Base gasket, how many holes?

[One1]

Thanks to keyword spam I can’t get a straight answer on which hole version of base gasket my 94 spx takes. It’s the 657 (non x) and I’ve included a picture of the base. Sorry, only ones i have.

So far I’ve found 3, 4, 6, and 8 hole versions. Is this relevant? It seems to be in an area no holes are needed, but i wanted to make sure the gasket didn’t change in other ways. Also, the hole positions change gasket to gasket.

 

[jts32]

The number of holes designates the thickness of the gasket. Different thicknesses are used to get the correct squish gap. Download a free manual, it will show you how to determine your squish gap and which gasket thickness you need

SeaDoo Manuals - FREE PDF Download!

 

[glsmohio]

The number of holes designates the thickness of the gasket. Different thicknesses are used to get the correct squish gap. Download a free manual, it will show you how to determine your squish gap and which gasket thickness you need

SeaDoo Manuals - FREE PDF Download!

Hes all over it!

 

[One1]

Many thanks. 320 pages and i saw nothing. I figured it would be around page 74 where the heads are being spoken about, also checked the back index. I guess I’m missing it. Maybe i can find a picture of my old gasket and see what was in there. As far as the rest of them I’m making them. I ordered a kit and today they refunded my order and said they were out of stock. I knew I couldn’t accurately make the base gasket, the rest are just regular gaskets.

 

[One1]

Found the old gasket. I had a 5 hole. Of course, the one I can’t find for sale, unless i wanna pay 3 times as much from the dealer. Tell me a 4 or 6 is close enough not to cause issue...... please. Would you go higher or lower? 4mm or 6mm?

My Starrett 733 says it’s accurate at 5mm.

 

[glsmohio]

Found the old gasket. I had a 5 hole. Of course, the one I can’t find for sale, unless i wanna pay 3 times as much from the dealer. Tell me a 4 or 6 is close enough not to cause issue...... please. Would you go higher or lower? 4mm or 6mm?

My Starrett 733 says it’s accurate at 5mm.

What your doing there means nothing. Let's start over so you can understand what needs to happen. 1st do you know what the squish gap is?

 

[jts32]

You're correct, I don't see anything about squish gap in the '94 manual. '95 and up show how to measure, but I don't see tolerance ranges for the 657. The 580 and 720 range is 1.3-1.7mm, and I would assume the 657 is in the same range.

 

[glsmohio]

Rotax Squish Gap Check Procedure - 2 Stroke

This should help you out. We can't just tell you what gasket you need and you shouldn't go off the old one.

 

[One1]

I know what my squish is, I didn’t know what gasket to get because the manual doesn’t say. I have 1mm of squish without a head gasket installed. Given that and the above comment I’ll re-ask should i go down to 4 or up to 6? 5 seems to have been reasonable, but none of these seem to be out of tolerance to the point of critical. So would I see an issue running less squish to be safe and using a 6? I’m concerned with reliability over performance. Thanks!

 

[jts32]

You need to measure both sides of each piston, directly above wrist pin. So 4 measurements total, then determine which gasket will get all measurements in factory specs

 

[One1]

How do you squish above the wrist pin? I went around the edges. And i TDC’ed it before and after putting the head on to verify the piston was even.

 

[jts32]

Yes, outer edge of piston, but directly above wrist pin centerline. If you don't measure directly above the wrist pin, the piston can swivel a little and give inaccurate measurements

 

[One1]

I did that as well as crushed 4 points at once. Still not sure what gasket to use that’s been the concern. Anyone else know about 657?

 

[jts32]

 

[One1]

Thank you for finding that.

This engine has hardly no hours. If it wouldn’t have hooked the exhaust on the mag jug it would have lasted a long time. Here is the piston that didn’t hook. No wear at all.

Still I don’t know where to place the squish at as far as gasket?

 

[One1]

Guys I’m in need of a set of OEM seadoo 77.94 rings for ONE piston. I don’t have to have two sets. I have a brand new OEM piston, rings, and jug. I just need rings for the other jug. All I’ve found is oversized so far.

Also, does anyone know the correct circlip part number? There are tons of them.

 

[One1]

Block off plate came. Unfortunately the bolts included are too thick and not even close. Thankfully i have the oem bolts. Also, fittment is a little loose in the hole where it should be chamfered to fit and keep from leaking. it'll need sealant. Maybe buy a different kit if you want one.

 

[mikidymac]

Just use some sealant on it. The good ones used to have an o-ring groove and fit tight but all this China crap is not the same quality.

For the piston clips there is only 1 number 290845100 .
For the bottom ring is is 290815020 and there is one on ebay for $15.
The top ring is 290915995 one ebay $20

At the right side of this page under "Seadoo Warehouse" you can look up all the part numbers for your ski.

 

[mikidymac]

Thank you for finding that.

This engine has hardly no hours. If it wouldn’t have hooked the exhaust on the mag jug it would have lasted a long time. Here is the piston that didn’t hook. No wear at all.

Still I don’t know where to place the squish at as far as gasket?

The squish is pretty basic, spec is 1.0-1.40mm so if you measured without a gasket and had 1.00mm then you should run a 3 or 4 hole gasket as the gasket is 0.30mm (3 hole), 0.40mm (4 hole), 0.50mm (5 hole), etc.

For squish you are better off going a little bigger to prevent detonation. If it was mine and I could find a 4 hole that is what I would do to be safe. Keep in mind all of the aftermarket gasket kits and rebuilds like SBT only have 1 gasket, typically a 5 hole that they use on everything to be safe.

 

[mikidymac]

Well, there you go, 10 seconds on ebay with the OEM 4 hole number 290931165, $12.92 and free shipping.

 

[One1]

I’m not having issues finding a 4 hole gasket. I have 3 on watch. I had a 5 hole which there are none of on ebay. I’ve been having issues finding a lower ring. I’ve had the upper ring on watch for 4 months. I've never been able to bring up a lower ring when searching. I saw one for $16 just now, i just need to make sure it’s correctly represented by the seller. It’s the only one so it must be a newer listing. Surely the one you saw, I’d guess. All the rest are sbt and wsm, which I've been ignoring for months. If it isn’t oem I don’t want it.

Thank you for the numbers, I’ll grab those clips. There are several seadoo clips on ebay and some are smaller. The ones i am finding don’t have the 290 prefix, they have 420. There is one single one that has 290 and he wants 5 times as much as ALL the other ones. It appears your part number is superseded and replaced with the 4wp, which is fine.... and cheaper.

 

[mikidymac]

Your making this way more difficult than it needs to be.

Just buy the 4 hole and be done with it if you are confident in your measurements.

For the clips and rings it couldn’t be easier.

 

[One1]

No, just tired of getting sent the wrong part after they say it’s correct.

Yep those are the only 290 and i need 4, as well these are 5 times the price of all the rest. I have bought some of this yesterday, but I’m just waiting on the seller to respond about the ring. That number comes up on 3 different sizes of ring when i searched previously so i need them to confirm. I want this built and breaking in by next week.

Speaking of break in, Ive always heat cycled my 2 strokes, what ways do you guys like?

Also, while typing this seller responded and is unable to comprehend the question so I’ll just keep looking. If he knew what he was doing he would be able to answer me. I’ll include the email.

Thanks!

 

[mikidymac]

The factory part number is right on the factory bag. Am I missing something here? It is pretty obvious that is the factory ring and in the standard bore size.

That number is directly from the seadoo parts catalog printed by seadoo, I don't understand why you don't believe it.

For the circlips the seadoo 650, 720 and 787 all use the exact same piston pin clips so you can get them anywhere.

 

[mikidymac]

No, just tired of getting sent the wrong part after they say it’s correct.

Yep those are the only 290 and i need 4, as well these are 5 times the price of all the rest. I have bought some of this yesterday, but I’m just waiting on the seller to respond about the ring. That number comes up on 3 different sizes of ring when i searched previously so i need them to confirm. I want this built and breaking in by next week.

Speaking of break in, Ive always heat cycled my 2 strokes, what ways do you guys like?

Also, while typing this seller responded and is unable to comprehend the question so I’ll just keep looking. If he knew what he was doing he would be able to answer me. I’ll include the email.

Thanks!

The seller isn't wrong. I don't know why you are having trouble with verifying the ring?

Straight from the seadoo parts catalog that part number....
14, 290815020, RECTANGULAR RING 78 MM
Is for the 1994 SPX lower ring for a standard bore OEM piston.

There is nothing else for me or the seller to explain. That is the part number for the ring you are asking for.