Riding after topend rebuild

[Nekromanzeri]

Hey!

Im in the middle of my first topend rebuild. Opened the 2010 250kxf and found that there were original ART piston still in. Was in good shape though, no problem.

Figured out that i insert  anew A piston (Heard Wössner was good, Thoughts?) 

Main question would be that, how do you guys ride the first 5 hours after topend rebuild? Should some adjustment be done to the carburator or just good warming to the bike and straight to the track?

 

[graziosip2250]

You will get different opinions and methods On break in procedures. I just recently rebuilt the top end on my CRF and here is what I did:

 

Always let the bike fully warm up. A good indicator is that you can feel the hot rads through your gloves. This is always key!

 

1) 10 minute easy break in ride. Varying loads and running a gear high. Under 1/2 throttle. Edit: let the bike fully cool down between all of these steps.

 

2) another 5-10 minute break in, varying loads running a gear high. 1/2-3/4 throttle. Do an oil/filter change.

 

3) went to the track and ran very easy laps for the first session.

 

4) let her eat after the first session! Change oil/filter again. Then use your preferred oil/filter change intervals.

 

 

[FaceDeAce]

Admitting - I am an oem guy for core engine component.  However, I do REALLY like the Wossner piston in the kx250f

For first ride, pretty much what grazio says above.  Take it easy for the first bit just so you can pickup on if anything is running odd, feeling off, sounding right, or being weird.   Once the bike is warm and all such things in sound and feel are good to you ... grip it, wrap it, and rip it.    Whatever you do, always ensure the engine gets a proper warm up before you go wacking the throttle.  Other than the warm up, no need to baby it at all.  If it doesn't pile up on you in the first 5 minutes of the first ride, it is not going to.

Edited October 21, 2018 by FaceDeAce

[Nekromanzeri]

Thank you for informative answers and links!

[Nekromanzeri]

Hey, 

Finally found some time to do the topend rebuild. Few questions occured

One of the camchain positionin ring was little bit worn out from the inner side of it. How bad?

Left side clearance of intake valve keeps going out of spec - tend to go from .15mm to smaller and eventually to non existent. Other valves tend to stay in spec. What does this indicate ? 

 

[FaceDeAce]

Left intake going to zero clearance while all others barely move is a remarkably common occurrence. Guys seem to think why of it to be from the inlet nozzle angle and that valve doing the most work. The inlet airflow geometry sends most of the flow is into that left intake side, causing faster wear on that valve. The wear is even quicker if the air filter is not a good one, not clean, or if riding alot in dusty conditions.

After shimming that valve twice, replace it. Just buy one new oem valve and install it (80$-100$). No other work is required, other than proper shimming for the new valve of course. No “valve job, head rebuild” is required. The wear is on the seating face of the valve. No other components. It is normal wear but high wear rate on that left intake valve. Now that you know about it, you know to expect it from that one whenever checking clearances. Keep a maintenance log and track how much it has moved and how many times you have reshimmed it.  After 2 to 3 major shim changes replace the valve. If you do not replace it and just keep reshimming eventually that valve will be knife edge cupped, will pull up into the seat, jam, and resulting damage will be catastrophic.  The cost will be significantly more than just replacing the one valve a few times.

Apologies for being a bit long winded there. Well, there you go ......

Hope that helps!

PS: unknown what you are referring to on the cam chain ring. ??

 

Edited February 28, 2019 by FaceDeAce

[FaceDeAce]

PS:  In case any of the above wasn't clear.  Replace that valve.  NOW. [emoji6]

 

 

[Nekromanzeri]

On 2/27/2019 at 2:56 AM, FaceDeAce said:

Left intake going to zero clearance while all others barely move is a remarkably common occurrence. Guys seem to think why of it to be from the inlet nozzle angle and that valve doing the most work. The inlet airflow geometry sends most of the flow is into that left intake side, causing faster wear on that valve. The wear is even quicker if the air filter is not a good one, not clean, or if riding alot in dusty conditions.

After shimming that valve twice, replace it. Just buy one new oem valve and install it (80$-100$). No other work is required, other than proper shimming for the new valve of course. No “valve job, head rebuild” is required. The wear is on the seating face of the valve. No other components. It is normal wear but high wear rate on that left intake valve. Now that you know about it, you know to expect it from that one whenever checking clearances. Keep a maintenance log and track how much it has moved and how many times you have reshimmed it.  After 2 to 3 major shim changes replace the valve. If you do not replace it and just keep reshimming eventually that valve will be knife edge cupped, will pull up into the seat, jam, and resulting damage will be catastrophic.  The cost will be significantly more than just replacing the one valve a few times.

Apologies for being a bit long winded there. Well, there you go ......

Hope that helps!

PS: unknown what you are referring to on the cam chain ring. ??

 

 

6 hours ago, FaceDeAce said:

PS:  In any case that the above wasn't clear.  Replace that valve.  NOW.

 

Haha yes! Thank you for informative answer again. I have done 2 major shim changes to bike already, and dont know what the previous owner have done for the bike so yes, i will definately change the valve. I have lived in the knowledge that the all valves need to be changed simultaneously, this is something new and welcome that infact they doesnt.

There are lots off different manufacturers valves in the stock that say they will last longer than OEM because they are not titan but steel - should all of the but OEM be avoided ? 

PS: unknown what you are referring to on the cam chain ring. ?? - Shouldnt be writing anything when tired, i meant camshaft positionin rings..

(14013A / 14013 in the picture) But yeah, i will just replace them too.

 

[FaceDeAce]

Keep it simple. Replace with OEM. There is nothing wrong or defective about the oem part. It is a wearable part which is worn = regular maintenance. The oem valves are light and tough titanium. Changing valve to a different material means a change in the mass of the valve which means a need for a change in valve spring.

Ensure to inspect the seating face of the three other valves while the head is off to replace the one intake valve.  Just press on the spring buckets one by one with your fingers to open each valve and look at the sealing perimeter of the valve, looking for wear (cupping).  No cupping, leave it.  Cupping, replace it.  If this is the first time the head comes off the bike or first valve maintenance ever done on it, you might also consider replacing all 4 of the valve stem seals while it is off.  Also a common wearable part which is cheap (20$) and easy to do.  Ensures you are not wondering about oil burning sometime later.

Also, attached a picture of the last valve check and replacement I've done here.  The valve on the left in the picture is fine. Shiny ring from the valve seat.  No discernible wear at all.  The valve on the right is worn, cupping, and required immediate replacement. You may or may not be able to see the cupping clearly in the picture.  Btw, it just so happens that the worn one is the left intake valve.

Hope that helps!

 

This is a really good video explaining visually.  Not my video. Very well done. Covers all discussion points thoroughly and clearly.  Basically, stainless valves means stiffer springs which transfers more stress and thus wear to other components resulting in things such as:  cam lob wear, cracked valve bucket caps, stretched or broken cam chains, burning camshaft journals, slipped cam sprockets, cracked camshaft retaining caps, ....

 

 

Edited February 28, 2019 by FaceDeAce

[Nekromanzeri]

On 2/28/2019 at 6:18 PM, FaceDeAce said:

Keep it simple. Replace with OEM. There is nothing wrong or defective about the oem part. It is a wearable part which is worn = regular maintenance. The oem valves are light and tough titanium. Changing valve to a different material means a change in the mass of the valve which means a need for a change in valve spring.

Ensure to inspect the seating face of the three other valves while the head is off to replace the one intake valve.  Just press on the spring buckets one by one with your fingers to open each valve and look at the sealing perimeter of the valve, looking for wear (cupping).  No cupping, leave it.  Cupping, replace it.  If this is the first time the head comes off the bike or first valve maintenance ever done on it, you might also consider replacing all 4 of the valve stem seals while it is off.  Also a common wearable part which is cheap (20$) and easy to do.  Ensures you are not wondering about oil burning sometime later.

Also, attached a picture of the last valve check and replacement I've done here.  The valve on the left in the picture is fine. Shiny ring from the valve seat.  No discernible wear at all.  The valve on the right is worn, cupping, and required immediate replacement. You may or may not be able to see the cupping clearly in the picture.  Btw, it just so happens that the worn one is the left intake valve.

Hope that helps!

 

This is a really good video explaining visually.  Not my video. Very well done. Covers all discussion points thoroughly and clearly.  Basically, stainless valves means stiffer springs which transfers more stress and thus wear to other components resulting in things such as:  cam lob wear, cracked valve bucket caps, stretched or broken cam chains, burning camshaft journals, slipped cam sprockets, cracked camshaft retaining caps, ....

 

 

Thanks for informative answer once again. Havent had a time to go and check those valves, but will definately do that because what is in my knowledge, i hasnt ever been done to the bike. Riding season is getting closer, will be pure joy to ride when engine is confirmed to run in perfect order. Thanks again.