getting hot

11 replies to this topic
  • electric outlaw

Posted June 14, 2013 - 07:53 PM


I have a 99 yz400f and it seems to be getting hot pretty fast when trail riding. I t does it when at slower speeds or sitting still. I know they tend to run hot when moving slow or just ideling but it seems to be getting hot quicker than it should. I run rotella oil and 50/50 coolent/water mix. Any ideas?

  • jwleonard

Posted June 14, 2013 - 08:38 PM


Try engine ice or any like coolants for starters. If that doesn't help then you likely have another problem. You could have a blockage or partial blockage in a line, radiator, or water channel. It could also be the water pump too, they or notorious for going bad but it is usually for an external leak from the shaft seal.

  • ekulb14

Posted June 16, 2013 - 02:39 PM


also think about some heat reflecting tape at slow speeds radiant heat can really add up. tape the under side of your gas tank and the small radiator hose that runs right past the header. Could also wrap your header and mid pipe in a fabric wrap to reduce unnceessary heat.

Edited by ekulb14, June 16, 2013 - 02:40 PM.

  • Yz400f Jeff

Posted June 17, 2013 - 05:50 AM


I run engine ice in my 98 Iv never boiled it over but I never let it sit or idle for long at all if i plan on stoping for a minute i shut it down. Fire it up cold with the rad cap off and make sure the coolant is circulating.

  • jsmith4816

Posted June 17, 2013 - 05:45 PM


I run engine ice in my 01 426 and never had a problem. Knock on wood lol

  • electric outlaw

Posted June 17, 2013 - 09:40 PM


good feed back thanks looking at aftermarket oversized radiators to help with holding more coolant.

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  • jwleonard

Posted August 16, 2013 - 07:33 PM


good feed back thanks looking at aftermarket oversized radiators to help with holding more coolant.

Did you ever get a resolution to this; if so what was it & how well did it work for you?

  • mikedabike

Posted August 16, 2013 - 09:07 PM


If you don't have issues with freezing temperatures you can run straight distilled water and water wetter.  This combination transfers heat better than any coolant.

  • NitrousR1

Posted August 17, 2013 - 03:07 PM


On my 06 450 I did a athena 478 kit and a boysen supercooler at the same time. Even with the stock rads the bike will idle at full operating temp well over 5 mins without a drip out the overflow. I know the athena cylinder has bigger water ports, so i don't really know which one of the 2 mods took care of the over heating. If its really bad then try the boysen.

  • Chase Goodling

Posted August 24, 2013 - 10:02 AM


I had the same problem with my yz450f, got super hot and coolant was coming out through the over flow tube, it turned out to be the head gasket,  check that, might not be the answer, but for sure a possibility! :ride:

  • electric outlaw

Posted August 26, 2013 - 06:05 PM


never thought about the head gasket. I am having the valves adjusted soon and while they are in that far I will have it replaced. I have looked at the Boysen water pumps but didn't know of they were worth they investment or not.

  • torkd14

Posted August 27, 2013 - 06:13 AM


Racig my 2006 YZ450 in cross country's and hare scramble made the thing boil over all the time in slow sections and mud holes. Put on the Boysen super pump and added engine ice coolant, the thing only heats up in really extreme situations. Did wonders for the heating issue. That Boysen pump is pretty pricey so if your looking to upgrade your bike anytime soon probably isnt worth it.

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