Question about Yamaha YZ 125 Motorcycles

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I have a 1978 yz 125 with a poor spark. It won't stay running.

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Poor spark or poor compression, replace the spark plug cap (piece that goes on spark plug to coil wire)

Posted on Feb 07, 2010

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1 Answer

Compression and spark but wont start


Hi, Anonymous are you getting fuel? for this scenario you will need your service/owners manual if you can't find the first and best tool you ever bought for your Yamaha, despair not, for a mere $0 you can download another one. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
98 YZ 125 won start
yz 125 wont start
Yamaha YZ125N1 Service Manual
OEM parts for Yamaha
http://mybikemanuals.com/yamaha/yamaha-yz-owners-manuals

May 03, 2014 | Yamaha YZ 125 Motorcycles

1 Answer

I just got a 1994 yz 125 and when i was riding it ,.. it would run good as long as i was going slow and not raping out the gears .. but when i would give it a lot of gas to take off it would bog out and...


if the plug is sooty your float is set wrong the air filter should have oil on it to catch dirt.sounds like a carb problem although it could be the power valve

Aug 24, 2011 | 2003 Yamaha YZ 125

1 Answer

My yz 125 made a loud popping noise when i tried to kick it up now it wont start any suggestions


They can do this from time to time. What can happen is the expansion chamber gets pumped with fuel vapor and then can be ignited, causing a large backfire. I hate to attempt to answer your question with a question, but how old is the piston and ring? A ring won't last very long in a 125. For racing, it's changed every race. For joy riding 15-20 hours of run time and it's time for a ring at least. Weak compression can make it impossible to start. If you have perfect compression the cause for the non-start could be something as simple as a burned up or fouled spark plug.

Start by re-ringing the motor (you can do this for about $25 inside of 2 hours time). Clean the carb out, clean the air filter, fill the tank with fresh fuel and replace the spark plug (NGK B9ES - from Autozone for $1.89). If the bottom end of the engine is good, the above steps should get it fired up - providing your ignition system is good, and based on the apparent backfire, I would say you have spark.

Scott

May 17, 2011 | 2003 Yamaha YZ 125

1 Answer

I jus want to know how i can find out the age of my yz 125


Hi, do you have any idea at all? 80's, 90's ? I have a 1978 YZ 125, and i can tell that from the engine number, all 1978 yz 125 were stamped 2K6----------
You can find out with a bit of research online, using your engine number. Also, look on the steering stem of the bike for a year date stamp.
Failing all that, make a phone call to your nearest yamaha dealer, and tell them the engine number, they can look it up and tell you what year it iwas built.
One more solution, go to a website like bikepics.com find YZ 125, and look for the model that resembles yours, they have photos of all models, from begining to most current.
So, really the only way to find out is from the engine or frame number.

Jun 18, 2010 | Motorcycles

2 Answers

My yamaha yz 125


if your getting spark than i would take the carb off and clean it you could have a cloged jet.( just because your getting fuel from tank to carb dont mean its getting from carb to jug) i would try that first......yz-maniac.

May 14, 2010 | 2004 Yamaha YZ 125

1 Answer

My 1978 125 will kick off some time and run for a min then die


Dis-assemble the carb and clean it. Clean the air filter and install a new spark plug.

Feb 08, 2010 | 1978 kawasaki KE 125

1 Answer

Sparks from my exhaust ??? Yamaha yz 125


if it still runs ok ,it was probably rust or debri from the muffler,if it dosent run ,or preformance changed after the sparks,internal engine damage would be a likely cause,part of a piston ring or something like that

Oct 05, 2009 | 2003 Yamaha YZ 125

4 Answers

What spark plug for yz 125?


I have a dennis kirk book, the correct spark plug is a --BR9ES--(NGK)

i always used SAE 10w-30 oil on all my dirtbikes,
no transmission fluid

for the chain you should move the back tire back until the chain is at a snug tension

Apr 21, 2009 | 2003 Yamaha YZ 125

2 Answers

Yz 125 2001 stays in gear when clutch pulled in


Lose the Honda transmission oil. It may have swollen the cork on the friction plates. Go with 10w40 in the gearbox. Any major brand; Mobil, Shell, Quaker State, Pennzoil, etc.. Try the new oil and give the cork a week to shrink back down > if they will. You may need to put in a new set of plates.

Apr 17, 2009 | 2003 Yamaha YZ 125

1 Answer

2003 YZ 125 RUNS AND ONLY STAYS IN FIRST GEAR


This is a shift fork or shift drum issue inside the transmission.


please rate this solution

Feb 21, 2009 | 2003 Yamaha YZ 125

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