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2006 CR 250R Won't Start

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This is a new topic from my jetting thread so for those who haven't followed that one here's a quick update:

I put the JD Jetting kit in my bike and couldn't start it, tried going back to original pilot and it started but with trouble until finally it wouldn't even fire.  Tried a couple different needle positions and nothing.  Put original needle back in still nothing.  So, one would assume it's not a jetting problem.

Here's my check list so far:

- Crankcase has 41.7 hours which includes reed valves, water pump, all bearings, all seals, and all gaskets

- Top end has 12.4 hours

- FMF Fatty has 17.2 hours

- Silencer is what came with the bike, never been repacked

- Fuel looks perfectly clean

- Carb and jets are clean

- Grease/oil residue on crank side of carb and boot after reassembling last night (see picture); To be fair I don't remember if I wiped the boot out or not

- Transmission oil level full

- Coolant level full and drained out perfectly clean

- Spark plug boot correctly seated

- Brand new spark plug that is arching

- Cylinder head and gasket appear unremarkable (see pictures)

- Piston contains some carbon/oil build up (see pictures)

- Piston has some lateral movement in the cylinder and gap is noticed, ring can be seen

- Motor rolls over with very little resistance

 

Before I yank this motor and split the cases and wait on parts, is there anything else you guys would try first?

 

Carb.jpeg

Carb boot.jpeg

Cylinder 1.jpeg

Cylinder 2.jpeg

Edited by Mike_80
Noted that spark plug is new

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Yeah that’s what I’ve been working on but I don’t trust what I’m seeing.  The resistance scales aren’t correlating.  New battery in my multimeter and best I can do on the contacts, see pictures:

76621E5C-5C5A-444F-BBDC-E7102B1755B1.jpeg

9C2C3B0B-EFE9-45DC-9148-29566DBAA26E.jpeg

7C7681F7-EEC4-456F-89EE-7E95E9F9F0BE.jpeg

70A70E6A-B42C-47F5-8296-39E5FF2505A0.jpeg

BCF4A081-AF0D-4B8F-9BBC-29C27838AFE2.jpeg

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I didn't see a compression test result. Did you do one before tearing it down? 

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1 hour ago, FPMXer said:

I didn't see a compression test result. Did you do one before tearing it down? 

No, I don’t have quality equipment to test it and I’m not buying cheap Harbor Freight on something like that.

I’m not saying this can’t be the problem, I realize low compression causes this, but how could that have happened in less than 13 hours of moderate riding?  Regardless I’ll order something to test it with.

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This is a great threat. Another I rebuild my engine and now can't start it thread.
If you spray some starting fluid into the back of the carburetor does it start? If not you have an electric problem. If it does start with the starting fluid you have a fuel problem. These are very easy to diagnose.

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3 hours ago, arthur6 said:

This is a great threat. Another I rebuild my engine and now can't start it thread.
If you spray some starting fluid into the back of the carburetor does it start? If not you have an electric problem. If it does start with the starting fluid you have a fuel problem. These are very easy to diagnose.

No, will not start with starter fluid.  And you can see the issues I’m having with electrical diagnostics.

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Waiting on parts and compression testing equipment which will arrive this week.

 

In the mean time, finally have some electrical diagnostic results:

IGNITION COIL = 0.5 ohms (Range: 0.1 – 0.3 ohms)

IGNITION COIL TO SPARK PLUG BOOT = 11,000 ohms (Range: 9,000 – 16,000 ohms)

ALTERNATOR COIL = 2.2 ohms (Range: 0.5 – 4.0 ohms)

IGNITION PULSE GENERATOR = 253 ohms (Range: 180 – 280 ohms)

 

Furthermore I'm noting the appearance of the ignition coil (see pictures):

 

Ignition Coil 1.jpeg

Ignition Coil 2.jpeg

Ignition Coil 3.jpeg

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Compression test results are in: 83 psi

So now, is it abnormal to lose this much compression this fast?  I could stand on the kick stand when I did my last top end.  Does this indicate a source problem?  Perhaps the issues I’ve had with my head gasket leak (refer to my leaking head gasket thread)?  Anything else I’m not thinking of?

9D29DBEE-F769-485A-9677-205C1CC0ED83.jpeg

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Let's step back to the beginning...
The bike was running well prior to the carburetor "enhancement" attempt.... meaning it started easily, did not require choke (or no choke) for extended periods, was not overly smokey, no backfiring, etc.
You have verified; air, spark and fuel... when you pull the spark plug after failed start attempt, you can smell fuel on spark plug.
You indicate starting fluid injection results in an engine combustion, but not an engine start.

Based on this, you have a carburetor issue, I believe.  The compression is not too bad at 90psi.  The carbon build-up on the piston suggests to me that the timing isn't correct or the fuel mix was too heavy.

Some information is missing here.  I'd remove and tear down the carburetor.  I suspect a clogged jet or stuck float... either too much gas or no gas at all is causing this problem - likely no gas at all based on the failure to run even with starting fluid shot.

Don't overthink it - gas, air and spark.  

IF you verify that there is fuel on the sparkplug, it could be the key on the flywheel is missing and thus the timing is off.


 

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1 hour ago, brianbenson said:

Let's step back to the beginning...
The bike was running well prior to the carburetor "enhancement" attempt.... meaning it started easily, did not require choke (or no choke) for extended periods, was not overly smokey, no backfiring, etc.
You have verified; air, spark and fuel... when you pull the spark plug after failed start attempt, you can smell fuel on spark plug.
You indicate starting fluid injection results in an engine combustion, but not an engine start.

Based on this, you have a carburetor issue, I believe.  The compression is not too bad at 90psi.  The carbon build-up on the piston suggests to me that the timing isn't correct or the fuel mix was too heavy.

Some information is missing here.  I'd remove and tear down the carburetor.  I suspect a clogged jet or stuck float... either too much gas or no gas at all is causing this problem - likely no gas at all based on the failure to run even with starting fluid shot.

Don't overthink it - gas, air and spark.  

IF you verify that there is fuel on the sparkplug, it could be the key on the flywheel is missing and thus the timing is off.


 

I'm listening and taking what you're saying into consideration but there's some things that I'm struggling with here.

1) If the engine had good compression the starter fluid should cause it to fire up and then die, that didn't happen.

2) What is a good compression value?  The service manual provides nothing on this.  How do we know 83 psi is sufficient?  The motor is a 9.0:1 compression ratio so shouldn't the atmospheric air at 14.7 psi be reaching 132 psi?  We're down to 63% of that.

3) I can absolutely guarantee you this carburetor can not possibly be any more clean than it is right now.  There is zero chance I have a clogged jet or a clogged port.  The float valve appears to have no stick to it and the bowl fills with gas every time I turn the gas on.  Furthermore, it must be closing off correctly because I'm getting no drip from the overflow.

4) I have not done any work on the flywheel or any other portion of the crankcase recently so I doubt the woodruff key is missing.  Especially since last time I rebuilt my crankcase I couldn't pull it out with a gentle grip to replace it.

 

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My 06 with a modified head cut for pump premium fuel will blow 210 psi.  I would assume a non modified 06 cr250, it should blow at least 180 if not more, which means that your motor is blowing 100psi low.  IMO that is your starting issue.  How does your piston look?  Excessive blowby? 

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15 hours ago, Mike_80 said:

Compression test results are in: 83 psi

So now, is it abnormal to lose this much compression this fast?  I could stand on the kick stand when I did my last top end.  Does this indicate a source problem?  Perhaps the issues I’ve had with my head gasket leak (refer to my leaking head gasket thread)?  Anything else I’m not thinking of?

9D29DBEE-F769-485A-9677-205C1CC0ED83.jpeg

Make sure your holding the throttle wide open when kicking to get an accurate number. Leaving the throttle closed will give you a low number.

I just read one of your threads about a leaking airbox. If this is truly your compression then that ingress of unfiltered air has ruined your top end. My guess is its time to pull it apart and rebuild. In general, most motors need over 100psi to run. I believe this motor when fresh should be near 180psi.

Good luck

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Yup your compression is about 100psi low. Hold throttle wide open, hold down kill switch to prevent damage to cdi, you have to kick several times to get an accurate reading. My 03 250 pumps up to 210psi pretty easily.

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2 hours ago, ericsXr600R said:

Make sure your holding the throttle wide open when kicking to get an accurate number. Leaving the throttle closed will give you a low number.

I just read one of your threads about a leaking airbox. If this is truly your compression then that ingress of unfiltered air has ruined your top end. My guess is its time to pull it apart and rebuild. In general, most motors need over 100psi to run. I believe this motor when fresh should be near 180psi.

Good luck

Yes I did exactly that, I held the throttle wide open and held down the kill switch.

I’m going to redo this after I get the top end back together to have something to compare it to.  And from now on, as part of my maintenance program, I’ll be able to check this and keep it logged so that I can more accurately predict when to do the top end service  which will subsequently prevent this from happening in the future and save money by only rebuilding the top end when it’s needed.

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