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Triumph Repair/GEAR ASSEMBLY FOR TACH

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Question
QUESTION: IS IT POSSIBLE TO REMOVE THE GEAR ASSEMBLY FOR TACH ON A TR 250 or 6
WITHOUT REMOVING THE DISTRIBUTOR FROM CAR AND IF POSSIBLE IS THERE ANY THING I SHOULD WATCH OUT FOR IN REINSTALLING THAT COULD AFFECT THE TIMING ETC

ANSWER: Hi Terry,

You can remove the distributor by marking it's position and not worry about the drive getting out of time because the drive shaft in the engine is an offset slot and thus the shaft can not get out of time with the distributor shaft. The only thing that can get you out of time is if you rotate the distributor itself and that can be safe if you just mark the case and the engine block so when you put it back in, just line up the two marks and it is in the same timing as when you took it out. The distributor shaft and the drive shaft in the engine block have offset key and slot so they can only go in one way.

I have seen a lot of cables brake but never seen the drive gear on the distributor fail but anything can break.

Look on the opposite end of the tach drive gear to see if there is a bolt on plate the holds the drive gear in like the fuel injected model had. It may just have what looks like a small freeze plug and if that is what it has you may have to drive the tack drive shaft out to push the freeze plug out to remove the tach shaft and gear.

Howard

---------- FOLLOW-UP ----------

QUESTION: Thanks Howard
My tach cable is not turning so the only thing could be the drive gear I agree the gear would have to be completely smooth, the cable is new and was tight on the threads, any suggestions what could be wrong other than gear
         Thanks Terry

Answer
All you need to do is remove the cable and cable housing from the distributor and use a mirror and a light to look into the part that the cable plugged into while the engine is running to see if it is rotating. Most mechanics keep a short broken off piece of speedometer (or tach cable) as a test tool which they plug into the tach drive and watch to see if it rotates when the engine is running. If it don't rotate then the problem is in the distributor drive so then they take it apart to see what is wrong.

If it is not rotating then you know the problem is inside and you can't fix it from the outside.

I did get one one time that the owner replaced the inner cable with a domestic "do it yourself kit" where you cut the cable and crimp a square drive end on the cable. The trouble is that some of the old British cables were larger diameter then the domestic cables so the square end would not rotate because it was spinning inside.

Another problem is that the inside gear slips on it's shaft that has the square socket and thus the square socket that is suppose to turn the cable is not rotating. (If you just look at it when the engine is running you will know this.

Howard  

Triumph Repair

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Howard M. Fitzcharles III

Expertise

Triumph TR-4 up & Spitfire, and Engine theory

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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