Blaster 61x Knocking Sound

W

WB1nMI

Location
Michigan
Hi all,

I've got a 94 WaveBlaster that blows 150 psi F/R and runs well, except it has an awful knock that is very present when the hood is lifted.

I pulled the coupler cover off last night to inspect the midshaft and didn't see anything, so I removed the spark plugs and began turning over the engine by hand. The knock was simulated on part of the up stroke.

Any ideas on what the source is internally? I plan on disassembling the engine this week to determine the cause, but wanted to hear y'alls initial thoughts.

Yamaha 701 61x Noise
 
Big Kahuna

Big Kahuna

Administrator
Location
Tuscaloosa, AL
sounds like a bearing going out. I had an issue a few years back, I was doing the same thing, rolling the coupler around and I could hear what sounded like marbles falling. 5 more minutes of riding and the crank would have failed and taken my motor out. pull top end and check.
 
Mike W

Mike W

Infidel
Location
North Florida
I had a blaster a few years ago that had he same knocking sound you are describing. The wrist pin bearings were on their way out. I would check them ASAP before it takes your motor out like BK said.
 
X

X2Kid

Location
Canberra, Australia.
And don't just replace the little end bearings and go on your merry way. Many years ago we lost a 650 Kawasaki engine. One cylinder was toast but the other was still pumping with the little end of the rod elongated in a visibly oval shape. Bearing was still together! This process may have started on your rod and replacing just the wrist pin and bearing will be pointless. Have the little end carefully checked to see if it can still run a bearing (assuming the little end is the problem).
 
DAG

DAG

Yes, my balls tickled from that landing
Location
Charlotte, NC
In regards to the arbitrary spot during the up stroke. Do you know if this was at top or bottom dead center? if so very confident its a crank and/or wristpin bearing on its way out.
 
W

WB1nMI

Location
Michigan
Pulled the top end and found the rear piston was like "a hotdog down the hallway" in the cylinder. Quite a bit of damage to piston itself and heavy scuffing on the cylinder walls. I can't see any damage on the ports so I hope a bore / hone will make the cylinders serviceable again.

Here's a video of the loose bore


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W

WB1nMI

Location
Michigan
Big Kahuna said:
how about the wrist pin bearings? did you try pulling on the rod? Rotate the crank around and listen.
Click to expand...

Connecting rods have no up / down play, and have minimal lateral play. Wrist pin and bearings looked OK.

I'll rotate the crank this evening to see if I hear or feel anything wonky.
 
W

WB1nMI

Location
Michigan
Another item - I've only had this WaveBlaster for a couple months. First time I rode the ski it seemed "slower" than it should be, so I installed a fresh SBN44 (jetted to factory specs) and pulled the oil injection. Ski ran well except for knocking sound.

Does any of the damage indicate a possible fueling issue? My riding season is pretty much over with, so I want to make sure the WB is 100% next year.
 
Mike W

Mike W

Infidel
Location
North Florida
Now is a good time to pull the motor. Crack open the case so you can inspect all the crank bearings, install new seals, new gaskets and new top end with new wrist pins and wrist pin bearings. Check your impeller for damage, check pump bearings and intermediate shaft, rebuild if needed. Open the ebox to check for corrosion and serviceability of components. Maybe throw in a fresh coil with new wires for good measure. Rebuild carb with a genuine Mikuni kit. Then it will be 100% for next season.
 
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