes off line

Anyway good luck, I'll keep fingers crossed for you getting back on the road soon

[nta16]

I'm with Bill on this so put the jet repair vid up first previously - HS Carburetor Jet Repair - http://www.youtube.com/watch?v=Elgfc1xZkt8&fea...

[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...

[nta16]

a small pick set is useful for these types of jobs

[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!

[nta16]

yes and as you'll use them so infrequently they don't have to be expensive or even that well made as long as they do the job at hand

http://www.ebay.co.uk/itm/4pc-HOOK-AND-PICK-SET-WI...

I've got a set of old carbs a mate gave me when I only wanted one fuel bowl screw so if you need any non-perishable parts I might be able to help you

[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.

[nta16]

yeah I always find less expensive alternatives after I've bought a tool and often because I can't remember the alternative names or proper name or more likely I spell it wrong