Knock in bottem end?

[XS650D]

I noticed that when my bike is cold it has a definate knock in the bottom end but it goes away once the bike is good and hot.I run 20/50 oil,changing the oil made no difference.
Would that be anything to worry about,I have 136lbs compression even.Apparently the previous owner (a yamaha mechanic) pulled engine apart to check over and all good,he did install new rings just because but engine only had approx 2000 miles when he got it.
It runs great and no smoke out the pipes when starting or running.Im not to savy on the bottom ends and was informed there pretty bullet proof on these bikes.Thx

 

[gggGary]

Well, bullet proof might be an exaggeration...

The most likely "bottom end knock" on an XS650 is the small end of the con rods. No it's not an ignore kind of problem. Sooner or later a rod sticking through the cases will spoil your bike's good looks.

So either find an engine transplant, or plan on surgery, winter is nearly here in Canada ehh?

 

[XS650D]

Wow!! Dam thats not good news Gary.When u say the small end off the con rod,do u mean the bearing in the connecting rod that attaches to piston.Excuse my lack off knowdge but if i am correct would that not be top end .I am more off a 2 stroke guy.

 

[TwoManyXS1Bs]

I noticed that when my bike is cold it has a definate knock in the bottom end but it goes away once the bike is good and hot...

That's kinda backwards from the normal rod knock.

A rod knock test would be to ride the bike at about 3000 rpms, and apply/release throttle, see if any knocking.

Some old Honda CB750s would have a louder grind/knock sound when cold, caused by rough/uneven cylinder firing, which would cause primary chain flop and snatch.

Thinkin' along those lines, maybe a problem with your clutch damper springs.
With bike on centerstand, engine off, put it in 1st or 2nd, then rotate rear wheel fore/aft, listening for your 'clunking'...

 

[XS650D]

Well thats better news,i will test that.I did notice the knock this season but just blocked it out off my mind and put it down to a typical symptom or trait off these old bikes until a friend with a mint 78 noticed it and stated that wasent normal,his definately did not do it.

 

[gggGary]

Well 2m is right, and the cam chain does make a fairly loud clunkish slap when the bike is cold. If it makes noise for a couple of seconds then quiets down, I figure I have the cam chain tension set perfectly. If you never hear it, your chain might be tight and it will eat the front guide. That'll make you 78 buddy worry.

Sure the con rod small end is inside the piston but it's usually considered to be more of a bottom end type thing compared to the higher pitched cam and valve noises. Here's hoping it's the cam chain. IMHO use the adjust at an idle cam chain tension setting method, it's what I do. Have you pulled and checked both oil screens? (recently)

 

[XS650D]

Thx for replys,I did pull both the filters to change oil near end off season while this noise was noticeable and found nothing in filters.I did notice the front screen was torn in the typical spot and replaced it.It was the original unit.I use the honda replaceable filter unit on the side that sits out approx an inch.Also maybe worth noting is that the knocking will decrease or become quiet if i raise the idle to say 2000 Rpms.I was thinking the oil was to thick when cold,maybe change to 10w40.I did cheak the cam chain and have it set to spec,maybe a lil loose 1 ml protruding when i slowly crank the kick start with plugs out.I will try adjusting with running engine and see if this changes things.

 

[gggGary]

It should never be so tight that it doesn't move in a out a bit. The D tensioners can be hard to keep set correctly when replacing the cap.

 

[XS650D]

I realize this is an older post but wanted to add that after adding synthetic 10w50 oil the knock is the same,maybe slightly louder when cold.Something worth noting is that it will not knock or very lightly if the bike is on the side stand but get it on the centre stand and it will start knocking immediatly.After driving for approx 1 mile
te knock will completely stop until the bike cools down some.Any ideas.Maybe i should post a video.

 

[TwoManyXS1Bs]

... it will not knock or very lightly if the bike is on the side stand but get it on the centre stand and it will start knocking immediatly...

That rings a bell. Have a look at this:

http://www.xs650.com/threads/are-these-noises-normal-3-vids.46700/

 

[XS650D]

Thx TooMany,Yours did sound different more like something dragging like a chain,not the same other
than the noise increasing when on centre stand.I am going to try and post a vid.I really dont want
to pull engine apart if its nothing to be concerned with but many on the forum are much more
informed than me on these old bikes and lots of noises seem to be normal on this motor!