Need help identifying mods / engine setup

[Wardvette]

I just bought my first stand up... a 94 SJ. The guy I bought it from got it from a friend that had a lot of work done to it but he didn't know anything about it. He said it had a different carb, head work, bored out, etc. I also found that it has a Riva red pipe, Moflo grate, Riva groovy ride plate, and a stainless impeller. The ski has a Solas sticker on it so I assume it is a Solas impeller. It was advertised as a 93 and didn't mention the pipe, grate, ride plate, etc. so I was very happy to see it was a 701 with those mods.

Once I got there, I found that it had about 150psi in the front cylinder but only 60 psi in the rear. I pulled the head off yesterday and was happy to see the head gasket was torn which would cause the low compression. However, I'm a bit confused on what work has been done. It appears to have 84mm pistons but a 6r7 head (650cc). He said it ran great when he put it away last fall. Here are a few questions:

Can I assume this is a 753 big bore engine?
Can I assume the head has been modified to work with this larger bore? If not, should I be looking for a 760 head?
Is a blaster 760 head gasket what I should get? SBT or OEM?
Can you tell if the cylinders have been ported?
What else should I be looking for in terms of mods?
What else should I check before bolting everything back together?

Thanks!

 

[TheBuzzard]

its definatly been ported. thats a stock 760 head gasket. what is the casting on the cylinder? 6m6, 61x, 62t ? not necessarily a big bore. i consider big bore when the sleeves have been replaced with oversized ones. any 701 sleeve can be bored to 84mm. those 93.92 pistons are some old stuff, cause nobody does that anymore.you can either measure the dome size on that head or just set the gasket on there and see if the sizes match up. if the domes are smaller, then the head hasnt been relieved for the 760 pistons. i'd say it has been. is the head damaged where the gasket was blown? i'd throw a new gasket on there and beat it. its probably got a modified CDI or an aftermarket one in there.

 

[tomski]

If that is a stock 650 head, it is the wrong one for that cylinder bore. You will need to install the correct head for it to seal.

This picture shows a 650 head that was used with an 82mm bore.



By the way, I have the head gaskets in stock when you are ready.

 

[Wardvette]

Thank you guys for the insight. Any idea what the markings on the head mean? It appears to say "4-23 Hvdak BB"

 

[CRJ]

im guessing date, name of person, and big bore.

i can also tell you bu looking at those pics that cylinder has been re-sleeved which is a good thing.

you will need a 760 head, or an AM head like a ADA or ATP. if you buy an ATP head i have 40cc domes that will fit your cylinder. they are for 84mm bores. they shoult give you around 150psi in each hole so you can keep running 87 octane.

 

[Wardvette]

Thanks again! Any idea how much power it should make with 185 psi heads and 93 octane?

 

[Big Kahuna]

94 Superjet came with a 701 motor.

 

[Wardvette]

94 Superjet came with a 701 motor.

Thanks for the help

 

[Wardvette]

Got the new head gasket in and it flies now! Just need to figure out how to get it to hookup now. Thanks!