2010 YZ450F Season rebuild. Which Piston?

Yamaha YZ450F 2010

27 replies to this topic
  • grayracer513

Posted January 07, 2015 - 01:26 PM

#21

I was waiting on his response and I was too lazy to blow the pic up to see the seating surface, but now that you did and I have, notice the circled area.  Does it appear to be running out?  Basically the distance between the seating surface face and the head appears to be getting smaller.  Like it is wearing off center. (Another reason to suspect the guides are worn) The face appears to be concave, which is typical wear and the seat is a mirror image of this.  This is the reason why just replacing valves is not the best method for longevity.

 

 

Might be wearing off center, but that's not really so unusual early on near the end of service life.  The coating, which, for those who aren't aware of it, is normally a lot less than .001 thick, is simply going to wear through in one single spot, which will then extend the rest of the way around the valve face fairly quickly.  The uneven nature of the wear often leads to some degree of "scrubbing" as the valve closes, and that puts a lateral (relative to the stem axis) twist on the stem at the valve head.  That can lead to he separation of the valve head from the stem, which is almost always a disaster.   Not good for the guides, either, even if the stem doesn't break.

 

The guides in YZF's and other "bucket tappet" engines last a very, very long time absent any heat or lubrication problems, because there is normally little or no lateral thrust force born by the the guide, unlike engines that use rocker arms.



  • Gravesdigger

Posted January 07, 2015 - 02:29 PM

#22

I appreciate all the feedback, I carefully read it all and tried to address each suggestion. 

 

My mind isn't "made up" so to speak on Stainless vs. Ti valves.

I'm just going off my personal (albeit limited) experience on Ti versus stainless valves.

 

The only additional experience I have is with two friends that have similar year Hondas (05 CRF450X and 06 CRF450r).

Both ride similar terrain to me, have similar skill sets, and have similar maintenance routines (to each other),

but the gentleman with the X (with Stainless valves)- I've only had to shim his valves once for him.

While the friend with the R has had to do 1 set of new valves and valve seats already. The Gentleman with the X has nearly 100 more hours on his bike than the R.

(I do understand the additional differences between the two bikes and don't intend to make this conversation about that or about Ti vs Stainless valves.... this is simply my limited experience).

 

According to the service manual I have for my bike, the original valves are out of spec. (I'd be happy to remeasure and record the measurements here when I get some time).

 

Also just to clarify the shop did replace the seals but not the guides (as shown in the photos of the intake and exhaust ports) (I miss-typed that... my excuse was it was really late last night).

I did have them do new guides when I took it in today (they did infact just misplace them), Very simple mistake.

 

I concur with the gentleman who spoke about the oil rings, my shop agreed with that hypothesis also (their comment was the oil rings were worn; I didn't measure to confirm this).

However, I believe the fuel map is not ideal either. (We'll sort this with a GYTR tuner after I reassemble the bike).

 

I was bugged about them not cleaning the exhaust port because I had asked them too, but it's not a big deal, I have an old toothbrush... and I'm capable. 

 

I asked the shop again if they did infact recut the seats (as this was the reason I took the head to them instead of doing it myself) and they reassured me they did.

I'm going to do a little leak test with some mineral spirits to confirm they are sealing correctly. And if it comes to it I'll also to the sharpie trick shown in the Hot Cams valve replacement video I linked earlier.

 

 

 

Any other suggestions?



  • kx450f63

Posted January 08, 2015 - 09:44 AM

#23

I appreciate all the feedback, I carefully read it all and tried to address each suggestion. 

 

My mind isn't "made up" so to speak on Stainless vs. Ti valves.

I'm just going off my personal (albeit limited) experience on Ti versus stainless valves.

 

The only additional experience I have is with two friends that have similar year Hondas (05 CRF450X and 06 CRF450r).

Both ride similar terrain to me, have similar skill sets, and have similar maintenance routines (to each other),

but the gentleman with the X (with Stainless valves)- I've only had to shim his valves once for him.

While the friend with the R has had to do 1 set of new valves and valve seats already. The Gentleman with the X has nearly 100 more hours on his bike than the R.

(I do understand the additional differences between the two bikes and don't intend to make this conversation about that or about Ti vs Stainless valves.... this is simply my limited experience).

 

According to the service manual I have for my bike, the original valves are out of spec. (I'd be happy to remeasure and record the measurements here when I get some time).

 

Also just to clarify the shop did replace the seals but not the guides (as shown in the photos of the intake and exhaust ports) (I miss-typed that... my excuse was it was really late last night).

I did have them do new guides when I took it in today (they did infact just misplace them), Very simple mistake.

 

I concur with the gentleman who spoke about the oil rings, my shop agreed with that hypothesis also (their comment was the oil rings were worn; I didn't measure to confirm this).

However, I believe the fuel map is not ideal either. (We'll sort this with a GYTR tuner after I reassemble the bike).

 

I was bugged about them not cleaning the exhaust port because I had asked them too, but it's not a big deal, I have an old toothbrush... and I'm capable. 

 

I asked the shop again if they did infact recut the seats (as this was the reason I took the head to them instead of doing it myself) and they reassured me they did.

I'm going to do a little leak test with some mineral spirits to confirm they are sealing correctly. And if it comes to it I'll also to the sharpie trick shown in the Hot Cams valve replacement video I linked earlier.

 

 

 

Any other suggestions?

 

If you want to confirm the seat operation, remove a valve and look at the seat.  If the seat face is at a 45 degree angle to the guide, flat, and clean then they did.  Based on your experience I would probably check too.



  • Gravesdigger

Posted January 08, 2015 - 10:55 AM

#24

If you want to confirm the seat operation, remove a valve and look at the seat.  If the seat face is at a 45 degree angle to the guide, flat, and clean then they did.  Based on your experience I would probably check too.

 

Not a bad suggestion. Easy enough to take a look.



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  • Gravesdigger

Posted February 09, 2015 - 08:25 PM

#25

So I'm having a bit of a problem after the rebuild. 

The bike will start very consistently on or before the 3rd kick... unless it's very cold out.

 

Bike will hot kill as if the valve lash was out of spec and won't start until it cools off. Sometime 20 minutes.

It also will occasionally do this as well if I turn it off while hot... it won't start until it cools off.

I also get the occasional flameout if I snap the throttle closed. (This issue seems to occur even if I clutch in: I also have a Rekluse EXP 3.0).

I have a newer High Flo brand fuel pump and filter and cleaned the injector (20hrs ago).

I started with a clean filter and plug after the top end rebuild.

 

What I've checked so far:

1.) Checked Timing

2.) Valve lash: 0.11 intake .23 exhaust so that's in spec.

3.) I've ohmed out the TPS in open, closed positions and verified 0 ohms when the throttle body is closed (via the slotted hole on the TPS).

4.) I verified intake boot hose clamps are tight to eliminate vacuum leaks.

5.) New coolant

At this point I was around 6.5hrs

 

6.) The radiators were a bit bent and the cross-over tube was kinked so I straightened them, cleaned them, straightened all the fins I could with a dental pick and replaced the cross-over radiator tube.

236a334a-8044-4bc2-a3e9-f4ca8bce648d_zps

b1a09085-e5b5-402f-980e-b66a106d6db7_zps

2015-01-29%2016.10.23_zps6q6j3yxx.jpg

7.) I added a Tusk 1.6 radiator cap (versus the stock 1.1 cap).

8.) New coolant.

9.) I removed and cleaned the contacts on the kill switch and ohmed the connection.

10.) Cleaned the air filter and the intake "horns."

11.) I cleaned the plug again (did not replace it: running an E3 if that matters: it has 20-30 hrs on it).

 

 

At this point it stopped overheating and is less prone to this hot kill issue, but it has still happened 3 times in an additional 3.5 motor hours

 

 



  • kx450f63

Posted February 10, 2015 - 06:56 AM

#26

There are a few minor things that stick out to me:

 

The spark plug, who makes that?  I would run an NGK iridium or the stock one and try that first.

The fuel pump, who makes that?  Might want to run some tests on it or try a know good one.

 

Can you coast start it when this problem happens?

 

Do you think you have truly overheated it?  That certainly could cause valve leakage issues.  May need a leak down test.

 

Have you tried to start it using the high idle knob?  Is the passage for the high idle knob clear?

 

There are a lot of things that could cause this issue, dare I say stator, coolant temp. sensor, and so on.  Might be best to have a good donor bike to rob parts from to verify the problem.



  • Gravesdigger

Posted February 10, 2015 - 10:37 AM

#27

There are a few minor things that stick out to me:

 

The spark plug, who makes that?  I would run an NGK iridium or the stock one and try that first.

 

E3 makes it. They are a reputable company. I can certainly try a stock plug.

 

The fuel pump, who makes that?  Might want to run some tests on it or try a know good one.

 

High Flow fuel pumps are made my Axiom performance and have a lifetime warranty. I can test fuel pressure.

Here is the thread http://www.thumperta...ter-15-minutes/

and the pump is here: http://www.highflowf...-2010-2014.html

 

Can you coast start it when this problem happens?

 

I cannot push start it simply: I have a Rekluse Auto clutch (one of the few disadvantages) .

 

Do you think you have truly overheated it?  That certainly could cause valve leakage issues.  May need a leak down test.

 

I don't think significantly, just some steam from the radiator cap, I shut it down as soon as I saw steam.

The machine shop that did the rebuild did a liquid valve leakage test, but I could borrow equipment to do a vacuum leakdown myself.

 

Have you tried to start it using the high idle knob?  Is the passage for the high idle knob clear?

 

I believe the passage is clear as I have used the high idle knob to start it in very cold weather and it does increase idle speed.

It does not seem to effect the ability to start it when it has the no hot start symptoms.

 

There are a lot of things that could cause this issue, dare I say stator, coolant temp. sensor, and so on.  Might be best to have a good donor bike to rob parts from to verify the problem.

 

I will order a new coolant temp sensor (Yamaha calls it a Thermo Unit) for starters: they are only $14.66 on Partsfish.com http://www.partsfish...13/electrical-1



  • kx450f63

Posted February 11, 2015 - 07:54 AM

#28

As far as a few of the main tests for your pump would be; max fuel pressure, max free flow (how many ounces in how many seconds) and how long does it hold fuel pressure after it has shut off.  Of course you would want to do these test when it's cold and when the problem arises. (hot)

 

Ya the Rekluse thing is an issue.  I believe if you can get the back wheel to spin it fast enough it will coast start, pull it with something.  I'm just curious if it will start when it's hot.

 

Wast the steam coming from the cap or from the overflow hose?  I guess either way it doesn't really tell us how hot it got and for how long.  I guess still warrants a leak down test to verify valves are sealing.







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