So a deal on a pretty clean 06 ls650 with 3700 or so miles on the clock fell in my lap. It had been purchased 2nd or 3rd hand about a year ago, tinkered with just enough to get it running... then ridden about 30 miles and parked. It sat in the weather untouched until I drained the varnish out of the fuel bowl and tank. I gave it some fresh fuel, set the petcock to prime till fuel ran out of the airbox. It fired up, to my amazement; immediately. I was able to ride it home (about 10 miles) with no problems per se` at cruising speeds, but it wanted to die trying to idle.

A little bit about me...
I'm a very seasoned mechanic, machinist, welder, blacksmith, and most recently taken up my hand as a beekeeper. I have pretty much all the tools and equipment in my garage to repair, rebuild, modify, or fabricate anything the mad scientist living behind my eyelids needs to set the robot apocalypse in motion.
I have plenty of experience with most assortments and configurations of internal combustion contraptions. The softest spot in my charcoal heart is for diesel, but I enjoy the intricacies of these small air cooled jobbers almost as much.
My forte` is diagnostic and forensic mechanics. I do so enjoy identifying and solving the root cause of a mechanical failure.

Back to the bike.

It has for certain been laid down on both sides in its life.
Minor dings and scrapes, busted foot pegs.
The turn signal posts all the way around need replacements.
Clear coat on the fenders is pretty badly oxidized.
Chrome is not in too bad of shape.
Some light oxidation on the aluminum all the way around.

The good...
Everything seems to work ok.
It pulls like a freight train.
Fairly decent mileage so far at 42mpg.
Absolute top speed of 84mph so I cant get too stupid on it.
Only 3700 miles on it when I rode it home.

So far I have pulled the carb and cleaned the jets... That cured my idle issues. I have 4150 miles on the clock now and getting pretty comfortable with it. On Saturday, I went for about a 100 mile ride and issues arose.

I was pushing it a little hard against about a 10mph wind for about 30 miles. I started to hear what sounded like a shroud rattling that soon progressed to correlate with rolling on throttle. First thought was exhaust leak at head due to overheat so I backed off of it and let the needle fall to 65mpg. Immediately started hearing double exhaust report. Echoing exhaust pops from the tailpipe, and the head. Shortly after it lost power and started to die like it was running out of fuel. Switched it to reserve on a whim and it slowly picked back up. When it reached what felt like full strength about 20 seconds later I switched it back to "on" and gently cruised the last 3 miles or so into the next town. Stopped at a gas pump and topped off and let it cool down for a few. It developed a tick on the left side. The exhaust wierdness seems to have subsided but the tick persists. Oil looks good and feels unbroken.

From what I have already read.... Im looking at a problem tensioner, a loose flywheel nut, or valve lash adjustment... That about the stone skinny of it?

It still pulls like a freight train, No smoke, No abnormal backfiring...
Exhaust is pretty much solid blue to the shroud, then a blue patch after the shroud on the tailpipe.

I'll be happy to fill in any blanks I may have overlooked.

Your under-load issue sounds like the vacuum petcock. I had the same problem. It ran around town OK, but on a day out with friends, trying to maintain 65 mph against a 20 mph headwind, I kept running out of gas. If I switched to PRI, it would pick right back up. Switching back to RUN would cause it to run out of gas again in a mile or two.

It was a combination of a low-vacuum operating situation (maintaining near WOT under a heavy load) and an old, to-stiff petcock.

Christof13T wrote on 08/15/17 at 10:29:09:



Define "delete kinda situation".

We need to know what you are working with before being able to advise you.  Open up your carb and find out what's in there.

What year is the bike?
Most likely looking at a petcock issue.  Read about swapping it out with a genuine Yamaha Raptor.  It's a direct fit, non-vacuum petcock that cures all kinds of woes.
Doubtful the tensioner is getting out there with so few miles.

Although it's pretty young to be the cam chain, you don't know the back history so I'd say it's worth a look.

Chain dragging, knocking low down are real red flags.
If it's cam chain, the knocking will occur just to the rear of the oil filter.
Put your hand there and you'll feel it.

Piston slap you won't be able to locate it.
Mine was due to a burnt piston.
If you have an eyeball on a stick, pull sparky and check the edge of the piston.
Mine was near the far intake.

verslagen1,

Looking at the modified tensioner you offer... it looks like the housing is slotted on both sides, the plunger is drilled, and a roll pin pressed in... If mine has not catastrophically failed... is there any reason I couldnt slap it on my mill and replicate your method to secure it? What is that about an 1/8th " slot? (Haven't pulled it apart yet so no frame of size reference lol)

Gotcha.

This tick/knock really has me scratching my head.
It's source seems to move with my ear lol.
I did not feel any significant vibration associated with the tick/knock at the case cover behind the oil filter cover. I previously did not hear the noise around the head... but listening to it earlier today I just can't be sure. It's not quite to that tell tell sign of a counterweight kissing the bottom of the piston from rod journal being chewed but darn if it doesn't sound like that double tick of slack being taken up at tdc and bdc and the lightest kiss of the piston to the head. I still cant fathom that much damage at the mileage unless someone ran it with no oil at some point?

verslagen1 wrote on 08/16/17 at 22:44:57:


So the rod length ensures clearance between counterweight and piston...
Counterweight should not contact cylinder unless mains have let loose and allowed the crank to walk around, correct?

After more reading I have the sneaking suspicion it's the wrist pin.
Still hoping it is something ... else... lol

I'm gonna see if I can get a decent video of it posted.