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HONDA NO MORE

Low compression / Sticky valve on 05 YZ450F

26 posts in this topic

Sometimes when I kick my bike over after I have turned it off with the kill switch, it will have no compression for 5-10 kicks, and I mean no compression, like it was a really tired 125 with old rings in it.

I try to find the compression stroke, but it nevers builds any compression. I think that a valve might be sticking open?? I experienced the same problem on my 04. Has anyone else ever had this happen??? I will kick it 5-10 times with no compression and sometimes it will build compression after a number of kicks, other times I give it just a little gas and it fires right up. This happens only on rare occasion, maybe every other ride. When I put my bike back on the stand I make sure to find the compression stroke so that all of the valves are closed.

Any ideas????

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My bike does the same thing every now and then. I have always assumed that it was an inssue with the Auto Decomp and not with the valves themselves.

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I've see this problem before and it usually occured on bikes that have been sitting for a while. As soon as they start up and run the compresion is restored. It's like the rings are dry. Only thing I can think of is a leaky fuel petcock or fuel left on.

Does your oil have a strong gasoline smell?

I've seen this happen on a WR426 and a WR400.........no auto compression release here.

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Auto decompression as used in a YZF cannot cause this problem. It is usually a result of carbon on the valve stems sticking enough to hold the valve off the seat.

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Auto decompression as used in a YZF cannot cause this problem. It is usually a result of carbon on the valve stems sticking enough to hold the valve off the seat.

A valve clearance check may tell a story!

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Thanks for the replies, they give me a little more confiedence in the old 450. I will be checking my valves this next week to make sure that there is nothing wrong in that area. I'll check the oil for the smell of gas, my bike usually gets rode at least once a week.

Grey, I can agree with what you are saying here. Do you see this as a problem or should I just learn to live with it? I don't notice any power decrease or any other problems from the so called "sticky valve" Like I said my 04 did it a few times, and it ran very well when I sold it. I have run Yamalube 20-40 in both bikes, and regularly change the oil every other tank of gas, could this be a cause of carbon build up? I have noticed the longer I have the bike, the more the problem occurs.

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Auto decompression as used in a YZF cannot cause this problem. It is usually a result of carbon on the valve stems sticking enough to hold the valve off the seat.

Is it something to be concerned about. I did a valve clearance check 3 hours ago and they haven't moved at all. Should we be pulling the heads off and cleaning out the carbon buildup?

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A valve clearance check may tell a story!
Indeed it will. If you catch the bike doing this when you have time to work on it, any valve being held off its seat by carbon or other artificial means will have an excess of clearance. (If you have no clearance, that's another, somewhat worse problem). On discovering a valve with too much clearance, you can often use a wood dowel or soft metal punch and a hammer to tap the lifter gently a few times. Tapping it will bounce it open a bit, after which it will bounce closed with more force than it normally closes with, and assuming the carbon obstruction was "broken", clearance should then be closer to normal.
Is it something to be concerned about. I did a valve clearance check 3 hours ago and they haven't moved at all. Should we be pulling the heads off and cleaning out the carbon buildup?
If valve clearance is correct, then it's not possible that any are off their seat, and if there is no loss of compression, there's not much to worry about.
I wonder if this would be a good spot to yammer on about the merits of "Easy OFF Oven Cleaner" :worthy:
I don't know about that, but there are "top engine cleaners" that do a good job. One of the best available is from the GM parts counter, imaginatively named "GM Top Engine Cleaner". But like all over the counter GM chemicals, it's pricey. Most TEC's are basically the same stuff as "Techroline", and are already present in the fuel you use in small quantities.

There are two ways to use them, usually described on the label. One is to add them to the fuel and hope it does something eventually. The other is more aggressive.

Warm the engine up thoroughly and remove the air filter. Clean up the air box well enough that you can safely run the engine. You need to put a small amount of TEC in a squeeze bottle that is small enough to put down into the air box and controllably squirt fluid with.

With the engine running at a fast idle, inject the TEC into the air stream fairly quickly, but not so fast as to cause the engine to stall, and especially not hydraulically lock up. When you have shot about 4 ounces into the engine, stop squirting and shut it down at once. Let the TEC soak into everything inside the engine for 10-15 minutes.

Restart it, and run some more TEC through slowly. Then shut it off replace the filter, and take the bike out for a serious rip through the gears.

This is about all you can do short of a tear down to remove carbon. It won't get it all, but it helps quite a bit.

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Sometimes when I kick my bike over after I have turned it off with the kill switch, it will have no compression for 5-10 kicks, and I mean no compression, like it was a really tired 125 with old rings in it.

I try to find the compression stroke, but it nevers builds any compression. I think that a valve might be sticking open?? I experienced the same problem on my 04. Has anyone else ever had this happen??? I will kick it 5-10 times with no compression and sometimes it will build compression after a number of kicks, other times I give it just a little gas and it fires right up. This happens only on rare occasion, maybe every other ride. When I put my bike back on the stand I make sure to find the compression stroke so that all of the valves are closed.

Any ideas????

are you using low grade fuel?

if so try using 94 octane

i carboned up my valves once with a few tanks of low grade and thought i needed a valve adjustment.

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are you using low grade fuel?

if so try using 94 octane

i carboned up my valves once with a few tanks of low grade and thought i needed a valve adjustment.

Octane rating has nothing to do with this. Using a major brand, high quality fuel does though. Fact is, a good brand of Regular Unleaded is more apt to have a high level of carbon/injector cleaner in it than the same company's premium is.

A little known fact is that in most major North American markets, all the gas sold under any brand comes from the same source, usually a pipeline from the refineries to a tank farm. The tanker trucks are dispatched from the various brand company truck yards, empty except for the appropriate amount of their proprietary additive package, to the tank farms where they are filled with two grades of the exact same fuel, regular and premium. Mid grades are blended at the pump itself. Super premiums, where they exist are usually just premium with an octane booster added. Discount stations hold their prices down, as a general rule, by adding less, or using less expensive additives to their fuel. It's all the same soup otherwise.

Another thing to do is to buy your gas from a dealer who does a lot of business, or at least, one who always seems to be getting visits from tanker trucks, since this indicates the fuel will be fresher.

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Octane rating has nothing to do with this. Using a major brand, high quality fuel does though. Fact is, a good brand of Regular Unleaded is more apt to have a high level of carbon/injector cleaner in it than the same company's premium is.

A little known fact is that in most major North American markets, all the gas sold under any brand comes from the same source, usually a pipeline from the refineries to a tank farm. The tanker trucks are dispatched from the various brand company truck yards, empty except for the appropriate amount of their proprietary additive package, to the tank farms where they are filled with two grades of the exact same fuel, regular and premium. Mid grades are blended at the pump itself. Super premiums, where they exist are usually just premium with an octane booster added. Discount stations hold their prices down, as a general rule, by adding less, or using less expensive additives to their fuel. It's all the same soup otherwise.

Another thing to do is to buy your gas from a dealer who does a lot of business, or at least, one who always seems to be getting visits from tanker trucks, since this indicates the fuel will be fresher.

"What the American consumer doesn't know.......is what makes them the American consumer"

Gotta love it!

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Indeed it will. If you catch the bike doing this when you have time to work on it, any valve being held off its seat by carbon or other artificial means will have an excess of clearance. (If you have no clearance, that's another, somewhat worse problem). On discovering a valve with too much clearance, you can often use a wood dowel or soft metal punch and a hammer to tap the lifter gently a few times. Tapping it will bounce it open a bit, after which it will bounce closed with more force than it normally closes with, and assuming the carbon obstruction was "broken", clearance should then be closer to normal.

If valve clearance is correct, then it's not possible that any are off their seat, and if there is no loss of compression, there's not much to worry about.

I don't know about that, but there are "top engine cleaners" that do a good job. One of the best available is from the GM parts counter, imaginatively named "GM Top Engine Cleaner". But like all over the counter GM chemicals, it's pricey. Most TEC's are basically the same stuff as "Techroline", and are already present in the fuel you use in small quantities.

There are two ways to use them, usually described on the label. One is to add them to the fuel and hope it does something eventually. The other is more aggressive.

Warm the engine up thoroughly and remove the air filter. Clean up the air box well enough that you can safely run the engine. You need to put a small amount of TEC in a squeeze bottle that is small enough to put down into the air box and controllably squirt fluid with.

With the engine running at a fast idle, inject the TEC into the air stream fairly quickly, but not so fast as to cause the engine to stall, and especially not hydraulically lock up. When you have shot about 4 ounces into the engine, stop squirting and shut it down at once. Let the TEC soak into everything inside the engine for 10-15 minutes.

Restart it, and run some more TEC through slowly. Then shut it off replace the filter, and take the bike out for a serious rip through the gears.

This is about all you can do short of a tear down to remove carbon. It won't get it all, but it helps quite a bit.

even pouring water in the motor while it's running can break up carbon on the piston. the easy off stuff is good for when it's on the back of the valves. It can save you the effort of taking the valves out.

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even pouring water in the motor while it's running can break up carbon on the piston.
If you doubt that, look at the combustion chamber of any engine that has had a coolant leak to the combustion chamber for any length of time. They're often totally free of carbon. Steam can be pretty harsh at 3000 degrees.

Top engine cleaners, when applied as in my second method also have the ability to remove carbon from the backs of the intakes, and the exhausts, for that matter, if you get them wet with it.

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No clue why I wouldnt have thought of this before but have you ever tried seafoam? I would use it decarbon the mercs on the boat.

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Octane rating has nothing to do with this. Using a major brand, high quality fuel does though. Fact is, a good brand of Regular Unleaded is more apt to have a high level of carbon/injector cleaner in it than the same company's premium is.

A little known fact is that in most major North American markets, all the gas sold under any brand comes from the same source, usually a pipeline from the refineries to a tank farm. The tanker trucks are dispatched from the various brand company truck yards, empty except for the appropriate amount of their proprietary additive package, to the tank farms where they are filled with two grades of the exact same fuel, regular and premium. Mid grades are blended at the pump itself. Super premiums, where they exist are usually just premium with an octane booster added. Discount stations hold their prices down, as a general rule, by adding less, or using less expensive additives to their fuel. It's all the same soup otherwise.

Another thing to do is to buy your gas from a dealer who does a lot of business, or at least, one who always seems to be getting visits from tanker trucks, since this indicates the fuel will be fresher.

http://www.toptiergas.com/retailers.html

If you have any doubts about the detergent addatives in your gasoline you can add this stuff;

http://www.chevron.com/products/prodserv/fuels/additives/concentrate_plus.shtml

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I did pick up some gas at a pretty shady gas station a few weeks ago, because we got lost and it was all we could do to get home. Maybe it was the culprit for this problem. I will have to try one of the suggested solutions, Thanks for the help:applause: :worthy: :worthy: :worthy:

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If you doubt that, look at the combustion chamber of any engine that has had a coolant leak to the combustion chamber for any length of time. They're often totally free of carbon. Steam can be pretty harsh at 3000 degrees.

Top engine cleaners, when applied as in my second method also have the ability to remove carbon from the backs of the intakes, and the exhausts, for that matter, if you get them wet with it.

Gray, thats so funny you should mention that. I tore apart an RC 51 Honda sportbike today that had that exact problem!!!!! Those valves were spotless on the front cylinder <where the leak was> and ugly black on the rear cylinder.

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You see that in cars quite a lot. One (or two together) clean cylinder is a dead giveaway.

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I have been having the "No compression " problem for awhile now...I also noticed that the auto decompression device hasn't been working right...

having a weekend ride planned this weekend I decided to take the cam cover off and find the problem......The first thing I found was very loose valve clearance......I found .010 intakes and .015 ex.....This wouldn't really bother me except I think the shims are trying to pop out and they get wedged in the

bucket and holds the valve open.....Thus no compression until the shim pops back in place.......Sound to hard to believe? Well then where does the

compression go? Also if the decompression device can't touch the shim during cranking it can't open the valve to release pressure, right...So loose valves can keep the decompression device from working...think about it.....A tight valve would make it work better because the valve would be open sooner.....

I think I figured it out...All I have to do is adjust the valve clearance and see if everything gets better:applause:

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