Power Problem 1999 720cc

[arsenic]

Hi guys,

I have a problem with my 1999 Seadoo 720cc.

It has no power, it does not go up in rpm.

The only time it accelerates is after jumping waves and taking off from the water... Unfortunately it only lasts a few seconds and then the problem returns.

And I have the impression that sometimes when hot it has a little more trouble starting.

The carburetor has been rebuild, the hoses changed by new ones, the air filter is clean, the battery recent and it is fully charged before each ride. The oil pump is removed and I mix it with 3% quality oil.

Can you help me please ? (Sorry for my english, I'm french )

 

[NickCawks]

Have you checked the compression?

 

[arsenic]

Hi NickCawks, thank's for your answer,
I don't have checked because sometimes it has a little power so I didn't think about checking the compressions...
I would have to buy the pressure gauge to see that

 

[NickCawks]

It might be worth investing in. If the ski running out of water but not in it definitely points towards low compression.

Just make sure not to buy a harbor freight compression gauge

 

[arsenic]

Thank you, i'm going to buy one and test it !

Coffret testeur de compression 9 pièces pour moteur essence

 

[NickCawks]

That should do the job. Let us know your results and we can go from there

 

[arsenic]

Hello, i don't have received the compression tool. But I was thinking about lot of things :
1/ the carburetor was rebuild by the old owner. Its possible than he don't buy a mikuni genuine rebuild kit (also can you send me a link for the good carb rebuild kit )
2/ the setting of the needle could be wrong?

I don't find the correct settings for my ski on the operator guide

 

[arsenic]

I forgot to tell you that the oil pump has been blocked and the jet ski runs on a mixture of oil and gasoline.

By removing the carburator I noticed that this orifice was blocked ... Is this normal?

Edit : I find the needle settings
LOW - 1/ HIGH - 0
I understand that it's the setting for low speed needle and high speed needle but don't understand what's this numbers...

 

[mikidymac]

Your choke has been removed, poorly that is.

 

[arsenic]

Thank you Mikidymac. And concerning the adjustment of the needles, the number corresponds to the number of turns to be unscrewed after having tightened them to the maximum?

Is it possible that my problem comes from the setting of the high needle?

 

[clegg]

The low and high are are the amount of turns out from when you have them turned in to a seated (closed) position. The low 1 and high 0 are the correct amount of turns out according to the manual.

 

[Legacy37]

I wouldn’t touch anything till you run a compression test...sounds like low compression. You can rent the tester at most local auto parts stores

 

[arsenic]

I wouldn’t touch anything till you run a compression test...sounds like low compression. You can rent the tester at most local auto parts stores

Yes, I received mine compression test tool Friday, I'm going to re mount the carb, take the compression and tell you the results.

I Can't tomorrow cause it's national day in France

 

[arsenic]

*I'm going to receive friday*

I also noticed that this part is blocked. I tried to blow or suck into it, without success ... Is this normal?

 

[mikidymac]

Yes, it should hold a couple psi of air pressure then release.

 

[Legacy37]

Yes, I received mine compression test tool Friday, I'm going to re mount the carb, take the compression and tell you the results.

I Can't tomorrow cause it's national day in France

Looks like it is getting sporty in France

 

[arsenic]

Obviously it only happens to me ... I received the pressure gauge except that the pressure gauge is defective ... I was able to read two values except that they are wrong ...

185 psi and 190 psi, obviously if we remove the starting margin we are around 130 and 145 psi for the two cylinders ... I don't think these values are precise enough to establish a diagnosis. So I made a request for product referrals in order to have a reliable pressure gauge and give you real values.

 

[Lothsahn]

Bonjours!

Vous aves Anglais bien!

For the adjusters, turn them until they close but don't turn them hard. Then unscrew the low adjuster 1 full turn.

Check compression first. If your engine is bad then you may not want to spend money.

I recommend osdparts.com for the carb rebuild kits but I don't know if they ship to France.

If the engine is good, you need to rebuild the carb because the previous owner removed the choke. That's strange so I don't trust him. You also don't know that genuine mikuni parts were used. If you don't have the choke you may need a new carb.

If you use your carb, check that the jets are the right size. The high speed jet should be 167.5 and the low speed should be 75. The numbers are printed on each jet (very small).

Good Luck!

 

[arsenic]

Looks like it is getting sporty in France

Do you want to talk about the vaccine?

Yes, it should hold a couple psi of air pressure then release.

Thank You Miki

Bonjours!

Vous aves Anglais bien!

Bonjour, Hello Lothsam, thank you for your compliment I have some knowledge of English but when it gets too complicated for me I use google translation

The company will finally send me a tested and functional pressure gauge.
I'll give you the results.

For the choke, I think he took it off because he installed a primer kit on the jetski.
Also I took advantage of having disassembled the carburetor to change a hose which split.

I will check the sizes of the jets if I come to rebuild it

Thanks for your help

 

[arsenic]

I just received the new compressiometer.

I measured 109 psi and 116 psi.

it does not look good...

So I have to buy a cylinder kit, pistons and rings and rebuild the top is that right?

 

[mikidymac]

I would pull the cylinder head and see how it looks inside.

 

[arsenic]

I would pull the cylinder head and see how it looks inside.

Yes I will take it all apart and post some pictures to you

 

[arsenic]

In any case, I'm going to have to change the piston kit, right?

Do we agree that I will have to measure the cylinder bore in order to choose the right piston bore?

Where then do you suggest that I dismantle in order to check that all the seals are in place, that the pistons do not have visible signs of wear?

In any case, I'll finish to work in 4 hours, I will hasten to dismantle it all and send you lots of pictures. Or maybe I'll make a video.

 

[arsenic]

I disassembled the cylinder head cover, a bolt broke inside despite the wd40 ... Once opened I noticed the presence of a lot of salt ... Maintenance was not respected . It promises for the future, for the moment I am stuck because the cylinder head cover is blocked. Do you have any solutions?

 

[arsenic]

Phew... I finally succeeded in removing the head from the engine!

One of the two cylinders is very skilled at the exterior level.
I think the water sealing will not be done as well ...

Regarding the pistons, one of them is much blacker than the other.

What do you think ?

EDIT : What do you think of a repair with Epoxy aluminum paste in order to repair the cylinder? (I show the location of the possible future leak with my finger).

Also I'm afraid to remove the nuts from the cylinder ...

I don't want them to get stuck. I thought about draining the water, filling with white vinegar overnight then draining the white vinegar and filling with WD40 one more night