09 kx250f no start (revisiting)

kb228
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kb228
About a year ago i rebuilt my kx250f. New everything in the engine. Couldnt figure out the problem then and im just now getting back to it.
Valve clearance: I=.15 E=.20
Leakdown= pass
Compression=~82PSI
Timing correct - 28 pins dot to dot and 12 between middle dot with TDC marks aligned
No airfilter installed at the moment
Dripped gas directly into the cylinder to bypass any carb issues
Stator resistance is within spec and no shorts to ground
Bright blue spark

The only thing this bike will do is afterfire from time to time. Im leaning towards a CDI issue. Thoughts?
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DynoDan22
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DynoDan22 4/8/2021 8:09pm
4/8/2021 8:09pm
Sounds like the timing is off but you have the correct number of pins on the cam chain. I know the Kawi's have been known to spin the cams relative to the cam sprocket. What's the history of the bike? Did it run fine prior to rebuilding it or was there a failure that led you to rebuild it?
Paw Paw 271
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Paw Paw 271 4/8/2021 10:01pm
4/8/2021 10:01pm
Try to start it using spray starter fluid, not gas.
Carb condition?
Are you sure you are using the correct valve clearance spec's?

Paw Paw
kb228
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kb228 4/9/2021 11:19am
4/9/2021 11:19am
DynoDan22 wrote:
Sounds like the timing is off but you have the correct number of pins on the cam chain. I know the Kawi's have been known to...
Sounds like the timing is off but you have the correct number of pins on the cam chain. I know the Kawi's have been known to spin the cams relative to the cam sprocket. What's the history of the bike? Did it run fine prior to rebuilding it or was there a failure that led you to rebuild it?
Bike ran before the rebuild. Bottom end was original from 09 and needed redone. @pawpaw, the head, valves, cams, and clearances are the same from when it ran. Its got hotcams. I will grab some starter fluid and report back. The carb was cleaned several times and reset to stock settings. Carb clean comes out of all of the orifices

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kb228
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kb228 4/9/2021 6:10pm
4/9/2021 6:10pm
Paul_Pitzonka wrote:
Shot in the dark here... auto decompression mechanism stuck?
It seems to function freely
Paul_Pitzonka
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Paul_Pitzonka 4/9/2021 6:14pm
4/9/2021 6:14pm
Crank was replaced or rebuilt? If replaced what’s the location of the Keyway in correlation with the old crank?
Polishhammer 4/10/2021 6:01am
4/10/2021 6:01am
Just thought I’d share some experiences with similar issues I’ve had with bikes before. I’ve races a lot of rmz450s as I’ve always liked them thats why there are more rmz issues noted here imo.
08 rmz450 found a slightly bent valve. Spark and a back fire while kicking.
12 rmz450 weak flywheel magnets. Spark tried to start but wouldn’t.
09 crf450r. Had spark no start. Replaced wiring harness and ecu at the same time and started right up.
16 kx450f spark no start. Replaced flywheel and stator at the same time and it started right up. Stator ohms were within spec but I replaced it anyway for a piece of mind.
kb228
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kb228 4/10/2021 6:39am
4/10/2021 6:39am
Paul_Pitzonka wrote:
Crank was replaced or rebuilt? If replaced what’s the location of the Keyway in correlation with the old crank?
Crank was rebuilt by ken oconnor
kb228
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kb228 4/10/2021 6:40am
4/10/2021 6:40am
Polishhammer wrote:
Just thought I’d share some experiences with similar issues I’ve had with bikes before. I’ve races a lot of rmz450s as I’ve always liked them thats...
Just thought I’d share some experiences with similar issues I’ve had with bikes before. I’ve races a lot of rmz450s as I’ve always liked them thats why there are more rmz issues noted here imo.
08 rmz450 found a slightly bent valve. Spark and a back fire while kicking.
12 rmz450 weak flywheel magnets. Spark tried to start but wouldn’t.
09 crf450r. Had spark no start. Replaced wiring harness and ecu at the same time and started right up.
16 kx450f spark no start. Replaced flywheel and stator at the same time and it started right up. Stator ohms were within spec but I replaced it anyway for a piece of mind.
Im about to that point of replacing things. Im suspicious that over the winter when the shop was heated snd things would sweat something electrical got damaged
kb228
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kb228 4/25/2021 3:44pm
4/25/2021 3:44pm
DynoDan22 wrote:
Sounds like the timing is off but you have the correct number of pins on the cam chain. I know the Kawi's have been known to...
Sounds like the timing is off but you have the correct number of pins on the cam chain. I know the Kawi's have been known to spin the cams relative to the cam sprocket. What's the history of the bike? Did it run fine prior to rebuilding it or was there a failure that led you to rebuild it?
I havent had time to dig into the bike yet.. but is it possible to install the stator or crank system backwards? Maybe its throwing off the ignition timing
harescrambled
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harescrambled 5/8/2021 9:09am
5/8/2021 9:09am
kb228 wrote:
About a year ago i rebuilt my kx250f. New everything in the engine. Couldnt figure out the problem then and im just now getting back to...
About a year ago i rebuilt my kx250f. New everything in the engine. Couldnt figure out the problem then and im just now getting back to it.
Valve clearance: I=.15 E=.20
Leakdown= pass
Compression=~82PSI
Timing correct - 28 pins dot to dot and 12 between middle dot with TDC marks aligned
No airfilter installed at the moment
Dripped gas directly into the cylinder to bypass any carb issues
Stator resistance is within spec and no shorts to ground
Bright blue spark

The only thing this bike will do is afterfire from time to time. Im leaning towards a CDI issue. Thoughts?
You said your dots are aligned and 28 pins apart with the piston at TDC? you don't set cam timing at TDC on that engine. It has a cam timing mark also. That's what needs to be lined up when the dots are properly aligned.
Paul_Pitzonka
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Paul_Pitzonka 5/8/2021 9:39am
5/8/2021 9:39am
kb228 wrote:
About a year ago i rebuilt my kx250f. New everything in the engine. Couldnt figure out the problem then and im just now getting back to...
About a year ago i rebuilt my kx250f. New everything in the engine. Couldnt figure out the problem then and im just now getting back to it.
Valve clearance: I=.15 E=.20
Leakdown= pass
Compression=~82PSI
Timing correct - 28 pins dot to dot and 12 between middle dot with TDC marks aligned
No airfilter installed at the moment
Dripped gas directly into the cylinder to bypass any carb issues
Stator resistance is within spec and no shorts to ground
Bright blue spark

The only thing this bike will do is afterfire from time to time. Im leaning towards a CDI issue. Thoughts?
harescrambled wrote:
You said your dots are aligned and 28 pins apart with the piston at TDC? you don't set cam timing at TDC on that engine. It...
You said your dots are aligned and 28 pins apart with the piston at TDC? you don't set cam timing at TDC on that engine. It has a cam timing mark also. That's what needs to be lined up when the dots are properly aligned.
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be rotated any direction and still produce current...
harescrambled
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harescrambled 5/9/2021 5:46am
5/9/2021 5:46am Edited Date/Time 5/9/2021 5:47am
Paul_Pitzonka wrote:
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be...
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be rotated any direction and still produce current...
How many marks are on the flywheel? There should be 3. One is ignition timing, next is TDC, then is cam timing. Valve clearance is checked at TDC, cam timing is the mark next to it. Same process as in 2004 with the 1st gen engine
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kb228
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kb228 5/9/2021 11:35am
5/9/2021 11:35am
Paul_Pitzonka wrote:
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be...
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be rotated any direction and still produce current...
harescrambled wrote:
How many marks are on the flywheel? There should be 3. One is ignition timing, next is TDC, then is cam timing. Valve clearance is checked...
How many marks are on the flywheel? There should be 3. One is ignition timing, next is TDC, then is cam timing. Valve clearance is checked at TDC, cam timing is the mark next to it. Same process as in 2004 with the 1st gen engine
There are 2 marks close to TDC. One is the TDC mark and the other is a timing mark. The timing mark is about 1/4” counter clockwise of the TDC mark.

So to make things confusing, the service manual says to time the cams with the TDC mark, however if i rotate my flywheel to the timing mark, the cam markings are about 1 tooth off clockwise.
Paul_Pitzonka
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Paul_Pitzonka 5/9/2021 12:09pm
5/9/2021 12:09pm
Paul_Pitzonka wrote:
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be...
I have this same bike mechanical timing is definitely set at tdc... and as far as your stator I don’t think it matters it can be rotated any direction and still produce current...
harescrambled wrote:
How many marks are on the flywheel? There should be 3. One is ignition timing, next is TDC, then is cam timing. Valve clearance is checked...
How many marks are on the flywheel? There should be 3. One is ignition timing, next is TDC, then is cam timing. Valve clearance is checked at TDC, cam timing is the mark next to it. Same process as in 2004 with the 1st gen engine
kb228 wrote:
There are 2 marks close to TDC. One is the TDC mark and the other is a timing mark. The timing mark is about 1/4” counter...
There are 2 marks close to TDC. One is the TDC mark and the other is a timing mark. The timing mark is about 1/4” counter clockwise of the TDC mark.

So to make things confusing, the service manual says to time the cams with the TDC mark, however if i rotate my flywheel to the timing mark, the cam markings are about 1 tooth off clockwise.
That’s the ignition timing Mark for checking base timing...
harescrambled
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harescrambled 5/9/2021 12:21pm
5/9/2021 12:21pm Edited Date/Time 5/9/2021 12:27pm
kb228 wrote:
There are 2 marks close to TDC. One is the TDC mark and the other is a timing mark. The timing mark is about 1/4” counter...
There are 2 marks close to TDC. One is the TDC mark and the other is a timing mark. The timing mark is about 1/4” counter clockwise of the TDC mark.

So to make things confusing, the service manual says to time the cams with the TDC mark, however if i rotate my flywheel to the timing mark, the cam markings are about 1 tooth off clockwise.
Use the timing mark next to TDC. The one which is well advanced of that is the ignition timing. One tooth off is enough to make it not run. You put a new cam chain in too, didn't you? I had one stretch enough that the bike wouldn't start when I put it back together. Had to pull and replace the cam chain. Once you reset the ignition timing, rotate the crank several revolutions by hand (with a socket or T handle) with the sparkplug out, to make sure nothing is binding. Then realign your flywheel mark and recheck your cam timing. My opinion is that your cam timing is retarded by one tooth. I did that once and got the same results you did.
harescrambled
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harescrambled 5/9/2021 12:25pm
5/9/2021 12:25pm
Paul_Pitzonka wrote:
That’s the ignition timing Mark for checking base timing...
The mark next to TDC is for cam timing. The other (the single) mark is ignition. I raced a similar engine for several years....the manual is misleading...I rebuilt that engine 8 times over the course of my time with it, so I know of what I speak. If the OP says his cams are a tooth off on the timing mark next to TDC, that's the problem
kb228
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kb228 5/9/2021 12:38pm
5/9/2021 12:38pm
Paul_Pitzonka wrote:
That’s the ignition timing Mark for checking base timing...
harescrambled wrote:
The mark next to TDC is for cam timing. The other (the single) mark is ignition. I raced a similar engine for several years....the manual is...
The mark next to TDC is for cam timing. The other (the single) mark is ignition. I raced a similar engine for several years....the manual is misleading...I rebuilt that engine 8 times over the course of my time with it, so I know of what I speak. If the OP says his cams are a tooth off on the timing mark next to TDC, that's the problem
The manual for this bike says the TDC mark is for timing the engine and the timing mark is for ignition timing.

I ordered a new CDI. I dont know what else it could be besides some electrical part that got messed up sitting on the shelf over the winter

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harescrambled
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harescrambled 5/9/2021 4:24pm
5/9/2021 4:24pm
kb228 wrote:
The manual for this bike says the TDC mark is for timing the engine and the timing mark is for ignition timing. I ordered a new...
The manual for this bike says the TDC mark is for timing the engine and the timing mark is for ignition timing.

I ordered a new CDI. I dont know what else it could be besides some electrical part that got messed up sitting on the shelf over the winter
Not gonna run
Paul_Pitzonka
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Paul_Pitzonka 5/9/2021 5:38pm
5/9/2021 5:38pm
I’ve had a couples sets of cams in and out and out of my bike (which is the exact same bike as the OP Post) ... as well as top ends and full rebuilds have always timed it off of tdc have never had an issue... base timing for this bike is 8* btdc which would coincide with the position of the ignition timing mark on the flywheel located directly prior to tdc... reading the marks incorrectly flipping tdc and the ignition timing mark would result in about a 4-5 degree change in cam timing or about 1/2 a tooth off (I believe one full tooth is roughly a 10 or 11 degree change)... I’ll reiterate I’ve always set this engine to tdc... verified tdc and installed the cams... never a problem...
harescrambled
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harescrambled 5/9/2021 5:55pm
5/9/2021 5:55pm
Paul_Pitzonka wrote:
I’ve had a couples sets of cams in and out and out of my bike (which is the exact same bike as the OP Post)...
I’ve had a couples sets of cams in and out and out of my bike (which is the exact same bike as the OP Post) ... as well as top ends and full rebuilds have always timed it off of tdc have never had an issue... base timing for this bike is 8* btdc which would coincide with the position of the ignition timing mark on the flywheel located directly prior to tdc... reading the marks incorrectly flipping tdc and the ignition timing mark would result in about a 4-5 degree change in cam timing or about 1/2 a tooth off (I believe one full tooth is roughly a 10 or 11 degree change)... I’ll reiterate I’ve always set this engine to tdc... verified tdc and installed the cams... never a problem...
OP says he did that and his bike won't run. I say he's on the wrong mark. In the end I don't care what happens. Not my bike. Just trying to help a brother out, but if you want to argue that's fine. I concede. When he wants his bike to run he can do it my way. Have a nice day
Paul_Pitzonka
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Paul_Pitzonka 5/9/2021 6:01pm
5/9/2021 6:01pm Edited Date/Time 5/9/2021 6:03pm
Paul_Pitzonka wrote:
I’ve had a couples sets of cams in and out and out of my bike (which is the exact same bike as the OP Post)...
I’ve had a couples sets of cams in and out and out of my bike (which is the exact same bike as the OP Post) ... as well as top ends and full rebuilds have always timed it off of tdc have never had an issue... base timing for this bike is 8* btdc which would coincide with the position of the ignition timing mark on the flywheel located directly prior to tdc... reading the marks incorrectly flipping tdc and the ignition timing mark would result in about a 4-5 degree change in cam timing or about 1/2 a tooth off (I believe one full tooth is roughly a 10 or 11 degree change)... I’ll reiterate I’ve always set this engine to tdc... verified tdc and installed the cams... never a problem...
harescrambled wrote:
OP says he did that and his bike won't run. I say he's on the wrong mark. In the end I don't care what happens. Not...
OP says he did that and his bike won't run. I say he's on the wrong mark. In the end I don't care what happens. Not my bike. Just trying to help a brother out, but if you want to argue that's fine. I concede. When he wants his bike to run he can do it my way. Have a nice day
Wasn’t trying to argue. didn’t mean to come off that way was just trying to clarify myself...
harescrambled
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harescrambled 5/9/2021 6:15pm
5/9/2021 6:15pm Edited Date/Time 5/9/2021 6:16pm
Paul_Pitzonka wrote:
Wasn’t trying to argue. didn’t mean to come off that way was just trying to clarify myself...
8° BTDC is the ignition timing at 2000RPM. The other two marks, as I said, are for TDC, and cam timing. The manual is poorly written. You obviously got it right since your bike runs...but OP bike does not. So I think the manual got him sent in the wrong direction. If he does what I said, his bike should run. Worst case he rolls it over by hand and has to retime it. However if the OP brings the bike to Mansfield MC this Sunday, I'll retime it. But if it runs I break it in for 2 hours in the harescramble. What ya think OP?
kb228
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kb228 5/9/2021 8:45pm
5/9/2021 8:45pm
Paul_Pitzonka wrote:
Wasn’t trying to argue. didn’t mean to come off that way was just trying to clarify myself...
harescrambled wrote:
8° BTDC is the ignition timing at 2000RPM. The other two marks, as I said, are for TDC, and cam timing. The manual is poorly written...
8° BTDC is the ignition timing at 2000RPM. The other two marks, as I said, are for TDC, and cam timing. The manual is poorly written. You obviously got it right since your bike runs...but OP bike does not. So I think the manual got him sent in the wrong direction. If he does what I said, his bike should run. Worst case he rolls it over by hand and has to retime it. However if the OP brings the bike to Mansfield MC this Sunday, I'll retime it. But if it runs I break it in for 2 hours in the harescramble. What ya think OP?
Didnt realize you were local. Ill give it a shot and see what happens. Im not trying to start fights here. Ive been scratching my head with this bike for over a year and just want it running
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harescrambled
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harescrambled 5/12/2021 2:24am
5/12/2021 2:24am Edited Date/Time 5/12/2021 2:26am
kb228 wrote:
Didnt realize you were local. Ill give it a shot and see what happens. Im not trying to start fights here. Ive been scratching my head...
Didnt realize you were local. Ill give it a shot and see what happens. Im not trying to start fights here. Ive been scratching my head with this bike for over a year and just want it running
It's all good. Just trying to help a brother out. Not exactly local. About 2 hours from Mansfield. Won my first harescramble at Mansfield M/C back in 2009
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kb228
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kb228 5/13/2021 3:44pm
5/13/2021 3:44pm
Ended up getting it to run. Didnt change anything in the engine. Ran for 10 seconds or so until i turned the choke off and it died a few seconds later. Something in the carb is wrong
kb228
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kb228 5/15/2021 4:34pm
5/15/2021 4:34pm
Got another update.. i tore the carb apart again and cleaned it and put new gas in it. Starts easier but still after lots of kicks. It idles high. After turning the idle down and it settling it revs to the moon once i touch the throttle. Intake leak somewhere.

Question, is there anything in the carb that can cause symptoms of a air leak? Im going to order a new intake boot and want to order any seals i might need to fix it

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