Over Heating!

Hello guys, I'm new to this forum so forgive me if I make a few mistakes. I recently bought a used 2006 KX450F and have been having so issues with with. First when I got it home I started taking it apart to see what I had bought. I noticed the left side radiator was bent and had alumiweld on it covering a hole. I bought a new racing radiator so that problem was fixed. I then removed the carburator so I could install a new rebuild kit and the plunger for the Hot Start got stuck and the two fingers that hold the cable in broke off and I cant get the plunger out. I ordered a new plunger, cable and Pro Circuit male adaptor end. Here's the problem, When I reinstalled the carb the bike instantly got hot and coolant was coming out of the overflow. Also the bike was popping. Keep in miknd I havn't got the parts yet they had to order everything. Does this sound like the bike it running lean due to the hot start being stuck in the on position? I know the popping it a lean mixture issue. Would running lean cause the bike to over heat in about 1 minute? Thanks guys.

Yes, definetly. I just picked up a used '08 and same thing. The same part of the Hot Start plunger was broke off. Ran good with choke on but when I turned off the choke it backfired and popped on decel. I had to drill the center of the plunger and use a tap to get it out. I cleaned up all the oxidation on the inside of the Hot Start port with a small oval file. Then I installed new plunger and spring using a good graphite assembly lube to lube the plunger. Bike runs perfect now.

Just because I could, I also made an aluminum overflow/recovery tank that mounts to the inside of the radiator which works perfectly. You'll never loose coolant anymore.

Thanks Marc, did your bike also overheat?

I did get hot. I wouldn't say overheat because I didn't let it get that hot before shuting off. But yes, it did get pretty hot and will with a lean condition it will.

Hopefully that will be your only problem also.

I have a 07 KLX450r (same carb) and my hot start lever went really stiff. I am doing some other maintenance and stuff and tried pulling the carb. Same thing that hot start plunger is stuck!!!! I cannot get it separated from the carb, plus the plastic threaded pieced that would normally thread it in looks stripped now. Should I just cut it and get a new cable too or how the hell do I get that thing out!!!

I just got mine out today, I drilled a #29 drill into it and treaded it with a #28 tap and screwed a screw into it, # 8 screw about 2 1/2 inches long. I grabbed the top of the screw with plyers and hit up with a hammer until it came out. There was alot of calcium build up in there holding the screw in. As far as the plastic piece, I bought an after market aluminum part they sell that replaces it. You can get them on eBay it you search "hot start KX450F". O hope this helps!

When we (carb bike owners) check valve clearances, we should always remove the hotstart plunger and flush light oil down the hotstarter cable. When we wash our bikes we should not put high pressure water near the clutch lever. When your bike stands after washing let the left handle bar fall down/left, so any water in those cables pours back out. I use my hotstarter often in summer (now). When inspecting it, it is always oily but sometimes has a drip of water on it. I have the plastic fitting on the carb and it works ok with the right spanner and some care to engage the thread each time it goes back on.

If an 06 is jetted right (not lean) it should cope with a substantial amount of heat. I often ride in 35C or more (90+F) on tight tracks which are mostly 2nd gear so not much airflow. I know I'm not in first gear, and I only hammer it for 20 min bursts when it's real hot, so woods is more heat demanding, but the bike gets very hot, it might overflow a little coolant, but it copes with it and have never boiled. I have the original stock radiator cap (and should prob get a new one!). I always use 98 octane fuel (which is 95 in the US I think). I change the fuel screw very often, but I dont lean out the main jet for summer. I accept the power loss of running a bit rich. Bike has done 165 hrs. 130 on the current Wiseco piston. Inlets reshimmed once at about 90hrs and they were holding last time I checked. The engine rips but I rarely rev the crap out of it.

Thanks robloe, I finally got mine out too, I was able to pull it enough to spray a bunch of lube in there and then I let it sit overnight. Popped out no problem. I'll look for that aftermarket piece.

On a side note, I pulled the carb right out, cleaned it up, and changed my needle. When I put it back together, the throttle now seems kind of sticky and doesn't spring back like it used too. I had the cables disconnected, but I didn't take apart the guts of the carb, so it's funny it's sticky now.

Same thing happend with mine when I put it back together. The service manuel says to oil the cable on both ends and oil the behind the pully on the carb. This fixed the sticky feeling you are talking about. Don't be afraid to lube it well. I used WD40. Also the manuel says to use 2 stroke oil on the throttle tube.

WD40 is good for cleaning, but not as a long term lube, use something specific for that task, it will last much longer. Paul Krause (Sidewinder) has some semi dry chain lube that is far and away the best I have used, its much like the SLP the US Army uses to keep weapons moving freely, and it doesnt attract dirt and repels water.

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