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mid 70's yamaha enduro not running well...

batty_110

Chimp
Jun 15, 2006
52
0
Minnesota
:help: I recieved an old yamaha enduro 175 from my grandparents as a gift a while back, but since it had been sitting so long, it doesn't work the best. Every time I try to hit the gas, instead of the r's getting higher, the motor starts bogging down and if I don't let up immediately, the bike dies. A friend said it was the carbeurator (sp?) if so, what should I do to make it run better? :imstupid:
 

jimmydean

The Official Meat of Ridemonkey
Sep 10, 2001
40,942
13,135
Portland, OR
Rebuild the carb, adjust the valves, make sure there is no old gas in the tank once the carb is rebuilt, make sure you change the oil and use a fresh spark plug.
 

S.n.a.k.e.

Monkey
Mar 12, 2003
524
0
N. Tonawanda, NY
It's prolly a 2 stroke, so check the reed valves for blockage. Check that the oil pump isn't drowning the cylinder with 2 stroke oil. As JD said, get rid of all the old fluids and start fresh with a new plug.

before putting the new plug back in, check the gap, and ensure that you have a nice bright blue spark when holding the base of the plug against the cylinder (connected to the spark plug wire of course) and kicking the motor over. Run the motor (as best you can) try a few throttle openings to see if you can get it to bog. After running for 5-10 minutes, pull the plug and inspect the ceramic.

The plug should be a nice light brown color.
If it's oily then it's either rings or 2 stroke pump
If it's wet, then carb is getting too much gas
If it's black sooty then mixture is too rich
Cant remember what too lean is, but in my experience with those motors your spark plug is the best indication of how the motor is running.

My .02

Let us know how it works out.

Marc