96 XP Revival

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Your oiler is oiling right? Just making sure that you have seen smoke and confirmed the flow.

My next move would be to try different carbs. I've had some that just would not run for some reason so I make sure to mark or discard those carb bodies. It's rare but it does happen. There is still the spark pick up possibility also. With that one you could put a cheap spark tester inline and watch it while it's running before you tear in.

Thanks Matt! I was thinking the same thing about the carbs. I actually just ordered a new set about an hour ago.

I did check the oil system. I put new lines on it about a week ago and watched the lines fill. I’ve got good flow there and have made sure all or the linkage is adjusted to spec. I do need to change the oil in the tank though. It does have an API-TC oil in it, but it’s a dual rated Pennzoil mineral oil, so I’m going to change it once I get this issue figured out. I know it goes against the grain here to use the dual rated stuff, but I’ve had good luck with it in non-rave motors, and it’s what was used before I had the ski. I’m dealing with enough variables already, so I didn’t want to add the possibility of oil gelling to the mix.
 
The only Pennzoil I’ve found that’s listed as meeting API-TC is the Premium Outboard & Multipurpose. It’s in the yellow bottle with a green label, and states that it meets API-TC on the label. Like I said, I’m going to change it on this ski. I’d much rather use a synthetic oil, especially since this one has Raves. My dealer is finally being “friendly” and selling the BRP oil to me at a decent price, so that’s what it will ultimately be run with. When they were asking $60/gallon, it led me to look for an alternative, but I can live with $40/gallon now.
 
The only Pennzoil I’ve found that’s listed as meeting API-TC is the Premium Outboard & Multipurpose. It’s in the yellow bottle with a green label, and states that it meets API-TC on the label. Like I said, I’m going to change it on this ski. I’d much rather use a synthetic oil, especially since this one has Raves. My dealer is finally being “friendly” and selling the BRP oil to me at a decent price, so that’s what it will ultimately be run with. When they were asking $60/gallon, it led me to look for an alternative, but I can live with $40/gallon now.

$40 is a really good price!
 
What Pennzoil are you running? The only ones I see listed are all TCW-3 only.

The reason I had used that particular oil in the past was that the aviation guys were having such success with it in the Rotax ultralight engines. I knew I had seen an article on it, and I finally found it again. They are using it in the Rotax 503 in these tests, but they run in a similar load and rpm range that our skis do, although they’re obviously air cooled. They mention that the 618 guys are running it with rave valves as well, but the consensus from everyone here seems to be to use synthetic. Anyway, it’s an interesting read.

Two stroke engine oil, two stroke engine oil test, testing results for two stroke aircraft engine oil.
 
The problem I see is their site now only shows it as only a TCW-3 rated oil and it isn't synthetic. For a cheaper alternative I would consider the Mystic and Lucas before the Pennzoil.
 
The problem I see is their site now only shows it as only a TCW-3 rated oil and it isn't synthetic. For a cheaper alternative I would consider the Mystic and Lucas before the Pennzoil.
I just noticed that as well. It’s still labeled as API-TC on the current packaging, but them pulling it off their site leads me to believe a formulation change may be coming. I wouldn’t suggest anyone else go experimenting with that oil at this point for that reason alone, but it was interesting. It’s one of the only instances I’ve seen of any testing done with a dual rated oil on any Rotax engines.
 
Well I got the new carbs today, so I threw them on and decided to go for a test run. The low end hesitation and spitter is almost completely gone. I need to tune just a bit, but it’s almost spot on. Once it warmed up, it ran solid at full throttle, although I’m still only getting 6300 to 6400rpm out of it, and I don’t feel that midrange hit that it should have when the raves open up. After running good for about 15 minutes, the power drop off reared it’s head again and it started to fall on its face at full throttle again.

I pulled the seat off again when it started acting up, and I had quite a bit of water in the hull and a leak from the regulator. It looks like it’s coming from where the housing threads into the fitting, and it’s loose, but its not tightening up when I turn it, so I’m going to pull it off and go through it. I have another housing I can use if the threads are stripped, so I can get that fixed.

I also still have the glass inline filter on the fuel line, and I noticed that there is some air at the top of that filter. I’m thinking this is where the issue lies, but I have no idea where there could be a leak. I guess I’ll go back to running straight from the reserve and see if that makes a difference, but in the meantime I’m still chasing ghosts...
 
You know, I haven’t checked the vent itself. I cracked the fuel cap a while back when I was trying different things, but I really should rule that out.
 
So I just confirmed that the fuel vent is working properly. It releases at right around 3psi when the hole under the hood is plugged and I attached a pump to the vent line from the baffle. I can also blow air in from the port under the hood and hear bubbles in the tank when everything is connected. I did find that the check valve on that line does not seem to stop flow in either direction though. If I pressurize the line without plugging that hole, it releases from both the under hood port and the vent under the rub rail. Is that normal? If so, what is the purpose of the check valve?
 
You shouldn’t get bubbles from the vent unless the tank is 100% full.

Are you sure you have the hoses correct on the baffle?

So the check let’s air into the tank to take the space of used fuel so a vacuum doesn’t develop. The check also keeps a little pressure in the tank to keep the fuel system primed. There’s also a pressure relief on the same hose as the vent to keep tank pressure from exceeding 3 psi and cracking the plastic tank. They are two separate valves.
 
You shouldn’t get bubbles from the vent unless the tank is 100% full.

Are you sure you have the hoses correct on the baffle?

So the check let’s air into the tank to take the space of used fuel so a vacuum doesn’t develop. The check also keeps a little pressure in the tank to keep the fuel system primed. There’s also a pressure relief on the same hose as the vent to keep tank pressure from exceeding 3 psi and cracking the plastic tank. They are two separate valves.

I double checked the routing of the hoses into the baffle, because I thought it was strange that I could hear bubbles as well. They are all on the correct nipples according to the engraving on the ring around the baffle.

I know they are two separate valves. I pulled the line off of the baffle and plugged my popoff tester into it to pressurize the line and both sides of the tee. I get air from both the vent by the steering stem under the hood and the pressure relief valve under the rub rail. If I put my finger on the hole by the steering, the pressure relief valve releases at a couple of psi like it should. I assume I need to replace the one way check valve in the line from the upper hole to the tee. I doubt this is my entire issue, but I guess it needs to be replaced.
 
Well I ordered a new check valve, a new selector valve, and some T-bolt clamps for the fuel lines as well. I’m going to make absolutely sure I have nowhere for an air leak to occur. I’m still wondering why I can hear the fuel bubbling when I put air through that vent line though. Anyone have any idea why that would happen? I thought the vent was high enough in the fuel baffle that it wouldn’t touch any fuel. The tank is at about half, so I don’t think that should happen. The baffle itself looks fine, no cracks or anything out of the ordinary...
 
You know it's been years since I actually looked at the vent connection inside a baffle, maybe it extends lower than we all assume. I should have a few out in a week or two that I'll take a look at.
 
I’d appreciate it. I was looking for a cutaway diagram of the baffle, and they all seem to show the fuel float mechanism, but not the vent connection for some reason...
 
Maybe the fuel pickup tube is sealed all the way down to where the fuel enters the tube. The vent might drop straight into the top of the fuel pickup/ gauge float tube and vent from there. If you blow air into, the only place for it to exit would be thru the bottom of the fuel pickup tube.
IIRC, the tube is sealed and only has an opening at the bottom.
Since you have half a tank, the bottom is still submerged.
 
Maybe the fuel pickup tube is sealed all the way down to where the fuel enters the tube. The vent might drop straight into the top of the fuel pickup/ gauge float tube and vent from there. If you blow air into, the only place for it to exit would be thru the bottom of the fuel pickup tube.
IIRC, the tube is sealed and only has an opening at the bottom.
Since you have half a tank, the bottom is still submerged.

That makes sense, it’s just a weird way to design a vent system. Then again, it is Bombardier...
 
Finally some success! When I swapped the carbs on Monday, the pulse line nipple was broken, so I had to pull the cover off of the old carb and replace it. It looked fine, but it’s been bothering me that I had this one part that was left from the set up that didn’t work. I had also already tried running directly from the reserve nipple and bypassing almost all of the fuel system to rule out an air leak. Well today I pulled the fuel pump cover off and replaced the diaphragm just to ease my mind, and I also went back to running directly from the reserve nipple on the baffle. I put it in the water and it ran great! I’m pretty sure that the fuel pump diaphragm was somehow leaking air when the pressure rose. There’s no crease or pinholes, so I’m not sure how it happened, but that seems to be it. I ran for about an hour today with a healthy dose of full throttle passes and it never even sputtered!

I also found my issue with the rpm drop at constant throttle. I’ve had the raves turned all the way in, and I think that drop off is just the point where they drop back closed. It was far more pronounced when I had fueling issues, but I turned them out to flush today and the issue is gone completely. When I crank the caps back down, I can feel it come back.

I’m still only getting 6400rpm out of it, but I have a good idea what’s causing that too. I think it’s a cable linkage issue and I’m not getting the throttle butterflies open 100%. I noticed when I adjusted the oil pump cable this morning that the nut is all the way back on the barrel to get it lined up. I’m going to play with the throttle cable and then readjust the oil pump, but I think that’s it.

So ultimately it appears to have been a combination of issues. I greatly appreciate all of the help from you guys. This has been driving me crazy, and I probably would have thrown in the towel if you guys hadn’t kept giving me direction...
 
i have had a FEW carbs that had the sealing edges leak. That is more common than not. The pulse barb being cracked was a big issue. You lost fuel and sucking air. I would call lucky there! Glad you found it!
 
i have had a FEW carbs that had the sealing edges leak. That is more common than not. The pulse barb being cracked was a big issue. You lost fuel and sucking air. I would call lucky there! Glad you found it!

The pulse line was broken on the new carbs. That was just poor handling by the good old USPS... It was never run with a cracked nipple. The fuel pump cover and diaphragm was the only part that I had to move over from the old carbs. I was lucky to catch it, because I would have been chasing this forever if I hadn’t been bothered by it so much and swapped that diaphragm just for the hell of it.
 
Good catch nonetheless. When tearing apart a parts ski, some folks can be kinda rough. I myself have pulled the carbs off and forgot to pull the pulse hose or cut it. You end up with a yank and don't think twice about it. Lesson learned.
 
I'm really glad this is getting sorted out. It's been on my mind. Man it must have felt great feeling it run strong and consistent for a change.
 
I'm really glad this is getting sorted out. It's been on my mind. Man it must have felt great feeling it run strong and consistent for a change.

It was nice for sure! I’ve still got to find my missing rpms, but that will get sorted out. This was a tough one to diagnose with so many little issues going on at the same time, but of course the main issue was something simple. It always seems to be something that gets overlooked that causes such difficult problems.

I was going halfway nuts running through what else we could have missed on this thing, so I can appreciate that someone else was stumped as well! I said I wanted a project when I rescued the ski from sitting on cinder blocks in backwoods TN, and I sure got one... There were a couple of times that I had to pull the 95 off of the trailer and wring it out just to renew my motivation to finish this one.
 
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