PoA Jet Ski Project

IIRC, if you take off the four vertical bolts from the manifold to the top angle pipe, remove the head discharge hose, and take off the other four bolts from the pipe to the chamber, then that big bolt on the side of the crankcase, you can remove all the exh without much trouble. Gives you a lot of room to look and work down there. Of course, I forgot the hose clamp around the chamber discharge.

Once you get the exh housing out you can inspect it real well, and see how the flow works. Don't drop anything into the exh manifold sticking up or it'll fall right into the crankcase below one of the pistons. Stuff a rag in there for safety. Remove the rag before assembly.

In skis that are used in salt water, this is where you would really clean stuff out well. Look at the preheat pipe, and make sure it doesn't have calcium crud blocking it. Also that drain fitting, and the mixing nozzles at the exh pipe where the water dumps into the gas exh discharge.
 
Well I haven't lost sight of purpose, which was basically to get my hands dirty. So I'm alright with this, though the kids were bummed when the day was over. And so was I, but not because the fun was done, but because I didn't immediately know what was wrong, and I don't enjoy being clueless. Once I flushed in the driveway and saw water building in the ski, the light bulb went off and I had a gleam in my eye; now I had a hint of the source of the problem and I could see a plan of action. The girlfriend even remarked that she could see my mood change. :D
 
asechrest said:
Well I haven't lost sight of purpose, which was basically to get my hands dirty. So I'm alright with this, though the kids were bummed when the day was over. And so was I, but not because the fun was done, but because I didn't immediately know what was wrong, and I don't enjoy being clueless. Once I flushed in the driveway and saw water building in the ski, the light bulb went off and I had a gleam in my eye; now I had a hint of the source of the problem and I could see a plan of action. The girlfriend even remarked that she could see my mood change. :D
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Order the manifold to exh pipe gasket, and maybe the exh pipe to exp chamber gasket. If you want to be pro-active, you can order all the rubber lines and one of those 'while you are in there' jobs just do all those lines at once. don't confuse the gaskets though, one has solid face, and one has ports for the water discharge. Then when you get it apart, you can stuff it all back together without waiting. As mentioned, check your bilge pickup for crud too. Easy to work on once the exh system is out.
 
If you have a lot of corroded chamber issues, don't forget to look at aftermarket solutions. Some of them on the 2 strokes make better power.
 
docmirror said:
My Kawa 900ZXI has run flawless for years. It gobbles batteries every other year, and uses a ton of gas, but it's the Energizer Bunny as long as the tank is full.

Does anyone know a battery that will last longer than two years? I condition them every winter, and keep them on a float, but by the third year summer, they are still dead, dead, dead.
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Try a gel cell battery.
 
Digging this one up since I finally had a chance to pull the ski out and look for the source of the leak. It appears to be coming from the outboard side of lower exhaust/cooling chamber. I could feel a stream of water coming out the side, and I can feel some sort of hole there, though I haven't laid eyes on it yet.

IMG_20151129_143152.jpg

I assume the side of the chamber has just corroded through. I am going to start disassembling the exhaust system and we'll see what I find.
 
If the manifold is 5+ years old, it has lived its design lifespan. That it went through the outside first is a good part design.
 
Alright, I got the muffler riser off. It looks fine.

IMG_20151129_213438.jpg

The muffler body (blue, which is the leaky bastard in question) appears to be bolted to the exhaust manifold (silver) by only two bolts. I have those removed, but the part won't budge. As far as I can tell, the connection points of the muffler and manifold are stuck together.

IMG_20151129_211229.jpg

Should I just be banging the **** out of the muffler body with a hammer until it breaks loose? :dunno:

PS - Here is a photo from an Ebay listing for a muffler body. See that little raised bump at the bottom? I think that's my failure point. Is that designed as a failure point so it warns you with a "small" leak vs. catastrophic failure once corrosion is bad?

s-l1600.jpg
 
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Bah, ok, figured it out. The connection points between muffler body and manifold have posts. I had to hammer a chisel between the connections and I was able to work it off. And here's the cause of the hull filling with water:

IMG_20151129_221628.jpg
 
I ordered a replacement muffler body off of Ebay. It appears to be in good condition. Also ordering new gaskets for the joints between upper and lower muffler chambers.

Am I supposed to add any gasket sealer to these metal-type gaskets?

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A wise man replaces wet exhaust as a unit. You cannot see them go bad because they go bad inside the water jacket. All the parts go bad at a similar rate. The first part that went bad leaked into the hull, the next point of failure may fill your engine with water. If they are 5 years or more old, they have made their "TBO" value, everything after that is a bonus, but if you over play exhaust, it costs you an engine.
 
Take a screwdriver to the replacement to make sure it's not rotted.
 
The part that is important to to prod at is the inside lining of the manifold and riser. When those go through is when you lose an engine.
 
Henning said:
The part that is important to to prod at is the inside lining of the manifold and riser. When those go through is when you lose an engine.
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I can't quite envision how the water flows through the manifold in my ski. I'll have to look when I get home. I know how it flows through the lower chamber (blue), and the riser (blue), but not if and how it flows through the manifold (silver). Does it have a water jacket like the other parts? It must, because it has direct access to the cylinders, so I know water doesn't flow through the main part of it.
 
asechrest said:
I can't quite envision how the water flows through the manifold in my ski. I'll have to look when I get home. I know how it flows through the lower chamber (blue), and the riser (blue), but not if and how it flows through the manifold (silver). Does it have a water jacket like the other parts? It must, because it has direct access to the cylinders, so I know water doesn't flow through the main part of it.
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There are two channels through your exhaust manifold and riser. There is an inside passage through which exhaust gas flows, and a passage between that casting and the outer shell casting that provides a water jacket to keep the engine compartment cool. This continues up through the riser, and somewhere down stream of the hump will be a mixing manifold where the water sprays into the exhaust stream cooling the muffler and the rubber coupling hose and plastic bits at the end. When that inner jacket perforates between the exhaust ports on the head, and hump in the riser, your engine will be ruined.
 
Henning said:
There are two channels through your exhaust manifold and riser. There is an inside passage through which exhaust gas flows, and a passage between that casting and the outer shell casting that provides a water jacket to keep the engine compartment cool. This continues up through the riser, and somewhere down stream of the hump will be a mixing manifold where the water sprays into the exhaust stream cooling the muffler and the rubber coupling hose and plastic bits at the end. When that inner jacket perforates between the exhaust ports on the head, and hump in the riser, your engine will be ruined.
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Ok, I see it now. I wasn't understanding that the water is also flowing around the actual manifold piece. Now I understand how failure of the inside casting of this piece ruins the engine -- water flows right into the cylinders. So I guess it makes a lot of sense to replace this, too. But I don't wanna. :D

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I didn't replace my entire exhaust system. I inspected and replaced as needed.
 
asechrest said:
Ok, I see it now. I wasn't understanding that the water is also flowing around the actual manifold piece. Now I understand how failure of the inside casting of this piece ruins the engine -- water flows right into the cylinders. So I guess it makes a lot of sense to replace this, too. But I don't wanna. :D

900_manifold__28597.1413297246.480.480.jpg
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Punch around the inside, if it passes that, smack it a couple of times wth a dead blow mallet, then shake it and listen for anything rattling. If you hear anything replace. Thing is, if it's 5 years old, you need to repeat this annually with still no assurance of no failure.
 
Henning said:
Punch around the inside, if it passes that, smack it a couple of times wth a dead blow mallet, then shake it and listen for anything rattling. If you hear anything replace. Thing is, if it's 5 years old, you need to repeat this annually with still no assurance of no failure.
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That photo is poached from the internet. Mine is still bolted on. I'll prod it as much as I can through the up-facing exhaust outlet. I wonder, though. Is the manifold designed to fail on the outer casting well before the inner casting, thereby warning you of the issue (with water in the hull) well before it "warns" you of the issue with water in the cylinders?
 
asechrest said:
That photo is poached from the internet. Mine is still bolted on. I'll prod it as much as I can through the up-facing exhaust outlet. I wonder, though. Is the manifold designed to fail on the outer casting well before the inner casting, thereby warning you of the issue (with water in the hull) well before it "warns" you of the issue with water in the cylinders?
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The part designed to fail first just did. Where it goes next is anybodie's best guess. You have received your warning, you are now gambling.
 
I doubt any of it is designed to fail first. Were it I, I would just make sure that a few stabs strategically done on each part in question doesn't penetrate or produce any noticeable yield. Then I would bolt it together, check again for leaks, and run it hard. YMMV.
 
Got the "new" muffler body (sorry for vid orientation):


I'm also replacing the exhaust riser. Something I don't understand is this; the gasket between the exhaust manifold and exhaust riser has only a single tiny hole. But the riser (and muffler body) itself has a bunch of long openings for the water jacket, so it looks like the gasket actually blocks nearly all of those openings. Which seems to mean that all the water flow from the manifold into the riser, which I think is the main coolant flow, comes through that tiny hole. What am I missing? (This has also caused a bunch of junk to build up behind the gasket in those "blocked" openings.)

IMG_20151208_230430.jpg IMG_20151209_000910.jpg IMG_20151208_230320.jpg

The new aftermarket gaskets are metal coated with some sort of material:

IMG_20151209_001705.jpg

Anyway, I'm cleaning everything up to prepare for the re-install.
 
Is there a correct term for being obsessed with necrothreads? Is that a Necrothreadphiliac?

I may be one. I'm gonna start surfing infomercials for the cure.
 
rolivi said:
Is there a correct term for being obsessed with necrothreads? Is that a Necrothreadphiliac?

I may be one. I'm gonna start surfing infomercials for the cure.
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I just figured they're remaking old movies, we might as well revive old threads.. Nice distraction from the elections. :)
 
Blast from the past! Thanks for pulling it back.

The jet ski sat without the exhaust pipes until just a couple months ago. I lugged it around through the purchase of my first home, and after laying my own flooring in the new house and various other home projects I finally got around to installing the new-used exhaust parts (procured on Ebay), with replacement gaskets purchased from SBT.

And...it's been working like a champ! I've had it out a bunch of times since and I'm real pleased with it. Top speed still 50-60 depending on seas. Who knew a 21-year-old boat could provide so much fun? (and I learned just recently that this model was watercraft of the year the year it came out.) The fuel sending unit is still busted but I cope. That's probably the next fix.

Good times.
 
asechrest said:
Blast from the past! Thanks for pulling it back.

The jet ski sat without the exhaust pipes until just a couple months ago. I lugged it around through the purchase of my first home, and after laying my own flooring in the new house and various other home projects I finally got around to installing the new-used exhaust parts (procured on Ebay), with replacement gaskets purchased from SBT.

And...it's been working like a champ! I've had it out a bunch of times since and I'm real pleased with it. Top speed still 50-60 depending on seas. Who knew a 21-year-old boat could provide so much fun? (and I learned just recently that this model was watercraft of the year the year it came out.) The fuel sending unit is still busted but I cope. That's probably the next fix.

Good times.
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Nice to see you back!
 
Digging this one up. Jet ski still runs great. This is the one of the all time great projects I ever did, and it's kind of amazing how you all had a hand in helping me.

But...I have a new project! A 2002 Derbi GPR (not mine in the photo). I bought it as-is. This is a Spanish-built "sport bike". In Europe there is a large market for small displacement bikes for young drivers as they are not allowed to ride larger displacement bikes. Really, though, this is a glorified moped. Typical set up is a 50cc 2-stroke engine, six speed. However, mine appears to have the 75cc engine with upgraded carb.

This version is called "Replica" because it's made to look like their 50cc and 75cc class racing bikes.

Anyway, this was an impulse buy. It's in bad shape. The seller rode it in front of me but the electrical system is in shambles. I'll post some pics maybe, perhaps in another thread. I also have never ridden a bike in my life.

Should be fun...
 
I can't imagine there's too much to the electrical system to begin with, lol. Probably less than a dozen wires, right?
 
SoonerAviator said:
I can't imagine there's too much to the electrical system to begin with, lol. Probably less than a dozen wires, right?
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Dunno. I'll count them. The wiring harness is in my trunk, and half the connections on the bike end in frayed copper wire.
 
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