Question about 2003 Yamaha YZ 125
I have a 1997 yz 125. the cylinder compression is between 115 and 120. plenty of gas, spark, and air, but wont start. it also backfires about every 8 to 10 kicks. I know the compression is a little low, but is it to low to make it fire?
2 stroke bike are very dependent on compression. and being a bike that is 12 years old my best educated guess is that the top end needs to be rebuilt. i usually have to have the top end done on my honda about every three years.
Posted on Jan 13, 2009
Check your reed cage assembly, if i back fires means the reeds arn't doing there job
Posted on Aug 18, 2009
Rebuild it, compression should be 155-160 at least. backfires and hard starting is a common problem with compression as low as yours.
Posted on Jun 02, 2009
Have a look at your power valves my bikes power valve pins broke and the power valve went into the piston and smashed the piston and power valves
Posted on Apr 18, 2009
No matter how new i think my plugs are in my 2 stroke bikes, i always replace them first in my troubleshooting sequence. never had much luck with NGK plugs. these would show a good spark (when grounded to the cylinder), but its just not enough for light it off. change the plug and see if that works.
also, if you try to start it and immediately pull the plugs, are they wet? if so, then gas mixture to the cylinder is good, just no spark to light it off.
Posted on Jan 18, 2009
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
Posted on Jan 02, 2017
Tips for a great answer:
May 03, 2014 | Yamaha YZ 125 Motorcycles
Dec 09, 2012 | Motorcycles
Oct 24, 2012 | 2003 Yamaha YZ 125
Mar 03, 2011 | 2003 Yamaha YZ 125
Aug 10, 2010 | 2003 Yamaha YZ 125
Jun 03, 2010 | 2003 Yamaha YZ 125
May 11, 2010 | 2003 Yamaha YZ 125
Feb 06, 2009 | 2000 Yamaha DT 125 R
Feb 28, 2017 | Suzuki Motorcycles
763 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: