CRF450 fuel injector issues

Reefer Sutherland
Edited Date/Time 12/3/2015 12:39pm
I've seen some people with issues on these. Sticking open and dumping fuel into the motor. I know the 10-11 were notorious for it. I watched it happen to a low hours 15 at the track not too long ago.

I thought "well, if this issue is common, surely I can get on the internet, google it, and see an aftermarket alternative, or a fix."

But there is next to nothing out there. Surprising. I can't imagine that the "fix" is to replace an injector that fails at 10 hours with the same injector. Is it related to pump gas? (I run straight Cam2 anyway)

How many cc does the stock injector flow? I'd like to start digging for an aftermarket alternative from RC, ID or someone reputable.
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slipdog
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slipdog 12/1/2015 6:10am
12/1/2015 6:10am
Find yourself a local shop that does ultrasonic injector cleaning and they can do floe tests. That's what I did and the flowed it, cleaned it and flowed it again with a chart of before and after readings.

I do think it's the crap in pump gas that mucks them up the fastest.
Rich Piano
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Rich Piano 12/1/2015 8:08am
12/1/2015 8:08am
2 stroke injectors work fine for 10 plus years, even 20+ on outboards.
Just Bosch brand usually. How come cars dont have these problems? And most dont even use a top tier gas.
Reefer Sutherland 12/1/2015 8:57am
12/1/2015 8:57am
Rich Piano wrote:
2 stroke injectors work fine for 10 plus years, even 20+ on outboards. Just Bosch brand usually. How come cars dont have these problems? And most...
2 stroke injectors work fine for 10 plus years, even 20+ on outboards.
Just Bosch brand usually. How come cars dont have these problems? And most dont even use a top tier gas.
That's what I am saying. I am going to find the automotive equivalent of that injector.

I even saw where MXA's "solution" is to "smell your dipstick before each ride, and if it smells like oil, change your oil."


That's like saying the solution to a bad headgasket is to check your oil for water, change your oil, add water to your radiator and go riding.
thomas mitchell 12/1/2015 11:48am
12/1/2015 11:48am
I have a 12 crf450, stone stock. It is hit and miss on gas in oil. I did wire in a fuse to the fuel pump to kill it - it didn't help. I have a twin air gas tank sock and put additive in the gas to help with ethanol related problems. When I start it I pull out the fast idle and don't touch the throttle until good and warm. That seems to help more than anything.

The bike runs well and in all of these cases you never hear of black smoke while running.

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kiwifan
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kiwifan 12/1/2015 11:54am
12/1/2015 11:54am
I raced a 2014 and 2015 Honda 450 and never ever had a problem, first time I have heard of it actually...the likely cause is dirty fuel rather than an injector/bike problem
Jaybird67k
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Jaybird67k 12/1/2015 12:16pm
12/1/2015 12:16pm
If my memory serves me correct I thought the CRF injector issue was that while sitting for a while the injector would weep and let fuel run on top of the piston and migrate down into the oil. Like it wasn't seating unless it was receiving voltage.
Just seems I remember reading that.

Jason
FGR01
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FGR01 12/1/2015 12:34pm
12/1/2015 12:34pm
Gas in the oil is a well known prob on all 4-stroke MX bikes and for whatever reason seems to be much more prevalent on the CRF450. There are tons of theories floating around on the cause but, as far as I've seen, no one has really been able to nail it down.

Some guys swap their injector and say it fixed it. Others say it didn't fix it.

Some guys put a switch to kill the voltage to the fuel pump to relieve the pressure behind the injector. Some say it stops the prob and others had no luck.

One guy on Thumpertalk removed his subframe and put a clean paper towel under the injector to verify if it was dripping while the bike sat. I believe he found no evidence of dripping.

Some speculate that overly rich mapping is the cause. Some feel if the bike was rich enough to cause blowby past the rings it would run horribly and show on the plug. Some have leaned their mapping way out and still have the prob.

Like I said, mysterious prob.
Skerby
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Skerby 12/1/2015 12:38pm
12/1/2015 12:38pm Edited Date/Time 12/1/2015 12:39pm
I heard that it had something to do with kicking the bike past tdc or something like that. Like theres a spot where the injector will just dump fuel.

Seems weird though, im sure that the capacitors dont store enough power to run the fuel pump for any long period of time.
BobPA
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BobPA 12/1/2015 1:03pm
12/1/2015 1:03pm
kiwifan wrote:
I raced a 2014 and 2015 Honda 450 and never ever had a problem, first time I have heard of it actually...the likely cause is dirty...
I raced a 2014 and 2015 Honda 450 and never ever had a problem, first time I have heard of it actually...the likely cause is dirty fuel rather than an injector/bike problem
This
Bruce372
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Bruce372 12/1/2015 1:10pm
12/1/2015 1:10pm
a friend of mine had it happen on a RMZ450 when he ran it a couple of times in cold conditions.
FGR01
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FGR01 12/1/2015 1:20pm
12/1/2015 1:20pm
Skerby wrote:
I heard that it had something to do with kicking the bike past tdc or something like that. Like theres a spot where the injector will...
I heard that it had something to do with kicking the bike past tdc or something like that. Like theres a spot where the injector will just dump fuel.

Seems weird though, im sure that the capacitors dont store enough power to run the fuel pump for any long period of time.
The pump doesn't have to be running. When the bike is running the pump keeps about a steady 50 psi of fuel pressure from the pump all the way through the high pressure hose to the back of the injector. When you shut the bike off your are killing the ignition. The theory is that this 50 psi is still sitting behind the injector and slowly dissipates as the bike is stored by weeping fuel past an injector that does not close/seal properly. This is the purpose of the fuel pump cutoff switch that some install. instead of stopping the engine with the ignition kill switch, you stop it by cutting off the fuel pump. that way the fuel pressure is relieved behind the injector as the bike dies.
FGR01
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FGR01 12/1/2015 1:24pm
12/1/2015 1:24pm
kiwifan wrote:
I raced a 2014 and 2015 Honda 450 and never ever had a problem, first time I have heard of it actually...the likely cause is dirty...
I raced a 2014 and 2015 Honda 450 and never ever had a problem, first time I have heard of it actually...the likely cause is dirty fuel rather than an injector/bike problem
BobPA wrote:
This
I've been running a tank filter sock on my 2012 CRF450 since day 1. It has never had unfiltered fuel. Yet I have a slight smell of gas in my oil, even though I change it every 3 hrs.

If dirt in my fuel is causing my injector to stick open it's some awesome shit because it is getting past my sock filter and my fuel pump filter. It would also be strange that dirty fuel seems to be affecting CRF450's disproportionately more than any other bike.
526
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526 12/1/2015 3:03pm
12/1/2015 3:03pm
Rich Piano wrote:
2 stroke injectors work fine for 10 plus years, even 20+ on outboards. Just Bosch brand usually. How come cars dont have these problems? And most...
2 stroke injectors work fine for 10 plus years, even 20+ on outboards.
Just Bosch brand usually. How come cars dont have these problems? And most dont even use a top tier gas.
Reefer Sutherland wrote:
That's what I am saying. I am going to find the automotive equivalent of that injector. I even saw where MXA's "solution" is to "smell your...
That's what I am saying. I am going to find the automotive equivalent of that injector.

I even saw where MXA's "solution" is to "smell your dipstick before each ride, and if it smells like oil, change your oil."


That's like saying the solution to a bad headgasket is to check your oil for water, change your oil, add water to your radiator and go riding.
And yet another reason to stay as far away from MXA as possible !!!!!!!
Reefer Sutherland 12/1/2015 3:26pm
12/1/2015 3:26pm
Putting it at tdc would only let it pool on the back of the intake valves. Dumps into the motor when you kick it.

The injector leaks when the bike sits because it sticks open.

lumpy790
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lumpy790 12/1/2015 7:00pm
12/1/2015 7:00pm
was at a shop a couple weeks ago when a Parts Unlimited rep came in with a Motion Pro injector cleaner. Maybe the injector is clogging open?
Rich Piano
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Rich Piano 12/1/2015 9:28pm
12/1/2015 9:28pm
sounds like a 4 stroke problem because EFI 2 strokes have never had these problems.
Hell outboards sit for months and months or years and start right up.
Fraser
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Fraser 12/2/2015 5:19am
12/2/2015 5:19am
I had issues needing a new injector and fuel pump on a yzf450. I put it down to duct getting into the fuel through the breather pipe, we'd had very dry dust conditions. Fitted a splitstream fuel filter sock into the tank filler cap hole, and have never had an issue since. Use the same on my crf, no issues.
Rich Piano
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Rich Piano 12/2/2015 6:20am
12/2/2015 6:20am
Dont most bikes have a fuel filter that's constantly filtering the gas?
Seems like guys using tank filters and everything still have problems.


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thomas mitchell 12/2/2015 7:12am
12/2/2015 7:12am
If its leaking while sitting and you have it at tdc wouldn't you feel it through the kickstarter as soon as the intake valves dumped the trapped fuel. It should kickback shouldn't it.

Jaybird67k
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Jaybird67k 12/3/2015 12:39pm
12/3/2015 12:39pm
thomas mitchell wrote:
If its leaking while sitting and you have it at tdc wouldn't you feel it through the kickstarter as soon as the intake valves dumped the...
If its leaking while sitting and you have it at tdc wouldn't you feel it through the kickstarter as soon as the intake valves dumped the trapped fuel. It should kickback shouldn't it.

No because the auto decompression is holding one exhaust valve open at kicking speeds.

Jason
gt757
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gt757 9/22/2017 11:00am
9/22/2017 11:00am
I have this same problem with my CRF 450 17 but instead of sticking open its sticking close, all of the sudden cuts off and would never run again unless i take it off and make it to unlock, thankfully the bike didn't cut off on a jump...

Does anybody know what could be making the injector to shut close?

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