Engine builders chime in please

SXlover

SXlover

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Minot, ND
I'm working on rebuilding a 92 Kawasaki 650SX standup jetski. If I was to bore the cylinders 1mm over would I need to do anything to the head? I've heard I could leave it as long as pistons don't make contact and somebody else said to take 20 thousandths off it...advice?

Also any grease you recommend for it? Has a double seal on the end of the crank with grease between them.
 
I have bored dirtbike motors, V-8's, And a few other sled motors(older doo's) and never had to do anything to the head. Now i believe when making a 780 from a srx 700, you want to open up the chamber to match the bore. I think with a 1mm bore u are fine.
 
Ottawaair is correct.

The only thing shaving .020 of the head will do is raise compression ratio. With todays fuels, I wouldnt. As far as grease goes, I would probably put some red tacky grease (like Wolfs Head or the Napa equivalent) in there for its superior metal adhesion and water resistance. Same stuff they use on big rig wheel bearings.
 
SX700triple said:
Ottawaair is correct.

The only thing shaving .020 of the head will do is raise compression ratio. With todays fuels, I wouldnt. As far as grease goes, I would probably put some red tacky grease (like Wolfs Head or the Napa equivalent) in there for its superior metal adhesion and water resistance. Same stuff they use on big rig wheel bearings.
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Wouldn't it keep the compression the same? I think what the person meant was to "bore" the domes in the head open more. Not actually shaving the whole head down.
 
SXlover said:
Wouldn't it keep the compression the same? I think what the person meant was to "bore" the domes in the head open more. Not actually shaving the whole head down.
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the compression will be slightly higher simply because the piston under the dome is larger in diameter.

you could simply open up the outer bore edge to the new bore. Most times your head is about .010" larger diameter then the cylinder is. with you going over 1mm your now .020" each side larger cylinder bore, total .040" bigger. Just put head in a lathe and open up the edge to the new bore diameter not cutting it deeper, just larger diameter.

ADD: I would just check the squish first then guage what to do, some watercraft have huge squish clearance and it might not hurt a thing to leave it.
 
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mrviper700 said:
the compression will be slightly higher simply because the piston under the dome is larger in diameter.

you could simply open up the outer bore edge to the new bore. Most times your head is about .010" larger diameter then the cylinder is. with you going over 1mm your now .020" each side larger cylinder bore, total .040" bigger. Just put head in a lathe and open up the edge to the new bore diameter not cutting it deeper, just larger diameter.

ADD: I would just check the squish first then guage what to do, some watercraft have huge squish clearance and it might not hurt a thing to leave it.
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Well I've been asking about leaving it because I just don't have the tools to do it, and the one guy in the area who could do it lost his tools to the flood.

How to you check squish? because this is all new to me
 
Look it up on you tube for squish band testing, but you use a piece of solder bent in a L shape and put it through your spark plug hole. move the piston till it goes all the way up and squishes the solder, use a mic. to measure the thickness of the solder. this is a very basic explanation i am sure others will elaborate.
 
How tight should I torque the cylinder head studs to on this? I can't find it in the service manual. They are 10mm stock studs.
 
SX700triple said:
22 ft-lbs per sbt forums here
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I came across that thread in my search as well. But I think that's the head and not the studs, I called sbt themselves since that's where we got the cylinders and they told me 25 ft-lbs with loctite for the studs and head, but I think I'm just gonna take it in and have it done. I'm too nervous about possibly wrecking brand new cylinders on a jet ski that isn't mine. Don't really want to strip out the studs, if somebody else does it then I don't have to worry about it.
 
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SXlover said:
How tight should I torque the cylinder head studs to on this? I can't find it in the service manual. They are 10mm stock studs.
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you dont torq the studs into the case then torq the nut. the studs you can just double nut till they seat lightly and your done, the torq will be the nut that holds the head/ctylinder down onto the stud. Thats the right torq value for the 10mm nut as well.
 
mrviper700 said:
you dont torq the studs into the case then torq the nut. the studs you can just double nut till they seat lightly and your done, the torq will be the nut that holds the head/ctylinder down onto the stud. Thats the right torq value for the 10mm nut as well.
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Thanks mrviper700, now I understand it. I'll definitely tackle this tomorrow then. Use loctite on the studs into the cylinder?

EDIT: How much squish should I be looking for on this motor? Since I'm going to test that due to the 1mm over bore with a stock head.
 
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Well seems like everytime you work on something you run into problems. Was on stud 13 of 14 and all was going well, I unthread #13 since it was just thread in until I could get to it, mind you it threaded in and out perfectly. I proceed to put some loctite on it and as I try to start it with my fingers it wasn't working, so I start looking at them since I don't want to force it and mess it up, and a bunch of the top threads in the cylinder are pretty much gone. Just my luck. Idk if SBT messed up on that one or what the hell. So my dad is gonna run the cylinders to town and see if they can helicoil it or something. UGGGGGGHHHHHHHHHH!!!

Getting a new insert put in it today. Glad I got that taken care of. Now to get that back and it all together and check squish. What is a safe squish range for this jet ski? I believe it runs at 6000rpm tops if that matters.
 
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