Seizing on the Intake Side

[BoLongo]

Got my boat out on the lake today. I was breaking in a new engine, so I was taking it slow, the first five minutes it ran great then it started stalling, and I got a little backfire more like a sputter. Came home and tore it down for the 4th time. (three seizures in the past month)

I am now seizing on the intake side. What do you think is causing this?

 

[ORION '95 Speedster]

If the piston is getting stuck, here are a few possible causes (everything possible thing I can think of, even if unlikely):

Lack of proper oil lubrication
Lean condition
Incorrect size piston
Out of round piston
Out of round cylinder
Clogged/blocked cooling system
Overheating
Ignition timing is incorrect
Wrong spark plug heat range
Wrong connect rod length
Wrong head
Wrong ring end gap measurement
Rings installed wrong
Piston installed wrong
Inconsistent cylinder bore measurements throughout the stroke
Debris entering the combustion chamber through intake
Wrist pin bearing problem
Incorrect two stroke oil type
Low quality fuel
Water in the oil/fuel

Some of those are far fetched, but it looks like your in need of ideas.

 

[ORION '95 Speedster]

Here is what I would start with:

Make SURE you measured the cylinder, the piston, and the ring end gap correctly. Also, you should be running 40:1 premix in the fuel tank, even if you have the oil injection system hooked up. Next, use a heat gun to check temps. Also, I could be wrong, but it looks like the pistons are way too small for that bore. The rings look like they are half way out of the groove. They could be binding, because they are not being supported by the piston properly. Could be wrong. Only measurements would answer that question.

 

[ORION '95 Speedster]

Upon further inspection of the pics, I think the piston is too small, or possibly a ring end gap problem. Either problem would be more pronounced when the engine warms up. Especially if its the end gap issue.

 

[BoLongo]

Thank you. I have come to the understanding that the current setup I have is just not working. My machine shop is an automotive and motorcycle shop; they do a few Seadoo's a year; something is obviously out of spec.

I just bought a complete top end kit; Juggs, pistons & ring, rave valves, and gaskets. Should have bought the full kit from the start; would have saved, I don't even want to think about what it would have saved.:banghead:

ORION '95 Speedster once again thank you for helping me end the insanity. :willy_nilly:

 

[ORION '95 Speedster]

The local shop your talking about, did they work on your engine at all so far?

 

[snikwad003]

agreed that measurements will only answer that but I too feel we are seeing too much ring.
Break
Out
Another
Thousand
:banghead: :cuss:

 

[BoLongo]

The insanity is not over yet.

YES the bore is too big you can see the skirt is slapping


SBT is now telling me that it will be 10 to 14 days before they ship.
Can anyone recommend a good shop/machine shop that specializes in Seadoos in the Southern California area?

 

[snikwad003]

Did you give the machine shop the pistons to measure before they bored it?

 

[ORION '95 Speedster]

I suggest that you don't order the top end from SBT, if you already did - cancel the order. All you need to do is get some new pistons/rings and hone the cylinder. You could get the whole thing running for around $100 give or take. Get everything you need on eBay.

 

[BoLongo]

Yes, I copied pages from the manual showing tolerances and ring gap. The manual shows four different engines, so I think they grabbed the wrong spec.

 

[ORION '95 Speedster]

If the machine shop did not put it together properly, take it back to them. Even if you supplied the figures, they should at least help you out for free at this point by taking all the measurements for you, so you can order the correct parts on eBay.

 

[BoLongo]

I no longer trust them! I took the jugs and pistons back after the first soft seizer; they honed the jugs, and I bought new rings. If they did not catch the issue the second time, I'm not going back.

That is why I am looking for a machine shop that specializes in Seadoos

 

[BoLongo]

I do not have the right tools to check the bore for roundness. The ring gap is .020, spec max is .016 but not sure that would cause the seizure.

I got a rebuilt crank from SBT could there be an issue with the stroke that would cause the piston slap?

 

[ORION '95 Speedster]

I think that if you were to take the cylinders to the machine shop, and have them measure the specs, then buy pistons on eBay, you could probably use the old rings and cylinders. Put it all together and it would run properly. The pistons are too small, so the rings are being pushed upward and downward from the proper orientation. As the ring tilts, the corner of the ring is touching the cylinder rather than the face of the ring. That would change the gap specs, compounding the problem. Can you visualize what I mean? Anyone else follow me on this? I will attach a pic in an attempt to illustrate.

 

[ORION '95 Speedster]

I think that if you just replace the pistons, you will be fine. The minimal damage down so far will be OK.

 

[ORION '95 Speedster]

In fact, more ring gap than what it has now might allow the ring to come out of its groove completely and destroy the top end. I think when the ring is being bent up and down, the gap goes away, and forces the ring to stay in place rather than getting torn apart by the ports.

 

[snikwad003]

Is there a .75 over? I think you should go next size up and have a different shop bore the jugs with pistons and rings in hand providing that your bores arnt already too big. First thing is first get them shits measured! :willy_nilly:

 

[ORION '95 Speedster]

I don't think he needs another bore, just a light hone if anything. 100% agree that measurements are a must at this point. Replacing the entire top end is excessive. Ya, it would solve the problem, but so would buying a complete new motor, or a new ski for that matter.

 

[racerxxx]

Google groupk send your stuff to them.

 

[snikwad003]

Yes, I copied pages from the manual showing tolerances and ring gap. The manual shows four different engines, so I think they grabbed the wrong spec.

So did they measure pistons before the bore or did they use specs in the manual?

 

[snikwad003]

The measurements will determine if he can get away with just a hone but i have never looked down in a jug and seen that much ring, and the piston slap leans me towards the bores are out of spec

 

[BoLongo]

I checked with Group K the turn around time is longer than I can wait. The kids are back in school on Aug 10, and I want at least one Lake Powell trip before summer is over.

Josh, I think the first bore was tight which caused the first soft seizer. When they honed the jugs, the 2nd time they opened up the hole too much. Using my caliper, I am coming up with a piston to cylinder clearance of 0.21 the wear limit is 0.20

I am going to 1.mm over.

Any opinions on the WSM Platinum pistons?

 

[snikwad003]

I have no experience with wsm so I cant say, Pro-x goes from 82.00 to 83.50 for the 787, that said I have no Pro-x experience in a seadoo but I flog the shit out of them in my kx250 with great sucuess

 

[Andy4k6]

How were the exhaust temps when it started to siesed?

Could this be an issue with the crank seals or carbs and not the bore and piston?

Andy