Engine removal for top end?

kb22
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kb22
Edited Date/Time 1/31/2021 5:31pm
Hey everyone,

You all have been a huge help for many things so far and I was hoping I could borrow some more advice. I bought this bike ( 2015 yz250F) over the summer and rode it a bit and just got done readjusting the valves. Since I am not 100% sure on maintenance I was going to do a cam chain and piston. It has the 270 kit and I will need to measure the piston to get the new one. Are you all taking the top end off while the engine is in the bike or dropping the engine?
Thanks in advance and look forward to hearing back from everyone.

Keith
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jamiechapman418 1/20/2021 12:17pm
1/20/2021 12:17pm
I've always done top end in the bike unless it had to come out for a different reason.
kb22
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kb22 1/20/2021 12:22pm
1/20/2021 12:22pm
Do you drop the throttle body or just unhook it from the engine?
GoggleFiend904 1/20/2021 12:30pm
1/20/2021 12:30pm
kb22 wrote:
Do you drop the throttle body or just unhook it from the engine?
If it’s like the 450 just take the airbox off and the throttle body is really easy to get to and will give you a ton of room to work with
2
kb22
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kb22 1/20/2021 12:56pm
1/20/2021 12:56pm
Awesome man thank you for the advice! I’ll tear into it tonight and get everything started.
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asax771
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asax771 1/21/2021 9:29am
1/21/2021 9:29am
I always remove the whole engine and take the opportunity to clean the places that is hard to reach and also grease the linkage etc. Much nicer to have the engine on the bench also when assembling everything. But if you are in a hurry then it is not neccesary on your bike.
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kb22
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kb22 1/21/2021 10:41am
1/21/2021 10:41am
I appreciate the insight, I’ve just now gotten to the head removal stage and may remove the engine when I get to the bottom end. Either way will take me some time since my wife and I work opposite 12s so I might as well get it a little cleaner while I’m at it lol.
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kb22
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kb22 1/25/2021 6:50pm
1/25/2021 6:50pm
Alright just an update and also further guidance 😂:
The bike has not been apart in a while so the head nuts were seized and I almost had to cut them off, awful experience. But after a lot of manipulation I finally got the head off. Everything looks pretty decent. Next will be the cylinder.
My question is; upon inspecting the head I checked out the exhaust port and it has a ton of carbon caked all in it. How should I clean this? It’s even on the valves and guide. I’m not sure I have the expertise to dismantle the valves or what that even entails. the valves have all been properly spaced prior so I know they are good from that aspect.



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Factor E
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Factor E 1/26/2021 1:14am
1/26/2021 1:14am Edited Date/Time 1/26/2021 1:16am
Use Maxima Clean up or the Air filter clean
same stuff in two different cans
Soak for a few minutes and scrub with small wire brush
Melts off
2
kb22
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kb22 1/26/2021 5:21am
1/26/2021 5:21am
Hey thanks for that, I have some laying around I’ll use for that, is there an easy way to get all that junk out afterwards?
YZed250
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YZed250 1/28/2021 8:49am
1/28/2021 8:49am Edited Date/Time 1/28/2021 8:50am
kb22 wrote:
Hey thanks for that, I have some laying around I’ll use for that, is there an easy way to get all that junk out afterwards?
I would hit it with some degreaser and/or dawn mixture and scrub all the parts as best you can with soap pads/jex/wire brush/tooth brush and rinse with warm soapy water. It's well worth the effort on cleaning. Your bike will look so much better when it goes back together.

If you have access to vapor blast and/or parts washer and/or media blaster, then that would be how the pros tackle something like this. Most auto shops will know whereto get this done locally and it's probably only $20 if you find the right shop.
kb22
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kb22 1/28/2021 9:24am
1/28/2021 9:24am
That’s awesome to hear, I appreciate the feed back and guidance. So I can clean it as is and don’t need to remove the valves and springs? My OCD is kicking into over drive and I want to make sure the ports and all are clean as can be.

Thanks again for the help!

Keith
YZed250
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YZed250 1/29/2021 9:33am
1/29/2021 9:33am
kb22 wrote:
That’s awesome to hear, I appreciate the feed back and guidance. So I can clean it as is and don’t need to remove the valves and...
That’s awesome to hear, I appreciate the feed back and guidance. So I can clean it as is and don’t need to remove the valves and springs? My OCD is kicking into over drive and I want to make sure the ports and all are clean as can be.

Thanks again for the help!

Keith
If it were my bike, I would definitely remove the valves and inspect the seats or have someone look at the seats with you (Iike a local shop). Valve compressor tool is not v expensive but there are other ways to get the valves out without a tool (check youtube). Just getting them back in without the proper tool is tricky.

You would want to leak test the valves before you strip them out of the head. Again, there is a number of ways to do this with air/gas/water. youtube has a few of these methods.

If you have a valve leak, then you should definitely remove the valves and expect to replace some valves and/or seats.


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kb22
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kb22 1/29/2021 10:09am
1/29/2021 10:09am
I’ll look up those methods and make sure undo that while the head is out of the bike. What’s the preferred method? I thought I head something about putting a fluid into the intake port and allowing it to set for a given time.
kb22
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kb22 1/30/2021 4:50am
1/30/2021 4:50am
kb22 wrote:
That’s awesome to hear, I appreciate the feed back and guidance. So I can clean it as is and don’t need to remove the valves and...
That’s awesome to hear, I appreciate the feed back and guidance. So I can clean it as is and don’t need to remove the valves and springs? My OCD is kicking into over drive and I want to make sure the ports and all are clean as can be.

Thanks again for the help!

Keith
YZed250 wrote:
If it were my bike, I would definitely remove the valves and inspect the seats or have someone look at the seats with you (Iike a...
If it were my bike, I would definitely remove the valves and inspect the seats or have someone look at the seats with you (Iike a local shop). Valve compressor tool is not v expensive but there are other ways to get the valves out without a tool (check youtube). Just getting them back in without the proper tool is tricky.

You would want to leak test the valves before you strip them out of the head. Again, there is a number of ways to do this with air/gas/water. youtube has a few of these methods.

If you have a valve leak, then you should definitely remove the valves and expect to replace some valves and/or seats.


Just snagged a valve compressor that should do the job, cleaning the valve faces I found at least 2 of the valves to be kibblewhite valves. I know it’s a crap shoot whether or not stainless steel is magnetic but these don’t seem to be so I’m hoping they could be titanium? Any way to confirm this? I have not read consistent reviews about these valves and I’m not to sure how I feel about continuing with them. Thanks again for the advice
kb22
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kb22 1/31/2021 5:31pm
1/31/2021 5:31pm
Just an update as I dive further into this, I did a leak test with a solvent (wd) here’s what I got when I put down a new piece of shop towel. It took a few hours but does this technically mean they are lot sealed?

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