[Aj1705]

Hi,
I was out on my CRF 250 X yesterday, riding a local track. The bike was running spot on, no coughing or farting or anything didn't miss a beat. i came off the track cut the bike out and put it in the van take take to the jetwash, washed it off and tried to start it. to all i got was backfiring and popping. i have taken the top of the engine off exposing the cam, and there is no clearance on the exhaust valves, (if that is the ones by the spark plugs) and too much clearance on the cam lobes. Please help.

[no teeth no problem]

Call me crazy but I think you just need a simple valve adjustment.That is where I would start. I know it sounds dumb but replace your spark plug while your in it. Start with the simple things you know

[Aj1705]

I'm goin to try that today. Hopefully it works if not could it be something more serious?

[no teeth no problem]

I honestly wouldn't worry about it unless it is blowing white smoke when it starts up. those engines are pretty bullet proof. Just go through your regular checks as you have it apart, OIL,FUEL,AIR, and Spark, to be safe.

[lightflight]

Hi,
I was out on my CRF 250 X yesterday, riding a local track. The bike was running spot on, no coughing or farting or anything didn't miss a beat. i came off the track cut the bike out and put it in the van take take to the jetwash, washed it off and tried to start it. to all i got was backfiring and popping. i have taken the top of the engine off exposing the cam, and there is no clearance on the exhaust valves, (if that is the ones by the spark plugs) and too much clearance on the cam lobes. Please help.

This leads me to believe you are off on getting it to top dead center.

seems like most of the time intakes close up first.

get it to TDC and try and check clearances again.

[Aj1705]

The engine is now at top dead centre, and i still cannot get a feeler gauge under the exhaust valves (lowest i have is .0015) also the intake is reading on the left 0.23 and the right is 0.15. starting to worry a little. is there any tutorial on here that shows how to adjust clearance on the exhaust. or where do i go from here.
thanks

[no teeth no problem]

Some good tutorial videos on you tube i would link the best one but i don't know how to run this site that well yet

[lightflight]

here is a tutorial on checking and adjusting valves

http://crfsonly.com/howto/crf250x/crf-v ... stment.php

[Aj1705]

One thing I don't understand. How am I meant to get around the zero clearence on the exhaust valves. In order to reshim?

[lightflight]

And you are absolutely sure you have it at top dead center with lobes facing the back?

[Aj1705]

Wasn't at top dead centre. The engine has no compression. Turned out piston rings are ruined! What is the best make piston rings to get. Genuine Honda or aftermarket. Once the head was removed. All valves are seated with no sign of damage, valves will be removed tomorrow to check for damage.
I'm guessing now I will need, all new gaskets and ring set? Anything I'm missing?

[crfsonly]

you're making progress. excellent. you'll want to replace the rings with the same rings. so, if it's an OEM piston, OEM rings. but you'll want to measure the piston and make sure it's within spec.

ken

[Aj1705]

Thanks ken.
What is the spec for a factory standard piston?
Also, air filters dead as well as there was grit in the engine and all over the air box behind the filter.
The ring gap was way too big, but the bore is not scored or damaged. All parts from the bike are goin to be cleaned and inspected tomorrow for further signs after cleaning.
These engines arent actually that hard to work on, I'm a car mechanic but this isn't too bad considering ive never worked on a bike before. Main thing I've found take it SLOW and mark everything.
Thanks for help everyone will keep you updated

[crfsonly]

Thanks ken.
What is the spec for a factory standard piston?
Also, air filters dead as well as there was grit in the engine and all over the air box behind the filter.
The ring gap was way too big, but the bore is not scored or damaged. All parts from the bike are goin to be cleaned and inspected tomorrow for further signs after cleaning.
These engines arent actually that hard to work on, I'm a car mechanic but this isn't too bad considering ive never worked on a bike before. Main thing I've found take it SLOW and mark everything.
Thanks for help everyone will keep you updated

you need the service manual if you are going to be doing this type of work. because the piston specs you'll also need torque specs and other valuable information. we stock them if you need them quickly. you will need gaskets. when inspecting the valves pay close attention to the intake valves. when the valves wear they sink into the valve seats. check the seat contact area of the valve. if they have sunk into seat you'll see a ring on the contact area. if you see this the valves need to be replaced and the seats professionally cut.

ken