Question about 2003 Yamaha YZ 250 F

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Loss of compression

Hi I have a yz mod it is a great bike have a bit of trouble with the compression lately.It used to have great compression at TDC but at the moment I can seem to kick through it.

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I dont have a 4 stroke, but lack of compression on any engine is bad news. You need to take the engine apart, the piston ring is shot or maybe you have valve issues. I love the Turtle Posse!

Posted on Nov 10, 2008

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Yz 426 was running and thought it was out of gear and let out on the clutch bike died and wont start back up and its hard to kick over even with the compression release lever pulled in whats wrong


Hi, Anonymous you may have transmission-clutch-valve issues for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. If necessary, transport your bike to the dealer or shop and have a professional technician take it for a test drive, if it is in running condition, and give you a written estimate of repairs and answer any specific questions you may have about your problem. 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.
Yamaha YZ426F Owner Service Manual
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May 05, 2014 | 2001 Yamaha YZ 426 F

1 Answer

I just changed my head gasket on my 1991 Honda XR250L. Now that I have it rebuild, the bike wont start. I have made sure the piston is at TDC, the cam shaft is placed right. I dont know what is wrong. any...


Their are 2 different top dead centers/TDC ,one is TDC of Exhaust stroke and the other is TDC compression stroke . You must have the TDC compression stroke . At this point -both valvesare closed.  If it is TDC Exhaust stroke You will be @ a point where the Exhaust valve is just closed and the Intake valve is just opening.After you have established the proper relation of the crankshaft and Camshaft ,you must do ignition timing.   

May 09, 2011 | 1983 Honda XL 125 R

1 Answer

I have a yamaha yz 250f 2006 bike will not start on kick start but will start with a push


if the bike push starts, i assume it runs good,
if the kick does not turn motor over, there is a spring clip that engages the kick gear that may be broken or misplaced
if the kick start turns the motor over, you have to use decomp to get just past TDC then kick

Apr 11, 2010 | 2004 Yamaha YZ 250 F

1 Answer

Power issues


if compression is below minimum you should put in a set of rings but i would first check to be sure the valves were adjusted correctly as this may cause loss of compression

Jan 20, 2010 | 2002 Yamaha TT-R 250

1 Answer

2004 YZ 250 4 STROKE PROBLEMS STARTING


There is a proper way to start the engine. Four controls are on your bike to assist in starting. Below are generic instructions.
  • The choke, used when the engine is cold. Pull the red knob for choke.
  • The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
  • The de-compression lever, always used.
  • The throttle, used to prime the cylinder, (power valve).
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Now release the de-compression lever. Give the throttle a 1/4 turn then let it snap closed. A diaphragm, (Power valve), in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. A flooded engine will often backfire. Now give a strong kick through the full sweep of the kick start lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from the kick lever. This happens in the case of a misfire, aka > backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), for six kicks. After six kicks go ahead and twist the throttle again for a second priming. A good battery, a clean spark plug, a clean carb and clean air filter will also aid in starting. Note that not all carbs have a power valve. When a power valve is not present you should crack the throttle open only 1/8 inch from closed on each kick.

Go to this site and you can download a free PDF service manual. The site may take up to 20 seconds to load the complete list of manuals. Yours is on the list.
www.carlsalter.com/motorcycle-manuals.asp

Nov 19, 2009 | 2004 Yamaha YZ 250 F

1 Answer

How i start my yz426 2002 yamaha the bike has a good compresion the carbulator true gas and the spare plug is good


these bikes are the hardest bikes to fix, easiest thing, kick the bike super slow until you piston is at TDC, you will know because it will be hard to kick, then pull the compression release down and as you start to kick release the compression release. NOT an easy task starting a 426 but good luck

Nov 02, 2009 | 2002 Yamaha YZ 426 F

2 Answers

Wich oil should i use for my kx250 98 mod


go for repsol tranmissiones and motul racing 2t oil

Jul 17, 2009 | 2003 kawasaki KX 250

1 Answer

Bike is sometimes hard to start.When bike stalls and goes dead,it is hard to start again.This is a 2003 honda crf450.


There is a proper way to start the engine. Four controls are on your bike to assist in starting.
  • The choke, used when the engine is cold. Pull the red knob for choke.
  • The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
  • The de-compression lever, always used.
  • The throttle, used to prime the cylinder.
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Now release the de-compression lever. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. A flooded engine will often backfire. Now give a strong kick through the full sweep of the kick start lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from the kick lever. This happens in the case of a misfire, aka > backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery, a clean spark plug, a clean carb and clean air filter will also aid in starting.

Jun 28, 2009 | 2003 Honda CRF 450 R

2 Answers

VERY hard starting takes way to many kicks usually play out befo


There is a proper way to start the engine. Four controls are on your bike to assist in starting.
  • The choke, used when the engine is cold. Pull the red knob for choke.
  • The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
  • The de-compression lever, always used.
  • The throttle, used to prime the cylinder.
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Release the de-compression lever. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. Give a strong kick through the full sweep of the kickstart lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from a backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery, a clean spark plug, a clean carb and clean air filter will also aid in starting.

Top rating for this answer? Thanks!

Jun 11, 2009 | 2003 Yamaha YZ 250 F

1 Answer

2005 250 f 65 kicks to start


Several things can cause the problem. First, spring for a new spark plug. The stock plug is NGK CR8E. Now the plug is eliminated as a problem. Next, pull the slide out of the throat of the carb. Now remove the jet needle. Put the needle clip on the 4th notch, (this is the stock setting). Use only premium gas. Next, follow the starting instructions below.

There is a proper way to start the engine. Four controls are on your bike to assist in starting.
  • The choke, used when the engine is cold. Pull the red knob for choke.
  • The " Hot Start " Lever, used when the engine is hot. Pull the lever to lean the fuel mix when the engine has been running.
  • The de-compression lever, always used.
  • The throttle, used to prime the cylinder.
Don't kick, instead, push the kick lever downward. You will feel the back pressure as the piston is going upward on the compression stroke to the point the pressure is great enough that the kick lever "locks up". You are very close to TDC. NOW, pull in the de-compression lever. Push the kick lever a little bit more to get the piston past TDC. Give the throttle a 1/4 turn then let it snap closed. A diaphragm in the carb gives a shot of gas when this is done. DO NOT do this multiple times because you will flood the engine. Leave the throttle closed when kicking. Release the de-compression lever and give a strong kick through the full sweep of the kick start lever. Quickly get your foot off the kick lever at the end of the kick to avoid any chance of "kickback" from a backfire. It can be very painful, and can even break a leg. I am serious about that. Repeat the process (but without the throttle priming), until the bike starts. A good battery and clean air filter will also aid in starting.

This will likely tame the beast for you. Please rate this answer. Thanks!

Jun 06, 2009 | 2003 Yamaha YZ 250 F

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