Help with 717 engine

[TheChad]

Hey all,

We took our newly aquired '96 GSX & '01 GS out today, they both ran great but the GS (717 Engine) had a little trouble starting/idling.

It would start for a second and die, it wouln't stay running unless I pushed in the throttle a tiny little bit, then it would fire right up and stay running.

I am thinking possibly that the idle is too low, but I have no way of checking as this machine doesn't have a tach. I am going to add a tach to it, but that may be a winter project.

Also if I floor the throttle from a complete stop the engine hesitates like it's not sure if it want's to go or flood, then it takes off.. Once going it runs great.

I wasn't sure if this was just because the engine's small and just doesn't have the bottom end that my GSX (787) has, or if there is another problem?

The plugs are brand new NGK BR8ES's Gaped at 0.018". I checked the compression and it is between 140PSI-150PSI (I crank the motor over a few times the needle hovers around 140PSI, If I keep cranking or stop then start cranking again the needle jumps up to 150PSI)

I am running atleast some XPS synthetic oil, there was about 1/2 tank of oil already in it when we bought it, I topped it off with XPS Synthetic.


The next issue is with the spitter in the back under the tow ring, on the GS there is no water coming out of it, I blew compessed air threw the line and it wasn't clogged. Obviously the engine is getting cooled as it didn't over heat, but I would like to get the spitter working just as a double-check. Any idea where to start with this?


Also is there any way to check of the Siphon bailer is working? My GSX is bone dry, but the GS always has about 8oz-16oz of water in the hull.

Thanks in advance for the help,

-TheChad

 

[kustomkarl]

You might want to start with checking the condition of new spark plugs to see if they got fouled. It could also be dirty spark plugs. The carbs could be out of adjustment or in need of a cleaning also.

Follow the hose in the "Tell Tale" to see if it is plugged somewhere. That is the only way to really know if you cooling system is working correctly under way, as it bleeds of cooling water as it runs.
Here is some information on compression tests;

Compression Check

You'll need a compression tester. Go to Auto Zone. I think they sell for like $25.00. The compression gage, will screw in the cylinder head in place of the spark plugs. To test compression, remove the spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check all the cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. The ratio of difference is 10% difference between cylinder readings. I hope this helps you.


Again check the hoses for being plugged in the bailers.

Karl

 

[Dr Honda]

If it runs good if you hold the throttle a little... then turn up the idle. You don't need a tach for that one.

As far as the hesitation... that may go away once you bring up the idle a little... but will the engine run at a mid throttle setting? If it will... then you are fine, and just need to tweak it. If it doesn't run at the mid positions... then the carb needs to be cleaned.

The pisser problem... you need to take hoses off the engine, and blow thought them until you find the plug. There is a chance that only the pisser hose is plugged, but where there is one plug... there will be more. Get it cleaned before you burn up the engine.

I am running atleast some XPS synthetic oil, there was about 1/2 tank of oil already in it when we bought it, I topped it off with XPS Synthetic.

If you don't know what was in the tank... you should have drained it!!! 2-stroke oils don't always mix. You could be heading for a melt down. Personally, I would drain it... clean it out... check the filter (or replace)... then bleed it.


Finally... a little water on the bottom is normal. The balers cant get everything, but pull the hoses, blow thought them... make sure the little screens are clean, and make sure the tubes are tight in the pump nozzle.

 

[aeboi863]

you also might want to try some marine sta-bil for the rough idle to full throttle i used that in my yamaha waverunners one time when it was running rough like that and it fixed the problem since the engines arent made for ethanol in the gas. there are a few gas stations in my area that offer no ethanol gas and it works too. just incase you arent already using sta-bil its the blue colored 1.

 

[TheChad]

Compression Check

You'll need a compression tester. Go to Auto Zone. I think they sell for like $25.00. The compression gage, will screw in the cylinder head in place of the spark plugs. To test compression, remove the spark plugs. Place spark plug caps on the plug cap studs near the cylinder head to ground the empty caps. This completes the circuit of the ignition electrical system and prevents any electrical problems from the caps being un grounded. Using the correct adapter for the threaded end of the tester,( same length of the spark plug threads length)screw in the tester in one plug hole. Hold the throttle wide open. Push the start button. Watch the compression gauge, when it peaks out at the most compression, let go the start button. Read the psi number. I would do it 3 times to be sure it is accurate. Check all the cylinders the same way. The ideal compression is 150 psi per cylinder. If it is less, it's not a problem as long as they are close to being the same. If the psi is less than 90 it might need be time for a tear down and a rebuild. If the psi in 1 cylinder is say 140 psi and the other is 80 psi you need to tear down and repair. This difference is a lot then there is a problem. The ratio of difference is 10% difference between cylinder readings. I hope this helps you.

Karl

That's what I did, So the highest reading I get is 150 PSI, Just thought it was weird that it jumps up to 140 PSI then hovers there, but if you keep cranking it'll come up to 150 PSI.

If it runs good if you hold the throttle a little... then turn up the idle. You don't need a tach for that one.

Yes it does, I figure the idle is probably too low, but with out a tach, I don't know what the RPM's are so I can't verify that the idle speed is too low and/or adjust it to the proper idle speed. I hate to just crank up the idle if it's actually another issue.

As far as the hesitation... that may go away once you bring up the idle a little... but will the engine run at a mid throttle setting? If it will... then you are fine, and just need to tweak it. If it doesn't run at the mid positions... then the carb needs to be cleaned.

I was thinking the same, if the idle is too slow that could be the issue with the hesitation. The engine runs great at mid throttle. Once the engine is up past probably 2k rpm everything runs great!

The pisser problem... you need to take hoses off the engine, and blow thought them until you find the plug. There is a chance that only the pisser hose is plugged, but where there is one plug... there will be more. Get it cleaned before you burn up the engine.

Yeah, I had to do this with my Outboard once, it was a long day, finally got it though. I assume if I run the engine with a hose, that the pisser should work? (So I can test it?) I've read the operators manual about starting the engine before turning on the hose, and shutting off the hose before turning off the engine.

you also might want to try some marine sta-bil for the rough idle to full throttle i used that in my yamaha waverunners one time when it was running rough like that and it fixed the problem since the engines arent made for ethanol in the gas. there are a few gas stations in my area that offer no ethanol gas and it works too. just incase you arent already using sta-bil its the blue colored 1.

Yeah, I put 1/2 can of SeaFoam in both of the ski's with a full tank of gas.


Thanks,

-TheChad

 

[TheChad]

Okay I looked closer at the "Tell Tail" on the '01 GS and it's a pretty simple system. there is a 1/4" or 3/8" (?) tube that comes from under the exhaust (Source), it Tee's off to a 1/8" tube and goes to the "Tell Tail" and continues on to discharge into the exhaust port at the back of the hull.

The 1/4" or 3/8" tube is a clear tube and I can see water in it. I pinched off the tube coming from the source and blew air threw the "Tell Tail". The air blew out of the exhaust port on the back of the hull. So I know that line is not clogged.

My only guess is that either there is a small clog in the nipple that the tube connects to coming from the exhaust, and only allowing a little bit of water to flow to the "Tell Tail" system, which is just pumping right out the exhaust port, and/or the water is just following the path of least resistance and all just pumping out the exhaust port instead of climbing up hill in the Tee to the "Tell Tail".

-TheChad

 

[TheChad]

I checked the compression again today, except the first time I checked the compression, I only checked the front cylinder. This time I checked Both.

The Front Cylinder is 150PSI (This time goes straight to 150), However the back cylinder is only at 105PSI, I checked it several times and every time I get the same reading.

How is it possible to have 150PSI in one cylinder and only 105PSI in the other?

I am going to guess this means I need to replace the pistons/rings? I assume I should do both even though the front cylinder is okay? Can this be done with the engine in the ski, or does the entire engine have to be pulled to do this?

I have only ever replaced piston/rings on small a small 27cc engine before.

Do you think the difference in compression is causing the starting & off the line hesitation issues?

Thanks,

-TheChad

 

[kustomkarl]

It sounds like you found your problem, low compression. Now you need to find out what caused the problem. Tear it down and look closely at it. It would be easier to pull the engine, for ease of head removal. I do know some mechanics that do it in the seadoo, but it is a tight fit.

Karl

 

[TheChad]

It sounds like you found your problem, low compression. Now you need to find out what caused the problem. Tear it down and look closely at it. It would be easier to pull the engine, for ease of head removal. I do know some mechanics that do it in the seadoo, but it is a tight fit.

Karl

What exactly does it take the pull the whole engine?

I'm mechanically inclined but a little worried/scared about pulling the engine.

What would I be looking for to have caused this?

Will I need to replace both piston/rings, or just the 1 bad cylinder?

My local dealer said they don't repair/replace engine top half's because the lower half almost always fails shortly after, so they said they just order refurbished engines from SBT and swap them, all for $1600-$1800.

I only paid $900 for the ski, so that isn't going to happen!


I took the like 10 bolts off the top of the engine, which I thought would allow me to take a peek at the top of the cylinder head/pistons, but all it exposed was the inside of the cooling head.

How would I get the top 1/2 of the engine off? I found This place, for $285 I'll have a new top half.

Should I really rebuilt the entire engine at this point?

Thanks,

-TheChad

 

[aeboi863]

when my yamaha failed i just did the top half and ordered a top gasket kit. mine was a kid ran it before i bought it without oil just gas and it got so hot inside that the rings couldnt even be taken out of the piston. also had some scratching inside the block walls we had to regroove it. i think you can order each piston kit separately but while your in there mine as well go ahead and replace both of them is what i was told you wont know if there it already some wear on the other piston. just a heads up for you