2005 Crf250r Valve Problem?...... Wont start

[Danbergie]

I have a 2005 crf250r and i bought it as a project because the guy had rebuilt the whole motor but forgot the dowel pins putting it back together on the top end. i got new gaskets and dowel pins and put it all back together and it wont run. I cleaned the carb, got new spark  plug(has spark), compression is good, must be the valves? or any ideas how to find out. When i kick it the bike pops and shoots flames out of the header pipe some times.

[tom02cr250]

Check the timing marks for the cam and on the right side next to the clutch for the crank. Timing could be off a little. Check valve clearances but if the compression feels really good then they should be fine. What size pilot jet is in it? Might have to make sure they pilot jet isn't drilled out too big, me and a buddy bought a bike that was hard to start sometimes and inconsistent idle, the pilot jet was drilled out way too big.

[Danbergie]

Check the timing marks for the cam and on the right side next to the clutch for the crank. Timing could be off a little. Check valve clearances but if the compression feels really good then they should be fine. What size pilot jet is in it? Might have to make sure they pilot jet isn't drilled out too big, me and a buddy bought a bike that was hard to start sometimes and inconsistent idle, the pilot jet was drilled out way too big.

I just purchased feeler gauges and I am almost 100% sure the timing is right because I got the dot lined up with the arrow on the right side of the crank case and on the left I have it in between the 2 marks on the fly wheel ..... and on the cam gear the marks are even with my head .... just checking if the bike is in Top dead center the lobes on the cam gear should be facing towards the back of the bike?

[Crf_noob]

Facing back yes

[Drodsgarage]

Yup she's in time than deft probably a shim issue. .12 on intake .28 on exhaust

[dakh]

Flames out of the header pipe?  Huh?  is there a hole in the exhaust other than the usual silencer exit?

 

Maybe the carb setting is way out of whack.  It's sometimes difficult to get it in the ballpark for the bike to even try to start.  I usually get idle adjuster all the way out, put the fuel screw to a setting from the manual and kick for a bit, if it tries to start give it a tiny bit of throttle or start screwing the idle in a turn at a time.

 

If it pops you might have a gross air leak in the carb boot (cracked boot, something not aligned right, forgot to tighten the collar, etc.), or maybe it's just way rich or float level way high.

[nbl300]

valves leak. shine a light in the intake and see if fuel bubbles up when you push the kicker down. if so the cheep not really way of fixing it is remove the compression release but then you can only start it on a certain stroke. If you want it done right bring the head to the machine shop and ask them to cut the seats and the valves where i get it done its 50$ for the 2 intakes.

[Danbergie]

Flames out of the header pipe? Huh? is there a hole in the exhaust other than the usual silencer exit?

Maybe the carb setting is way out of whack. It's sometimes difficult to get it in the ballpark for the bike to even try to start. I usually get idle adjuster all the way out, put the fuel screw to a setting from the manual and kick for a bit, if it tries to start give it a tiny bit of throttle or start screwing the idle in a turn at a time.

If it pops you might have a gross air leak in the carb boot (cracked boot, something not aligned right, forgot to tighten the collar, etc.), or maybe it's just way rich or float level way high.

I have the sub frame off right now I'll try putting it on and seeing what that does

Edited January 26, 2017 by Danbergie

[Danbergie]

valves leak. shine a light in the intake and see if fuel bubbles up when you push the kicker down. if so the cheep not really way of fixing it is remove the compression release but then you can only start it on a certain stroke. If you want it done right bring the head to the machine shop and ask them to cut the seats and the valves where i get it done its 50$ for the 2 intakes.

I can hear this weird bubbling sound when I kick it slowly will check in a bit ..... I just checked the clearance and I have .004 for both intakes and .005 for both exhaust. So what do I need to do to the intake valves get them cut and then what put in new ones or I don't know much when it comes to the valves

Edited January 26, 2017 by Danbergie

[nbl300]

 look down into the motor with a flashlight in the intake and push the kicker down it will push gas back up if they dont seal properly. or you can take the head off flip it over on the bench and pour water onto the head where the bottoms of the valves are and push air into the intake with an air compressor if it bubbles at all they leak. If your fixing it to flip it get the valves resurfaced and the seats cut. If your fixing it to ride long term just replace them with stainless steel valves and get the seats cut.