787 Engine running rich

[TheChad]

Hey all,

I just purchased a used '96 SeaDoo GSX with the 787 engine, When I lake tested it, they had to put new plugs in because the old plugs were fouled, I lake tested it for about an hour.

I just pulled the plugs to check them, and while they are working just fine, they are wet fouled, they are dark black and look wet.

When the dealer installed the new plugs they didn't gap them, so whatever the factory gap was is what it was at. I just re-gaped them to the correct gap of .020", Per the operators manual.

I don't know if that will make a difference? What else do I need to do to get the engine running at the correct mixture so I wont keep fouling plugs?

I am new to Jet Ski's so forgive me if I ask a dumb question.

Do these carb's have adjustable needles or do you have to change jet's to adjust mixture? Since the Oil is automatically injected, I assume that the oil mixture doesn't need any adjusting?

I don't know if it makes a difference, the RAVE valve's on top of the engine look as though they are brand new, the one on the exhaust looks old(er).

Thanks in advance for the help.

-TheChad

 

[Dr Honda]

2-stroke engines will generally make the plugs look black from the oil it's burning. Unless it's fouling pugs every ride... don't try to lean it out.

With that said... there are a few things to check.

First... how's the compression? when the engine was first built, it had 150 psi compression, and it was able to burn all the fuel. As the engine wears, and the compression drops, it will burn the fuel less efficiently. If you have 135 to 145 psi... they will look dark.

Second. Just because the black parts look new... are the valves clean? (inside) You may want to pull them out and check them. If they aren't opening... you will burn a little rich since the exhaust timing will stay low.

 

[TheChad]

2-stroke engines will generally make the plugs look black from the oil it's burning. Unless it's fouling pugs every ride... don't try to lean it out.

Understandable. But should the plug be wet?

With that said... there are a few things to check.

First... how's the compression? when the engine was first built, it had 150 psi compression, and it was able to burn all the fuel. As the engine wears, and the compression drops, it will burn the fuel less efficiently. If you have 135 to 145 psi... they will look dark.

Second. Just because the black parts look new... are the valves clean? (inside) You may want to pull them out and check them. If they aren't opening... you will burn a little rich since the exhaust timing will stay low.

I didn't have a compression gauge, so I just went to the store and bought one. I may not be doing it right so bare with me..

I took the plug out and screwed in the hose to the compression gauge, I turned the engine over several times and took the reading? Is that correct?

I got 160 PSI.

I have not taken the rave valves apart, because they looked new I wasn't going to mess with them, but I will try and take them apart tonight..

Thanks,

-TheChad

 

[Dr Honda]

Dripping wet.... No. Glossy wet... yes.

OK... if you are a purest, and are tuning for absolute power... then yes, you can tune the engine to give a dark brown electrode, with an very dry surface to the electrode... but for the average person, a little rich is safe on a 2-stroke.

Personally, I worry about my 2-stroke engines if the plugs look light and dry. (a 4-stroke is a different story)


160 PSI... ok. That's good, as long as you didn't put any extra oil down in the spark plug holes, and the engine was cold. (your engine is healthy)



OK.... let's take a step back.

Is the ski running well? Does it start easy? is the top speed good??

If you are answering yes to those questions... don't worry about dark plugs. The cure to that is run it at higher speeds. High speed/RPM's will make more heat in the plug, and it will burn it self clean.

 

[TheChad]

Dripping wet.... No. Glossy wet... yes.

I won't say it was dripping, buy it was glossy for sure!

OK... if you are a purest, and are tuning for absolute power... then yes, you can tune the engine to give a dark brown electrode, with an very dry surface to the electrode... but for the average person, a little rich is safe on a 2-stroke.

Yeah, rich is definitely better than lean, but just seems richer than any other 2-strokes I've owned. With plugs at over $5 a piece, I just hate to foul them up even semi often.

160 PSI... ok. That's good, as long as you didn't put any extra oil down in the spark plug holes, and the engine was cold. (your engine is healthy)

Nope, didn't put anything in the spark plug hole, just unscrewed the plug and screwed in the gauge. The engine was definitly cold.

OK.... let's take a step back.

Is the ski running well? Does it start easy? is the top speed good??

If you are answering yes to those questions... don't worry about dark plugs. The cure to that is run it at higher speeds. High speed/RPM's will make more heat in the plug, and it will burn it self clean.

Yep, starts right up, plenty of power, runs great... As long as the plugs arn't fouled.

This machine is new to me so I just want to make sure everything is good. I don't know any of it's history, so all I can do is try to make sure everything is right from here forward.

Having 160psi with a 14 year old engine seems impossible unless it wasn't run very much and/or the engine has been rebuilt. Right? Or if taken good care of is that normal for one of these engines to still be in top shape after 14 years??

Thanks for the help..

-TheChad

 

[Dr Honda]

Yes... 160 for a 14 year old engine is impossible, since the spec at the factory was 150. So... either they put in new pistons/rings, or it has very little time on it. (slightly higher than spec could just be the gauge, or a little extra fluid on the rings)


If you get over to a dealer... they can read the computer, and tell you how many hours are on it.


If I get a chance a little later... I'll blindly pull a plug out of one of my SeaDoo engines, and post a pic. I'm sure they will be dark.

That engine is designed to run at high speed... so if you are running at half power, or even idling for long periods (like in a no wake zone) the pugs will "Load-up" and get dark. Once they get dark... it's hard to get them to totally burn clean.


One last thing. Since the ski is new to you... what kind of oil is in it?? Seadoo's are very specific on it's oil. It needs an API-TC oil.

 

[TheChad]

Yes... 160 for a 14 year old engine is impossible, since the spec at the factory was 150. So... either they put in new pistons/rings, or it has very little time on it. (slightly higher than spec could just be the gauge, or a little extra fluid on the rings)


If you get over to a dealer... they can read the computer, and tell you how many hours are on it.


If I get a chance a little later... I'll blindly pull a plug out of one of my SeaDoo engines, and post a pic. I'm sure they will be dark.

That engine is designed to run at high speed... so if you are running at half power, or even idling for long periods (like in a no wake zone) the pugs will "Load-up" and get dark. Once they get dark... it's hard to get them to totally burn clean.


One last thing. Since the ski is new to you... what kind of oil is in it?? Seadoo's are very specific on it's oil. It needs an API-TC oil.

The oil tank was/is plumb full when I bought it, but I have 1gal of XPS Synthetic oil waiting. I actually figured like the gas tank that the oil tank would be empty, so I bought a Gal of XPS. It was my suprise when I looked at the oil tank it was plumb full.


The hour that I road the ski since they put the new plugs in, I did do quite a bit of idling, the lake had a HUGE no wake zone to get away from the dock's, and after riding around for ahwile the wife and I were idling out in the middle of the lake discussing if we wanted to purchase the ski.

We are going out riding all day Sunday, So I'll check the plugs when we get back sunday. I am thinking though that I probably am not going to be going full throttle for long periods of time, short bursts probably most of the time. For one thing this ski is fast and a full throttle run runs out of lake pretty quick.

If after a few trips to the lake I see that I'm definitly not doing speed runs, is there something I can do to prevent the plug fouling? Either hotter plugs, or adjust the carb?

As I said I'd rather be safe then sorry and be rich rather then lean, but I definitly don't want to be droping $11 in plugs every couple trips to the lake.

How often do you have to change plugs on yours? (So I'll have an idea if I'm running about normal).


Speaking of hours, when I bought the ski the Info Center gauge was water logged and didn't work. I purchased a new (used) one from ebay, and installed it. The gauge displays "----" for hours, I was hoping that the gauge would read the hours from the computer. Any idea on this?



I just checked my wife's compression on her '01 SeaDoo GS (717), and the gauge hovers around 140psi, then if I keep cranking it or if I stop, then start cranking again it'll jump up to 150psi.

What's that mean? Still okay? At what PSI does it start having problems and need to be rebuilt?

Thanks for the help,

-TheChad

 

[Jeff_5_7]

Not trying to hijack your thread but i have the same problem. Got a GTX 787 crab motor it was just rebuilt 3 days ago. I but new plugs in it yesterday and it ran on the garden hose for about 10mins then today i go to the lake its running good. I started off just cruising at 5000 rpms 30mph after doing that for 5min i gave it some gas and it jumped up to 6500 rpms and then started running bad. Was only on the water like 7 mins. I pulled the plugs and the are dark black and wet a little more than glossy wet. I am running 32 to 1 premix and the rings are just seating as they are new. Also it smokes a good bit while idling white smoke. Do i just need to lean out my high fuel jets on the carb?

 

[TheChad]

Okay, we ran all day today, mostly in the 1/2-3/4 throttle range, some full speed runs, some idleing.

Here's a picture of the plug:

Sorry for the bad quality, it was taken on a camera phone.

It definitly looks better than before. It's not soo wet. Still black, but dryer.

I rechecked the compression tonight, and I am still getting 160 PSI.

-TheChad

 

[Dr Honda]

Chad....


for a 2-stroke, running at mid throttle, and idling a bunch... that plug looks great. The electrode, and porcelain are both dry, and gray. I even see a little brown on the flat of the ground electrode, and back on the porcelain.

Finally... our seadoo's don't have a thermostat, so they run on the cool side, unless you are on the throttle. When you have a 2 stroke dirt bike... there is a heavier load, and they run hotter... so it's easier to tune the engine to a nice dry, dark brown plug.


With what I'm looking at... I wouldn't change a thing.


Oh... as far as the $5.50 per plug thing... stop buying them at the dealer for full retail. I buy my plugs at the local auto parts store. (AutoZone, or Advance Auto) and they are $2.25 each. (half price) and if you watch their sales... you can get them for $1.50. (I buy them by the box [10] when they are on sale)

 

[TheChad]

With what I'm looking at... I wouldn't change a thing.


Oh... as far as the $5.50 per plug thing... stop buying them at the dealer for full retail. I buy my plugs at the local auto parts store. (AutoZone, or Advance Auto) and they are $2.25 each. (half price) and if you watch their sales... you can get them for $1.50. (I buy them by the box [10] when they are on sale)

Sounds good, I won't change anything! It ran GREAT and that plug looks alot better then it did before. Sometimes it takes a few cranks to get it started if it sits at the dock for a little bit, but it's a Carbureted 2-stroke, so I don't expect it to fire first crank every time like a fuel injected 4-stroke.

As for the plugs, I was going to order some on eBay they were like $2.50/each, but then I read This and assumed that the dealers would carry those plugs instead of the 'standard' larger gap ones. So I went to the dealer and told them I wanted 6, once they rang them up I was shocked at the price, then I got them home and found they wern't pre-gapped at 0.018" and I had to regap them all anyway!

So lesson learned, I will buy them cheaper in the future. Any idea where to find those 0.018" pre-gapped ones though? I Couldn't find them anywhere on google. I guess it's an aircraft plug?

I have 2 extra plugs on both ski's, so I wont have to buy any at the dock store again.

** I looked at AutoZone and the P/N for the BR8ES's they carry is 5422 (Removable Terminal Nut), the model I bought from the dealer is 3961 (Solid Terminal Nut). NGK says "Solid terminal top cannot be removed. Some application require a solid top due to its greater durability than an aluminum terminal nut and will not unscrew under high vibration conditions."

Thanks for all your help,

-TheChad