Bad Knock/Ping

[hockey911]

Hi all i was riding my bike (200 miles) this morning, my engine may have kicked the bucket on me while riding....

It lost power, gave me a low oil pressure light (Killed the motor), i cruised it into a gas station, i took off the valve cover and cant see anything wrong other than maybe the timing chain slipped (it wasnt as tight as i remember it being)


anyways the bike starts up no problem first hit, but makes a deadly knock/ping noise and has no power

I checked the oil and i have full oil on the dip (clean)

Any ideas?

Im thinking a bad rod/link pin at worst.... and at best bad timing chain???
Anyone know


Bike 82 gs450 29000 miles, 2000 miles since last oil + Shim Check

 

[tom203]

"took off the valve cover and cant see anything wrong other than maybe the timing chain slipped (it wasnt as tight as i remember it being)"

How about checking crank to camshaft timing before any more starts? Do you understand how camchain tensioner is supposed to work?

 

[chuck hahn]

Me thinks it may be too late if the chain jumped. Thats knocking is most likely the piston beating the crap out of the valves.

 

[Guest]

The oil pressure loss would indicate a rod bearing; timing chain jumped wouldn't affect that. It can be a touch slack if the motor kicked back a bit when stopping. One rotation and a check of the cam timing will tell that story.

My guess is the left rod; that's the one that goes first, probably because it's furthest from the pump although the size of the gallery below it should balance that. I'm sure that somebody has blown a right rod, but all the knackered cranks I see are the left.

 

[hockey911]

Just verified the timing and oil!

Ran a compression test
(from sitting on bike)
Dry + Cold
RHS 150psi
LHS 90 psi

Oil pressure light goes off after first crank

 

[Guest]

If the rod is loose enough, the compression will be lower. If you put an appropriate sized screwdriver or similar down the plug hole [don't lose it down the hole] with the piston about halfway up, moving the crank a bit back and forward should give a smooth motion; if it's a clunk clunk with some lost motion the bearing is gone. Both sides should feel the same. Don't turn by the small 10mm bolt but by the big 19mm [3/4"] one.

You may have seized a piston, although that's rather rare. Usually a bent or burnt valve won't generate 90 psi, but a scuffed cylinder wall might leak enough.

The oil pressure with cold oil could be enough to turn the light off even with a spun rod bearing. One thing to check is the cam cap bolts; they can get stripped out so don't over tighten.

 

[hockey911]

Oil is gold, spun bearing

Is it worth replacing bearings?

Or should i part my gs450 tx out?

 

[Guest]

Too bad you're on the opposite end of the continent from me; I have a spare motor looking for a bike and I love the '82 450T. Too far to ship and a border in the way.

It's just way too much complication to replace a crank, and the crank will be toast. You could look for a replacement motor; not much to slipping those in and out, but the dealers seem to want an arm and a leg for them and they're usually in Idaho or wherever.

Any idea as to what caused it to fail?

 

[hockey911]

Too bad you're on the opposite end of the continent from me; I have a spare motor looking for a bike and I love the '82 450T. Too far to ship and a border in the way.

It's just way too much complication to replace a crank, and the crank will be toast. You could look for a replacement motor; not much to slipping those in and out, but the dealers seem to want an arm and a leg for them and they're usually in Idaho or wherever.

Any idea as to what caused it to fail?

My best guess was an overheat, 75 f night at 65mph for 45 min.... But i dont know why that would kill it

 

[Guest]

My best guess was an overheat, 75 f night at 65mph for 45 min.... But i dont know why that would kill it

65 mph is under 6000 rpm and these motors should do that indefinitely, even at 90F. In fact, they run cooler at that speed than in town with stop and start. There's no way the oil got too hot doing that speed.

What sort of oil were you using? Was the filter recent? I'm almost suspicious of the pan gasket; there's a section that seals the filter cavity with two holes and if that goes it can dump your oil pressure back into the sump. These holes act as a dump for crud from the filter cavity and lead to wells in the pan which are convenient for cleaning, but if anything goes wrong with the gasket you are in trouble, as there is no external leak. The oil pressure is something like 70 psi max.

The bottom end is the same as a GS500 and people run the hell out of those with only rare blowups. Just seems to be a random thing, but you wonder if there may be a reason, but going 65 all day is nothing; do it all the time and often faster.