rhino jet jon

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PSG-1
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rhino jet jon

Post by PSG-1 »

How is your fuel tank vent set up? Do you have a check valve? If not, you should. The check valve will allow air to flow into the tank, but not out. This slight pressurization assures proper fuel delivery. Note that when you remove the fuel cap on jet skis, they are under pressure. If you are just letting it free flow without a check valve, this could be starving the engine of fuel.

This is what was happening with the Tigershark engine I previously had in my boat....although, I did not figure that out until about 3 or 4 engine rebuilds later, and then blowing it up the final time and swapping to a 4 stroke. Every time it happened, it was a hole in the center piston. Tried everything with the carbs, jets, new fuel pumps, etc. The vent is an important key to a properly operating fuel system, especially on 2 stroke PWC engines. Outboard motors don't seem to care about a pressurized tank, but PWC's need that extra pressure to feed gas to the engine.
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brianb2247
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Post by brianb2247 »

My pop off is set up right the carb has a clean fuel filter , I do have a check valve, now if it works or not ill check
I went and put carbjets back to stock a removed the high flow air filter and put the stock air box back on, so everything is back to stock except the pistons which are105 psi in both cylinders

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Post by brianb2247 »

Should I be running 87 or 92 because of the lean running condition

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Post by brianb2247 »

Should I be running 87 or 92 because of the lean running condition

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Post by brianb2247 »

Also the 4 stroke conversion what were the expenses to upgrade and what would be some need to know info on the upgrade

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Post by PSG-1 »

Running higher octane gas may or may not solve the problem. Typically when a hole is burnt through a piston, it's from a lack of fuel.

As for a 4 stroke conversion, the main expense is the motor, and having to re-fabricate motor mounts for that engine. I paid 2500 dollars for my FXHO engine, hardly used, with just 67 hours on it. This being after p*$$ing away about $5K in rebuilds to the Tigershark engine. #-o
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Post by brianb2247 »

just before leaving for work i tested the vent i sucked on the end like a straw and couldnt get anything, but when i blew through it it would pass through but i can hear air escaping the tank somewhere when i blow in. from what im understanding the tank should hold a pressure of some sort right?

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Post by PSG-1 »

Yes, the fuel system should be holding pressure. Check all your fittings and clamps. As a side note, remember that ABYC codes require double-clamping all hose connections (with the exception of factory carb fittings, etc) This way if one clamp fails the other one is still holding, and that's very important with potentially explosive fuel.
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rhino jet jon

Post by brianb2247 »

ok got ya will do.

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Post by brianb2247 »

i made the repairs last night it was the fuel tank level sending unit the 20 year old sealant gave way , i ran the engine this morning and when i removed the plugs they were richer more than ever before . lets keep our fingers crossed

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Post by PSG-1 »

Good deal! Sounds like you might have found the problem if your plugs are now showing normal coloration.

That fuel leak was not only bad as far as potential engine damage, but it could have also been a potential fire/explosion hazard :shock:
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Watch it all right here:

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Post by brianb2247 »

well the engine is trashed once again rear cylinder piston has another burnt hole, im considering doing a yamaha 701 conversion or the more expensive 4 stroke yamaha install was wondering if i could get the info on where to buy the adapter for the drive line and maybe post some pics as to what the piece looks like when installed thanks guys

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Post by PSG-1 »

The driveline coupler is 2 halves like this:
I17283749.jpg
And there's a rubber 'spider' that goes between them,
images.jpeg
You will most likely need to cut new threads into the coupler, or possibly on your driveshaft, for it to work. You may also have to cut your driveshaft shorter if you go with a 4 stroke, as it's a few inches longer than a 2 stroke 3 cylinder engine.

If you are lucky and the threads of your driveshaft are larger than the existing internal threads of the coupler, all you have to do is put the coupler on a lathe, bore it out, and re-thread it to match the threads on your driveshaft.

If, however, your threads are much smaller, then you will need to bore out the coupler to 1 inch diameter, and TiG weld a piece of 1 inch solid round to the coupler. (As long as you bevel the joint and weld it properly on the front and back sides, it will hold, trust me!) After welding the solid round stock in place, put the coupler on the lathe and proceed to bore and then cut internal threads to match your driveshaft's threads.

Drilling/boring/threading the coupler is a precise operation....the threads must be cut square, and the hole must be centered. Any mis-alignment will cause the coupler to run eccentric, and this can lead to failure of thru-hull bearings. In other words, a lathe must be used. To simplify the operation of cutting the internal threads, you can use a tap, and secure it in the chuck of the tailstock, and unlock the tailstock lever, so it can move along the bed of the lathe.

MAKE SURE THE LATHE IS TURNED OFF, AND PLACED IN NEUTRAL FOR THIS NEXT OPERATION!! Start the tap into the hole of the coupler by sliding the tailstock toward the chuck until the tap contacts the coupler. Begin turning the chuck of the lathe by hand, while maintaining slight pressure with your other hand against the tailstock. After a couple of rotations, the tap should begin to bite into the material. Once you get it started, proceed to cut the threads in this manner, using a wrench or other appropriate tool to turn the lathe's chuck, and remembering to back it out and use some compressed air to blow clean the shavings out the hole every couple of turns.

Yes, it's a slow, PITA process to cut those threads. But unless you are good at setting up the lathe to cut threads, and you have a good sharp bit made for aluminum, I don't recommend trying to cut them by conventional means. And under no circumstances should you apply power and try to cut with a tap....you will shatter the tap like glass!!



Engine/pump alignment is as follows: when you set the engine on the motor mounts, and slide it back to engage the 2 halves of the coupler, you will need to determine if it needs to be shimmed. Using a small straight edge, lay it across the 2 halves of the coupler, and, using a feeler gauge, check the gap between the edge and the coupler, on both halves. Anything under .020" is within acceptable margins. More than that, and you will need to use shims between the engine and the mounts to get proper alignment.

Well, that's a general rundown of how to modify the driveshaft/coupler, and install it to match the pump. Hope this helps!
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Fishing, jet skiing, target shooting, jet-boating, and even a little oyster harvesting with Larry The Cable Guy.
Watch it all right here:

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brianb2247
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Post by brianb2247 »

i really appreciate the info , im definetly yanking out the tigershark junk im looking for a 4 stroke ski any tips on which ones to go for like hours or a certain model? im looking at yamaha products . also which direction does the engine turn from the back side of the engine , if there is any other info i should know feel free. thanks all

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rhino jet jon

Post by amk »

I bought a 2011 yamaha vx110 it's a four stroke has 900 hours on it I was going to put it in a ski but I've been to busy. Point being the 4 strokes can have some hours and be good.