06 yz450f hot and has hanging idle!!!


14 replies to this topic
  • asg5265

Posted August 14, 2010 - 06:49 PM

#1

So as a few of you may have read, I bought an 06 450. 2100 bucks and a hand full of problems. first cams were off 8-10 teeth each, fixed that, :banana:. changed sparkplug/ pilot to 48 and cleaned carb out. So I have a few problems now. It has a terrible hanging idle and just bad iddling habits. first it wont idle consistently, then when given a little bit of throttle, it revs up really quick and then hangs for a long time, I fix the hanging by touching the kill button which settles it. To add to this problem it gets HHHOOOTTTT!!! very quickly!! to quickly. So Im going to take the carb off tonite and check a few things, AP bladder is it in right position? and the carb slide. I need help knowing which way they go...Now about the thing getting hot. I think I am going to change the coolant, I should have already, I KNOW! :eek:. One radiator is slightly tweaked at the bottom, SLIGHTLY. Ive seen worse and they still work. So what should I check? the entire motor gets hot, the rads get hot, the header is hot 6 inches from. I just dont know. The coolant is my first guess cause its the easiest to do. But I think a bad impeller and deeper problem on the clutch side exists. I noticed that the idle settles out when I pull in the clutch, it slows a very tiny bit and smoothes out. sooo help me please! My 07 WR runs fine. I bet there is a serious problem with the valve seats since the valves were so far off. I think im going to take the head off any second now just to check. thanks for any help, any more details needed just reply back!

  • sacfelix

Posted August 14, 2010 - 07:11 PM

#2

My 06 had a hanging idle until I removed the plastic hot start cap and replaced it with an aluminim one. You should also check for air leaks around the carb and check the clearance on your valves. As for the bike over heating I only boiled over my bike a hand ful of times in the 4.5 yrs I owned it. I would not worry about the rads being slightly tweaked as long as they hold water with no leaks. What type of riding are you doing to make the bike over heat? The YZ's dont like to get lugged in tight single track and will almost always boil over if your not getting enough air flowing through them.


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  • asg5265

Posted August 14, 2010 - 07:18 PM

#3

well I checked/adjusted the valves when I did the cams. one intake was at .35!! .15 is max limit!!! hoot start isnt seized. and just letting it idle down in the street, not even putting it in gear, the bike will overheat or get very hot in just a couple of minutes, around 2 mins was what I did tonite. there is a problem somewhere in the cooling system. I just cant point my finger at it. ive never had the bike running for more than 3 minutes since I bought it 2 weeks ago.

  • Racerboi023

Posted August 14, 2010 - 07:33 PM

#4

I have 07 YZ450 like sacfelix said these bike will boil over if you putt around and idle allot you need to get moving and put some air thru the radiators. Your fast idle is a lean condition in your idle circiut. You can adjust this by turning the Pilot screw out this will richen the idle mixture. The pipes will glow on these bikes the 450 Quads do this also, good luck with your bike.

  • sacfelix

Posted August 14, 2010 - 07:43 PM

#5

well I checked/adjusted the valves when I did the cams. one intake was at .35!! .15 is max limit!!! hoot start isnt seized. and just letting it idle down in the street, not even putting it in gear, the bike will overheat or get very hot in just a couple of minutes, around 2 mins was what I did tonite. there is a problem somewhere in the cooling system. I just cant point my finger at it. ive never had the bike running for more than 3 minutes since I bought it 2 weeks ago.




The bike will boil over every time if you just idle the bike in the garage or the street. I would check the oil for any milky conditions and check the water pump cover for leaks. There is a weep hole in the cover that will leak fluid when the water pump seal is bad. You have owned the bike for 2 weeks now and you need to take it out and ride it to see if the bike will over heat from riding it. I would also replace the coolant as a peace of mind. As for the hot start plunger, mine was not seized either but the plastic cap was in bad shape so I replaced and my hanging idle went away.

What is your current jetting? I noticed the pilot but what about the rest of the jets?

  • asg5265

Posted August 14, 2010 - 08:23 PM

#6

i think a 168 main? and a jd kit at 4th clip from top.
usually I can idle a bike for a while and it wont get hot like that. I get my bikes hot before I ride em, but Ive just never had a problem with them getting this hot. Its crazy how hot it gets and how quickly it does. my KXF has the most inefficient cooling system on the planet and it will warm up from cold it takes about 3-4 mins before it gets real heat. this is my first 450 though. Ill try the carb cleaning again, all the little passages and what not, and look into a hot start connector. I was supposed to buy the thing, fix it up then sell it. hmmm... I think the valve seats and valves are all toast from being off for so long. Ill try running it tho just to see what happens. ill change the coolant first.

  • sacfelix

Posted August 14, 2010 - 08:37 PM

#7

When you fixed the valve clearances what shims did you replace them with? I know my YZ came stock with 178 shims on all three intake valves because after I broke her in I had to swap the two outside ones for 180's. You will know if the valves are shot because they wont stay in spec after a few rides. If you happen to take the head off you could pour some raw fuel in the intake and check for leaks or else you could just remove the valves and check them for cupping. I warm my bike up before I ride but it usually only takes a little over a minute to get her warm. You should not let any of the modern four strokes idle for 4 mins and not expect them to over heat.

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  • kylerf150

Posted August 15, 2010 - 06:31 AM

#8

i think your running lean in your pilot circuit.

1) high heat is a sign of a lean condition
2) A hanging idle is a sign of a lean condition

take her out for a ride and see how it runs if you get alot of popping on decel that is another sign of a lean condition (a perfectly jetted bike will have some decel popping) but a lean bike will have alot.
my yz 450 big bore gets hot fast just sitting still without moving and its running a little rich it also has a boyesen super cooler pump.

hows it start?
i agree with sacfelix get some miles on you shims and check them after a few rides. that will tell you if your valves are bad or not

  • asg5265

Posted August 15, 2010 - 06:41 AM

#9

thats the thing. Im running the JD kits recommended settings, 48 pilot and FS at 2 turns out. I think the carb has a clogged pilot circuit. Im going to take it apart today, clean it all up blow out all the little holes and ports. Ill check the timing again as well.

  • sacfelix

Posted August 15, 2010 - 10:55 AM

#10

i think your running lean in your pilot circuit.

1) high heat is a sign of a lean condition
2) A hanging idle is a sign of a lean condition


[COLOR="blue"][COLOR="Red"]It's also a sign of tight valves and an air leak from the intake boot.[/COLOR][/COLOR]

take her out for a ride and see how it runs if you get alot of popping on decel that is another sign of a lean condition (a perfectly jetted bike will have some decel popping) but a lean bike will have alot.
my yz 450 big bore gets hot fast just sitting still without moving and its running a little rich it also has a boyesen super cooler pump.

hows it start?
i agree with sacfelix get some miles on you shims and check them after a few rides. that will tell you if your valves are bad or not



[COLOR="Blue"][/COLOR]

I would think that a 48 pilot is by no means lean but a little rich for summer riding. I use a 48 pilot in the winter for that extra fuel the bike will need with the colder air but run a 45 in the summer because of the heat. Is your bike running the JD needle as well? Does it have the stock bore or a big bore kit? How many hours do you think are on the bike?

  • asg5265

Posted August 15, 2010 - 12:00 PM

#11

yes I have the JD needle in there, but i havent even opened the throttle past a quarter. the bike is believed to be a stock 450. I can only come to the conclusion that the pilot circuit has a clog in it. it has too! there is no other reason it would get that hot that quick then back fire and hang idle and do every thing else a lean bike would do. I bet the FS is effed up some how. well I cant tell you guys much more about the bike. other than it gets really hot really quick. only starts with choke on, hangs on idle, backfires a lot!, and just is a B! I have set everything to the best settings of my ability from previous four stroke experience. ill clean the carb, replace coolant, and check for cracks air leaks in the intake system. I might check the header to head connection to look for the crush copper gasket since the guy put on a different system.

  • asg5265

Posted August 15, 2010 - 09:46 PM

#12

So miraculously enough, one small jet was slightly clogged and good disassembly and clean of the carb and bam! runs like a charm. Im going to replace the coolant tomorrow with some real stuff, IDK whats actually in there...And then call it good. I did notice when the carb was off that the left and right intake valves had a been backfired into, thus there was debris and buildup on the seat and stem. Im not going to do much with that as of now, just try and ride it a little. I know the valves wont last being Ti and the valve seats being messed up Im sure...but they are alreay done for so wut du hey? I put the seat on and its ready to go! BTW the jet on the intake side of the main jet on the bottom, the one no one ever touches or changes was the clogged one thats the end of the story we can all sleep now.

  • grayracer513

Posted August 16, 2010 - 06:10 AM

#13

I did notice when the carb was off that the left and right intake valves had a been backfired into, thus there was debris and buildup on the seat and stem. Im not going to do much with that as of now, just try and ride it a little. I know the valves wont last being Ti and the valve seats being messed up Im sure...but they are alreay done for so wut du hey?

This is normal, and has nothing to do with backfire. As the intake port branches out into three ports, the heavier-than-air fuel droplets tend to travel straight down the middle port, washing the center valve clean in the process. The outer two get less of the fuel, so less of the deposit cleaning additives typically included in it, and stay dirtier.

The irony is that under most normal conditions, the center valve tends to go first of the three.

There is no reason to think that deposits on the back of the valve will shorten their service life. Again, what you describe is a normal condition.

  • kylerf150

Posted August 16, 2010 - 06:48 AM

#14

Im glad to see you got her running.Good luck and have fun.

  • asg5265

Posted August 16, 2010 - 06:59 AM

#15

I ordered some rads last night, so I can fix the twisted one then get ride!





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