951 DI Squish Band

[tkarvelis]

I have seen how to measure the squish with solder for all engines except the DI. I know it can be done by measuring the cylinder volume, but I would rather do the solder as it appears to be easier.

Does anyone have the specs for the solder thickness?

I found one site that said it was 1.7 to 2.3 mm, but it did not say it was the carburetor or DI model.

Thanks in advance.

 

[jhjesse]

Don't know if this helps but my manuals state to remove injector roll piston to TDC fill with 50/50 mix of oil and gas to top of hole, insert a burette scale (looks like syringe) and let set for 10min then read. should be between 45.7 and 48.4cc.

Maybe measure out the correct amount, inject liquid into injector hole and see if it comes all the way up to the top.

 

[tkarvelis]

Thanks [MENTION=20888]jhjesse[/MENTION]. I saw that in the service manual for my gtx also. I was hoping for the easy solder method, but if no one has a better idea, I might go that route, and then do the solder measurement for future reference.

 

[mikidymac]

Ok, so on my 951 I decided to buy the burette from Amazon and tried to fill with the 50/50 oil gas mixture. First off it is a huge mess and second as soon as you have it full it starts to leak past the rings.
So stupid idea if you ask me but that is how seadoo wants it. I will never do it again.

 

[68ragtop]

I have some info for you.

I did it both ways a couple years ago. I did the squish test & 50/50 chamber fill on the same engine. This was with oem pistons one size over & clean heads with no previous machining or destruction pits.

With .5mm gasket, I checked the squish & came up with an average of .087" The thinnest gasket that came in the BRP gasket kit was a .5mm. The fluid test measured 47.5cc's spec was 45.7 -48.4cc's

The casting on those chambers is a little inconsistent. Pretty much got to check all 4 locations & take the average. Very rarely are they the exact same because of the non uniformity.

Are you using oem pistons?

 

[68ragtop]

Ok, so on my 951 I decided to buy the burette from Amazon and tried to fill with the 50/50 oil gas mixture. First off it is a huge mess and second as soon as you have it full it starts to leak past the rings.
So stupid idea if you ask me but that is how seadoo wants it. I will never do it again.

I didn't think it was that bad. it seeps past the rings, but not very quickly. I was able to test & the roll the engine over to get it back out fairly easy. I think where it might be a good idea is if the chambers have been more than cleaned or de-burred, machined, etc. I think as long as the squish stays tight enough to keep the combustion heat away from the ring lands but not so tight the gained compression causes detonation issues it will be perfect. Knowing I always run 91-93 octane gas I would be tempted to run a 3-4 holes gasket on the next one just to see if does much for performance. Probably would do more in a carb'd engine though.

 

[tkarvelis]

I am using an oem crank, with pro x pistons because I needed to go oversized.

I called one of the shops in the south west and he said they aim between .005" and .007" on a di

 

[68ragtop]

I am using an oem crank, with pro x pistons because I needed to go oversized.

I called one of the shops in the south west and he said they aim between .005" and .007" on a di

Wow, that is crazy tight. Unless the pistons are designed to fit that close, I'm not sure there is a base gasket that would get you there. I would double check that info, especially if your first squish test yields a much higher number. Do you still have some old base & head gaskets? Easy test, especially if you leave out the rings

 

[tkarvelis]

My bad.. should be 50 to 70 thousands... typing early in the am.

I do not have any old gaskets... I have the stock kit from wsm

 

[68ragtop]

My bad.. should be 50 to 70 thousands... typing early in the am.

I do not have any old gaskets... I have the stock kit from wsm

Whew, scared me...... lol

 

[tkarvelis]

I measured mine this morning. All four readings over the piston pin

Mag cylinder: 0.0855" on Mag end
Mag cylinder: 0.0855" on PTO end
PTO cylinder: 0.0855" on Mag end
PTO cylinder: 0.0870" on PTO end

Average: 0.0859" = 2.18mm

I would love to get it tighter, but I have a 5 hole base gasket, and I can not find a thinner base gasket.

 

[68ragtop]

Sounds perfect! Seems like the 5 hole is the most common & I don't believe there is an oem gasket with less than 5 anyway. I might have a 3, or 4 hole in the shop, but its aftermarket. I can look if you wan't to tighten it up even more, but I think your spot on otherwise.

 

[tkarvelis]

I will leak test it first. I had a spot of the base gasket that had a small nick, so I am hoping it will hold. I put the base gasket on dry, but the head gasket I used 1211. If I have a leak, I will let you know and buy it from you. I will need to get a new head gasket too.

 

[jhjesse]

Man those numbers are perfect! If ir were me I wouldn't touch it. Build that sucker and go ride.

 

[tkarvelis]

I will once I get her together, painted, and leak tested, but not in that order lol