Carb rebuild or compression

[JeremyD615]

The correct way to do it is to have the cylinders sent out and bored before you order pistons. You want them to bore as little as they can to get the cylinders back into spec, and you won’t know how much that is until the machine work is done.

 

[jemery.wa]

Understand but isn't the machine shop going to need some sort of goal, by looking it seems that they sell pistons in certain set increments.

 

[JeremyD615]

Understand but isn't the machine shop going to need some sort of goal, by looking it seems that they sell pistons in certain set increments.

Yes, the machine shop should be boring to the smallest oversize that gets the cylinders in spec. Most of the manufacturers make oversized pistons in .25mm increments, You could just have them bore to .25 or .50 over, but you may find that they have to go beyond that to get the cylinder cleaned up, and won’t know that until they get the work done.

 

[jemery.wa]

would they also be able to do rave valve?

 

[JeremyD615]

They might be able to, but I think generally people do the raves themselves. It’s a fairly soft material, so you can use some sand paper wrapped around the old piston to take them down a bit and then polish them up with some Emory cloth. It really depends on how far oversize you go as to how necessary it is. If you can get away with .25mm on the pistons, you shouldn’t have to trim. Any more than that and you’ll have to do something with them. There should be some write ups if you search the forum for trimming rave valves.

 

[jemery.wa]

Had cylinders bored over .75mm to clean up scoring, matched with the pistons. Have the motor almost back together will be rebuilding the carbs soon.

What should I be doing to break this in? I have the block off plates to go to premix but am not sure if I should wait until after I break it in to do it or should I do it now while the carbs are out?

 

[JeremyD615]

At .75 over, you do need to make sure you clearance the rave valves. It shouldn’t take much at all to get there.

For break in, I suggest running 50:1 premix along with the oil injection for the first tank. Let it idle in the water for about ten to fifteen minutes and get up to temp while you check everything over for leaks and get the idle set. Then shut it down and let it sit for half an hour or so. That’s the first heat cycle, so don’t even take it out and ride it. Once it has sat and cooled off, you can take it out and run it for about 30 minutes just putting around. Don’t give it any more than 10-20% throttle, and then let it cool off again. The next time out you can go to 50%, and then the time after 75%. Don’t go wide open for the first tank, and try not to hold any one throttle position for more than a few seconds. After you get through the first tank, I like to add just a bit of oil to the second, like 100:1. You don’t have to, but I like to have something mixed in there just to be on the safe side. You may foul a plug or two during break in, so keep a few spares handy.

As far as the block off plate goes, there’s really no good reason to go premix on a Sea Doo. The oil pumps are extremely reliable, and the only maintenance they require is changing the small injection lines every few years and the filter every so often. The upside to keeping the injection is you use way less expensive oil, foul fewer plugs, and don’t have to worry about mixing fuel or filling up at the marina.

 

[jemery.wa]

Carbs rebuilt and tested, hold pressure and pop off close to spec. It is all back together and ready to take down to break in. It has almost a full tank so I will add oil and top off. Have to pick up some extra spark plugs as well.

 

[Ckrawiec]

Carbs rebuilt and tested, hold pressure and pop off close to spec. It is all back together and ready to take down to break in. It has almost a full tank so I will add oil and top off. Have to pick up some extra spark plugs as well.

Good luck with it.....not to be a debby-downer but the Seadoo manual references a cylinder overbore of .25MM for the first overbore (82.25mm).....THERE is no second overbore, SO with you being at 82.75mm you are over the shop manual limit so be gentle with it.....

 

[jemery.wa]

Took it down to the lake, left it on the trailer and had it running for around 15 min at idle until it died and wouldn't restart. took it home and took the plugs out, MAG one was black and wet and the PTO one was also wet but not as black. I put new ones in and it started back up. I am wondering if there is a dual output fuel pump for this machine? and if so is it worth installing? I have a triple output for my Polaris that I have to install but based on the compression of that one it may needs help, 120, 30, and 0 psi!

 

[GGuillot]

Took it down to the lake, left it on the trailer and had it running for around 15 min at idle until it died and wouldn't restart. took it home and took the plugs out, MAG one was black and wet and the PTO one was also wet but not as black. I put new ones in and it started back up. I am wondering if there is a dual output fuel pump for this machine? and if so is it worth installing? I have a triple output for my Polaris that I have to install but based on the compression of that one it may needs help, 120, 30, and 0 psi!

Why let it sit on the trailer in the water idling for 15 minutes? It needs a load on the engine to break it in. Next time push it off in the water and go for a ride...

I have a 97' GTX, same as the 96', it doesn't need any additional fuel pump assistance. Rebuilt carbs with OEM kits, good pop off, (I get 34-35 psi) set the lows at 1 turn out, it should run fine.

What's the compression now after the new top end?

 

[jemery.wa]

Read one of the above posts, this is my first experience with 2 stroke motors (with the exception of nitro rc) so I have to rely on the information that has been provided to me about how to break in the top end. It seems that there are many opinions on these subjects like break in and whether to do the block off and I have to make my decisions based on what i am being told and what I read since I have nothing else to draw from. When I was at the boat ramp the sheriffs where patrolling very heavily and I wasn't sure if I was ready to go out anyways (tags are good but haven't transferred title and reg, also from different state). I plan on going back out soon and will take it out for a lite ride. So far it has been a very rocky experience with watercraft and I haven't had a successful ride yet with either of them, so forgive me if I am VERY gun shy about getting stuck out in the middle of the lake AGAIN. I haven't taken a compression reading yet, I needed to charge the battery to make sure it was full before I go out again. I will probably check it today when I start to assess WTF is wrong with my Polaris. Thanks for the advice it is appreciated.

 

[jemery.wa]

So here is my update, hadn't had a chance to take it to the water since I had to rebuild the top end of my Polaris as well. but when I did I couldn't get it started. Checked the compression at home, 145psi Mag and 50 PTO. turns out that I DIDN'T get all of the needle bearings out of the crank case after all, see the aftermath below. I have ordered a new piston and a cylinder so hopefully will get it back together by this weekend.

On a good note my Polaris break in went great, ran awesome and probably put around 2 hours on it so it gives me some hope that I can do it.

 

[GGuillot]

I have ordered a new piston and a cylinder so hopefully will get it back together by this weekend.

You're kidding right? I wouldn't just put another cylinder and piston on it and go. I'd pull the engine and tear it down, clean it out and so forth, otherwise you'll repeat this again. Are you absolutely sure pieces of needle bearings didn't get in the crank bearings and aren't still there? Your call, but there's no way in hell I'd skip it..

 

[JeremyD615]

Yeah, that looks rough! You’ve definitely got metal in the rest of the case...

 

[jemery.wa]

Pulled the motor because upon further inspection there is damage to the intake side of the case, there is an angled runner that must aid in fuel entering the crankcase and it cracked and displaced that area. I have ordered another case and I guess I will figure out how to completely dismantle this thing.

 

[jemery.wa]

So I thought I would update this thread since a lot has been done, it has been put back together with the new (used) case, oil injection block off done and back in the ski. I broke it in and have been running it with a 40-1 ratio with red-line oil and premium gas. I still have some adjustments to do with the carbs, it has some hesitation when you go from idle to acceleration, if you pin the throttle to quick it will die but if you ease into it it gets up and moves. I have had it up to 50 mph on the lake but have been afraid to go full throttle for an extended period of time.

 

[amcreativ]

So I thought I would update this thread since a lot has been done, it has been put back together with the new (used) case, oil injection block off done and back in the ski. I broke it in and have been running it with a 40-1 ratio with red-line oil and premium gas. I still have some adjustments to do with the carbs, it has some hesitation when you go from idle to acceleration, if you pin the throttle to quick it will die but if you ease into it it gets up and moves. I have had it up to 50 mph on the lake but have been afraid to go full throttle for an extended period of time.

I have the same hesitation and bog on my 951 carb that I just started breaking in yesterday. I'm literally about to light my '98 GTX Limited on fire.

 

[POPPS]

everything is ordered, based on my compression will I be able to run it before the top end rebuild?

If it was me I wouldn’t.
That 125 psi has something going on.

Listen to the tech's,,,Miki,,,and company,,,they have tons of experience,,,your motor is not going to run right, if at all!,,,change the top end,,,it's messed,,,then go through the carbs with a fine toothed comb,
If it's not on premix, check that the oil pump is working properly throughout its full range,,,You need to find out what caused your problems,,,it's like doing an autops,,,on any motor repair,,,I will do an autopsy of the dead body/motor,,,no guess work...hundreds of dollars and countless hours are at stake! I can't rebuild a motor for the customer, without being able to tell him why it failed in the first place,,,otherwise, the cycle will repeat,

 

[jemery.wa]

Listen to the tech's,,,Miki,,,and company,,,they have tons of experience,,,your motor is not going to run right, if at all!,,,change the top end,,,it's messed,,,then go through the carbs with a fine toothed comb,
If it's not on premix, check that the oil pump is working properly throughout its full range,,,You need to find out what caused your problems,,,it's like doing an autops,,,on any motor repair,,,I will do an autopsy of the dead body/motor,,,no guess work...hundreds of dollars and countless hours are at stake! I can't rebuild a motor for the customer, without being able to tell him why it failed in the first place,,,otherwise, the cycle will repeat,

I did find a spare oil pump in one of the storage compartments, I believe that the original reason for the damage could have been a faulty oil pump that was replaced by the PO, that and someone had started the process by putting a T in the crankcase lines to connect them together, removing them from the oil tank. I re-connected the rotary valve and counter weight lines back up to the tank and capped off the injection pump lines. From everything I have heard if your oil pump goes out there is no warning and very little time before permanent damage occurs. It was this information that made it an easy decision to go premix, that and I had the engine apart. I have been through both carbs 4 times with the last time rebuilding them with Mikuni kits and new needles and seats, the pop off tested out consistent on both right around 25lbs. I had brand new spark plugs in it from when it was damaged but I went ahead and replaced them anyways. I replaced the crank seals as well. I probably have 3 tanks through it now and it does really well except for the hesitation off of idle, I tried some quick adjustments yesterday but they didn't help. I have a friend at work that pretty good experience with 2 stroke and jet skis and he told me he would help me tune both of my skis up soon.

 

[jemery.wa]

I have the same hesitation and bog on my 951 carb that I just started breaking in yesterday. I'm literally about to light my '98 GTX Limited on fire.

My 94 Polaris had a REALLY bad hesitation last week to the point that you had to pull the choke halfway to get it to accelerate on to a plane. I replaced all 3 diaphragms in those carbs since they were old and crunch, while i was putting it back together I reached under the fuel pump to get a rag and got dripped on by the fuel pump, my lines were leaking, I put better clamps on the lines and when I took it out on friday the hesitation was gone and it accelerates like it should.