[mscuddy]

A buddy of mine has a '94 XR600 Honda that's been maintained well enough (indestructable bike) but lately something strange is happening:

When the bike is started up, hot or cold, it makes a knocking noise that goes away in a couple minutes.

Bike runs fine and pulls good, no noises when running or under load. Just when it's sat for a few minutes, the knocking noise starts again, and goes away. Plug is clean and the motor uses no oil. Oil & Filter is clean. Using the recommended 10/40 Honda Motorcycle oil. Ignition timing checks out.

Any ideas you MOrons?

 

[Buzglyd]

A buddy of mine has a '94 XR600 Honda that's been maintained well enough (indestructable bike) but lately something strange is happening:

When the bike is started up, hot or cold, it makes a knocking noise that goes away in a couple minutes.

Bike runs fine and pulls good, no noises when running or under load. Just when it's sat for a few minutes, the knocking noise starts again, and goes away. Plug is clean and the motor uses no oil. Oil & Filter is clean. Using the recommended 10/40 Honda Motorcycle oil. Ignition timing checks out.

Any ideas you MOrons?

Could be those pesky hydraulic lifters.

 

[The_AirHawk]

Sounds sorta-like the classic "Piston Slap" symptoms. Did those things come with forged pistons? Hard to diagnose something like this over the Intersex.

 

[63955]

could be the automatic decompression thing...is it knocking like miss firing or just making a bunch of noise.

 

[mscuddy]

Knocking like something's shot in the lower end. Then it goes away...

 

[12er]

My KLR started making a similar noise and it turned out to be a pitted crank. But the noise never went away... Oil pump starting to go or did the "splasher" fall off and something isnt getting oil right away?

 

[longride]

Low oil pressure at idle causing a rod knock?

 

[seruzawa]

A knock? Not a tick or a tap but a knock? Not many parts in an engine make a knocking sound. Usually it's the rod. I'd say that something very bad is going to happen very soon. Better pull the head and cylinder and check the rod end play. It's not hard to pull the top end on a single. An ounce of prevention beats a pound of cure.

Unless it's pre-ignition. Bad gas?

 

[sarnali2]

It's the lower rod bearing, that's the only thing that will give a deep knocking sound. Valves, piston slap or an upper end bearing make more of a ticking or chattering sound. It goes away after a few minutes because of thermal expansion and enough of an oil film builds up to let it qiet down. I had the same thing happen on my V65 Sabre

 

[mscuddy]

I was thinking since it's a dry sump system, maybe there's a ball check valve somewhere that's letting the oil drain back into the tank (front downtube)and for a few seconds the lower end is dry at startup, until the pressure comes back. I called Glendale Honda and spoke with one of the mechs, he had no idea what "dry sump" meant, so I hung up.

 

[sarnali2]

That could be, if so then it'll probably be in or near the oil pump. If it's accessible you could disassemble and inspect, if not you might try draining the oil and refilling with some 5w20 or add half a quart of kerosene. start it up and let it circulate for a few then drain it back out and refill w/ the correct weight. It might act as a flush and let the ball reseat..

Cheap and dirty fixes are my speciality !

 

[seruzawa]

That could be, if so then it'll probably be in or near the oil pump. If it's accessible you could disassemble and inspect, if not you might try draining the oil and refilling with some 5w20 or add half a quart of kerosene. start it up and let it circulate for a few then drain it back out and refill w/ the correct weight. It might act as a flush and let the ball reseat..

Cheap and dirty fixes are my speciality !

Even if you find such a problem and fix it it's still dollars to donuts that that rod bearing is not long for this world. I'd still pull it and mike it.

 

[sarnali2]

True, they don't last long without oil

 

[longride]

"Cheap and dirty fixes are my speciality !"

That and motors that clunk and leak oil. Because you ride a Harley, you are an expert at these things!

 

[sarnali2]

"Cheap and dirty fixes are my speciality !"

That and motors that clunk and leak oil. Because you ride a Harley, you are an expert at these things!

Not only that but I'm a flaming cheapskate as well..."Patchwork Patty" is my twin sister...."beat to fit, paint to match" is my moto... why spend a dollar when a nickle will do......I beat washers flat and use them again.....gaskets+Gasketcinch are a long term investment....sprockets can be turned over and used again....I drain the oil out of my bike and use it in the car, 20K later I drain it out of my car and lube the chain with it.....oil filters can be swished around with gas and re-used, the gas then goes in the lawnmower....bent nails make excellent cotter pins....a little Bon Ami down the intake will break the glaze on any cylinder

I could go on....

 

[seruzawa]

Ha!

Not only that but I'm a flaming cheapskate as well..."Patchwork Patty" is my twin sister...."beat to fit, paint to match" is my moto... why spend a dollar when a nickle will do......I beat washers flat and use them again.....gaskets+Gasketcinch are a long term investment....sprockets can be turned over and used again....I drain the oil out of my bike and use it in the car, 20K later I drain it out of my car and lube the chain with it.....oil filters can be swished around with gas and re-used, the gas then goes in the lawnmower....bent nails make excellent cotter pins....a little Bon Ami down the intake will break the glaze on any cylinder

I could go on....

You walk a lot, eh?

Though I can testify to the longevity of gaskets when the magical Gaskacinch fluid is applied.

BTW, old motorcycle wiring harnesses can be used to create new ones.... old handlebars make great ratchet/wrench extentions... The chrome ring can be pried off of a tach or speedo and the needle glued back on...