05 CRF450 Idle/Overheating Problem

BlackForestCO
Edited Date/Time 1/27/2012 8:24am
Hey guys,

My dad recently started his 2005 CRF450 for the first time in a while and he noticed a couple problems almost right away.

He said that it worked for a little while he was just running around the yard checking it out, but it suddenly died. He figured it was because of the old fuel, so he swapped that out for some new fuel.

I guess after this the bike would start, but didn't want to idle. He said he changed the idle adjustment and go it to where it would idle, but it was erratic and would speed up and slow down.

Then, he took the bike down the driveway and back after letting it idle a few minutes (he said the total time riding the bike was a little over a minute), and that in just that amount of time the bike was acting like it was overheating, and even spit up a little coolant.

Has anyone experienced anything similar to this before? Are the problems separate or related to one another?

Also, does anyone happen to know the average idle temperature of the bike on a normal day (65-70 degrees)?

Thanks in advance to any information on the this problem, I appreciate you guys taking the time to look at it.
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mxgreg85
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mxgreg85 7/20/2010 6:19pm
7/20/2010 6:19pm
Make sure the rubber on the radiator cap is clean and smooth, no dings or cracks that would compromise the seal it makes with the radiator itself- if the seal is poor, coolant may sneak by at normal operating temp which would otherwise not be enough to depress the spring and spray coolant. The rubber might be a little worn and brittle if its the original cap. If thats not it, may be a water pump issue. As far as the idle, as its sat for a while, you might want to start by pulling the float bowl and make sure all is clean- doesn't take much condensation/debris to make it run funny. Good luck.
BlackForestCO 7/20/2010 6:29pm
7/20/2010 6:29pm
Thanks, my old man did mention something about the radiator cap possibly being bad, he just wasn't sure if the symptoms would be noticeable as quickly as they were if that were the problem. I think he was planning on checking that tonight though.

I will mention your other suggestion to him also.

Thanks for the help, I appreciate it.
mx295
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mx295 7/20/2010 9:11pm
7/20/2010 9:11pm Edited Date/Time 7/20/2010 9:13pm
4 Strokes run a lot hotter then 2 strokes because there are a lot of moving parts in the head. You can't let it sit and idle for a long period of time because all those moving parts create heat. There needs to be air flow threw the radiators to cool the coolant. Im pretty sure there isn't a problem with coolant "spitting" while it's moving right? And for the idle temp of the bike..It's WAY higher then 65-70 degrees. Start the bike up at night with very to no lighting around it. You will see the head pipe will be so hot it with be glowing red. That will prove how hot a 4 stroke runs.
BlackForestCO 7/21/2010 5:51am
7/21/2010 5:51am
mx295 wrote:
4 Strokes run a lot hotter then 2 strokes because there are a lot of moving parts in the head. You can't let it sit and...
4 Strokes run a lot hotter then 2 strokes because there are a lot of moving parts in the head. You can't let it sit and idle for a long period of time because all those moving parts create heat. There needs to be air flow threw the radiators to cool the coolant. Im pretty sure there isn't a problem with coolant "spitting" while it's moving right? And for the idle temp of the bike..It's WAY higher then 65-70 degrees. Start the bike up at night with very to no lighting around it. You will see the head pipe will be so hot it with be glowing red. That will prove how hot a 4 stroke runs.
I wasn't trying to imply that the idle temperature was 65-70 degrees, I was wondering what the average idle temperature was on an average day where the ambient temperature was 65-70 degrees.

I am aware the temperature is much higher than 65-70, I was just wondering what the range was because it didn't seem to specificy it in the service manual.

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Cygnus
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Cygnus 7/21/2010 6:35am
7/21/2010 6:35am
Sounds like the pilot jet is semi clogged. A lean condition will cause the bike to overheat.
lumpy790
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lumpy790 7/21/2010 7:41am
7/21/2010 7:41am
The running part is posibly gunk in the carb from sitting. As a bike sits the gas will evaporate and it leaves the additives in the carb......clean the carb and it should be fine. Sitting as little as 3 months can have this happen.

All modern race 4 strokes will puke coolant is you let them sit and idle for a minute......this is 100% normal.
motofab36
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motofab36 7/21/2010 7:54am
7/21/2010 7:54am
As these fellas said, it sounds like you definately need to clean the carb. The pilot jet is more than likely plugged or close to it. Remove the jets and spray them out with carb cleaner and blow through them with compressed air. If you look through the pilot jet and there is any doubt that it still is not prefectly clean then buy a new one. As Cygnus said, it will run hot if its lean.
CamP
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CamP 7/21/2010 8:28am
7/21/2010 8:28am Edited Date/Time 7/21/2010 8:29am
As mentioned, the pilot jet is probably blocked with fuel varnish. These jets are difficult to clean so you may want to spend $5 on a new one before you even start the job. You can remove the pilot jet without disassembling the carb. Rust remove the 17mm bolt on the bottom of the carb and this exposes the main and pilot jet. Remove the smaller brass jet with a flat head screw driver. I don't recommend taking the rest of the carb apart. THE FCR carb is fairly complex and you'll more than likely put it back together incorrectly and have bigger problems.

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