2 Stroke Experts Help Me!

maDDtraPPer · Jul 12, 2009

I have a 2004 KDX 220R it has low hours and it's been running fantastic. I have been riding fairly hard lately and working long hours and so I parked the bike for a few days until I could catch up with the oil changes and chain cleaning ect.
So today did the maintenance, I use AvGas thats left over in drums from refueling aircraft, and I run my mixtures on the rich side. (32/1)
I finished up and went to warm the bike up and it started right away and ran for a few minutes and when I shut the choke off and it quit, I tried to cacth it with throttle and it just bogged out.
I checked around and I did find a spot where the air filter box was off a little bit and maybe some dust may have been getting in there. I fixed that and same thing. Start great on choke and bog out as soon as you shut it off.
Bike is bone stock, low hours. Only thing I do different is run 100LL AvGas. I am suspecting maybe someone here at work has done something as a joke to screw it up but thats also me bieng paranoid. I just don't know what could change in 2 days of not riding it?
Thanks

berger · Jul 12, 2009

I would change the plug first, it may be fouled. If that does not help I would disassemble and clean the carb.
Have you ever changed the muffler packing?

maDDtraPPer · Jul 12, 2009

Holy Fark! Too stuborn to go to bed I started with air first, removed the air filter and tried running it. Nothing. Well next is fuel obstruction so I take the line off the carb and the farkin thing is full of "Red Line High Performace Two Stroke Racing Oil" guarenteed to remain soluable my ***. I just mixed the friken stuff.
So I got a carb and airbox full of 2 stroke motor oil that for some reason didnt mix with the gas or seperated in the matter of minutes which seems unlikely. So here I go. Draining fuel, starting the bike - what a smokey mess.

schultzy · Jul 12, 2009

I used to run 50:1 without any problems. I remember getting an FMF pipe and Fredette sent me some new jets for my 98. Loved that bike! Wish I never got rid of it.

maDDtraPPer · Jul 13, 2009

I have been reading that a lot of people run 50:1. I think I will lean it out a bit. I think the AvGas burns cooler, and with the lead I really don't need that much oil.
I love the KDX. FOr up here it's perfect the damn thing is a mountain goat, and you don't even need a trail. Just point and go. Little on the soft side and I would like to get a bit more power out of it but thats only when the trails open up which is not very often.
Harder to ride then the Husaberg though. When I got back on the KDX after 7 months absence I crashed 2 times exiting the corners, just not used to that 2 stroke throttle response.

Freaky · Jul 13, 2009

I used to run a KDX250 a few years back and ran it 50:1, as long as your just using it off road it will run great 30:1 will just foul plugs if your tootling around. If your doing more fast road stuff then you'll need to increase the ammount of oil due to the longer durations you're off the throttle, no throttle no fuel and no oil. They are also jetted very rich from the factory, I had to go down 15 on the main jet until the plug chop came out right but it was a different bike afterwards. If you want to unleash some power then change the stock exhaust, I used a DEP front pipe with a KX back box and the difference was astounding.

http://www.dirtrider.net/justkdx/ is a geat site for more info.

Regards Freaky

Johnf3 · Jul 13, 2009

maDDtraPPer said:
Holy Fark! Too stuborn to go to bed I started with air first, removed the air filter and tried running it. Nothing. Well next is fuel obstruction so I take the line off the carb and the farkin thing is full of "Red Line High Performace Two Stroke Racing Oil" guarenteed to remain soluable my ***. I just mixed the friken stuff.
So I got a carb and airbox full of 2 stroke motor oil that for some reason didnt mix with the gas or seperated in the matter of minutes which seems unlikely. So here I go. Draining fuel, starting the bike - what a smokey mess.

You didn't mix the oil in the tank on the bike, right? The problem with the oil you describe happens when you mix the oil in the tank on the bike.

This can still be done, but the trick is to shut off the fuel petcock first, so the oil doesn't sink down and foul your lines and plug.

Otherwise, I have not heard of modern two stroke oils not staying mixed, once done properly.

maDDtraPPer · Jul 13, 2009

You didn't mix the oil in the tank on the bike, right? The problem with the oil you describe happens when you mix the oil in the tank on the bike.

This can still be done, but the trick is to shut off the fuel petcock first, so the oil doesn't sink down and foul your lines and plug.

Otherwise, I have not heard of modern two stroke oils not staying mixed, once done properly.[/quote]

Oops! Guilty on that one. When I scavenge the barrels of AvGas I usually end up with a surplus of gas and a shortage of jerry cans...and I had just the right amount left over for the gas tank...and yes I may have done exactly what you have accused me of doing. hahaha still not running but I only have 10 minutes here and 10 minutes there to work on it. Thanks!

Johnf3 · Jul 13, 2009

Yep, as soon as I read what happened, I sorta figured out the cause.

Just turn off the fuel at the petcock, and make sure the oil is mixed/dispersed before you turn it back on, and you won't have further issues.

maDDtraPPer · Jul 13, 2009

Well I flushed it, cleaned the plug which was nasty, and it still dies after taking the choke off. I am thinking that the air filter is maybe full of dirt and oil? Sounds like it's getting gas but not enough air when it bogs out on me????

Johnf3 · Jul 13, 2009

maDDtraPPer said:
Well I flushed it, cleaned the plug which was nasty, and it still dies after taking the choke off. I am thinking that the air filter is maybe full of dirt and oil? Sounds like it's getting gas but not enough air when it bogs out on me????

A couple of things--

First, replace the spark plug with a brand new one. Cleaned two stoke plugs are never the same once they become oil fouled.

Second, pull the float bowl off the bottom of the carb and remove the pilot jet and clean it really well. The holes in the pilot jet are tiny and are easily clogged, and straight two stroke oil can sure do that. While you are at it make sure the float bowl is clean and the main jet is clear as well.

Your air filter is probably not the issue, especially if it was fine before.

Do these two things above and I bet your bike runs fine again.

F+ · Jul 13, 2009

50:1 worked for me.

grasstrackpete · Jul 13, 2009

Use 50:1 def, what plug is in your bike?

BundyBear · Jul 13, 2009

Could easily have a puddle of oil in the bottom of the crankcase too? Nothing that a cloud of smoke when run under power shouldn't fix - if you can get it going well enough to do that.

maDDtraPPer · Jul 13, 2009

Ok so it's tip top now. I took the carb off, and took the bottom of the bowl off and saw a small amount of mix oil (the red stuff that caused the prob) so I took a can of contact cleaner and blasted into the top of the carb and a hole crap pile of red oil came spilling out of the bottom. I can only imagine that the actual bowl itself must have been clogged with it which explains the choke running but not the throttle. Lesson learned my tank must have empty when I put the oil in and then filled it.
Since I have the attention of the two strokers here what can I do the get some spring back into the rear? Is the nitrogen system rechargable or do I need new springs? I am in the central arctic so parts hard to get the season will be done by the time the parts arrive here. Have to make due and go with a winter shopping list for the rest.
Thanks for the help guys and also for that justKDX website. Awesome! It's no Berg but it is a great bike for trail riding.
My plug is a BR9ES and appart from the recent oil fouling I was able to clean it up nicely there was some slight lead fouling but nothing too serious. Once again no plugs around here so it's make due.

BundyBear · Jul 13, 2009

The nitrogen charge is only there to stop cavitation in the oil. It really does not add much to the spring force of the shock as the only area it can act on it the diameter of the rod.

You can increase the pre-load on the spring, but if this has sagged it is only a stopgap measure and does not really do the correct thing.

Is it sagged or is the shock not damping properly?

grasstrackpete · Jul 14, 2009

You need to change your plug up a heat range to BR8ES if your running avgas.

Pete

maDDtraPPer · Jul 14, 2009

Saggy Bottom

Well when the bike is sitting on the side stand I can push it down the first 4 inches with very little to no resistance. It's a 2004, the kid I bought it from used it very little (still on the original tire) but I seem to find the bottom more and more. Maybe I am just riding harder. I also may have put too much weight back there as I occasionally took people (female) for rides around town as there are no bikes up here so it's a bit of a novelty for them.
We actually use Nitrogen in the tailwheel actuator on the A/C so we have a bottle handy. But I think I will just ride as is and bring the parts I need up for next season to open the bike up and beef up the suspension.
So I am going to lean the mixture out and I will see about the spark plug. They might have some here as there is an abundance of snowmobiles around. Any quick and easy things I can do to open the bike up a bit? That was the first time I have ever seen the inside of a 2 stroke carb. Such a newbie huh? Damn.

schultzy · Jul 14, 2009

It sounds like your preload isnt set up correctly. I dont remember the sag requirements but it should be in the manual. If this fails i would send the shock to FRP racing. Jeff is a good guy and will set you up right!

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