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MG TD TF 1500 - Sticking Jets

This is a TC question, but I hope nobody here minds, because it's really an XPAG/SU carb question.

What causes the jets to stick?

In my case, I've had a terrible time with plug fouling. I just found out tonight that the jets in both carbs are not coming all the way back up after the choke is pulled. The front carb is worse.

They pop right up if I give a push from the bottom. I think the springs are good. The jets just seem to be binding, somehow.

Thanks a lot, Greg
Greg Van Hook

Greg - Have you or someone replaced the jet seals with 'O' rings? Even the viton 'O' rings, that are supposed to be imune to gas, will get sticky after awhile when used for jet seals. If you are using the original cork seals, you might replace them (after soaking the new ones in oil overnight) and see if that cures the problem. If youhave trouble getting the cork seals to seal properly, contact Tom Bryant at tbryant@clinic.net to get some teflon 'O' rings. They work quite well and don't leak or stick. Good luck - Dave
David DuBois

Greg
I have had a similat problem, a stiff front carb lever and plug fouling. I disconnected the jet lever link, removed the top of the carb and squirted some 3in1 oil into the needle orifice, then exercised the jet lever thoroughly. The rear was OK but I oiled it too, plus all the interlink joints. I also bought a new choke cable (which I graphite greased) from the local bicycle shop. The choke is workng smoothly now but I still have an over rich mixture on the front carb which was partially explained by an incorrect high float level, I'm still trying to fine tune the mixture and will most likely have to lower the front needle about 1/32' to free up a few more flats on the adjusting nut.
John
John James

Thanks Guys,

Actually, the reason I was taking the carbs apart was to try lowering the needles a bit, even tho' I installed them level at the "shoulder" (I think).

I rebuilt them last Fall, and had soaked the seals in oil for days before putting it all back together.

I can't beleive after all of this, three sets of fouled plugs, even putting in a Lucas Sports coil and BP5ES (hotter) plugs, it's something so simple.

Usually is tho, huh?

Greg
Greg Van Hook

Yes Greg, it's called MGitis. Nothing is as it first appears! I have been alternating between N5C's and BP5ES and both types seem to soot up the same amount. I have just checked the front float and it is not leaking, so I have lovered the level a bit. more. I am also wondering if the Castrol Valvemaster I add for the leaded head could be something to do with the soot. The engine runs well and always starts first time since I fitted the pertronix Ignitor.
John
John James

Greg,

Are the needles centered? Is the timing correct? Could the coil be reversed?

I drove the TD today. Mid- 50's, top down. One word: Superb!

Ira
Ira Spector (PA)

Greg,

Can you get a good mixture at all or is it only rich when choking? I had to lower the needle (further than the shoulder) on my YA to get a normal mixture.
A full refurbishment of my (single!) carb is planned in the spring.
Willem van der Veer

Some years ago, I bought jet seals from Moss motors and had a great deal of trouble with them. They were simply short pieces of rubber tubing. Beside binding, they tended to leak, so the mixture was always rich. I replaced them with real cork seals from SU-purchased from Joe Curto (see Sacred Octagon) and the problem was solved.
Steve Tobias



The correct position for the needles on SU carbs is flush with the bottom of the piston, if you can't get the mixture correct by adjusting the jets the correct procedure is to fit an alternative needle.Check the mixture on the piston lifting pins, or alternatively lifting the piston a small amount with a thin screwdriver, if the engine cuts out when you lift the piston the mixture is too weak, if it keeps revving it is too rich,you should aim for for a point where it revs up then dies off
H.E.W. Walker

Un-sticking the jets finally solved my plug fouling problem! Actually, the rear freed up, and the front was better, but I still had to give it a push upward.

It must be the seals. The kit was a master rebuild kit from Abingdon Spares and has cork seals (new jets, needles, etc., too). I wonder if I soaked them in oil too long before I put everything together. I'll go ahead and get the teflon O-rings, and new springs just to be sure.

I did a 20 mile drive along and across the Delaware River on Sunday and it ran sweetly. First time in a long time. With 4.55 gears (normal is 5.125) and those 19-inch wheels, it is a nice cruiser. Climbing the hill back to the house is another thing!

Thanks for your help.
Greg
Greg Van Hook

This thread was discussed between 07/03/2004 and 09/03/2004

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.