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1973 Yamaha TX750 no spark / no start...?
I have inherited a 1973 Yamaha TX750 from a great unclue of mine.
The bike had been sitting in a barn for over 20 years.
Just got it home a few days ago, and started tearing it down for inspection and cleaning.
Flushed the system, as well as cleaned the carbs.
The bike has compression and will crank over, but no fire.
I checked for spark on each cylinder, but no spark.
In the manual it states to honk the horn and test the brake lights.
If the horn and brake lights do not work, there is a bad wire or broken wire.
The horn does not work, and the rear brake light sensor is missing from the pedal.
Not sure where to start with this one.
Would like to hear it run before I dump a ton of money into it.
Any suggestions would be great.
As far as the no spark, could both coils be shot? Is that a likely situation?
I don't understand why the manual would suggest that if the horn and brake light don't work, there is faulty wiring that could cause no spark.
The bike was given to me by a family member.
I'm just looking to get it running and ride it around town.
Only has 7K miles on it and all the parts are there.
5 Answers
- Anonymous10 years agoFavorite Answer
The TX750 (1972-1974) was a failure for Yamaha. I wouldn't spend any time or money on it.
It featured Yamaha's "Omni-Phase Balancer". This was a balance shaft to counter the vibration of the motor. Unfortunately, it caused the oil in the crankcase to froth, resulting in crankshaft failures due to lack of lubrication. Also, the chain-drive to the balancers stretched over time, leading to excessive vibration. Also, parts are difficult to find for older Yamahas.
- Candid ChrisLv 710 years ago
Phuck the horn and lights for now, you need SPARK to the cylinders!
WHY? Is the big question.
Check the coil, wiring to the coil for loose, corroded fittings, the coils themselves for output, all ground wires to the frame that have any connection to the ignition system.
My guess is that the coils have aged, split/cracked and have oxidized on the inside.
Added- Sorry, I assumed you installed a fresh battery, you may wish to start there.
Source(s): A semi-educated guess. - guardrailjimLv 710 years ago
The front brake lever has a switch for the brake light.
The horn & brake light have nothing to do with the coils and spark.
Check the engine kill switch on the right handlebar switch.
- 4 years ago
try this. With the ignition turn on(lighting fixtures furniture up the sprint) pass to the distributor and with the cap off and the rotor off take a popsicle stick(wood) and open and close the standards. If there is not any spark while the standards open, the condenser is the two no longer linked(the black cord is grounding out or fried. replace. No restore. So get entire component music up equipment that would desire to incorporate factors, condenser, rotor and do it. would desire to restore the electrical powered subject.
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- Anonymous10 years ago
The coils could burn out if the ignition was left on for a long time (accidently) This happened to me with a Yam 250. Are you in the uk I'd like to see it.
Source(s): 35 years of bikes
