HELP: 09 KX450F Turns off after about 15 minutes of running

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6/24/2022 1:21 PM

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up immediately. I have to wait about 20 or so minutes (maybe to let it cool down?) to kick start it and it'll start right up. Along with this, I noticed when I rev the engine at a high RPM in neutral, the coolant overflow hose spews out coolant, or water... I'm not sure which.

I have read online that the cause could be many things, blown head gasket, bad radiator cap, or other things.... I recently had the head gasket replaced so I doubt it is that.

Will overheating cause the bike to turn off(stall) automatically? Any advice and information would be greatly appreciated.

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6/24/2022 1:40 PM

Maybe a bad water temperature sensor?

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Don't ever let facts get in the way of a great story

6/24/2022 2:55 PM
Edited Date/Time: 6/24/2022 3:08 PM

Anthony_Horner wrote:

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up ...more

"the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever you put in your radiator is what's coming out the overflow and unless you are running straight water then its coolant, why would you put straight water in the radiator unless your road racing or drag racing? You need to take it to a shop and let them handle it.
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6/24/2022 6:35 PM

Anthony_Horner wrote:

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up ...more

lostboy819 wrote: "the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever ...more

Try being kind.

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6/24/2022 6:57 PM

Anthony_Horner wrote:

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up ...more

lostboy819 wrote: "the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever ...more
Roczoff wrote:

Try being kind.

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut out to work on modern motocross bikes plain and simple. If you don't know what's in your radiator the you are one of those people.

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6/24/2022 6:59 PM

It's the head gasket... What else can pressure up your cooling system? Can you ride it around? Is it even worse under load? I guess it could be a cap lifting when the water pump is screaming, but I kind of doubt it. I would try the cap first though, it's cheap...

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6/24/2022 8:00 PM

Have you tried a new spark plug? I know that may sound stupid but my 09 kx450 did the same thing but it only took about 5-10 minutes to shut off. I had a friend bring his to the track and we switched out everything including fuel pump, stator, coil etc. He finally said have you changed the plug and I said no because it would start firing again by the time I got it out and it had cooled off. Just a thought.

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6/24/2022 8:13 PM

lostboy819 wrote: "the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever ...more
Roczoff wrote:

Try being kind.

lostboy819 wrote:

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut ...more

Facts.

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6/24/2022 10:24 PM

If it’s randomly dying you might want to get your valves checked just to be safe. I had a Yamaha 450 that started to cut out after riding for a little bit until one day a valve hit the piston and shattered. Not sure if that’s causing your problem but it’s worth having them adjusted/shimmed if you have someone take the top end apart

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6/25/2022 6:28 AM

Roczoff wrote:

Try being kind.

lostboy819 wrote:

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut ...more

bichwolf wrote:

Facts.

It's kind of funny when people post an issue asking for help and then only look for the answers they want to hear... To me, the coolant coming out of the overflow speaks volumes as to why the bike is shutting down after 15 mins. Motor is probably filling with coolant. Or water. Or something... It's even more suspect if "the head gasket was just changed". Who did it? Were the bottom end and cylinder decked flat? Checked for cracks in cylinder and head? Is there smoke coming out the tailpipe? Is the base gasket sealing around the coolant ports? Coolant in oil? Oil in coolant? Pretty obvious stuff to look for but if you have no idea, then get someone who does before you fuck shit up.

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6/25/2022 7:33 AM

i had a 2010 kx450 and rebuilt the motor using the moose brand gaskets and it blew the head gasket after a couple hours. use only oem stuff.

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6/25/2022 7:38 AM

Hey everybody. There is no reason to be rude here. I am just trying to learn and understand. The head gasket was changed by a professional shop along with an entire top end rebuild. I know the radiator is filled with coolant however I read that water from the water pump can be also the problem. Clearly I am a rookie and I don’t need disrespect for simply asking a question. I’m simply posting to get an understanding of the problem so a mechanic doesn’t screw me over.

To those who gave me positive comments - thank you, I appreciate your advice.

There is no cracks in the cylinder head, the entire top end was just rebuilt by a professional shop. It cost me a ton of money, all gaskets were replaced, new spark plug was inserted, gaskets were sealed with proper sealant.. had an oil change, multiple times to assure oil was clean.

“He’s in way over his head” - thanks for your disrepesctful comment. As mentioned - I am just trying to understand. I suspect it could be 1. Faulty cap, 2. Warped head, 3. Radiator clogged, 4. Thermostat malfunction, 5. Faulty water pump. - This is just what I’ve obtained from a Professional service shop that did not see the bike in person and gave me advice over the phone.

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6/25/2022 7:42 AM
Edited Date/Time: 6/25/2022 7:43 AM

lostboy819 wrote: "the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever ...more
Roczoff wrote:

Try being kind.

lostboy819 wrote:

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut ...more

Just extremely disrespectful. Im clearly a rookie looking for advice and I don’t need self proclaimed professionals making fun of me for not understanding. I’m not working on the bike myself as mentioned, I just want an understanding of what’s wrong before a mechanic charges me for 15 things that’s not actually wrong with the bike. Hey “roczoff” - thank you for supporting the extreme disrespect these people are commenting with.

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6/25/2022 7:45 AM

Roczoff wrote:

Try being kind.

lostboy819 wrote:

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut ...more

bichwolf wrote:

Facts.

As mentioned in my latest comment. There’s coolant in the radiator. I read online that water pump failure can cause water to to spew out or mix with the radiator fluid.

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6/25/2022 7:46 AM

Anthony_Horner wrote:

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up ...more

lostboy819 wrote: "the coolant overflow hose spews out coolant, or water... I'm not sure which.

What do you mean your not sure which? what ever ...more
Roczoff wrote:

Try being kind.

Roczoff - thank you again. Clearly you understand where I’m coming from unlike these disrespectful self proclaimed professionals.

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6/25/2022 8:07 AM

Anthony_Horner wrote:

As mentioned in my latest comment. There’s coolant in the radiator. I read online that water pump failure can cause water to ...more

Your water pump actually moves coolant, not water.

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6/25/2022 8:50 AM

Check your gas cap to make sure its not air locking. It may suck fuel out but not be letting air in fast enough, then over time it eventually lets the air back in. I suspect its lack of fuel flow because your gas cap may be bad. Is the air hose on your gas cap plugged or kinked? And again, may just be the gas cap itself.

I'd start there first.

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6/25/2022 8:53 AM

A rule of thumb about mechanical stuff. If it wasn't shutting down, spewing coolant before the shop worked on it...you must first suspect that something they did is causing your current problem. That's not 100%...shit just happens sometimes. I'd go back and explain to them what's going on. They'll either tell you to kick rocks or they'll diagnose the problem and charge you to fix it or best case...they'll fix your bike at no cost (highly unlikely but who knows). Good luck.wink

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If it ain't yer's don't take it, If it ain't the truth dont say it, If it ain't right don't do it...Marcus Aurelius

6/25/2022 8:55 AM

Anthony_Horner wrote:

My 2009 KX450F will run fine for about 15 minutes before it shuts off. Once it shuts off I cannot start it back up ...more

On your coolant, don't over fill the coolant. When the bike is cold, the coolant should be right at the top of the fins, not with the radiator completely full of fluid. If the radiator has too much coolant, its going to overflow out the drain, and it will do more of that when the RPMs are up.

Again, Id start with your gas cap first before the big stuff.

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6/25/2022 9:01 AM

lostboy819 wrote:

That is being kind, he is in way over his head and he will just end up costing himself a lot of money, some people are not cut ...more

bichwolf wrote:

Facts.

Anthony_Horner wrote:

As mentioned in my latest comment. There’s coolant in the radiator. I read online that water pump failure can cause water to ...more

The "water pump" is a pump that moves whatever liquid you have in the radiators. If you have coolant in your radiators, it's moving coolant. If you have water in your radiators, it's moving water.

The pump transfers the coolant from the radiator, through the radiator hoses, into your engine where it cools the engine but is made warmer from the heat transfer during this process. That coolant is then pushed back to the radiators to be cooled while the coolant that was just cooled in the radiators heads towards the engine. Repeating the process in a constant flow.

The easiest check here would be to swap your radiator cap with someone else's and see if it that process continues. When you state you're holding it at a consistent RPM, how long are we talking? If the bike is hot enough, it'll push coolant out no matter what as the stock 1.1 radiator caps aren't typically efficient for most track riding.

Back in 2009, many OEMs, Kawi included...were having fuel pump issues that would appear with heat and run time. Your fuel pump could be an issue. A bad stator could possibly be causing the problem as well.

Do you know what brand of parts the shop or mechanic used when rebuilding the engine and how long ago did the work happen? If you just got the bike back and it's having these issues, I would return to who did the work or find another reputable source to assist you. If your experience is as lacking as it seems, you could really chase your tail on this one and either cost you more money just trying things or worse, cost you a bundle more if there's a serious problem and the bike receives further damage.

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6/25/2022 9:11 AM

plowboy wrote:

A rule of thumb about mechanical stuff. If it wasn't shutting down, spewing coolant before the shop worked on it...you must ...more

When you get told that something isn't the cause because it was just worked on, you can pretty much guarantee that it actually is the problem or that something else went wrong during the repair. When I repaired machinery for a living, I learned fast to just follow the normal flow of diagnostics and not let someone lead you astray by telling you what is and isn't the cause. In this case, I would do a leak down on that engine.

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6/25/2022 11:27 AM

bichwolf wrote:

Facts.

Anthony_Horner wrote:

As mentioned in my latest comment. There’s coolant in the radiator. I read online that water pump failure can cause water to ...more

ML512 wrote:

The "water pump" is a pump that moves whatever liquid you have in the radiators. If you have coolant in your radiators, it's ...more

This is extremely helpful information thank you. My radiator cap is 1.3, should this be different? The gaskets that replaced are tusk gaskets. Replaced the spark plug with the standard NGK spark plug. Some mechanic thinks the head may be warped, causing water to leak into the cylinder. But he did not check if it is warped he spoke to me over the phone.

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6/25/2022 11:45 AM

Make sure the fuel hose isn’t pinched somewhere. That happened on my 09 kxf

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6/25/2022 12:10 PM

Try a 1.8 cap. And never let your bike sit on the stand running for any length of time, they all overheat doing that.

If the head is warped, nothing is going to help you until it's fixed/replaced...

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6/25/2022 7:49 PM

I ran into a similar problem with a 14 YZ450F. It was slowly losing coolant and then would stall and not start for a while. Give it 10-15 min and it would start up. I chased cooling issues for a while. New hoses, bigger radiators, high pressure cap. Come to find out the head gasket was leaking ever so slightly because the head bolts were a torque to yield bolt. (Which I have learned, are a 1 time use because you are stretching them when installed properly.) So IF your KX used the same style of head bolt, and your repair guy reused the head bolts, your probably not getting a good seal on the head.

My theory on the stalling and not starting for my YZ450, was the coolant was slowly leaking out while running, making the engine hotter. The coolant temp sensor would try to compensate for the higher engine temps and lean the bike out to a point where there wasn't enough fuel to run. Shut down for 20 min and it would cool off and start right back up.

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6/26/2022 5:08 AM

ktmdan wrote:

Make sure the fuel hose isn’t pinched somewhere. That happened on my 09 kxf

Especially if it has one of those stupid ‘stubby’ vent hoses. Try another bit hose, it’s an easy thing to start with.

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Now a member of the Orange brigade

6/26/2022 6:23 AM

I remember a friend with a kx250 with a perpetual head gasket leak issue. Changed head studs solved problem. Now I’m superstitious on engine rebuilds and swap studs regardless.

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6/26/2022 1:01 PM

KurtJ99 wrote:

I remember a friend with a kx250 with a perpetual head gasket leak issue. Changed head studs solved problem. Now I’m ...more

Is it injected? If so check the tank for debris. Had a similar issue on a crf, the dirt would block the fuel filter after a time. After sitting for a while the dirt would move and the filter would unblock then the bike would run for 10-15mins and shut off again.

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6/27/2022 7:55 AM

How many professionals are using Tusk gaskets?

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6/28/2022 9:04 AM

TbonesPop wrote:

Check your gas cap to make sure its not air locking. It may suck fuel out but not be letting air in fast enough, then over ...more

Word

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