Superjet engine question..

[nightrider05]

Forgive me if this is a noob question..I am still learning about these motors. Ok..so I understand my 94 Superjet has the 701 motor with 61x case and 61x cylinders..but is it supposed to have a 62T head? I bought this ski not really knowing much about these and am learning alot as I go. Thanks!

 

[sflsurfrider]

they come stock with a 61x head.

 

[nightrider05]

So what exactly would the 62T head do for this motor?

 

[John_Ciocca]

Nothing....I believe the only difference are the water passages are slightly different. Performance wise it do zipo for you.

JC

 

[nightrider05]

Nothing....I believe the only difference are the water passages are slightly different. Performance wise it do zipo for you.

JC

Alright. Just wanted to check. Trying to figure out where all the previous owners were into.

 

[John_Ciocca]

I have the exact same ski you have. What mods have you done so far?

 

[sflsurfrider]

it could be a 701 62t head. if its a 760 62t, itll probably lower your compression.

 

[nightrider05]

it could be a 701 62t head. if its a 760 62t, itll probably lower your compression.

Thats seriously the reason why I wanted to ask this. I had thought a 62t could be from a 760..My compression is about 15psi low if I remember right..maybe even a bit lower. Was trying to troubleshoot and see if the 62t head could be the cause of this.

 

[sflsurfrider]

there could be specific markings or castings that would let you know the diameter of the domes w/o removing the head.

however, i dont know what they are. not sure if a 701 62t head looks identical to a 760 62t head or if yamaha put 61x heads on their 701 62t cylinders. :dunno:

ill bet someone here knows....

 

[WaveDemon]

isn't the 760 head stamped with a different number? 64x or something like that.

 

[Ottis]

Doesn't the 760 head use different exhaust mounting bosses?

 

[John_Ciocca]

it could be a 701 62t head. if its a 760 62t, itll probably lower your compression.

Why would a 62T head lower your compression? They are both mounted on a 61X cylinder.

 

[sflsurfrider]

Why would a 62T head lower your compression? They are both mounted on a 61X cylinder.

wider domes?

 

[John_Ciocca]

The 62T engine and 61X engine both use the exact same cylinder (a 61x cylinder). The pistons are the same in a 62T and 61X. I don't think inter-changing the (stock) heads changes compression.

Now if the heads have been modified all bets are off.

JC

 

[WaveDemon]

The 62T engine and 61X engine both use the exact same cylinder (a 61x cylinder). The pistons are the same in a 62T and 61X.

this is only true in a stock 1996+ superjet or 1996 blaster engine. There are plenty of 62t engines with 62t cylinders out there.

 

[nightrider05]

Its really no big deal. I am planning on buying an aftermarket head in the near future but was just trying to figure these motors out more.

 

[John_Ciocca]

If you were smart you would just get the head you have cut to the compression you want.

JC

 

[nightrider05]

If you were smart you would just get the head you have cut to the compression you want.

JC

Who would do that for me?

 

[Mouthfulloflake]

Not on a 61x cylinder, that is NO WAY smart.

if you want more compression on a 61x cylinder, get a girdled head, otherwise there is a greater risk of the cylinder cracking, ESPECIALLY with a head mounted pipe.

If you were smart you would just get the head you have cut to the compression you want.

JC

 

[John_Ciocca]

Not on a 61x cylinder, that is NO WAY smart.

if you want more compression on a 61x cylinder, get a girdled head, otherwise there is a greater risk of the cylinder cracking, ESPECIALLY with a head mounted pipe.

You're crazy...I've been running 180 psi on a B-Piped Superjet for years..no issues. Milling the stock head to 180 psi is a legitimate and safe modification. Give Pro-Tec a call....they do it all the time.

JC