Engine Quickly Overheating

[iforce]

hi guys

my 05 trx450r overheats very quickly. i plan on tearing it down this winter. but......can anyone suggest what i should check (or replace) first?

[Pacheco_450r]

Just throwing some stuff out to check for...

-Lean Jetting
-Thermostat
-Water Pump
-Badly adjusted clutch

I would check these things BEFORE you tear it down.

[eastside 400]

what is making you think that its overheating? blowing coolant out?

[mhsrb23]

make sure theres no air in the coolant lines did you change anything?

[iforce]

thank you for the responses.

-lean jetting: haven't changed the jetting, so shouldn't be that
-thermostat: i never thought about this
-water pump: how do you know if this is bad?
-clutch: the clutch probably could use a little adjustment. but, i think its ok.



the reason i think its overheating, is because i can hear bubbling/gurgling in the radiator after a very short ride (couple trips around the yard). haven't noticed any spewing though.

[eastside 400]

easy check on the thermostat is to just remove it and see what happens. Another possiblity is a blown head gasket, it might not be actually overheating, it might just be putting cylinder pressures into the cooling system

[iforce]

Originally posted by eastside 400
easy check on the thermostat is to just remove it and see what happens. Another possiblity is a blown head gasket, it might not be actually overheating, it might just be putting cylinder pressures into the cooling system

very good info, man. i appreciate it.

[Ruf Racing]

Originally posted by iforce
the reason i think its overheating, is because i can hear bubbling/gurgling in the radiator after a very short ride (couple trips around the yard). haven't noticed any spewing though.

Take it for a longer ride. If it is the head gasket, it will blow out the overflow. If no blow by, maybe just some air in the system.

[Kovatch]

Originally posted by Ruf Racing
Take it for a longer ride. If it is the head gasket, it will blow out the overflow.

You will definitely get a nuclear green substance from the tubes if you have coolant & oil mixing. Looks like a radioactive snot rocket. It may not pour out, but you might notice it building up on the end of an overflow tube.

Also, check your radiator's coolant level. Check before you ride/start the engine, after letting it warm up, then after a longer cruise, enough to keep some heat on the motor and "allow" coolant to blow out if that is the issue.

[eastside 400]

theres a few ways for a headgasket to blow, it can mix the oil and coolant or it can just go between the coolant passage and cylinder which just causes the cylinder pressures to go into the cooling system with no oil mixing. This is more common in my experiences on the quad/dirtbike engines.

[JBplays]

1. Take your plastic all the way off and clean the radiator fins. Sometimes you can't see a mud clump when the plastic's still on the bike.

2. Check carefully for any intake or exhaust leaks. If youve had the carb off or exhaust off make sure everything is lined up and torqued back down. And you dont have any leaks...

3. Is the fan not coming on?? That may be your problem right there. If the radiator is bubbling and the fan's not coming on you have a faulty fan motor or connection. You can check the fan by grounding the wire to the frame when the bike's running.

4. Has the bike sat for a long time with fuel in the carb? The float valve could be sticking and causing an issue.

5. If you get mad at it, take the thermostat out and ground the fan so it runs all the time.
That's what I did.

If none of that works check the manual... :D

[eastside 400]

i wouldnt think the fan would be a problem since he says it does it after a short time of running it around. i dont run a fan at all, as long as you dont sit and idle for long times the fan doesnt do a whole lot

[iforce]

to answer a few of the additional questions......

yes, it has sat for awhile. its been ridden only a handful of times over the past 2 years.

the fan does not come on any more


i'm wanting to get it ready for xc racing (again) next spring. its also got a nasty rattle/slapping sound when lugging. the power is still there, though. i'm thinking this could be the cam chain tensioner?

[fomospede]

its known that the timing chain will stretch when hot so probly is shot
as for the overheating pressure test it

[400exrider707]

Unreal...

Do NOT take the thermostat out, that's a sure fire way for it to OVERHEAT!

The thermostat not only aids in heating the engine up faster, but it also regulates the flow of coolant. Without it there, the coolant will flow TOO fast and blow through the radiator without enough time to actually dissipate heat. So do not remove it.

However, I bought an 04 450R that we built from the ground up, and oddly enough never checked the thermostat situation out when we built it. Had it together and it would overheat pretty quick. Went to yank the thermostat out to test it, and sure enough... there wasn't one in there. Someone had removed it previously. Threw one in, worked like a charm and didn't overheat again. This was a 14:1 compression bike with no fan either.

You can test the thermostat by removing it from the quad. Throw it in a pot of boiling water. If it opens, it's still good. If not, it's junk.

[DnB_racing]

Originally posted by 400exrider707
Unreal...

Do NOT take the thermostat out, that's a sure fire way for it to OVERHEAT!

The thermostat not only aids in heating the engine up faster, but it also regulates the flow of coolant. Without it there, the coolant will flow TOO fast and blow through the radiator without enough time to actually dissipate heat. So do not remove it.

lol......think about it,

the crf head has no thermostat and many run that with no heat issues,

the thermostat is for letting it come up to temp when its already hot the thermostat is full flow, it doesn't slow down flow when hot, it lets it flow fully

[JBplays]

I'm not going to argue with anybody about thermostat or no thermostat. Figure out what works for you and go with it.

But your fan helps ALOT in XC racing b/c your radiator gets clogged up with mud OFTEN when racing in that discipline.

I run my fan constant to blow the mud away from the radiator as well as keep air flowing when waiting to go during a bottleneck. And it does help!!
I wouldn't even start an XC race without a working fan.

[fomospede]

I agree with dnb
I've ran with without and gutted
And have best luck with in place OEM unit

As for running fan constantly
Will generate a lot of heat at the stator and where it out quick

If u race xc the radiator should be cleaned every race period
with a hi pressure cap

[DnB_racing]

Originally posted by fomospede
As for running fan constantly
Will generate a lot of heat at the stator and where it out quick

If u race xc the radiator should be cleaned every race period
with a hi pressure cap I 100% agree, a clean radiator is an absolute must to keep cool!!


but I dont think running the fan for extended time will prematurely wear the stator,

this is why I think this, but i might be wrong?
the fan has an amp draw of 2.5 amps X13.5 volts =33.7 watts... so its about the same as running the lights all the time,

the stator has a rating of either 130 or 150 watts (I forget)so even at an 80% power factor the stator has a safe working limit of at least 104 watts

[fomospede]

Honestly I doubt the fan would help clearing the radiators I spend as much time riding as cleaning thje radiator sometimes it is a meticulous job that works wonders on your ride!

[eastside 400]

you will not overheat without the thermostat, ive been running without one for 4 years now, hard MX racing, mud races and everything, no problems. Like said already, no dirtbike uses one and we have the same motor for the most part. I understand the concept but even with my high flow pump, it still is working flawlessly without a thermostat. I keep an eye on my temps with an infrared gun periodically and no problems what so ever even without the fan. all my riding is MX though