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MG TD TF 1500 - SU carb

Hi. when inspecting and cleaning various parts in this case the SU carbs, I noticed that one of the vent holes in the oil cap nut is closed of with solder.
Is that standard or for some special reason ?

Thanks in advance

Gerard
Gerard Hengeveld

Gerard - if you have the original carbs without vent holes in the intake flanges (ie only two holes for bolting on the air intake), then you need vented caps.

Tom Lange
Bar Harbor, Maine
t lange

Gerald, whether or not blocking off the vent hole in the cap is OK will depend on the type of suction chamber you have. The volume above the piston in the suction chamber must be vented to the atmosphere for the carb to function correctly. The vent is either through the cap or through an internal drilling in the suction chamber. If the carb has the internal drilling then there whould be a web down the side of the tube where the cap screws on. If your carb has this web then it may or may not be drilled. The only way to determine this is to remove the suction chamber and piston and have a look inside the chamber. The carb will not function correctly if both vent holes (cap & internal) are present, you must have one or the other.
The bottom of the suction chamber is vented to the atmosphere either by holes drilled in the aircleaner attachment flange or in the body of the carb under the chamber. The latter is the situation on TC and TD carbs including MK2.
Cheers, Hugh Pite Sidney, B.C., Canada
H.D. Pite

Correction to my last post. The area above the piston in the suction chamber is NOT vented to the atmosphere. The vent hole in the cap or the internal one is to vent the pressure in the small volume above the damping rod. If this were not vented then, as the piston moves up, the air above the damping rod would be compressed. Note that if both vents were present then the suction chamber would have access to atmospheric pressure.
Hugh Pite
H.D. Pite

Thank you all Gentleman for our answers, It seems by looking at pictures in various books: my carbs are not original TD ??? ( I don't know ) they are however 1.1/4 " that's for sure.. Stelling & Hellings air filters where mounted . Don't like them because they do everything except filtering air. Like to have 2 filters mounted any recommendations ??? K&N perhaps ?
Thanks,

Gerard
Gerard Hengeveld

This thread was discussed on 25/01/2012

MG TD TF 1500 index

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