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Valve Life? Are the KLX250S heads different than the KLX300R

Valve Life? Are the KLX250S heads different than the KLX300R

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  #1  
Old 04-05-2006, 05:24 AM
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Default Valve Life? Are the KLX250S heads different than the KLX300R

SO I'm a subscriber to newsgroup of KLX300 owners. They report very short valve service lifes and consider 2500-3000 miles normal life expectancy. Thsi is around 100 hours of operation. I guess a WR450 can get 7000 miles and that's considered best in class. SO what gives? Are these poepl nuts? I'd expect a full on motorcross bike ot have shorter service life, but I'm think that a trail bike would be more similar ot a KLR650 or KLR250 which I beleive will go 10's of thousands of miles without any valve service.

Anyone have any expereicne with this? I f i knew that most trail bieks only got 5000 miles out of their valves, I would have stuck with sportbikes. What's strange is that sportbikes have twice the specific output (HP/cc), but their engines last a very long time. 30,000+ miles is no big deal for a modern sportbike even with occasional track use and LOTS of freeway use crusing at over 8000RPM. Most sportbikes redline at 13,000 or higher as well.

Why are the valves and valve seats so different on a dirtbike? The compression is lower, the output is much lower per cc. IS it because of the compact size? Is it older technology? Is it some issue with single cylinder engines?
 
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Old 04-05-2006, 06:03 AM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

ORIGINAL: motoguy128

SO I'm a subscriber to newsgroup of KLX300 owners. They report very short valve service lifes and consider 2500-3000 miles normal life expectancy. Thsi is around 100 hours of operation. I guess a WR450 can get 7000 miles and that's considered best in class. SO what gives? Are these poepl nuts? I'd expect a full on motorcross bike ot have shorter service life, but I'm think that a trail bike would be more similar ot a KLR650 or KLR250 which I beleive will go 10's of thousands of miles without any valve service.

Anyone have any expereicne with this? I f i knew that most trail bieks only got 5000 miles out of their valves, I would have stuck with sportbikes. What's strange is that sportbikes have twice the specific output (HP/cc), but their engines last a very long time. 30,000+ miles is no big deal for a modern sportbike even with occasional track use and LOTS of freeway use crusing at over 8000RPM. Most sportbikes redline at 13,000 or higher as well.

Why are the valves and valve seats so different on a dirtbike? The compression is lower, the output is much lower per cc. IS it because of the compact size? Is it older technology? Is it some issue with single cylinder engines?
[sm=insomnia.gif] WHA??
I am really hoping that someone comes on here and sais that this does not apply to our nice little fun KLX 250s[]. 2,500-3000 miles?? The manual describes the valves to be checked at 7,500 miles, was this in the KLX 300 manual as it is in the KLX 250?? I would have not bought this bike if this was the life expectancy, so lets hope this is not so, that would be very sad.
 
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Old 04-05-2006, 09:07 AM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

That's what my reaction was to the messages I was reading. Hell, the tires and brake pads last longer. I guess it's only hte intake valves that are a problem. I just don't understand how a KLR250 motor is so dramatically different. I know the redline is a little higher, but I thing that just because the KLX storke is shorter. From what I read, revving the motor high isn't the issue either.

Maybe we're lucky and Kawi was smart enough to use a diffrent valve seat material and/or valve material.

The other thing to remember, is that these guys are ridding their KLX300R's exclusively on trails. I rode for 4 hours the other day and only put on 30 miles. The trails were really tight and I only average 15-20mph around the MX track.

Either way, I think the valves should last as long as any other part in the motor. In my opinion, the piston rings or head gasket should fail first, followed by valve seats, then main bearings. This goes in the order of how much normal wear these items should be subjected to.
 
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Old 04-05-2006, 06:46 PM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

Say it isn't so[sm=boosign.gif][sm=dontgetit.gif][sm=nothatway.gif][sm=sigh.gif]
 
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Old 04-05-2006, 06:57 PM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

I've been worried about this too. Here's what I know:

1) The intake valves are the issue. Once they start to wear, they wear fast.

2) The intake valves are the same on our bike as on the KLX300R.

3) The exhaust valves are different on our bive vs. the KLX300R.

4) The head is essentially the same except for the air valve port on ours. There's no way to tell if the valve seat area is different but it's at least possible since the heads have different part numbers.

5) I'm going to be pissed if I can't get 20K miles out of this bike without an valve overhaul.

Here's what I think I know:

1) Frequent air cleaner maintenance and oil changes may help.

2) Frequent valve clearance checks are more important of us than on other 4s engines.

3) I'm glad I got the extended warranty.

I'm going to ping the guys at FSW to see what they think.


 
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Old 04-05-2006, 07:01 PM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

ORIGINAL: bmwhd

I've been worried about this too. Here's what I know:

1) The intake valves are the issue. Once they start to wear, they wear fast.

2) The intake valves are the same on our bike as on the KLX300R.


Well that doesn't make me feel any better.[]. I'm still hoping that things will last longer, this is a great little light weight dual sport and can handle very well off road, I hope that the life is not short on it, I will be pissed.[:@]
 
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Old 04-05-2006, 08:22 PM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R


ORIGINAL: motoguy128

They report very short valve service lifes and consider 2500-3000 miles normal life expectancy.
I have already exceeded 3200mi. Most of that was over 7k rpm. Remember most of us have cooling fans to keep cylinder temp under control. If I have to adjust my valves again before the warranty is up, or 7500mi, I will be camping at my dealer, until they are replaced. Lets hope it's like my KLR250, I put 22K before I sold it. It had just over 66K on the ODO.
 
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Old 04-05-2006, 08:41 PM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

Another thought. How many dirt bikers adjust their valves? None that I know. Once those valves get out of spec they can burn darn quickly. I'll be quite now.
 
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Old 04-06-2006, 12:19 AM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

Found this interesting quote in the Dirt Bike archives:

"...When I worked at Kawasaki back in 1994 and the KLX250 was intorduced, we had motors coming back in to the shop that could use a set of intake valves after just a few hours. We found that DETONATION WAS THE MAIN CAUSE of this and when better fuel was used, this trouble all but went away. I think I can reinforce this with guys who are taking their new CRF250X's to Mexico. I have talked with guys who've said that they rode 400 to 500 miles and the valves have tightened up. Fuel in Mexico is very low quality, and these guys have told me that the bike was brand new befor the trip. Nearly every time they return after running that gas, you can plan on a valve job, because the top end takes a beating..."

So, premium for me from now on...
 
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Old 04-06-2006, 12:22 AM
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Default RE: Valve Life? Are the KLX250S heads different than the KLX300R

Well theres a plus,
I have always used premium in my bike since the day I got it, no matter what. It only costs me $2-3 to fill up a tank, so I'm definatley not taking a big hit there.
 
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