Heavy knocking/pinging

[lexkyboater]

My Dad has an older white and red Yamaha WaveRunner that's like a 400 or 500 cc I believe and it knocks or pings heavy at idle, then clears up as you accelerate. My brother replaced plug and impeller shaft seals, but it doesn't accelerate very good at all. Any ideas? Could this be a crankshaft balance problem, or maybe an issue with the crank bearings? It sat for several years, but seemed to crank good when my brother got it going, it just knocks like it's going to come apart in short order. TIA, Steve

 

[Jeff Walkowiak]

Re: Heavy knocking/pinging

rebuild the carb, it sounds like there is a fuel issue

 

[lexkyboater]

Re: Heavy knocking/pinging

Okay, but does almost sound engine related. It is NOT a light knocking like it's detonating, if that helps describe it better. And it happens consistently as the engine rotates. Really sounds like something internal to engine mechanically.

 

[Jeff Walkowiak]

Re: Heavy knocking/pinging

if it were a internal problem it would get worse when it goes faster, 2 stroke engines knock and bang if they are not getting the correct mixture while idling as they shake and cause things like the exhaust system to rattle

 

[lexkyboater]

Re: Heavy knocking/pinging

Okay, will take a look. That is definitely a possibility after it's set for a while, and not sure my brother cleaned the carbs. Will see if we can check that out.

 

[jayp0209]

Re: Heavy knocking/pinging

interesting, i just bought a 2001 yami GP1200R and it does the same thing... new engine 3 hours on fresh SBT engine, dealer just put on 2 NEW, not rebuilt, but new yami carbs and rebuilt 1.... the work was done in a tank to make sure the ski performs ok under pressure..... ( new to me ski ) i put it on the hose to hear it run, when it idles it has that knocking sounds like its coming from the motor... but revves up nicely and sounds good when it does, and it idles right back down , does not run away at all... ideas?

 

[jayp0209]

Re: Heavy knocking/pinging

anyone?

 

[Jeff Walkowiak]

Re: Heavy knocking/pinging

lots of things make noise, the drive shaft bearings going through the hull can make a lot of noise if they are bad, the impeller hitting a bulge in the pump liner can make noise, a bad rod or crank bearing also can do that. to check the rod bearing play, remove the plugs and rotate the engine by hand, bring up the piston just past top dead center to where you see it going down, then use a screwdriver to push on the top of the piston, if it clunks there is a bad bearing usually the rod bearing but sometimes a wrist pin bearing, if it feels tight it's ok. do this to each piston if one is loose and clunks the engine will need to be fixed.