please help??

5 replies to this topic
  • Mark_UK

Posted May 14, 2002 - 08:01 AM


my 98 yz400 was over heating in slow stuff
so i added a overflow tank off a wr.
the cap isnt an air tight seal and it seemd to empty but never fill

still the bike over heated
so i tried a 1.6 rad cap off a kx500
ok so as far as i can tell its not bubbled over since,
but twice now there has been water leaking from the front of the barrel, from the o-ring on the metal tube that connects to the water hoses.
i assume the higher pressure from the rad cap is highlighting other weak links in the cooling chain.
ive replaced the o-ring once and am about to do it again.

ive been filling the radiator to the top with pure distilled water, i guess the higher pressure cap isnt allowing the excess water to vent.
ideally id like some WR / YZ426 radiators which are slightly wider.

any ideas how i can cure this so i dont keep blowing orings?

  • Shawbridge Husky

Posted May 14, 2002 - 09:02 PM


Just a thought but have you ever tried a vented front plate?

  • Mark_UK

Posted May 15, 2002 - 01:27 AM


yeah hugh tried that didnt make to much difference

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  • Tony_Miller

Posted May 15, 2002 - 01:42 AM


I believe your problem is the "pure distilled water" part. You should always use some sort of coolant additive (anti-freeze), as these additives not only prevent freezing, they also raise the boiling point of the mixture above that of plain water. There are some motorcycle high performance pre-mixed coolants like Engine Ice that you might try (I have good luck with it).

  • PumpkinHumper

Posted May 15, 2002 - 01:51 AM


Ive had problems with my 99 yz400 overheating here are some ideas.

1. Redline Water Wetter in the radiator. supposed to make it run cooler.

2. Vented front Number plate

3. Drill a series of 3/16 holes on your radiator guards "black louvered things" to get more air to flow.

4. Boysen is supposed to be making a new water pump cover and impeller that is supposed to flow more coolant. IE run cooler.

5. Have a radiator shop strip the paint off the radiators. Bare aluminum is supposed to disipate heat away better than w/ paint.

6. Ive seen some company offer a fined round tubular aluminum gizmo that goes inline of your radiator line. It is supposed to help disapate heat. Looks a little sketchy to me though.

Ive done the top 3 things and it seams to help mine. I diddn't want to do a higher pressure cap. That diddn't seam like the right thing to do as you are finding out. Hope this helps.

  • PumpkinHumper

Posted May 15, 2002 - 01:53 AM


Hey. Try gearing your bike down. I went to a 13 tooth front. For some reason this seams to help out a bit. Plus it works a heck of a lot better in the tight stuff.


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