top end problems after overheating

[accbr]

Finally got to take the ski to the lake yesterday with the new topend. I was trying to tune the carb by just blipping the throttle, half throttle runs, etc... when the overheat sensor kicked in. I noticed there wasn't any water coming out of the pi$$er either. Went straight to shore to check it out. Popped the hood, and there was water sizzling on the top of the motor. I let it cool down for about 10 minutes while I make sure no cooling lines came loose. Start it back, and watch the cooling lines. There's no water coming in from the pump. I'm guessing there's something stuck in the line coming off the pump????? Haven't checked that yet. My friend tows me back to the ramp as fast as a 750sx can pull an SJ with a 15 foot rope. He thought it was funny. :bs2:

I check compression today after work and I get 70 in the front and 170 in the back :banghead: :banghead: :banghead: I take the head off, and this is what I see. I'm hoping I can just change the head gasket. It was running really rich from looking at the plugs, but idled and ran great before this happened. Will a new head gasket fix this?? Please say yes!!!!! I have more pics of the both cylinders if that would help. Piston wash looks the same on both.

 

[aqua]

man what a bummer. so the head gasket is what was causing the compression issue? i would try another head gasket and see what the compression is then. hopefully it didnt mess up the cylinders. did it score them at all.....do the cyl walls look the same between the two cylinders...if they look close to the same i probably wouldnt worry about it and unclog that pisser next time.

hard to tell by looking at pics.

 

[cookerq62]

The compression is def that head gasket. How true is your head and cylinder?? It probably was over heating because of the head gasket but make sure to check all the lines and fittings.

 

[#ZERO]

That head gasket looks split around the metal sealing ring so if you were to do just the gasket you might be okay for a while.

I had a cooling line fitting break once and the engine ran without water for about a minute. The compression checked out okay but after a few weeks of riding one of the skirts on the front piston decided to break into a million pieces. Cast pistons do not like to be overheated for any period of time and that's one reason why I went with forged wiseco pistons.

 

[accbr]

The walls look the same on both cylinders, so I hope a gasket will fix it. Something clogged the line coming in from the pump. I started it after it cooled down to see if I had any water leaks, and there wasn't even any water coming in. I use the clear water lines, so I can see if there's any flow. I'm sure that's why it overheated. Would they heat up enough to blow the head gasket like that??

I'm never going to that nasty a$$ lake again. I've had two ice bags in my prop, two chunks wood, and now this.

 

[Mike W]

Just looking at the picture it looks fine. A new headgasket should fix it. To find the cooling issue I would blow compressed air thru the lines untill you find it.

 

[accbr]

I'll take the topend off just to get a better look at the bottom of the pistons too. I'll have to order a head gasket anyway. I was planning to go riding this weekend.

 

[SUPERTUNE]

Only use a OEM headgasket from Yamaha! Aftermarket headgaskets are not near as good and do blow out much easier. Make sure you get the right one too,
61X for the SN or the 62T for RN ski as the stock heads require the right one!

 

[accbr]

I'll order a couple on Monday. Do I need to worry about water ingestion in the crank since this gasket blew??

 

[accbr]

I found the other gaskets in the garage that I didn't use. They're WSM. I got them last year from a vendor on pwctoday.

 

[Mike W]

I used WSM head gaskets in the past and I believe one is still in use on my Blaster.

 

[accbr]

The problem was definitely a clogged cooling line. I don't know if an OEM gasket would have held up any better.

 

[accbr]

Well I thought this was a clogged line since there wasn't any water coming in from the pump. I took the ride plate off today to fix it, and noticed this plug was gone. It was on there when I put it back together. Would this keep water from being forced into the motor? This hole is bigger than the one that feeds the engine, so is the water taking the path of least resistance?

 

[Matt_E]

No, you would still get water through the other fitting.

 

[accbr]

That makes sense. The hole out the back of the nozzle is the path of least resistance. I'll blow some air through the lines and back flush it when I get the new head gasket.

 

[jeepmark4x4]

When you were testing the compression, you can hear if you are getting a leak out of the head gasket sometimes. I had the same thing happen to my 650sx motor, but than I ran a true two cooling lines from the pump and that made a HUGE difference.

 

[accbr]

That head gasket if definitely toast. Legdrag is sending me another one tomorrow, so hopefully that'll fix it. I still have to find out why water stopped flowing though.

 

[SurferSmurf]

check the flatness of your head on a granite plate if you can. my water line got clogged on a 650sx and the head warped. it was warped as much as 15 thousandths.

 

[keefer]

Only use a OEM headgasket from Yamaha! Aftermarket headgaskets are not near as good and do blow out much easier. Make sure you get the right one too,
61X for the SN or the 62T for RN ski as the stock heads require the right one!

Take Chucks advice and spend the extra couple bucks on a stock Yamaha head gasket. They have that good adhesive and will seal like no other. Check that head for flatness like the other guys are saying. Stock heads warp pretty easy. Be aware that the stock head gasket holes are bigger on one side. The bigger holes should be on the carb side to achieve more even cooling in the head.

 

[#ZERO]

Yep... That's good advice, also try not to touch the gasket on either surface, just grab it by the edges when handling it and set it into place. Another good tip is to wipe down the cylinder and head surfaces with acetone on a clean rag to remove any oil residue.