mid rpm bog

[snoopjonnyjon]

I took my KX500 out tonight and it just wouldn't run right. Still will pull off idle, and seems to pull on top, but just hits a wall in the midrange. So I did a compression check, which was fine, and cleaned the carb. Took it for another ride and it still has a mid-rpm bog. I'm thinking I might have a problem with the KIPS being stuck or a broken reed. Maybe an ignition problem. I really don't know what to check next. I'm running VP110 mixed 32:1.

[Hillclimb#42]

 It could be that the powervalve is all gooped up in there and is just slow to open. Was it running well up to now? Did you recently change the needle or anything? If you pull the powervalve's little pastic cover off, start the bike and watch the rod. It should come all the way out with the rise of the rpms. 32:1 may not be burning off all the way, or maybe the brand you use at that ratio. Do you have alot of goop coming from silencer?

[Polar-Bus]

I agree, I am thinking a "spooged" KIPS.

In my experiences, if you have a broken reed you will hear intermittant backfiring.

[snoopjonnyjon]

This sounds like the likely answer. There's no goo out the silencer, but I have some coming out between the cylinder and the pipe. The bike was running strong up until now. I don't have much experience with liquid cooled engines with power valves, I am used to old air cooled engines with no power valves. My Can-ams and Husqvarnas seem to love a ton of oil (I normally run 15:1 to 20:1). As long as they aren't fouling plugs, there hasn't seemed to be a downside.  And the first couple tanks through the KX500 I was running C16 (117 octane) mixed 20:1. The engine ran awesome on this mix for 2-3 tank fulls, but it sounds as though its going to need a cleaning now because of it. Can I get at these parts with the cylinder on the bike, or do I need to pull off the top end?

[Polar-Bus]

20:1 !!!!!!!!!!!!!!!!!!   

Cripes, might as well pour a bucket of oil down the carb! LOL

seriously, run your premix around 42:1 even 50:1 if you are just a casual weekend play rider. Now I am thinking your crankcase is simply loaded with oil. The richer the premix ratio, the leaner your engine will run, because the added oil in the fuel moves slower through the carb.

Try 42:1, jet leaner (from stock) one or 2 main jets and you will be amazed at how a KX500 responds to leaner jetting...

[stock500]

Snoop, you need to get some Amsoil Intercepter, and run it at 50:1.  You may need to fatten up the jetting one size, but your bike will like it.  I run that oil at 50:1, and my bike likes it. 

[snoopjonnyjon]

So, if my crankcase has a bunch of oil pooled in it... what's the best way to deal with it? Just run at high speed for an extended period of time, or do I need to get in there to clear it out?

Polar-Bus says to jet leaner... stock500 says go richer. Any agreement here, or should I just leave the jetting alone for now and try less oil in the premix?

[martinfan30]

Snoop, you need to get some Amsoil Intercepter, and run it at 50:1.   You may need to fatten up the jetting one size, but your bike will like it.  I run that oil at 50:1, and my bike likes it. 

If you go leaner on the oil ratio, why would you increase the A/F ratio more to be even richer? Isn't it fact that when you go lean on oil ratio, that the A/F ratio richens?