Help with a rod knock please.

[mmaleney]

Hi all.

 

I was working on my 1987 projects testing a set of carbs I was working on and had it set up with a gravity feed, it looks like a float needle let gas into a cylinder, I hit the starter and the motor locked would not turn over I then pulled the spark plugs out and one cylinder was full of gas, I got the motor running again later but that was when i heard the knock sound.

 

So anyone ever swap a rod on a venture. ? Any thing I should know before I start ?

 

I have a spare rod from the same year bike so that should work its the bearing that will have to be checked for size I was thinking I could reuse the old bearing if it was the right size or is that not a good idea.

 

I was going to reuse the piston and rings, will I have to hone the cylinder ?

 

Thanks all.

[BlueSky]

You won't know exactly what you are dealing with until you pull it apart. The rod is bent evidently and it could be hitting the block or something else. You will need new rings I think. Used rings don't reseat well.

[Prairiehammer]

Unless the engine actually fired before the hydro lock stopped the crank, I don't think the starter would generate enough force to bend the rod.

Have you had it running before this episode? If you have not heard it run before, it is possible that the knock was there before and the hydro lock was just an unfortunate, but harmless episode. The excess gasoline may have diluted the motor oil sufficiently to cause the rod knock.

Rod or crank bearings are not known to wear much on these engines (they are plain bearings, just like your car) UNLESS there is a LOT of mileage.

There are other (less serious) things that can generate an ominous sounding "knock", but are not caused by bad crank or rod bearings. Believe it or not, I had a bottom end knock on a very low mileage 1990 19,000 miles), that went away after a proper carburetor synchronization.

Edited August 14, 2018 by Prairiehammer

[mmaleney]

Thanks guys.

 

I did have the motor running before and did not hear the knock.

 

It was about a month ago and I did check compression at that time and that did not show one cylinder out more than the others. Then I tried to take a reading of the pistons at TDC but found that to hard to get a accurate reading.

 

So I was hoping there was a way to check with the bottom engine plate off a way to measure piston to bottom of cylinder without having to remove the head, If for some reason I look up in to the motor and can not visually see anything bent/ broken.

 

The kawasaki Concourse 1000 was notorious for bending rods on start up from gas leaking past the carbs, I always had to shut off the gas on mine.

[BlueSky]

A compression test will tell you if the rod is bent for sure. That is what I would do next.

 

I used to have a 2004 Concours and hydrolock was a popular subject on their forums at that time. And it had a fuel valve that was supposed to shut off the fuel when the engine wasn't running. The carbs didn't have an overflow so it overflowed into the engine.

[venturesome]

I had an exhaust collector on mine that had a baffle break loose. To me, it sounded like a knocking rod. I cut the collector open, removed the loose baffle, and welded it back... no more noise! Probably far-fetched, but worth keeping in mind. Search this forum for comments and solutions on this problem.

[mmaleney]

I'll check compression again this weekend again will let you know what numbers I find.

 

Thanks for all the help.

[Patch]

First off it is worth noting that Pairiehammer provided very realistic potentials.

 

For myself when I F*** the pooch on an engine/ first thing is to not beat myself up over it.

 

Now because we are comparing none comparable bikes, I can tell you that the old Susie's 1100 Kat had a over simplified fuel feed that ruined many an engine. If we fired one of those after they had a leak down, well like an old washing machine in a basement closet they would rattle and knock hard!

 

So what to do next? You can measure all 4 @TDC using 2 straws and a 1/4" washer preferably one with an OD. large enough to not fall into the jug then, mark position with a felt marker ! Let us know if you aren't sure how to set this up.

 

Or you can measure the compression again, and is what I would do.

 

Now as I've mentioned to others never spin an engine with fluid above the pistons, unless there is zero chance of compression! Apart from braking rings you may bend rods if one cylinder fires and very likely, can crash the caps against the journals.

 

Drain the engine and oil filter, remove the plugs, blow out the cylinders, get a cheap gallon of 40 weight oil, check compression if reasonable, start the bike. Now with a big mans screw driver that places your ear something like a foot and a half away from the engine listen to each jug at the base, just above the crankcase, and just at those 4 inside locations, listen to each one for about 10 sec.. Why we want a thick piece of rod with a solid handle on the end, is to dial out much of the other higher pitch noises! Same drive move to 2" below the top of the jug or head gasket, listen to the wrist pin, first clicking will be the valves they will click crisply, always in a rhythm/ you may also hear a very faint click which we ignore/ what you are listening for is is a knock similar to the end of a hammer rapping on a steel plate.

 

Hopefully you'll just hear some minor clicking and swirling stuff, remember there's chains top to bottom it isn't a quiet place to begin with. If no hard knocking (remember the caps are not hardened steel) move on, if you suspect the journals then I would check oil pressure next, if that's low then...

Patch

[Patch]

Was wondering how you made out?

[mmaleney]

Well good news I think, I set up a tool to recheck for TDC and they all came out the same, then I did a check for compression, had to play around with the valves on one cylinder to bring it up to match the others that worked out fine. Thing is when I took of the valve cover there was a chip broken off of one cam retainer the thread that holds the valve cover on had split and nowhere in sight, so not sure what that means. I put on a new old retainer with some oil on it.

 

So as I looked around to find what could be making a loud knock or tick I did find maybe 4 tight valve buckets as in I had to force them to move when the cam was off the shim.

 

At this time I do not have a clean set of carbs to fire the motor so things may have to sit for a while.

 

Thanks again all will let you know what I find when I get to fire it up.

[BlueSky]

I've noticed on my 89 venture and my Kawasaki ZN700 that when they are idling poorly at low rpm they make a knocking sound. I'm fairly sure it's caused by the timing chain.

[Patch]

Thanks for letting us know.

 

Not sure why you chose not to post the readings?

 

Now if it were me and I saw what you saw, I would measure the cams. Maybe they have been swapped out??

 

Depending on where the chip is or how close to drainage that may be, it may be sitting harmlessly in the sump?

 

Not sure your meaning as to playing with a valve but I assume something between the seat surfaces?

 

When you switch out cam retainers it is usually important to take some measurements for matching.

 

All this a side whit what I am reading I would certainly check oil pressure before dropping money..

Patch

[mmaleney]

So how would one go about measuring a cam retainer I did not see anything about that in the manual.

 

The compression readings were #1 155 #2 175 #3 220 #4 172 I reshimmed #1 cylinder it came up to 170. The motor was cold.

 

I think the cams are stock in that motor.

 

When I say the buckets were tight what I meant was they would not spin free when the cam was off the shim so that is what I think was making the tap noise as opposed to a rod knock which I think I no longer have.

[Patch]

I think you can improve these numbers.

I'll think on this a bit in the mean time there's a post we have in general tech talk called a case for fogging, if you have'nt read it it would be worth going thru.

 

The no. 3 could this be the valve/spring bucket you struggled with?

[Patch]

Page 3-29 top left hand corner.

 

With the posted numbers I don't suspect the shims tight, not to say from here tho they they meet spec.

 

Anyways a shortcut to the cap issue would be to measure the thickness and compare to what was there. If it's way out then I would consider switching to the old cap that is the replaceable part of the retainer!

 

Next the cam specs you would check is on 3-28 you really only need to compare one lobe on each to see if they match spec.

BUT... because of no. 3 I would also include those exhaust and intake lobes if that happens to be the sticky bucket!

 

So what might have happened is no. 3 ran way rich built and or leaked carbon up the valve stem (speculation) if so some aggressive maintenance may help. Another is that with the higher temp from this may have coked in the bucket and around the lifter, again some aggressive behavior will resolve that and is easier to then valve stem stuff..

Edit: sorry scratch the lifter, but you get where I'm going..

Edited August 28, 2018 by Patch