Fouled plug?

[tomcat&family]

Fouled plug? 1999 GTX RFI issues.

Hello-

We bought two used 1999 GTX RFI boats on Saturday to go along with our RXP. Before we put them in the water, we changed the spark plugs to some high performance plugs (the brand eludes me at the moment), cleaned them up well, etc.

We had a blast on them yesterday out running in Lake Huron (there were 2-4 foot waves with the occasional 5-6!). The boats ran fairly well- not as peppy as the RXP, but that's to be expected! Neither of them idle very smoothly, but one is worse than the other.

GTX RFI #1: I saw RPM's at idle (after driving for a little while) anywhere from the high 1200's to the low 1400's, and the idle would slow as the boat idled longer. If I turned it off and let it sit for a bit, the idle would be fine after I turned the engine back on. However, after a short run, it would be idling rough again. At the end of the run (it had been running for an hour to an hour and a half), the RPMs dropped down below 1000, and I had almost no power. After further inspection on the lift, I noticed that the front plug was fouled (really dark black and dry). The other plug was slightly wet- exactly like the two in the second GTX. After installing new plugs, the engine fired right up and was idling normally. What could cause this issue? The guy we bought them from said that one had an problem with fouling plugs, so we kind of expected it.

GTX RFI #2:

This boat ran well (like the other), but the idle seems to be a touch rough and also low. To be sure, what should these boats be idling at in and out of the water?

Also, how does one go about tuning one of these engines. Can you even tune them? I run nitro R/C trucks; is tuning one of these anything like tuning a smaller nitro engine?

Both boats performed well other than the issues at idle. They accelerated quickly, didn't hesitate or bog, etc. I was surprised at how well they ran, to be honest. I'm pretty new to working on jet skis, so that's why I came here. If anyone has any input on how to remedy these problems, I would greatly appreciate it.

Thanks,


Tom & Family.

 

[timmyboy76]

Which kind, LOSI/Associated....Drake edition, with the wasp(ported).
Remove the RAVES and clean them, there under the 2 red dots housings. With being injected, maybe fuel system/injector could be clogged little/filter...also, check out air system, screan/filter may be choked little....:cheers:

 

[tomcat&family]

I run Traxxas R/Cs.

Thanks for the recommendations. I will be sure to check those things out.

I did some testing not long ago, and have some more information.

#1: After warming it up and doing several runs at WOT, it would idle pretty constantly around 14xx. But you could hear/feel it kind of reving up a bit or something- it's hard to explain. I don't think that it is idling right. This ski topped out at 58mph @ 6600 RPM. After I put it on the lift, I pulled the plugs. The rear one had a golden brown/dark brown plug and it was slightly oily at the tip of the threads. The front plug was pretty dry with less discoloration (it was more white).

#2: This one ran faster than the other and at a higher RPM: 63mph @68xx-69xx RPM. It starts out idling around 14xx and slowly goes down. The furthest I let it get was around 11xx RPM. Both plugs on this one were like the rear one on #1. This one did have less fuel (about half as much).

We ended up going out for a run with the two GTX's, since the water conditions were so perfect. Running side-by-side at around 20ish mph, they were both running around 3900RPM. Not long into the trip, I spotted a smaller craft near shore with someone trying to wave us down. I was just barely able to make out the person waving from the distance, but I'm glad I saw them. It was an older couple with an engine that just quit on them. They were about a mile from there house, so we towed them over. Though I tried not to accept it, they volunteered to pay for our fuel (gave us $20). They said that if we didn't take it, they would just come down and find us to give us the money! They actually thought our skis were new, too.

Anyway, after we got them back home, we continued on. We run out in the Straits of Mackinaw, and we were heading towards the bridge. It was the best jet skiing ride I have ever been on. Between the perfect water conditions, the nice weather, and the overall great ride... awesome. The skis were running beautifully at 30-40mph, and we were having a great time- you can't ask for better conditions. I didn't check the plugs after the run, due to the fact that I was running later than we had planned, and was late for dinner!

Again, thanks for the help.


-Tom and Family

 

[tomcat&family]

Well I tried to work on it just a bit ago, but I wasn't having much luck. The weather is nowhere near as nice as it was yesterday, and it looks like it might rain. I am working on these boats while they are on the boat lift, so if the weather is bad, I'm out of luck.

The first thing I messed with was the RAVE valves. For starters, it appears that I have three of them; two on the engine and one in the back. I tried to disassemble them, but I didn't get far. I remove the cap and spring and used a 10mm ratchet wrench to loosen the black cap. That only went a little ways before it just kept spinning and not coming off any more. There was a green seal around the edge with a spring retainer around it. Do I have to remove that spring retainer and the green seal to get the black cap off? That is what I thought I had to do, but since I wasn't sure, I thought I'd put it back together and ask you guys. Now if I push the cap in, how should that react? Should it stay low, should it come back out a little bit, should it come all the way back out, etc?

Then I tried to check out the air filter system. Could the engineers at Sea-Do have found a worse spot for the front lower clip? I cannot get to this clip enough to release it. With the other 5 clips removed, I was able to peer in side of the air box and examine the metal mesh filter. That looked clean, but I did notice some oily residue towards the bottom of the air box. Is that normal?

I have been reading a little bit on RAVE valves around these forums, and read about adjusting them. The red caps on GTX #1 are screwed all the way in. One post I read mentioned how he noticed lower RPM's and a lower top speed when he had the caps screwed all the way in. Should I try flushing those up and try it that way?

 

[timmyboy76]

Tommy...dont adjust the one on the waterbox, but the 2 on manifold, the geotins screw into it, so you should after remove'n the 2 allen bolts, should pull them up and out, on the raves, yah, theres a spring arm hold'n black cap down, remove the spring arm, pull cap, dont lose the spring though, then proceed remove'n the 2 bolts on each...

 

[tomcat&family]

But how does the spring arm release? I unscrewed the bolt as far as it would go, and I wasn't able to get the black cap to come out. Is the spring arm you refer to the spring retainer I was referring to? The long spring that wraps around the green seal?

 

[tomcat&family]

I got the RAVE valves cleaned up and reinstalled (see this thread for details). I also checked the compression, and got 150 psi on both cylinders.

That being said, anyone else know what could be wrong with GTX #1? I haven't had a chance to test it since rebuilding the RAVE valves, but do you really think that those would be causing the fouled plug, the lower peak RPM, and the lower top speed? The compression is great, so that's definitely not the problem. Possibly the air/fuel/oil mixture? How do I go about adjusting the idle speed on these boats?

 

[tomcat&family]

Yikes, three posts in a row! More info to add:

I have service records dating back to 2004. It appears that this problem (fouling plugs) started back in 2003. I have an invoice describing the issue, and here's what the Sea-Doo dealer did:

In 6/04 the boat seems to have fouled a plug by the description (sounds just like what happened on Sunday). There is also a note stating that the same thing happened last year. Then in 10/04, the description reads: "Unit fouls spark plugs. After replacing the plugs you can maybe get a days use out of it, but no more." Here's what the dealer checked: "Checked RAVE valve, compression, spark, all were good.Put unit on buds and found no faults. Reset, close TPS, and set to 6.7." It goes on to say that they will have to test it in the spring because the conditions were too bad to take it out for a test drive. Obviously those things did not fix the problem.

With this newfound information, what do you guys think is wrong? I am new to the sport, and am going to need some help figuring this out.

Thanks.