YZ400F Coolant Overflow

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jb_dallas

Member
Feb 17, 2009
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I have read several threads on this topic and it seems there are alot of differing opinions. Today, I was riding some trails on my YZ400F and following a guy on a slow 4 wheeler. I dont know if we were not going fast enough to cool the radiators or if it is another problem. I would guess the first place to start is my radiator cap would you all agree? Arent the radiator caps on these bikes fairly universal? Couldnt I find a higher pressure cap? How would I know which one to buy? I read a thread about a guy that had my same bike and installed a radiator cap off of a KX500. Do I need to install an overflow bottle? I am running about 50/50 tap water and automotive antifreeze. The bike wont overheat on short rides, usually only when its ridden hard or really slow. Do the different types of coolant really help?

Thanks
 
J

jb_dallas

Member
Feb 17, 2009
498
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Ebay has several high pressure radiator caps. Some are labeled 1.6 and
others list from 20 to 30 pound ratings. My manual doesnt list any information on the pressures. If I bought a high pressure cap that keeps the coolant in the engine, I have a hard time believing that the engine would get hot enough under normal conditions to cause damage, but I guess it is possible. Does anyone have any information on this?
 
J

jb_dallas

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Feb 17, 2009
498
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Thanks Thump

Yamaha wanted $54 for the stock cap, I am wondering if Kawasaki is the same. I am thinking about buying one of those high pressure caps on Ebay. Do you all think that would work? I have a real moral issue with paying $54 for a radiator cap...ridiculous. Has anyone installed a temperature guage on these larger bikes? There is a place called jokersracing.com that sells a digital temp guage, mainly for racing atvs, but will fit most bikes. I am paranoid about my temperature issue now.
 
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_JOE_

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May 10, 2007
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Also, avoid using tap water. It's quite corrosive to the internals of the cooling system. Be sure you use coolant formulated for aluminum engines too. Next trip the grocery store grab some distilled water, it's really cheap and won't corrode or form deposits in the cooling system.
 
J

jb_dallas

Member
Feb 17, 2009
498
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I will use distilled water next time and the special antifreeze. Has anyone used those temperature strips? They have a reading from around 150 to 248 degrees and they are cheap. I suppose the disadvantage vs a guage mounted on the handlebar is that you would need to stop and read the strip.
 
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jb_dallas

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Feb 17, 2009
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I am curious why more people dont use the temp guages. I have read several threads about engine overheating/damage on this site. The one I found for $85 is digital, small, and light. An $85 guage or $10 temp strip could prevent the damage.
 
J

jb_dallas

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Feb 17, 2009
498
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I guess no one has comments about the temp guage/strips. I bought a high pressure cap and some temperature strips....I guess I will find out if that works the next time I ride.
 

Rich Rohrich

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Temp strips can only read the skin temperature of the cylinder, or radiator. There is a boundary layer between the skin and the moving fluid, so the skin temp doesn't provide much in the way of useful info.

While a temperature gauge is a nice idea in theory, it isn't very practical in this type of application. Shock, vibration, dirt, water, etc will kill it quick. Not to mention, it's next to impossible to read in realtime.

Keep the radiators clean, use the KX500 cap, fill the system with distilled water and a surfacant like Watter Wetter and you should be good to go for most MX situations that the bike was designed for.

Running slow in the woods isn't what this bike was built for and the radiators are small and light as a result. For this type of riding rigging a fan system like the Honda CRF450X uses may be necessary, or using some of the cooling system components from the WR400 might help.
 
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jb_dallas

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Feb 17, 2009
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The bottom line is that I need a CR450X or similiar, the delimma is that I dont want to fork out $4K for a decent used one. I paid $1300 for the YZ and love the bike, it is just not versitile. It is in good shape for a '99 and I see them sell all of the time on Craigslist for $1500-$1600. The wife would crap if I bought a $4K bike. In retrospective, I probably should have done more research before I bought the YZ. I am getting into riding after a long layoff and the world of 4 strokes has changed. When I was riding years ago, there were not 4 stroke MX bikes. Eventhough I love the YZ, I may consider an upgrade to something more trail friendly..... eventually.
 

Ol'89r

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Jan 27, 2000
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Install a coolant catch bottle from a WR. This will give you a little extra coolant in your system and a place for the coolant to go when it overflows. Also, gear your bike a little lower for the tight trails. Unlike a WR that has a low first gear for trail riding, the YZ has a tall first gear for MX. Gearing it lower will make is easier on the engine in the tight stuff.
 
J

jb_dallas

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Feb 17, 2009
498
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A guy here at work runs a 530 KTM and he installed a baby bottle for an overflow. He says it works great. He cut the tip and zip tied it around the hose. I will see how much Yamaha wants for a WR 400 overflow...if the price is in line with their $54 radiator cap, I will be getting a baby bottle.
 
J

jb_dallas

Member
Feb 17, 2009
498
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Thanks for all of the advise...

Hopefully, I will get my high pressure cap before the weekend. As for the temperature strips, I understand the whole barrier idea. However, I was thinking of using them as more of a benchmark than an accurate reading tool. For example, I would run the bike under normal conditions, get a reading, then I would have a benchmark to compare against when I was riding it hard or slow trail riding...just an idea. We will see if my theory works.
 
Y

youngnbald

Member
Oct 13, 2008
40
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This is what I have on my CRF450R.

http://trailtech.net/vapor.html

The trailtech vapor is AWESOME. I have hours of run time, RPM, engine temp, current speed, max. speed, max. enging temp., max RPM, etc. The temperature reads the coolant and is installed in line in the hose. I love this set up and have knowledge about what I am doing.
I made my own overflow bottle with parts from walmart. Cost about $8 at best. I think $50 otherwise. Instead of a baby bottle or turkey baster, I went into the automotive department in walmart and found what held the 2-4 ounces needed to be an overflow bottle. The part was by the engine cleaners and radiator fluids. I can't remember what is was at the moment, but I think it was a syringe to mix oil and gas to certain ratios. In the plumping department at Lowes, I bought a pvc cap that fit perfectly into the syringe (1/2" I think). Super glue the cap on top of the syringe and make a vent hole in the top. I can send my pictures if you would like.
Two BEST add-ons I have done to the bike!!!!
 
Y

youngnbald

Member
Oct 13, 2008
40
0
I am new on motorcycles and just bought the bike in October '08. Had the trailtech right away and love it. I have riding thru winter and a few trail runs in March. Never had issues with the trailtech and using the internal battery. This weekend I am hoping to wire the trailtech into the bikes electrical system. Right now I do not have the two LED warninging lights operating due to using the internal battery.
For the cost, you can't go wrong! So much knowledge is gained with the bikes performance and easy to schedule the repairs.
 
J

jb_dallas

Member
Feb 17, 2009
498
0
My wife bought me a vapor for my birthday. So far, I am very impressed. I will report on its durability, which would be my only concern. I already had the temp strips, so I tested their accuracy. I was surprised that the strips are very accurate, within about 2-4 degrees (I mounted mine at the top of my radiator). They came in a pack of 2, so I gave one to a guy here at work and he said that it works.
 
Y

youngnbald

Member
Oct 13, 2008
40
0
I have been using the trailtech all the time. Still loving it and no issues. I finally wired it to the bikes electrical and now have the yellow and red lights operational. The backlight is now brighter also and stays on. I made a custom mount for the handlebars and didn't even try to use the plastic mount it came with. Didn't want to spend $50 on their aftermarket mounts. With the ruts I made in the mud and now its dried up, the ride is extremely bumpy and tears you up. The trailtech is not phased by it.
 
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