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YZPaGuy

Overheating, I'm probably overreacting

7 posts in this topic

I bought an 08 YZ450F in August. Love the bike. Yesterday I was riding with family and friends when two of the girls stalled their bikes and couldn't get the started again. I left mine idling and helped them with their bikes. When I returned to my bike it was puking water out of the overflow. I immediately shut the bike down and pushed it back to the garage. After it cooled down I removed the radiator cap to inspect the fluid level. Of course it was low because of the puking.

The original owner used straight water and water wetter for the cooling system. Not knowing exactly how much water was in the system I dumped half a bottle of Water Wetter in the radiator and filled it up the rest of the way with water, it only took a small amount of water. I then looked up the specs on the cooling system and realized it only holds approx 1 quart of coolant total. I know I should have checked that first!

I then started it up and ran it about a half mile up the driveway and back to the garage. I pulled the cap and noticed bubbles at the top of the radiator. With cap on a small amount of water came out of the over flow.

Shortened version;

1)riding bike for 20 minutes between 2nd and 3rd gear

2)let bike idle for a couple of minutes

3)bike puking water

4)shutdown bike and let cool off

5)put too much Water Wetter in and some straight water

6)ran bike again and had small bubbles at top of radiator and small amout of water puking

7) put bike away before causing more damage, wanted to consult someone who knows

I searched the forum and came up with a couple of good posts but none matched my problem exactly. Just wanted to double check with you guys but so far I think I caused the problem by letting it idle. I didn't know I shouldn't do that. I did put too much Water Wetter in. Is that a problem? Should I drain the whole system now? Is there anything I should check before riding again? What temp should the side of the motor be when hot using a laser temp gauge?

I am in Pa and the bike has to be drained in November because the current fluid will freeze. What can I use that will give me good cooling but will not need to be drained for cold weather?

I know it's long winded but I don't want to cook my engine. Like the title reads I am probably overreacting but would rather ask some guys who know then cause a bunch of motor damage.

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Shortened version:

1)riding bike for 20 minutes between 2nd and 3rd gear

2)let bike idle for a couple of minutes

3)bike puking water

4)shutdown bike and let cool off

5)put too much Water Wetter in and some straight water

6)ran bike again and had small bubbles at top of radiator and small amout of water puking

...I dumped half a bottle of Water Wetter in the radiator and filled it up the rest of the way with water, it only took a small amount of water.

I highlighted your two biggest mistakes in bold.

  1. The YZ450 was intended to run a 50/50 mix of either ethylene glycol or propylene glycol coolant and distilled water. Straight water cools better than any coolant or coolant mix, but it boils at only about 235 with a 16 pound cap. A 50/50 mix, or any of the ready-to-use EG coolants will boil at around 265, and PG mixes at about 270. They don't cool quite as well, but they stay in the radiator better. A lot of guys find that a 30-35% EG/65-70% water mix works best for them. Freeze protection at 50/50 should be to at least 0℉.
  2. There is no cooling fan to force air over the radiators, and the water pump doesn't circulate much at an idle. The bike cannot normally be left to idle for more than 45 seconds, if that, without boiling over, especially when running straight water. Keep it moving, or shut down.
  3. Water Wetter is not a coolant, it's an additive. Read the label. You should only be using an ounce or two in a system as small as yours.

Drain and refill the system with the right coolant mix and a dash of WW. Fill it to only about 3/4" below the neck. You can fill it to the top, but it will push fluid out as it expands when it heats up.

If you avoid lengthy idling, the bike should not use coolant or boil over. Normal cooled off coolant level should be just over the tops of the tubes in the radiator. If you do a lot of serious or very technical trail riding or off-road racing, you may find that you need a battery operated fan system, or one of the several extreme high temp coolants that are available for that, but most people don't need those measures.

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Thanks for the reply greyracer! After reading several of the posts you answered on I figured it was my fault but I wanted to make sure. I will be racing harescrambles on this bike in April but for now the standard 50/50 should work.

I am assuming I can just use any over the counter 50/50 antifreeze? Or should I go to Yamaha and buy whatever expensive stuff they recomend?

Thanks for all the help. I just don't want to mess something up

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Most any good coolant will work, but try to get a first tier product that doesn't contain silicates if you can.

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With racing my shifter kart we are not allowed to run a traditional antifreeze. The do allow coolant "additives", and i've had great luck with Engine Ice. I observed about a 10 degree temp drop over straight water. Of course the stuff is pricey at $18/ half gallon.

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That's an example of people making rules they aren't smart enough to enforce. Engine Ice is nothing special, and it's not an additive. It's propylene glycol coolant and water premixed, with a surfactant added, and is a ready-to-use coolant. If the rules are that you aren't to use coolants because they present a traction hazard, as in Super Moto, then EI will put you in violation.

The 10 degree drop can be misleading if it's coolant temp you are reading. Coolant mixes will often show lower temperatures because they don't pick up heat from the engine as well as water. This will give you lower coolant temperatures entering the radiator from the engine, but higher cylinder head temps. To really gauge the efficacy of a coolant, you need to measure head temp, the temperature of the coolant leaving the engine, and the temperature of the coolant leaving the radiators and returning to the engine. The more effective coolant will be that which shows lower head temps, higher (at least proportionately) coolant temps entering the radiator, and a greater drop in temperature through the radiator.

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