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Discussion Starter #1
Hey guys,

I have a 2001 Yamaha XLT1200 that has a knocking noise at idle. It seems to get better(Quieter) with RPM and is also smoking pretty good. I am new to 2-stroke engines so im not sure what is normal but it shakes pretty bad at idle and knocks with a metallic sound.

Videos are attached of it running and pictures of what I found.

Could it be bad gas from storage (I added Stabil marine before winterizing)? Something worse?

This is what I checked so far. No results


Compression is 110-100-110 front to back.
Pulled powervalve cover on the middle cylinder – pictures attached.
Power valves are actuating together
Changed spark plugs – no change in mentioned sound
Checked spark – have spark in each cylinder
No lack in power(That i know of)or bogging

Any ideas?
[VIDEO]

[VIDEO]

[VIDEO]



Also, what is that wire coming off of the exhaust? its not plugged into anything....Looks like exhaust temp?


Please help....
 

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Based on your pics, compression is good at 115, 110, 115. Slight gap, but still inside 10% rule.

How many hrs on ski?

In the 3rd video from under ski. The rattle is from your pump. It's the impeller ringing. It may be the blade hitting the wear ring. Has the original wear ring been replaced with a plastic replaceable?

The wire is as suspected, the temp sensor. If the cat has been replaced by a D-plate then it is disconnected on purpose. And a chip is plugged into the other end to fool the computer that it's gone.

Again based on your pics it appears that there are no wave eater clips or updated power valve links installed. This can allow the pin to fall out and into the cyl. If the link that lifts the valve is open on the end and you can see the pin end. You'll need to fix asap. With either wave eater clips or updated links. Wave eater clips are installed over the original links and are easiest. Updated links require disassembly of the valve drive shaft to install.

Also if this ski is still oil injected you should check and replace the oil lines asap as well. The injection system is bulletproof with the exception that maintenance is always overlooked. The lines from the pump to carbs harden, shrink, and pull off or break. Starving motor of oil.
 

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Discussion Starter #3
The ski was rebuilt recently. Im not sure of the hours but it should be minimal. It was rebuilt only a year or two ago from what im told.

I havent checked the wear ring. is this something that is easy to do for someone mechanically inclined? also i only found parts for a housing for the wear ring, not the ring itself(Other than a stainless one).

Im not entirely sure of what you mean by "pin end". is the pin the shaft that connects to the couplers and go thru the power valves front to back horizontally?

I was told the oil injection was bypassed.
 

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In pic, the valve pin is circled in red. The link with open end in tagged in green. When assembled in the motor the pin is in that open ended slot in the link. There is nothing to stop the pin from sliding out and into the motor. This end most get blocked either with the wave eater clips or the updated links that have the end closed to keep the pin in.

The oil injection being bypassed is fine if properly done. IE, pump removed, block off installed and system properly cleared.
I personally like the injection as they are a variable ratio pump. Mixing 200/1 at idle up to 30/1 at full throttle. Saves on fouled plugs in no wake zones or extended idle time.

The wear ring if original is a stainless insert in an aluminum housing. Some after market assemblies use a plastic replaceable ring. If the ring is the problem they are easily replaceable with minor effort. If it's plastic I'd find a good used original on eBay and go back to factory style.
 

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Discussion Starter #6
hey, so i tried to take the nozzle off today.... i got the reverse hood, all the linkage and hoses off and the 4 bolts... but it wont budge. is there a trick i dont know of or do i need some mechanical advantage. If so, i think im going to
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have to take off the plate under it.
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Thanks again
18735
 

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Yes it's easiest with the ride plate removed. Becarfull removing bolts without plenty of soak time with pb Blaster. From you pic it doesn't have a plastic insert type wear ring from what I see.

There are spots on the side of the pump to pry. Use easy pressure. A small wedge like a chisel works well.
 

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Discussion Starter #8
removed ride plate, came off with a little persuasion. It doesnt look too bad to me. is it supposed to be super smooth? should i fire it up without the shaft in there to see if i get the same sounds without it spinning the prop? or will this cause damage to the ski?


Thank you
 

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Wear ring looks good. Impeller shows a little damage. Nothing major though.

How do the brgs in the pump feel? When you turn the shaft is it smooth or a bit gritty?
You can run motor without pump. Won't hurt anything.
When you put it back check the clearance between the edge of impeller and the Wear ring. It should be .014/.018" less then .014 is ok. Just not below .008/.010. Clearance should be even all the way around. you'll have to remove the intake grate to do it.

It could be a bit of vibration from Ballance being off a bit causing it to bounce around the ring. But the noise in the video is definitely impeller blade ringing. Should be fine with load on it in the water.
 

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Discussion Starter #10
the shaft has a little resistance but is smooth and not gritty at all.

I am going to get the feeler gauges out tomorrow and check. Im also going to start it up to see if it still makes that sound.

Viedos to follow.

The pictures attached are the blades. would this pitting cause an imbalance? and is that normal to have?

Also, it looks like a pain in the ass to remove the exhaust to check if there is a d-plate or not. The picture attached is where it would be installed can you tell from that? also, when i pulled back the boots and stuck my endoscope inside, i couldent see a d ring or cat. just the curvature of the inner part of the exhaust.

Thank you and happy friday!
 

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Impellers are balanced of coarse when there new so any damage will throw it off a bit. Those marks in pic appears to me as cavitation burns. With the impeller being out now would be the time to change it. The Salas Concord work very well in these skis. Yours is a set strait pitch impeller. an after market will be dual pitch giving you better low-end/top-end performance. Impros is who I order from. They carry everything you'll need including the shaft holders.

Yes that is where the D plate would go I believe the piece of metal you see in-between the two halves is the D plate. If it weren't in there your and system set up for it I believe you would have a temp alarm going off with that wire disconnected. Look for the other end off that wire. It should have a chip taped into the end of it.
 

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Discussion Starter #12
It looks like the problem is something with the impeller like you said. Started it up today without the pump attached, and no metallic noise. video attached. still choppy but that was a cold start, right to idle with stabilized gas -less smoke this time as well.

There looks to be a chip on the plug. so Im going to assume the d-plate is in there.
Im going to check gap on the impeller.

I do have a few questions though.

1. what impeller do you recommend? im not sure what they mean by "limited engine"
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2. is there something that will tell me if im overheating if i am running hot?
3. is there anything i should grease/lube/change/check with this ski to get it ready for the season?
4. should i grease the shaft before i put it back in?

This is the video of it running. Is the motor noise considered normal for this? I may just be me. Thank you.

 

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Yf-cd-12/18 stock motor. Is what you want others are highly modified motors.

Yes there is still temp switch in the exhaust the disconnected one is for the cat only.

Only thing to need grease is the mid shaft. Using a good Marine grease. The zerck fitting should be on top of the exhaust right where it turns down at rear of motor.

Before putting the pump back in clean the splines on the shaft end and clean the 6" area below the splines with very fine sand paper. Then apply Marine grease to splines and a light coat on first few inches of shaft. There is a seal just below the spline area that should be lubed.

Video: I don't see or here anything. It's hard to tell from video. There not the smoothest idling motor out there. After it's run a tank or so check to see what the plugs look like. The center electrode should be a dark brown. If one cyl isn't then you'll need to resolve.
 

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Discussion Starter #14
I am going to take these out for a spin in a few weeks. After that i will check the plugs and see how they look. I dont have the time or $$ at the moment for a new prop , so i did some light filing on the prop to smooth it out and it seemed to help. Also, this my wife's and i first full year of skis so im sure well suck up something and i figured its better to put a new one on then than now.


Thank you all again for the help.
 
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