03 yzf250 wont start

[Yz250FinAZ]

i have an 03 yz250f that wont start. i just had the carb redone, cleaned from the shop, but it still wont start. They replaced the fuel mixture screw, and put a new gasket...stuff i couldve done, but w/e.

any ideas?

Im going to check the valves later today, or tomorrow, depending on how much sunlight is left, but is there any other possibilities?

 

[Matt90GT]

3 things needed to start a motor:

compression
fuel
spark


Check all 3. You will find your issue. Go back to the basics.

 

[Yz250FinAZ]

i put new gas in, and a new plug is in, getting spark.

What should i do to check the compresion?

 

[02yz426f]

take out spark plug and use a compression gauge to measure while you kick it over. I have heard it should read about 250 PSI. Somebody correct me if i'm wrong.

 

[Yz250FinAZ]

K, ill look and make sure what the exact range of compression should be, thanks.

 

[Matt90GT]

Just cause you put gas in the bike does not mean that gas is getting to the CYLINDER!!!

A new plug does not mean there is spark! Check these things

With the auto decompression exhaust cams, you will never read very high. Within 5 kicks you should be around 100psi.

 

[02yz426f]

Ok that makes sense. My bike has the decomp lever, so keeping all of the pressure bottled up, would mean it would be higher. Maybe the plug wire is the problem. Test to see if you get an arc from it.

 

[Yz250FinAZ]

ya i knew i had spark(grounded it to the head, kicked over, got the spark, knew it was getting gas to the cylinder.

i took the head off, and the valves are almost gone, couple more rides and ill need a new top end/valves. one of the intake valves was at like 185, and its supposed to be at 165, cuz it was stuck open, thats why i couldnt get it started.

Ive been looking through my rockymountain catalogue, and they have the kibble white valves, any good info on? are they reliable valves for my bike?

 

[02yz426f]

their good

 

[Matt90GT]

What are you talking about? Are you saying the shim sizes? THere is no specific shim size, it is all about clearance! a 185-165 shim will not result in a "stuck open" valve. May leave slightly open and bleed off a bit of compression making it hard to start, but not stuck open.

Personally I dont think that will be your problem.

 

[Yz250FinAZ]

ya, the 165 shim size, is what it was originally, and it was an intake valve, that was open, wether it was because of the shims, idk.

 

[mikieobryant]

yea kibblewhites are very good. i have them in my bike and havnt had any problems with them

 

[Ol'89r]

The Kibblewhite valves are an excellent choice. Be sure to buy the entire kit complete with springs. The Kibblewhite valves are stainless and heavier than the stock valves. Stock springs won't last.

Just my $ .02