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Squish Clearance

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SurfBeat

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I am helping a neighbor replace his crankshaft in a 94 GTX, 580cc.

Last summer when I did mine I did not check the Squish clearance because I "thought" that the procedure was only necessary under circumstances where work in performed on the top end.

In my case, since I only replaced the CS, when I completed that task, I simply replaced the gasket between both cases and sealed it up!

Was that a mistake? Should I go back and check the "squish," or was my thinking correct.

I don't want to screw-up my neighbors Doo and if I have to, I wil go back and pull my engine and figure out the Squish procedure.

I am asking because of a recent Thread posted where a member rebuilt his engine and fried a piston. Dr. Honda opined that the "squish" factor, maong others, could be at play.

I learned last summer to listen to what the Man (Dr. Honda) says.
 
You should always check it if you have the engine apart, and something changes. It's easy to check. All you need is a hunk of solder, and calipers.

If you changed the crank, and since it had new rods... it should have been checked, but... once you've been using the engine, it's hard to check. Any carbon on the piston will throw off the numbers. I would just check the compression. It should not exceed 150 psi.

Right now I have a boat at my shop that came in with a complaint that the left engine wasn't running properly, but was just rebuilt last year. After checking compression... the PTO jug was 170 psi, and the MAG jug was 120. The problem is the squash band is WAY to tight, and the MAG jug just melted down.

So... the top end needs re-built, but this could have been avoided if the shop who did the re-build would have just used the proper gasket. :rolleyes:
 
Fortunately, I haven't fully installed the engine because I bought a couple 97 Kawi 1100 STX's about the same time I was winding down my project, so since it is just lying in the hull and has not been started, one of these weekends I betta pull the engine back out of the hull and check the Squish to be on the safe side.

Heck, I shouldn't even need to pull the engine out of the hull; just take the top end off to check the Squish? Right?
 
All you have to do is to take the spark plugs out... put a length of solder into the engine though the spark plug hole, and turn the engine over. (do it over the wrist pin so the piston doesn't twist) Then, pull the solder out, and measure it with the calipers.

If you have the manual, it will give you the spec, and the procedure. If you don't... I'll look it up for you.
 
I had the book in front of me..


587 engine should be 1.3 - 1.7mm (.051 - .067 in)

Adjust with a base gasket. The number of holes, is the thickness in mm. So... 3 holes, is 3mm (.012")4 holes is 4mm (0.016").... and so on.



A final FYI... the tighter you set the squash band, the engine will potently make more power... but it will become exponentially less tolerant of a lean run. If anyone reading this decides to get a few more HP by putting on the thin gasket... be aware that you will advance the port timing, and make preignition a probability. It's best to set it in the middle of the range whenever possible.
 
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All you have to do is to take the spark plugs out... put a length of solder into the engine though the spark plug hole, and turn the engine over. (do it over the wrist pin so the piston doesn't twist) Then, pull the solder out, and measure it with the calipers.

If you have the manual, it will give you the spec, and the procedure. If you don't... I'll look it up for you.

Dr H: Thanks again for some very helpful advice.

I have both the Clymer's and Sea Doo shop manuals, so, I can find the info. Thanks for offering to get it for me. I really appreciate that.

Now, if the Squish is off, then I presume I have to split the cases and replace/find the right size head gasket, yes?
 
Dr H: Thanks again for some very helpful advice.

I have both the Clymer's and Sea Doo shop manuals, so, I can find the info. Thanks for offering to get it for me. I really appreciate that.

Now, if the Squish is off, then I presume I have to split the cases and replace/find the right size head gasket, yes?

You don't split the case. You just replace the base gasket with the proper one.
 
Oh baby, that is good news. I guess it is time to get my skinny butt in the garage and pull the manuals to find where the "base" gasket is.

Thanks again Dr. H.

How is the Polaris running?

I thought they looked bitchin when I would see them on the River and a few years ago I was thinking of buying a pair until the mechanics over at the Kawi/Honda/Polaris shop here in Riverside told me that the Polaris is a piece of crap and pointed me to a Kawi or Honda.

That same year Polaris stopped making PWC's, so maybe that is the reason for the mechanics opinion??? That said, I recall they had a dozen for sale at that time and they looked bitchin.'
 
Off topic... but it's your thread... so I guess it's OK.

Polaris made some very good skis, and they weren't "Crap"... but, everyone is entitled to their opinion.

The big problems with Polaris are...

1) the mid 90's had a bad CDI, but they made a new kit available relatively cheap

2) the "Start stop Module" in 99 and 2000 were bad. (the problem with mine when I got it) but it's $100 part, and easy to fix.

3) The 4-stroke skis had a Webber engine, and they had problems. BUT... you can get the MX hull with a 2 stroke if you like the newer style.

4) Originally Polaris said to use TC-w3 oil, but in 2000/2001 they switched over to a synthetic which was API-TC. (sound familiar??)

The first thing I did was to drain out the junk oil, and re fill the system with a good API-TC oil. (XP-S Syth bled) That will let the engine have a good long life.


Basically, every company has issues, so just pic the ski you like, and live with it.

If I had to make a quick list for why seadoo is bad (from complaints I see on the board).... it would look like this...

1) have to use $80 /gal oil

2) The carbon seal crap

3) the wear ring is stupid, and wears out too quick

4) the MPEM is expensive, and fragile


Personally, I like all the ski's, and no one company has any more issues than an other.



FYI... Polaris stooped making skis because of 2 reasons.

1) They lost a huge law suite involving someone's rectum being damaged by the jet thrust.

2) Sales were way down.

Officially, 2004 was the last model year, but they had designed 2005 skis, and even made a promo vid.

I will say this though. Even though they pulled the plug on their PWC... they made parts available for ALL of their skis up until just a few months ago, but there are still tons of parts out there. (SeaDoo doesn't support anything older than 5 years, and almost doesn't' admit to making the Merc powered stuff)


A good rule of thumb is to never trust what a mechanic tells you. Most of them are morons.
 
Off topic... but it's your thread... so I guess it's OK.

Polaris made some very good skis, and they weren't "Crap"... but, everyone is entitled to their opinion.

Personally, I like all the ski's, and no one company has any more issues than an other.

Even though they pulled the plug on their PWC... they made parts available for ALL of their skis up until just a few months ago, but there are still tons of parts out there. (SeaDoo doesn't support anything older than 5 years.

A good rule of thumb is to never trust what a mechanic tells you. Most of them are morons.

Dr H, as usual, your comments are helpful and informative.

FYI, I was not slamming you on your Polaris. As I pointed out in my Thread, I always thought they looked bitchin and was going to buy two (Verage I recall) on several occasions, however, several mechanics I talked to told me they were prone to have many mechanical problems.

I was also concerned about getting parts.

On the parts issue, SD dealers rarely had parts in stock for my 93 GTX's and when ordered from Canada, I thought I was buying parts made of gold.

It was difficult finding simple bolts and screws for my 93 GTX engine project that the screw fairy swiped from my work bench. (A wise man like me surely could not have lost or misplaced them)

I've heard more good than bad about Kawi's and Yami's when compared to SD's, however, knowing that SD sells many more PWC's than K&Y combined, I know that fact is relevant to the problems issue.

In my case, as you know I recently chose two 97 Kawi 1100 STX's over two 96 GTX's because I noticed that rental shops preferred Kawi's over SD's and Y's. (I also beat the Kawi owner down to $4800 from $5800. The SD owner would only go down from $5800 to $5400 and of course, being a "thrifty) kinda guy that I am, that fact could not have been relevant in my decision, right)

I also did not want to be spending $30 for a gallon of API TC oil when I could get a good blend (Pennzoil) for half that price.

Doc, were you aware that the American Petro Institute (API) has not conducted tests on 2-cycle gasoline engines since 1993?

Hell, PWC's have come a long way since then, so, I've been wondering about the relevance of an API TC rating for a water cooled engine such as a SD!

Being the inquisitive kind of guy that I am, albeit I conducted several searches I couldn't even find one test that was conducted by API to ascertain whether API performed tests on water-cooled engines (PWC's) or limited their tests to air cooled snow-mobiles, motorcycles and ROTAX aircraft engines!

I am starting to wonder, has SD and the API been selling snake oil to the SD consumer?

As you know, I used Valvoline TCW3 in one of my 93 GTX's for over five years with zero problems, however, the mechanic that I sent my crankshaft to for a rebuild told me that the bearings showed signs of overheating. (green/blue tinge). He recommended that I start using Amsoil Interceptor.

Now, considering the foregoing sentence and applying it to your "good rule of thumb:" "to never trust what a mechanic tells you" because "[M]ost of them are morons," I am wondering, unless your statement was made tongue in cheek, then, a wise person should adhere to your rule.

Just some thoughts from a thinking man to a wise man.



IMO, a person that owns a 96 + SD should focus more on a JASO or ISO rating than a rating from an obsolete test.
 
I didn't think you were slamming me. I was just throwing out my 2 cents. (as I normally do) With this polaris... I have officially owned all of the major brands. And as far as the K&Y statment... I have no idea how a marital aid would work as a PWC. :rofl:

As far as the tests... the API wasn't doing the tests. They just set a standard. The tests for the manufactures are always done by a private testing company. That way the "Influence" is removed.

Without turning this into a oil thread... yes the JASO standards are more current, and some of them are harder to achieve. (but not all)

Yes, it was tongue in cheek... but there is truth in that. The bulk of the mechanics out there do it, because they couldn't cut it in something harder. I have a few buddies who are Pro mechanics, and a couple of them are OK... but one of them... let's just say, he will NEVER touch any of my stuff.

Now... with that said, I would hope that people will always think about things, and not just trust what they hear.
 
Well, here comes summer and the time has come for me to consider keeping my 97 Kawi 1100 STX's, or selling them and keep my 93 SD GTX's which have been great machines, AND, much more fun to ride than the JS's.

Before that decision is made, since I got lazy after pruchasing the Jet Ski's and did not finish my engine project, I have to check the Squish. If I keep them, or sell them, according to Dr. H, the Squish has to be correct.

Now I think I have the procedure down; 1) uncoil a few inches of solder; 2) bend it so when I put in into the spark plug, it can travel to the end of one side of the piston; 3) turn the PTO until it hits TDC; 4) pull the line of solder out and measure the clearance against the specs; 5) ditto above for the opposite side of piston (be sure to discard squished solder); 6) compare the "squished" solder to the specs; 6) if within specs, everything is kool; 7) if not, get a new gasket that is within specs and replace old gasket with new.

Dr. H, does that narrative pass muster? If yes, great. If no, please advise accordingly.
 
Almost.

1) Roll past TDC so you can get the solder out of the engine. (your #3 makes it sound like you are stopping at TDC)

2) make sure you put the solder over the wrist pin side of the piston. (more stable) if you put it 90 degrees out from the wrist pin... the piston will pivot under pressure, and give you a false squish band thinness.


I like to set the squash band on the thin side, for more power... but it will become less tolerant of a lean run. For the most reliable engine... get it as close to the center of spec as possible.
 
Thank ya Dr. H. Weather is cool outside today, but, I've been procrastinating (fear factor) long enough on "squishing" some solder. If my "squished" solder task is favorable, then, its time to install the jet pump (maybe call SeaDooYa) to see if he has the shaft to perform the task right. I had been pondering over the idea of simply loosening the motor mounts, stick the drive shaft into the PTO, then crank the engine to align it, however, I recall you informing me last summer that doing so would not be wise. Since I will probably sell the SD and keep the Jet Ski's, I want to ensure that everything was done properly. My Doo's have always ran great, except for normal wear and tear parts that had to be replaced and I want them to keep running great for another ten years. Maybe then they will not be called old, but vintage, like a 56 Chevy Nomad????
 
Ok, this morning when measuring the "squish" clearance on my 587 engine, the gap was 1.97mm/1.73 on the PTO cylinder and 1.99/1.72mm on the MAG cylinder. I took measurements from both sides of each cylinder. According to my manual, Piston Squish GAp for a 587 engine is 1.3mm to 1.7 mm, thus, as compared to the squish gap on my 93 GTX, I am .03mm over the max tolerance spec on the right side of each cylinder, however, I am off .27mm on the left side of each cylinder. IS THAT WAY TO MUCH?

If so, then Guru's, where do I go from here? Hopefully close to finishing my project and dropping this 93 GTX in the water.
 
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Squish Clearance - 1993 GTX

Ok, this morning when measuring the "squish" clearance on my 587 engine, the gap was 1.97mm/1.73 on the PTO cylinder and 1.99/1.72mm on the MAG cylinder. I took measurements from both sides of each cylinder. According to my manual, Piston Squish GAp for a 587 engine is 1.3mm to 1.7 mm, thus, as compared to the squish gap on my 93 GTX, I am .03mm over the max tolerance spec on the right side of each cylinder, however, I am off .27mm on the left side of each cylinder. IS THAT WAY TO MUCH?

If so, then Guru's, where do I go from here? Hopefully close to finishing my project and dropping this 93 GTX in the water.
 
Another insipid question: In a previous post it was advised that I place the string of solder "over the wrist pin side of the piston." I shall presume form that advisement that the solder should flow in parallel with the crankshaft, facing the PTO, then to the right facing the MAG, rather than facing the exhaust and carbs? I apologize for appearing so obtuse, however, since I am definitely not a mechanic I want to ensure I complete this project correctly the first time.
 
Finding myself in chartered, but confusing waters is not fun. Hopefully this Post will bring me safely to shore. After what appears to be a simple procedure that I have made confusing, I promise not to laugh at another "what kinda gas should I use in my Doo" again. With doubt, though I am an educator and law school grad, it should be clear I am a border-line idiot when it comes to being a mechanic.

Let me try to get a handle on my Squish predicament.

This morning I started the process, (engine installed in hull) beginning with the cylinder head adjacent to the PTO. I pulled the spark plug then placed a string of solder through the spark plug hole, proceeded in parallel with the flow of the crankshaft until the solder stopped on the wall of the cylinder jug facing the PTO.

I then rotated the PTO until TDC, then backed off so I could remove the solder.

Upon retrieving the solder I took a reading with my digital caliper and the results were 1.97mm. (SD specs are 1.3mm to 1.7mm)(I am off specs)

I next repeated the process with the same cylinder, running the string of solder in parallel with the crankshaft until it stopped against the cylinder jug facing the MAG side of the cylinder. The reading was 1.73mm. (closer in specs, but still .03mm off from maximum)

I next repeated the process with the cylinder adjacent to the MAG, the first reading PTO side was 1.99mm and the MAG side 1.72mm.(off again, but almost identical to the other jug - .02mm difference, but still off .27mm)

From what I have read about the subject today off the SDF, I should next take an "average reading" of both figures in each cylinder.

If that information is correct, then applying it to my situation would result in an "average reading" of 1.85 for the PTO cylinder and again, 1.85for the MAG cylinder.

The Piston Squish Gap specs for a 1995 587 engine is 1.3mm - 1.7mm. I shall presume the specs are the same for my engine, a 1993 Type 587!

As clearly noted above, if I applied the correct procedures, then my squish gap if off about .35mm. (mid range of specs)

My question for the Guru's is: 1) Is the squish gap too far off to be tolerable for my engine; 2) is yes, what size gasket should I stack to the existing gasket; 3) if I don't stack, what the heck do I do?

There are not many Threads on the SDF (I only found two) covering this subject and though the responses to this Thread have been helpful, however, I am still having a difficut time navigating through it. The good thing, however, is that should another dummy like me find themself facing the same questions as I, then the charts will be clearly published herein. Thanks Doc for your continued patience.
 
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Yes... the solder should be in line with the crank.

If you are over spec... you won't hurt the engine... but you won't make as much power as you could. If you want to pull it tighter into spec... you have to take the top end apart, and put in a thinner base gasket.
 
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