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Will start and idle, runs fine when on throttle, dies when I come off of throttle. Starts back up and idles? I got the bike from someone, so dont know what settings he had dialed in...............thanks a million- I want to go ride!
 

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I am having the same exact problem. I just bought a power commander 5 to try and take control of the situation. Can anyone tell me if the power commander can fix an ecu problem if the problem actually lies in the ecu? My bike is getting drowned in fuel so I cut back the fuel ratio for the stock map on a stock bike. It didnt really help but have added a jeep coil that works great. I have checked and cleaned the wiring all over it. I've replaced the coolant temp sensor, I've calibrated the tps and cleaned the 30amp fuse connector. I was hoping that if it is the ecu not working correctly that since both the fuel and ignition now comes from the commander that the problem may disappear. I am going to get an auto tuner as well. Can an injector be dumping way too much fuel?

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The power commander is only a piggy back unit.

It won’t fix an ecu issue.

Verify the battery is 12v+

The auto tune still requires a close base map to adjust from
 

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Ya the battery is at 12.8 and since I've been working with it I periodically put a trickle charger on it just because I'm spending more time starting it instead of having it running because of this issue. It's to the point now that I foul a spark plug after 5 min of it idleing due to far too much gas. I can tell that the gas is raising my oil level after maybe 15min idleing.
I am guessing that for as bad as it is I should start by replacing the ecu? I wont be able to test the injector or fuel pressure until sat. But I'm looking for ideas.

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Ya the battery is at 12.8 and since I've been working with it I periodically put a trickle charger on it just because I'm spending more time starting it instead of having it running because of this issue. It's to the point now that I foul a spark plug after 5 min of it idleing due to far too much gas. I can tell that the gas is raising my oil level after maybe 15min idleing.
I am guessing that for as bad as it is I should start by replacing the ecu? I wont be able to test the injector or fuel pressure until sat. But I'm looking for ideas.

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(Your quote: I can tell that the gas is raising my oil level after maybe 15min idleing...)

It might NOT be an ECU problem...low compression can cause your symptoms too...!!!

Check if fuel is getting into your oil by smelling it for gas....If so...you might have bad piston rings...also do a compression test...!!!

•Hold the throttle wide open and crank the engine with the
electric starter several times. When the gauge stops ranging,
stop cranking and read the gauge.

Cylinder Compression
Service Range 49.0∼ 81.8 psi) @900 r/min (rpm)
 

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Damn I was hoping it wasnt going to be low compression. I just got this kfx and I dont have any history with it.
I'm going to attempt to explain exactly what's going on in hopes that maybe you think its something else...I have a compression gauge but I need an adapter for it that's smaller than the one I have for the spark plug hole. I'll order one today.
Anyway yes I have smelled the oil and yes its diluted with gas. From tuning car engines I know that even with half way decent rings, if way too much gas is being added it makes it's way to the oil.
It only idles and I cant ride it more that 30 sec without it stalling and fouling the spark plug. I can start it pretty easily and it will run for 30 sec to a min before stalling. It wont stay running at 22 clicks ...I have to put it at about 15 clicks to get it at about 1800rpm. I can rev it fast but fully, and when the rpms come down it goes strait to stall. My spark plugs are saturated in fuel and I have to leave a plug out for maybe 10min so the flooding in the cylinder dries a lil and makes it easy to start again. With the pc5 I was able to turn the fuel percentage down a full 100% and it would run better but randomly miss about every 10 revolutions. I advanced the timing about 3deg and it helped but not too much so I put it back to zero. I am thinking about just ordering parts one by one until I figure it out. But I think a smart person would check the compression before that happens so I'll start by ordering that today.

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One more question...is the jug sleeves? Like I can take it and have it bored out? Or I have to buy the whole cylinder. I dont want to run race fuel so can I use a high compression piston and hotter cams?
Thanks for the help

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One more question...is the jug sleeves? Like I can take it and have it bored out? Or I have to buy the whole cylinder. I dont want to run race fuel so can I use a high compression piston and hotter cams?
Thanks for the help

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(only) If the cylinder is bad/scorn or worn out...such as dirt getting in through the intake....!!!

No it's not sleeved or can be bored out like a typical steel cylinder...the kFX cylinder is aluminum with a nikasil coating...So you'll have to have it re-plated if bored out...!!!

bore & re plate I recommend https://www.millennium-tech.net/serviceInfo.php?id=1

or you can have it sleeved locally or send it out to be sleeved.... https://www.lasleeve.com/cylinder-sleeves/l.a.sleeve-sleeve-ka5675
 

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One more question...is the jug sleeves? Like I can take it and have it bored out? Or I have to buy the whole cylinder. I dont want to run race fuel so can I use a high compression piston and hotter cams?
Thanks for the help

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The highest piston ratio to remain on pump gas is 12.8:1 that will require around 93 octane...13:1+ is 98 or higher octane...!!
 

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The more I think about it the more I think ur right. I ordered the compression fitting for the tester. So I will know on sat or sun. I really appreciate the info.
I will likely stay with the stock compression ratio. Do I understand this correctly that I can just buy a pair of 06' kx450f cams and slap them in there with no extra work?

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The more I think about it the more I think ur right. I ordered the compression fitting for the tester. So I will know on sat or sun. I really appreciate the info.
I will likely stay with the stock compression ratio. Do I understand this correctly that I can just buy a pair of 06' kx450f cams and slap them in there with no extra work?

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Yes! 06~08 KX cams will work...you'll have to check & adjust the clearance if needed when you install them...!!
 

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I see where some kx450f cams fit 06-13' model. Stage 1 and 2. Is my only option to use stock kx450f cams from only 06 to 08?

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I went ahead and ordered a wiseco stock top end rebuild kit. Hopefully I can just replace it and get a few months out of it. I'll rebuild the entire engine top and bottom probably next winter. I need time to read and plan a path to get the most amount of power possible with out using anything over 93 pump gas....what would you recommend?
I already have a fci intake and a full dasa exhaust but I haven't installed them yet. I wanted to leave it alone until I could find the problem. I will also get the auto tune for the pc5.



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I see where some kx450f cams fit 06-13' model. Stage 1 and 2. Is my only option to use stock kx450f cams from only 06 to 08?

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KX450F cams 06~08 work great,

09 ~ present only the intake can be used due to the change in the KX head being 5mm shorter

The exhaust 09~present will have piston/valve contact...!!
 

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Well I just did the compression test and cold engine throttle closed was about 63 and cold wot was 75psi. So I dumped the fuel out into a clear jug and it was obviously mixed. I've had 2 strokes my entire life. I already have the kx cams... how much work would it be for me to put them in without a top end rebuild?

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Well I just did the compression test and cold engine throttle closed was about 63 and cold wot was 75psi. So I dumped the fuel out into a clear jug and it was obviously mixed. I've had 2 strokes my entire life. I already have the kx cams... how much work would it be for me to put them in without a top end rebuild?

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It's easy with basic mechanical skill...!

If you have a service manual for torque spec's & this thread will take you through the valve clearance measuring/adjusting... https://www.kfx450hq.com/forums/important-information/7948-valve-clearance-cam-timing-valve-cover-gasket-plug-o-ring-decompressor.html
 

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So the guy I got the bike from says that he thinks that there are stage 2 hot cans in the engine right now. I have these kx cams and I have the head apart. How do I identify hot cams or stock kfx cams... or do I have to use a caliper?

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Well the kx cam lobes are clearly about a quarter in. taller than the cams in the engine so I started to remove them and the front right bolt on the exhaust cam is stripped and just sitting there. I'm very versed in mechanical engineering but I find it much more useful to ask someone who is experienced on a particular platform about that platform. I now have the idea that I may need to do a complete engine rebuild.

Is it possible to heli coil this or is there another alternative?

I removed the hole covers to check the timing marks on the left engine cover. Should there be small amounts of oil in there or is a lower end seal gone bad?

I really appreciate you helping me out.
Thank you

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