blown head gasket

[jetkid]

This is what happens when you put on the wrong head gasket and a cheep one at that on a superjet. Thanks to the company, that is no longer in business in the grand rapids area, for doing such a good job rebuilding this motor, haha. There were only two very little holes in the westcost head that were not blocked. Water was still coming out the pisser but not enough to keep it cool i guess. As soon as I felt it bog down i stoped riding and swam it in. Looked everything over, pulled the plugs and everything looked good. went back out when motor cooled but I stoped it after 15 ft because it was running like :soapbox: Did a compression test, 178 front hole, 120 back hole. Thought I just blow up a new motor! pulled the head off and found the wrong and cheep head gasket. Luckly it was just the head gasket. The pistion and walls still look great. Put on an OEM head gasket and trimed it a little bit to fit the westcoast head better and got 180 psi in each hole!! Ski ran great today but I feel like the motor and pipe got a little hotter than it should have. The heat sensor did not kick in. I will have to keep an eye on it next time i go out.

 

[Mile9c1]

What makes it the wrong head gasket? It's been awhile since I've seen an OEM head gasket but it seems it also had small holes for the water to flow through. The holes act as sort of a thermostat.

 

[jetkid]

yes I know that not all of the holes need to be open on the head but there still need to be some. The gasket covered up all the hole on the westcoast head. it did not line up. I use and oem and at least three of the bigger holes lined up.

 

[SUPERTUNE]

There are 2 type of headgaskets for 701cc engines!
The 61X headgasket is for the early model single carb 701's
and the 62T late model twin carb headgasket.
The differences are where the cooling holes are located in the gasket.
The early heads have long waterjacket slots around the chamber and are very prone to blowing the headgasket when upping the performance with bolt-ons and or milling the stock head and bigger bores that increase the compression ratio.
The newer design late heads have bridges instead of the long slots and this cured the headgasket failure problem the early heads had, but in doing so the old water bleed holes are right where the new head casting are so it blocks them! Can you spell disaster? You always can use the 62T Yamaha headgasket on any year, any combo, but not the 61X gasket!
Use OEM Yamaha headgaskets only for freestanding sleeve design cylinders!

 

[cattledog]

hey thanks for the great info supertune