2013 kx250f

gharmon
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2748
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Location
Valley, AL, USA
Edited Date/Time 12/10/2019 11:22am
We need some assistance guys. A couple weeks ago we went racing. The bike cranked up initially and ran for maybe 45 seconds or so, warming up. It then just died. After many kicks and pushes it never fired again or even it. Pulled plug, bike is getting fire. Sprayed ether in intake, nothing.

Early the next week i start testing things. Bike for sure has good fire. Kicking bike over with fuel line disconnected and gas comes out fuel line. Spray ether again and nothing. Timing all good. This should only keave one thing, compression. Compression gauge confirms there is very compression. Just to verify gauge is good (cause bike seemed to kick over normally)i stick it in lawn mower and pull 3-4 half ass pull and get 70psi. So. Gauge good.

I break bike down and slap in a top end. This is friends son bike so no idea if its ever had a top end. He has had it two years (i agree, shitty maintenance) but doesnt have the ability to do this type work.
Of course i checked the valves and exhaust is good left intake at about .0035" the right intake appears to be right at .000 i say this as i put about a .004 bigger shim and that was now my gap.
Putit all back together and still wont crank. Nothing. Just for hell of o did a compression check and only got about 60 psi but ill be honest im not sure what is correct psi for a brand new top end thats never been cranked?? The kicks werent exactly trying to get the best readings. Tbh i just wanted to see the needle move.

Any got any ideas, hints. Clues?

Thanks
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Paw Paw 271
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Location
Benton, LA, USA
11/17/2019 7:19am
Compression will be low as the bike has an auto decompression device.
Sounds like a fuel delivery issue, except for the attempt while using ether.
Cam timing correct? If no maintenance then it would be suspect that the cam chain is bad and thus altering the cam timing.
Valves leaking? Do a leak test.
Can you hear the fuel pump run? Remove and check it.

Paw Paw
gharmon
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Location
Valley, AL, USA
11/21/2019 1:20pm
Compression will be low as the bike has an auto decompression device. Sounds like a fuel delivery issue, except for the attempt while using ether. Cam...
Compression will be low as the bike has an auto decompression device.
Sounds like a fuel delivery issue, except for the attempt while using ether.
Cam timing correct? If no maintenance then it would be suspect that the cam chain is bad and thus altering the cam timing.
Valves leaking? Do a leak test.
Can you hear the fuel pump run? Remove and check it.

Paw Paw
When i had the head off I put gas in all the ports and let is sit. The weren't leaking and gas at all. I know gas isn't air but I am pretty sure the valves aren't leaking enough to not crank, at least I don't think so.
Its kinda hard to hear the pump with kicking at the same time. Put with the lines off and the hanging out if you kick it over a few times gas does come out of the lines. Do these pumps have a history on going bad?

The bike is dead on with the timing. And don't you think the ether would at least let it "hit". My sons CRF250 had a stator/flywheel go bad and it would provide enough juice to give the bike fire but not enough to open the injectors. But the difference on this bike vs the Honda is that if you sprayed ether in the intake it would always fire and usually crank but would at least "hit" while cranks or backfire or do something. This one won't do anything.

Any known common problems with these bikes?

Thanks Paw Paw. We can always count on you for a response. BTW I assume you are a Paw Paw? Me to. Best thing every!!! lol
gharmon
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2748
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Location
Valley, AL, USA
11/22/2019 3:22pm
After doing some more kicking I was getting the occasional subtle backfire, which might indicate a timing issue?
Upon further researching it appears that when the valves on these bikes get too tight the cam gears can spin on the cam itself as they are only pressed on and not one piece or tac welded. I found this picture online that shows how the cams should be positioned when the timing marks are in fact set perfectly.

The diagram kinda shows the hole on the cam gear inline with the intake cam at about 2:30'sh. on this engine the timing marks are perfect. The hole on this gear isn't inline with cam lob at all. the hole is still 2:30'sh while the actual cam lobe is close to 4:00-4:30'sh. I would guess it's 40-50 degrees off where its supposed to be? What do ya think??

Anyone ever seen this issue before? This is my first Kawasaki experience (4 stroke wise)

Thanks
Paul_Pitzonka
Posts
693
Joined
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Location
Grand Terrace, CA, USA
11/22/2019 3:37pm
post a picture of the cams and gears in question if you can... in short; yes, pressed on cam gears can and will spin...

The Shop

gharmon
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2748
Joined
4/1/2008
Location
Valley, AL, USA
11/22/2019 5:59pm
Here they are. Pics of the timing being correct and the rear view of the cam lobes. There is a front view of the cam gears also . I can't really get a good pic that would show a front view of the cam gear in relation to the lobes.







Paul_Pitzonka
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693
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Location
Grand Terrace, CA, USA
11/22/2019 6:21pm
Looks to me as if you found your issue. Cam gear appears to have spun...
pCp 252
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689
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Location
Hampden, MA, USA
11/22/2019 7:29pm Edited Date/Time 11/22/2019 7:30pm
Your intake cam has definitely spun as other’s have said. The exhaust cam looks about right. The only round hole on each cam’s gear should be aligned with the lobes. Happened to a couple of my KX250F’s as well. I carefully used a 3 jaw puller to remove the gear from the shaft. Then index/align the gear’s hole with the center of cam lobe. Carefully press it back on and tack weld in place to secure it.
gharmon
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2748
Joined
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Location
Valley, AL, USA
11/23/2019 8:22am
pCp 252 wrote:
Your intake cam has definitely spun as other’s have said. The exhaust cam looks about right. The only round hole on each cam’s gear should be...
Your intake cam has definitely spun as other’s have said. The exhaust cam looks about right. The only round hole on each cam’s gear should be aligned with the lobes. Happened to a couple of my KX250F’s as well. I carefully used a 3 jaw puller to remove the gear from the shaft. Then index/align the gear’s hole with the center of cam lobe. Carefully press it back on and tack weld in place to secure it.
Impressive! But it's only $126 on Rocky Mountain. I have indexed a few cams on car engines. I wouldn't even begin to know how to do this. I guess it would be a good learning experience but this is a friends son bike so I will let him buy one. lol.. Thanks for the help guys. I report back if in works out for us.
gharmon
Posts
2748
Joined
4/1/2008
Location
Valley, AL, USA
12/9/2019 8:18am
I just wanted to come back and report that with a new intake cam we are back to running just fine now.
1
Paw Paw 271
Posts
3632
Joined
4/3/2013
Location
Benton, LA, USA
12/10/2019 11:22am
Great to hear! That is a hard issues to spot, but it does happen.

Paw Paw
1
9/11/2025 3:50pm
pCp 252 wrote:
Your intake cam has definitely spun as other’s have said. The exhaust cam looks about right. The only round hole on each cam’s gear should be...
Your intake cam has definitely spun as other’s have said. The exhaust cam looks about right. The only round hole on each cam’s gear should be aligned with the lobes. Happened to a couple of my KX250F’s as well. I carefully used a 3 jaw puller to remove the gear from the shaft. Then index/align the gear’s hole with the center of cam lobe. Carefully press it back on and tack weld in place to secure it.
gharmon wrote:
Impressive! But it's only $126 on Rocky Mountain. I have indexed a few cams on car engines. I wouldn't even begin to know how to do...
Impressive! But it's only $126 on Rocky Mountain. I have indexed a few cams on car engines. I wouldn't even begin to know how to do this. I guess it would be a good learning experience but this is a friends son bike so I will let him buy one. lol.. Thanks for the help guys. I report back if in works out for us.

Howdy! Who knew 6 years later this would be so helpful. I do have a question though. You bought a new cam and replaced it so the hole on the lobe and the hole on the cam sprocket line up? 

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