Spitfire tuning problem. HELP

[sierranut]

Ok. Heres the problem. I have just bought a triumph spitfire mk4 and seem to be having slight difficulties tuning. The car itself has been sitting for many years and as such I am slowly going around the car fixing little problems as i go. I have just fixed the timing and she seems to be running like a dream but there is still quite bad black (Not Blue) smoke from the exhaust. I seem to be thinking that the problem is the mixture but with twin SUs fitted I am quite sure that this cannot be adjusted. Is it time to admit defeat and call in the home tune boys?????

[JeffYoung]

Black smoke is probably the car running way rich. Not sure about HS SU's, but the mixture adjustment on the ZS's is very easy -- hex wrench in the top of the carb to adjust needle height.

Haynes has a fairly cheap and readily available manual on your carbs. It is entitled "Weber Carburetors" of all things, but includes lengthy sections (nearly 2/3 of the book) on ZS and SU carbs. Get that and give it a go.

If the car is running ok, then it is probably not something internal and probably is the carbs. Have you pulled the plugs? Blackened/rich?

Do correct it though. Running too rich for too long and cause premature ring and bore wear.

[sierranut]

Car otherwise runs fine. I have changed/fixed/adjusted quite alot with the engine as there was so much wrong after so long. Initialy the plugs were very black and carbon covered. I cleaned them but it didnt take long to get back to its origional state. On a car this old do you think it might me needle wear? I understood that minis, when tuned, there is a needle book and a range of needles to select from. but alas I am not sure if the carbs are even similar let alone the same...

[railtracksport]

hello
firstly check that the air filter is't blocked i.e renew
to set the mixture on twin su carbs is simple
under each carb is hex nut screw these both all the way in then unscrew exatly 2.5 tuns eac this should give you a basic setting then you need to balance each carb so as one is not doing all the work
you can roughly do this with apiece of rubber or plastic pipe with the air filter removed other wise buy a carb balancer . hope this helped ask me anything else engine related and i will help

[AJLintern]

That's intersting advice as I'm just about to replace the jets on my Spit. It failed the MOT because of a fuel leak that I haven't been able to locate. I'm hoping its the pipe between the float chamber and the jet. I replaced the seal on the pipe, which didn't help. I don't think it's the float chamber needle valve as it continues to leak even when the engine isn't running, until the float chamber is dry.

[railtracksport]

hello
it could stil be the valve sticking open when did you last service the carbs because they are useally trouble free check for a hole in the float
you will need to partly strip the carbs but this is quite straight forward just take your time if you are a novice if you need help just ask
rgards john

[weatherboard]

I had a 1500 with the waxstat SU's and they were a right pain and gave very similar symptoms as you have posted.

If it has them it may be the stat that is causing the problem.

In the end I gave up and put some 13/4's on - drank fuel but it did seem to go better!

Jon