Jump to content

06 CRF250x new valves and rings and now it won't idle.

Recommended Posts

I have a 06 CRF250x that will not idle with the choke off. I did a bunch of work(Keep reading to find out what) and now its having problems. This isn't my only bike so working on it was not a priority. However, it was my dads bike before he passed so it is important to me.

My question is do I need to lapp valves in when putting in stainless steel ones. Heres my back story.

About two years ago I decided it was time for new valves since I had re shimed a bunch of times and one valve was visibly sucked into the head and getting ready to go. I went with a stainless steel intake set with springs and guides. No need to do exhaust. I also decided it was a good time for new rings since I was in that far with the motor anyway. Honda rings, new gasket set, all torqued to spec. I get it all back together after about a year of it sitting apart. I cleaned the carb for good measure before putting it back together. New oil, oil filter, new air filter from honda, new tranny fluid, new throttle cable(old was kinked) fresh gas.

I get it started(first kick pretty much) and it will not idle with the choke off. Then I spend a year checking any and everything I did(clean the carb 6 times and have the local shop do a cleaning and rebuild job for about 200 bucks, check all rubber boots for cracks and loose connections, check throttle cable tension, make sure the carb was connected properly and all hoses are in place, new pilot jet, float valve and all rubber gaskets new)

At this point I only have a few options that I can think of. The carb is bad and I need a new one or, the valves need to be lapped in(something I have been told I don't need to do) If anyone can think of another reason that this bike is running like this I would love to hear it. My real question though is do I need to lapp in new stainless steel valves? 

Thanks and have a nice day.

Share this post


Link to post
Share on other sites

You mention new SS valves, springs and guides but

did you re-cut the valve seats when installing the new valves?

That far into the engine I hope you also preventatively replaced the cam chain and tensioner.

 

Since the engine seems to start easily, I would not suspect the valves at first but rather the carb settings / air leak etc.

Edited by mlatour

Share this post


Link to post
Share on other sites

Also, during those numerous cleanings if the carburetor was dunked or sprayed with certain harsh solvents

there is a chance some internal seals (mid body gasket) and slide seals were damaged, causing various running & tuning problems.

Not all carburetor or parts cleaners are actually 100% safe for these carbs.

Edited by mlatour

Share this post


Link to post
Share on other sites

Let's start with this:

" the valves need to be lapped in(something I have been told I don't need to do)"

You never should.  What should be done is the seats cut and the valves fitted properly along with making sure the valve guides are in good shape.   Can you lap SS valves? Yes. Would I?  No. Proper valve fitting is critical for longer life and lapping just doesn't cut it.   And the stock TI's should never be lapped (which is probably where you got the 'I don't need to').  They have a coating for heat dissipation and lapping takes that off.  If you lap a TI valve, it will quickly die.  Keep in mind, this is a racing motor that revs out to over 10K.   It's not by any stretch something like an XRL where you can get away with things.  Doing things right is critical or you'll be repairing it often.

As far as the idle, it's probably the carb as mlatour said.    Not sure what was done with your carb rebuild and cleanings and how, but the passages mid-body along with the air passage for the slow circuit are extremely difficult to clean without taking the carb apart mid-body. In the past before the gaskets were available, people would junk a carb.   Now you can take it apart.   If you are sure that was done, then you need to look else where.   If not, then it would be something I would do.  

Check out this thread and take a look at the pics of what was inside *after* cleaning:

With that said however, I would double check a few things first:

1. That the hot start nut is not cracked.

2. That the hot start plunger is not hung up.

3. That the slide seal is not installed upside down

3. That the spring, washer, and o-ring on the fuel screw are in the proper order.

4. That you don't have more than one o-ring on the fuel screw.

5. Adjust the fuel screw and see if it wants something other than a #42.

The typical setup for the 250 is about 1 3/4 out on the screw with a #42 jet.   If your way outside of that, then your compensating for something that is wrong.

Jim. 

 

  • Like 1

Share this post


Link to post
Share on other sites

If the symptoms are still leading to ONLY running with choke on, I'd be reviewing the pilot circuit again. Not only the pilot jet, but the passage into the venturi to be free of debris. 

  • Like 1

Share this post


Link to post
Share on other sites
6 hours ago, Jim Dettman said:

Let's start with this:

" the valves need to be lapped in(something I have been told I don't need to do)"

You never should.  What should be done is the seats cut and the valves fitted properly along with making sure the valve guides are in good shape.   Can you lap SS valves? Yes. Would I?  No. Proper valve fitting is critical for longer life and lapping just doesn't cut it.   And the stock TI's should never be lapped (which is probably where you got the 'I don't need to').  They have a coating for heat dissipation and lapping takes that off.  If you lap a TI valve, it will quickly die.  Keep in mind, this is a racing motor that revs out to over 10K.   It's not by any stretch something like an XRL where you can get away with things.  Doing things right is critical or you'll be repairing it often.

As far as the idle, it's probably the carb as mlatour said.    Not sure what was done with your carb rebuild and cleanings and how, but the passages mid-body along with the air passage for the slow circuit are extremely difficult to clean without taking the carb apart mid-body. In the past before the gaskets were available, people would junk a carb.   Now you can take it apart.   If you are sure that was done, then you need to look else where.   If not, then it would be something I would do.  

Check out this thread and take a look at the pics of what was inside *after* cleaning:

With that said however, I would double check a few things first:

1. That the hot start nut is not cracked.

2. That the hot start plunger is not hung up.

3. That the slide seal is not installed upside down

3. That the spring, washer, and o-ring on the fuel screw are in the proper order.

4. That you don't have more than one o-ring on the fuel screw.

5. Adjust the fuel screw and see if it wants something other than a #42.

The typical setup for the 250 is about 1 3/4 out on the screw with a #42 jet.   If your way outside of that, then your compensating for something that is wrong.

Jim. 

 

Number three is a very common one, and easy to check/correct.

Share this post


Link to post
Share on other sites

I had the same issue after having my head rebuilt and putting everything back together. The solution? I had an air flow blockage between my air filter and carb. It was a seriously duhhhhhh moment. So, before you go crazy, just make sure you don't have anything blocking the air passage. Your symptoms  are identical to what I experienced.

Share this post


Link to post
Share on other sites

Thanks for all the help you all are giving me. I did not re-cut the valve seats because the shop that I took my head to for them to look at it said I would not need to. Seeing as the bike starts easy and has plenty of compression(kicker is plenty stiff) I don't think its my problem. It may be something that could be done for optimal performance but I think the bike would run just fine without doing a valve seat job. 

I did pull the carb apart at the mid body and it didn't look that bad. I pulled out and flipped over the slide seal and tried it both ways and no difference. Just put a new 42 slow jet in and still no difference. The shop that did the cleaning told me that all passages would be cleared from the cleaning. Not that Im not skeptical but thats what they said. After the cleaning that I did and the cleaning that they did I can only think that the carb is clear but maybe the mid body gasket is damaged or air is getting in somewhere else. The hot start nut looks ok and plunger works as far as I can tell.

Thanks again for all the help. I don't have much time to work on this project so I will be slow on getting back to this but I will try to update this thread as I often as I can.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×