1998 SPX intermittent problems

[OSiRiSNZ]

Hi there,

I bought my first PWC, a 1998 SPX a month ago from today. Ran absolutely brilliantly for the first month of use, took it out probably 15 times (Summer here in New Zealand :hurray and never skipped a beat.

I have learnt that my SPX has had a few modifications;
UMI racing bars with finger throttle conversion
Primer kit installed
Converted to premix
Reserve selector valve removed
Worx sponsons

I have learnt quickly now to ride my little SPX, and just over the weekend I used a full tank (approx 2 hours use) at "Half Moon Bay" which was very calm. Filled it up again with the correct mixture 40:1 and felt a little brave and took it for a 10 minute ride through rough water from "Eastern Beach" around a peninsula to the calmer waters of "Half Moon Bay".

The little SPX ran fine through the rough waters and when I reached calm waters it was running as normal. Did a couple of full throttle runs then brought it into shore. Stopped then engine and achored it. Jumped back on 5 minutes later and it wouldn't start at all! Took the seat off, everything seemed fine but could not get it to start at all. I even changed the spark plugs while floating just off the beach! After 5 minutes of trying to start it, the battery started getting weaker so I put it on the trailer and took it for it's wash out. Washed the outside etc. as normal then tried starting again, would not start. I left it for the night.

The next morning I tried it out, started up first crank as normal! I was very surprised. Flushed the engine and then took it out to "Eastern Beach". Water was flat this time and the craft ran fine for about half an hour. I rode it out to the 200m bouys then gave it full throttle, slowed down, turned around then full throttle the other way. Seemed ok. Brought it back in to shore and let my mate have a ride. He took it out, full throttle, did a tight turn and then all of a sudden lost power. He limped it back in to shore. He said that the craft felt as if it was "rev limited" just above idle, even with the finger throttle pulled wide open. Eventually after about a minute it picked up and went back to normal but it would "limit" itself intermittently.

Floating in the water at the beach trying to figure out what it could be, I realised that we had left the funnel type thing that is normally under the seat at home. I realised that the vents near the front where your knees would be positioned when you are sitting down lead up to the seat, and air flows through the seat and then down that funnel. If water was induced it would flow through and be directed to the bottom of the craft via the funnel, I could imagine if the funnel wasn't there that water would go everywhere. Which would explain why there was splashes of water sitting on top of the exhaust.

I got a towel and unplugged the wire that goes into the top of the black box next to the battery, I found that the plug was a little wet. I dried this with a towel and all other wires that were wet. Meanwhile my mate went home to get the "funnel" and when he came back about 20 minutes later we put it in and fired it up. Started straight away and rode it out. Everything seemed ok for about 10 minutes until a hard turn around a buoy it was on it's "limit" again. Limped it back into shore, put it on the trailer and took it home.

While at home, puzzled, we began a strip down, after reading many many articles on this forum I felt pretty confident I knew what I was doing. Checked the fuel filter, looked completely clean. Bear in mind I have only ever used 95 RON and BRP Seadoo 2 stroke oil premixed to 40:1. I then proceeded to remove all the exhaust pipes and the factory airbox. I then removed the carbs and inspected the little (TINY!) carb filters. These were very clean compared to some photos of black dirty filters here on this forum. I cleaned them anyway and put them back in. I also noticed that all the important fuel lines have been converted to reinforced black fuel lines.

Scratching my head not knowing where to go next I decided to have a look at the rave valves, just to learn more about how things worked. Pulled the black and red caps off (the red adjusters were flush at the very top adjustment) and then slid the "guillotine" valve out of the MAG side. Looked ok, just a little dirty. Pulled the valve out of the PTO side and was very surprised at my finding. I have attached an image. It seems as if a piece has broken off the valve. I looked inside the cylinder with a light and I can't see any traces of metal or any scrapes or damage to the piston. I also pulled ALL of the exhaust piping out and could not find the missing piece. I came to the conclusion that the broken piece went out the exhaust.

My initial thoughts were that the electrics were getting wet when turning sharply or splashing through waves which is what is causing the jetski to lose power.

Questions I have;
1.) What caused the valve to break? Bearing in mind that the jetski ran fine up until the rough ride in the water.

2.) What symptoms would a broken valve exhibit?

3.) Would the broken valve cause the jetski to run intermittently? I can't understand how this would be related though.

Thanks in advance, and my apologies for the long post. I just wanted to make sure that I got every bit of detail leading up to this problem.

:cheers:

 

[seadoosnipe]

Well written.......

You never have to apologize for a thread where your description is this detailed. I loved it. If you think it's long, you've obviously not read any of mine!........:rofl:

Yes, the broken RAVE is your running problem. What your going to need to do now is pull the head to inspect the piston. It's possible that the piston has a hole in it.

Did you do a compression test? If so, let us know what you got. Or, put everything back together as it was, then do the test.

This type break usually occurs when someone mods an engine with oversized pistons and doesn't take into account, they have to shave the guillotine valves. I'm not sure if this is the case for you because you don't mention it. But you do mention that you have mods that you were unaware of.

Get back with us after the compression test.:cheers:

 

[OSiRiSNZ]

You never have to apologize for a thread where your description is this detailed. I loved it. If you think it's long, you've obviously not read any of mine!........:rofl:

I have read many article of yours actually, just recently the strip down submerged 787 engine Very informative :hurray: After reading your article I felt confident enough to work on my jetski, considering this is my very first jetski and I have no prior knowledge of how this engine worked.

Yes, the broken RAVE is your running problem. What your going to need to do now is pull the head to inspect the piston. It's possible that the piston has a hole in it.

Did you do a compression test? If so, let us know what you got. Or, put everything back together as it was, then do the test.

This type break usually occurs when someone mods an engine with oversized pistons and doesn't take into account, they have to shave the guillotine valves. I'm not sure if this is the case for you because you don't mention it. But you do mention that you have mods that you were unaware of.

Get back with us after the compression test.:cheers:

Ok I have ordered a new valve, which should arrive tomorrow. Once I receive that I will put everything back together then conduct a compression test and post the results.

What makes you sure that water isn't getting to the electrics? Or anything else? I'm not doubting your knowledge, I am just interested to know why a broken valve will cause intermittent problems, not just a constant "no power" problem.

 

[timmyboy76]

possible senerio..

I say, take a gander at fuel system/delivery...carbs, selector valve, lines, o-ring on inline filter...etc. Also, replace the Rave.

PERFORMANCE TIPS
The "Left Turn Syndrome"
You will find in all instances that your watercraft will turn more easily to the right than to the left. The reasons are basically simple. First, engine torque constantly places pressure on the hull to turn right. If your engine's performance is marginal, you can notice a dramatic falloff in power in a hard turn. This power falloff can't always be blamed on the engine, being over-propped can also cause the engine to slow enough to fall off its power peak. An engine with a peaky power curve is especially susceptible to a very dramatic power loss in a hard left turn. Most recently, with the increase of Sport and Runabout racing, there has been a marked improvement in hull design with a dramatic increase in "G" forces encountered while turning: over 2.5 G's. In some instances such a hard turn can cause momentary loss of power due to fuel starvation in the carbs. Jetting changes cannot correct this situation, the best solution is to rotate the mounting of the carbs 90 deg, so that their throttle shafts are perpendicular to the crankshaft axis rather that parallel. To date, this solution to the problem has been 100% successful.

 

[OSiRiSNZ]

I say, take a gander at fuel system/delivery...carbs, selector valve, lines, o-ring on inline filter...etc. Also, replace the Rave.

I have cleaned the carbs including filter, there is no selector valve as this has been removed already, lines have been converted to black reinforced fuel lines, o-ring and fuel filter have been checked and are ok.

RAVE valve ordered so should be here in a few days.

 

[OSiRiSNZ]

This type break usually occurs when someone mods an engine with oversized pistons and doesn't take into account, they have to shave the guillotine valves. I'm not sure if this is the case for you because you don't mention it. But you do mention that you have mods that you were unaware of.

Do you have any information on how to grind down the RAVE valve?

 

[seadoosnipe]

suffocation?.......

The description you have posted shows signs of suffocation. This happens when you have an exhaust leak or a build up of CO2 in your engine compartment. You need oxygen for combustion to take place. I'm thinking with the RAVE valve broken, you may have had CO2 building up from this. I haven't seen the whole picture yet, but with the broken valve, this is the first place to start.

The comression test is important but more important is the condition of your piston. You'll need to inspect it before putting in that new rave valve. You might, and I mean, "might" be able to bring it up TDC and look through the open port of the RAVE and get a good enough look, with a flashlight to see if you have a potential problem. But I would not grind or re-install that new RAVE until you find the root cause to the problem.

You asked about water into the electronics? These systems are sealed from water. They are considered water resistant, not water proof. You can sink the ski and as long as you get it up fast enough, you should be able to recover with little or no problems to the electrical system.

Oh, BTW, please never be sorry for doubting my ideas.........that's why it's a forum. I'm as human as you and everybody else here in the forum. There are several good mechanics here, not just me. So, if you get confused or are in doubt, please, post it!.......don't hide it.:cheers:

 

[6KJR]

This thread is interesting as sometimes I have had that problem of getting a bog from the engine after horsing around in the water for a while, and it generally goes right away after a few pumps of the throttle. I didnt think anything of it because my friends 1200 yamaha will do the same thing sometimes when hes out going crazy on it.

 

[Stunnerable]

Something else to take not of is the spark plug wires and the ground wire for the battery. It's always good to remove the wire from the boot and cut it back.. after a few years corrosion can build up weakening the spark. I bought a 96 XP years ago that was heavily used.. went out wavejumping and it died on hard impacts.. this was the problem. It can also make your boat feel like its dieing.. you can pin the gas and not make it above 3K rpm.

 

[OSiRiSNZ]

New valve and gaskets arrived.

I have also obtained a new racing head and air filter.

Because I had the jetski apart I have sent away items to be cleaned up and coloured. I aim to put everything back together on the weekend of the 7th of March, as I will be away on holiday until then :hurray:

 

[timmyboy76]

carbs...

think'n, with the new mods ur install'n, ur gonna need to rejet/tune the carb/s..(needle and seat psi), for optimal performance, or you'll have mess on ur hands...

 

[OSiRiSNZ]

think'n, with the new mods ur install'n, ur gonna need to rejet/tune the carb/s..(needle and seat psi), for optimal performance, or you'll have mess on ur hands...

What specs will I need to tune to?

 

[timmyboy76]

manifold pressure...

when install'n a "free-flow" arrestor, ur lowering the manifold pressure, in which the carb n/s works off of..relatively speeking. So for carb to function properly, the n/s will need to "pop-off" at a much less "psi" than it would with the stock-restrictive arrestor.
With the set-up ur goin at, i'd say get a 2.0n/s with "black 95gm spring, achieve around 20-25psi, which should be ok.
With the mod-head, you'll need to go up in jets, might even need to bump up octane, depend'n on the compression reading...:cheers:

 

[OSiRiSNZ]

when install'n a "free-flow" arrestor, ur lowering the manifold pressure, in which the carb n/s works off of..relatively speeking. So for carb to function properly, the n/s will need to "pop-off" at a much less "psi" than it would with the stock-restrictive arrestor.
With the set-up ur goin at, i'd say get a 2.0n/s with "black 95gm spring, achieve around 20-25psi, which should be ok.
With the mod-head, you'll need to go up in jets, might even need to bump up octane, depend'n on the compression reading...:cheers:

When I get it all back together I will post compression details on here then take it from there.

On a side note, when the new valve arrived I noticed it was made it Italy. No wonder why it was so expensive :ack:

 

[timmyboy76]

factorypipe.com../carb tuning...

When does it become necessary to adjust pop-off?
When personal watercraft come from the factory they have fairly high pop-off due to the fact that they also have somewhat restrictive air intake systems that cause the engine to generate very high manifold pressures; the higher the manifold pressures, the higher the pop-off pressure required to properly regulate the fuel delivery to the engine. As you modify or change your watercraft's flame arrestor to a less restrictive type you will most likely start to experience a lean hesitation caused by a decrease in manifold pressure. This change will require an adjustment in pop-off pressure to regain crisp throttle response. Because most aftermarket flame arrestors are less restrictive than stock, you will need to decrease pop-off to compensate.