Go Back   Motorcycle Forum > Motorcycle.Com General Discussion > Motorcycle Mods and Maintenance

Reply
 
Thread Tools
Old 04-16-2008, 02:11 PM   #1
mscuddy
MODERATOR X

 
mscuddy's Avatar
 
Join Date: Jun 2007
Location: Next to my still checkin the temp.
Posts: 5,448
Default '94 Xr600 Knocks On Start Up

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?
__________________
A gun is a tool, Marian; no better or no worse than any other tool: an axe, a shovel or anything. A gun is as good or as bad as the man using it. Remember that.
mscuddy is offline   Reply With Quote

Sponsored Links Remove Advertisements
Motorcycle Forum
Advertisement
Old 04-16-2008, 03:14 PM   #2
Buzglyd
Founding Member
 
Buzglyd's Avatar
 
Join Date: Nov 2001
Posts: 10,904
Default

Quote:
Originally Posted by mscuddy View Post
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.
Buzglyd is offline   Reply With Quote
Old 04-16-2008, 03:43 PM   #3
The_AirHawk
Founding Member
 
The_AirHawk's Avatar
 
Join Date: Jun 2007
Location: Leanin' Tower O' P-P-P-P-POWAAAAAAAAA!!!!
Posts: 11,491
Default

Sounds sorta-like the classic "Piston Slap" symptoms. Did those things come with forged pistons? Hard to diagnose something like this over the Intersex.
__________________
Parfois, on fait pas semblant
Sometimes, it's not pretend
Oderint Dum Metuant
Let them hate so long as they fear
политики предпочитают безоружных крестьян
Politicians Prefer Unarmed Peasants
Nothing to see here, Citizen. Move along now...
The_AirHawk is offline   Reply With Quote
Old 04-29-2008, 12:30 PM   #4
jamesdemien
Registered Member
 
Join Date: Jan 2008
Posts: 20
Default

could be the automatic decompression thing...is it knocking like miss firing or just making a bunch of noise.
jamesdemien is offline   Reply With Quote
Old 04-29-2008, 01:10 PM   #5
mscuddy
MODERATOR X

 
mscuddy's Avatar
 
Join Date: Jun 2007
Location: Next to my still checkin the temp.
Posts: 5,448
Default

Knocking like something's shot in the lower end. Then it goes away...
__________________
A gun is a tool, Marian; no better or no worse than any other tool: an axe, a shovel or anything. A gun is as good or as bad as the man using it. Remember that.
mscuddy is offline   Reply With Quote
Old 04-29-2008, 03:54 PM   #6
12er
Founding Member
 
12er's Avatar
 
Join Date: Nov 2001
Location: SF
Posts: 2,801
Default

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?
12er is offline   Reply With Quote
Old 04-30-2008, 03:42 AM   #7
longride
Super Duper Mod Man

 
longride's Avatar
 
Join Date: Nov 2001
Location: Anywhere they let me
Posts: 10,479
Default

Low oil pressure at idle causing a rod knock?
__________________
I'm a knucklehead
longride is offline   Reply With Quote
Old 04-30-2008, 04:04 AM   #8
seruzawa
The Toad

 
seruzawa's Avatar
 
Join Date: Nov 2001
Location: 8501 ft.
Posts: 17,461
Default

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?
__________________
"Make no mistake, Communism lost a big argument - one we know today as the 20th century."

Last edited by seruzawa : 04-30-2008 at 05:21 AM.
seruzawa is offline   Reply With Quote
Old 04-30-2008, 06:20 AM   #9
sarnali2
Aging Cafe` Racer

 
sarnali2's Avatar
 
Join Date: Jun 2007
Location: Sittin' down by my window, lookin' at the rain.
Posts: 8,719
Default

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
__________________
"Carpe` Throttelum -Loud Suits Save Lives"

"He said he's farting because of his medication"...
sarnali2 is offline   Reply With Quote
Old 04-30-2008, 06:50 AM   #10
mscuddy
MODERATOR X

 
mscuddy's Avatar
 
Join Date: Jun 2007
Location: Next to my still checkin the temp.
Posts: 5,448
Default

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.
__________________
A gun is a tool, Marian; no better or no worse than any other tool: an axe, a shovel or anything. A gun is as good or as bad as the man using it. Remember that.
mscuddy is offline   Reply With Quote
Reply


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off