kdx50 oil injection?


30 replies to this topic
  • DesertCR

Posted October 26, 2012 - 06:23 PM

#1

Just bought one for my nephew and was wondering if I can just run mixed gas in the fuel tank instead of using the oil injection? Also, anything I should know about the bike. Ive read that there are some power restrictors on the bike and can be removed? Btw not sure on what year it is, still waiting on the title from my friend.

  • lethalweapon100

Posted October 26, 2012 - 07:05 PM

#2

Just bought one for my nephew and was wondering if I can just run mixed gas in the fuel tank instead of using the oil injection? Also, anything I should know about the bike. Ive read that there are some power restrictors on the bike and can be removed? Btw not sure on what year it is, still waiting on the title from my friend.


Yes, you can. Make sure there's no oil in the injectors though

  • DesertCR

Posted October 27, 2012 - 01:59 PM

#3

Ok thanks. How about the power restrictors?

  • lethalweapon100

Posted October 27, 2012 - 02:14 PM

#4

Not sure, never owned one. Someone in the thread did the oil thing and said it worked.

  • Chokey

Posted October 27, 2012 - 02:34 PM

#5

If I'm not mistaken, the KDX50 engine can't be run on pre-mix because the right side main bearing won't receive any lube that way.

  • lethalweapon100

Posted October 27, 2012 - 03:48 PM

#6

Oops

  • Smacaroni

Posted October 29, 2012 - 06:09 AM

#7

I don't know the specifics on the KDX50, but the oil-injection systems are stone cold reliable. They just work and they work well. I know of one confirmed failure on a 30-someodd year old bike that had been ridden hard, put away wet and left outside most of it's life. It was TS125, IIRC which is one of the bikes that require a pump because of lubrication issues, fortunately, the owner realized something went wrong before it cooked the crank bearings. There are several bikes that will die quickly if you attempt to bypass the oil injection.
OTOH, I have met many people who think they are doing something positive and find that they're facing an uphill challenge, many eventually give up and go back to oil injection. A few determined individuals have completely hosed a motor. I have one that I intend to dismantle and rebuild when I have time, both a crank bearing and the big-end bearing are trash - on a PW80 which are practically indestructible.
Oil injection is a good system, let it work the way it's intended.

  • lethalweapon100

Posted October 29, 2012 - 07:32 AM

#8

I don't know the specifics on the KDX50, but the oil-injection systems are stone cold reliable. They just work and they work well. I know of one confirmed failure on a 30-someodd year old bike that had been ridden hard, put away wet and left outside most of it's life. It was TS125, IIRC which is one of the bikes that require a pump because of lubrication issues, fortunately, the owner realized something went wrong before it cooked the crank bearings. There are several bikes that will die quickly if you attempt to bypass the oil injection.
OTOH, I have met many people who think they are doing something positive and find that they're facing an uphill challenge, many eventually give up and go back to oil injection. A few determined individuals have completely hosed a motor. I have one that I intend to dismantle and rebuild when I have time, both a crank bearing and the big-end bearing are trash - on a PW80 which are practically indestructible.
Oil injection is a good system, let it work the way it's intended.


Yeah, ignore my advice. Use the oil injection

  • m_herb_h

Posted October 30, 2012 - 09:08 AM

#9

There are 2 restrictors installed from the factory. One is a washer in the headpipe and the other is a spacer in the carb.

1.To remove the headpipe washer, simply unbolt the headpipe from the cylinder and you'll see it. It reduces the exhaust hole size to about 1/4" - 3/8".
2.To remove the carb spacer, unscrew the top cap on the carb, and you'll see a brass spacer preventing the slide from opening all the way.

To be honest, the bikes are so anemic with the restrictors in place that most dealers removed them before they were sold.

  • DesertCR

Posted October 30, 2012 - 06:47 PM

#10

Thanks Herb. I've actually got a new problem. The bike all of a sudden started bogging really bad at mid to full throttle, almost as if really lean. Im hoping that the spark plug may need to be replaced because my friend did run the bike with premix and oil in the oil tank, probably fouled the plug, atleast Im hoping so...

  • Smacaroni

Posted October 31, 2012 - 04:11 AM

#11

If they ran it with premix in the tank, they probably didn't rejet it and thus it would run lean causing it to run poorly and hot.
That's assuming it's not one of the bikes that requires the pump and your friend hosed it. If so, the good news is replacing the crank and crank bearings are not that hard the bad news is to my knowledge, the only source for that bikes crank and bearings is Kawasaki, although having the crank rebuilt may be cheaper.

My suggestions for every new to you bike purchase:
#1 wash it if needed (I don't normally suggest buying bikes that need a bath, but I've done it.)
#2 tear down and soak the carb. Rebuild if necessary, but usually the gaskets are fine.
#3 general maintenance/inspection required per bike specs:
  • vale adjustments (4T)
  • Reed/cage inspection (2T)
  • spark plug
  • air filter cleaned and inspected
  • muffler packing inspected or replaced
  • tire inspection/pressure adjusted
  • brakes inspected
  • chain inspected/lubed if replacing, replace sprockets too (you wouldn't believe how many people I've bought hooked/lobed sprockets from who insist they're still good)
  • replace broken levers (almost always a problem on bikes I buy. Sometimes I straighten them out with a torch.)
  • check torque on "important bolts" (pretty much all the fasteners that if they come loose will kill you, steering stem, fork clamps, swing arm, etc.)
#4 start bike, if hard starting, drain gas and refill, drain carb bowl, start and ride for 20 minutes or so to ensure you're not refilling the carb with crap and check for undiscovered issues during pre-purchase test ride. Drain float bowl and put away unless I'm planning to ride it within a few days, then I won't drain the bowl.

  • Chokey

Posted October 31, 2012 - 10:12 AM

#12

Running premix in a bike with a functioning oil injection system will not cause it to run lean. The injected oil does not pass through the fuel system.

  • Smacaroni

Posted October 31, 2012 - 10:39 AM

#13

No, but diluting fuel with oil (and not leaving the jetting the same) will cause a motor to run lean.

ETA: clarification

Edited by Smacaroni, October 31, 2012 - 10:39 AM.


  • Chokey

Posted October 31, 2012 - 02:39 PM

#14

No, but diluting fuel with oil (and not leaving the jetting the same) will cause a motor to run lean.

ETA: clarification

But the oil injection does not dilute the fuel at all. It is injected directly into the crankcase (in most cases, some designs differ), without affecting the jetting at all. Yes, it will make the engine receive too much oil and will likely cause oil-fouling issues, but it won't cause lean jetting.

  • Smacaroni

Posted November 01, 2012 - 03:58 AM

#15

I see what you're trying to tell me, but forget the oil injection system at the moment....

What happens when I run 16:1 pre-mix in a bike previously jetted for 50:1? Runs very lean, right?

16:1 6.25% oil
50:1 2% oil
__________
----- 4.25% oil displaces this much fuel

Edited by Smacaroni, November 01, 2012 - 04:00 AM.


  • Joshx221

Posted November 01, 2012 - 04:27 PM

#16

I see what you're trying to tell me, but forget the oil injection system at the moment....

What happens when I run 16:1 pre-mix in a bike previously jetted for 50:1? Runs very lean, right?

16:1 6.25% oil
50:1 2% oil
__________
----- 4.25% oil displaces this much fuel


I'm curious now.... what would that amount to jet wise? One size, two sizes? In regards to the main.

  • Chokey

Posted November 01, 2012 - 04:36 PM

#17

I see what you're trying to tell me, but forget the oil injection system at the moment....

What happens when I run 16:1 pre-mix in a bike previously jetted for 50:1? Runs very lean, right?

16:1 6.25% oil
50:1 2% oil
__________
----- 4.25% oil displaces this much fuel

Adding or subtracting oil in the fuel makes the jetting richer or leaner because it changes the percentage of fuel flowing through the jets that is gasoline. Oil injection does not flow through the jets, so it does not change the fuel/air ratio of the fuel that is entering the engine. So yes, it will make the engine receive too much oil, but it won't make it run lean.

  • Joshx221

Posted November 01, 2012 - 04:43 PM

#18

Adding or subtracting oil in the fuel makes the jetting richer or leaner because it changes the percentage of fuel flowing through the jets that is gasoline. Oil injection does not flow through the jets, so it does not change the fuel/air ratio of the fuel that is entering the engine. So yes, it will make the engine receive too much oil, but it won't make it run lean.


This is exactly what smacaroni is talking about. Take the oil injection bike for example. Like you said no oil flows through the jets. Now forget the oil injection for now. Lets add some premix to the gas at any ratio. Same jets, now with premix through them, = Less gasoline to the engine at a rate directly proportional to the premix ratio.

  • Chokey

Posted November 01, 2012 - 05:28 PM

#19

This is exactly what smacaroni is talking about. Take the oil injection bike for example. Like you said no oil flows through the jets. Now forget the oil injection for now. Lets add some premix to the gas at any ratio. Same jets, now with premix through them, = Less gasoline to the engine at a rate directly proportional to the premix ratio.

Yes, you are correct, and I overlooked that aspect. Running premix would require re-jetting. I stand corrected! :thumbsup:

  • Smacaroni

Posted November 02, 2012 - 01:45 AM

#20

I'm curious now.... what would that amount to jet wise? One size, two sizes? In regards to the main.

It's more complicated than that and if it's a direct to bearing injection bike you'll kill it real quick
It would be quicker to link to the people who tried to outsmart the oil injection and finally realized how well OI works.





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