Time for me to address the 800lb Gorilla in the room.(Engine knock thread) REVIVED!

[joedrum]

wow gerry ...thats cool it pretty much spells out whats going on ....i knew it to well to test it ...but it sure confirms it would be nice to have new springs ....but now i have to confess to the fact of streching springs on a farm tractor that had valves as big as wing pistons ....right in the middle of feild ....tools used a drill that spun freeness in the stuck valve ...and hydralic cylinder to strech the spring...and an act of god to get it back together ......down time about 4hrs....that tractor never gave that same problem again ....i know the common thought is that dont work to get more tension ....that tractor work thousand of hrs at full blast throttle after that and never made the noise it made before the fix .....it was still running when i quit farming so it lasted longer than me :mrgreen:

 

[dan filipi]

Just for information, I checked the skirts side to side and the pistons are not loose. I cranked them to just past TDC and gave a push and there is little if any play. If the lower bearings were shot and causing the knock, I would have thought there would be a lot of movement in the bearings.

The head gasket looked good and is intact otherwise. There are no signs of any damage other than the water stain in the bottom of #1 cylinder. Could all of this have been from a bad carb setup in the first place???

Hmmm, interesting.

 

[scdmarx]

View attachment 1

You can fill the port with solvent (or water) and the closed valve should not leak for at least 10 seconds.

If it won't hold for at least 10 seconds, then maybe clean the carbon with a wire wheel and lap it back into the seat, then try it again.

 

[mcgovern61]

View attachment 1

You can fill the port with solvent (or water) and the closed valve should not leak for at least 10 seconds.

If it won't hold for at least 10 seconds, then maybe clean the carbon with a wire wheel and lap it back into the seat, then try it again.

I filled both exhaust ports with hot water and they did not leak down after 3 minutes. Maybe it just looks like they are not sealing.

 

[dan filipi]

Just for information, I checked the skirts side to side and the pistons are not loose.

I wonder if there IS skirt play it wouldn't show up with the pistons in the cylinder?
Maybe like the rings are holding the piston from moving side to side or rocking that's why it seems to be tight?

 

[mcgovern61]

Just for information, I checked the skirts side to side and the pistons are not loose.

I wonder if there IS skirt play it wouldn't show up with the pistons in the cylinder?
Maybe like the rings are holding the piston from moving side to side or rocking that's why it seems to be tight?

I can ever so slightly move the pistons side to side within the rings after they pass TDC and are 1/3 of the way back into the block, hardly measureable.

 

[dan filipi]

What is piston slap anyway?

Google here I come.

Edit: never mind. I forgot the head shop told me the noise is bell like when starting then goes away which I DO hear.

 

[Omega Man]

I only hear my knock in the hot Summer months...why does it go away in the Winter?

~O~

 

[mcgovern61]

I only hear my knock in the hot Summer months...why does it go away in the Winter?

~O~

Maybe because we park them in the winter? :smilie_happy: :smilie_happy: :smilie_happy: Just kidding!

 

[Omega Man]

I only hear my knock in the hot Summer months...why does it go away in the Winter?

~O~

Maybe because we park them in the winter? :smilie_happy: :smilie_happy: :smilie_happy: Just kidding!

Yeah, lol...but seriously, anyone have an idea why the soft knock goes completely away during the cold months?

~O~

 

[mcgovern61]

I only hear my knock in the hot Summer months...why does it go away in the Winter?

~O~

Maybe because we park them in the winter? :smilie_happy: :smilie_happy: :smilie_happy: Just kidding!

Yeah, lol...but seriously, anyone have an idea why the soft knock goes completely away during the cold months?

~O~

Actually Randy, it is more than likely because the oil is running a tad thicker due to the cold temps and filling spaces longer with a slightly thicker lubricant.

 

[dan filipi]

Actually Randy, it is more than likely because the oil is running a tad thicker due to the cold temps and filling spaces longer with a slightly thicker lubricant.

That's what I think too.

Mine would knock much louder after the temp gauge goes above 1/2.
Maybe your's is running cooler than that?

 

[mcgovern61]

I measured some springs. Outers were within stock measurement, both inners were at the serviceable minimum. Tells me these springs are done.

Did you remove the springs or measure them in the head?

 

[dan filipi]

I measured some springs. Outers were within stock measurement, both inners were at the serviceable minimum. Tells me these springs are done.

Did you remove the springs or measure them in the head?

I measured them removed from the head.

 

[slabghost]

Are the springs still available? Are they perhaps the same as the 1500 springs? Maybe Geo?

 

[scdmarx]

I measured some springs. Outers were within stock measurement, both inners were at the serviceable minimum. Tells me these springs are done.

Did you remove the springs or measure them in the head?

I measured them removed from the head.

You do have to remove them to measure them.

As far as I know, the inner valve spring is there to dampen vibration of the outter spring. Next time you're at the head shop, Dan, can you ask them what the purpose of the inner spring is? It would be interesting to know.

 

[joedrum]

yea it would sure be nice to know of a supply or sorce....but if not ill just use some of my hillbilly tech to fix it :smilie_happy: :smilie_happy: :smilie_happy: :smilie_happy: :mrgreen:

 

[AApple]

In automotive applications, the inner spring is indeed called a "damper" spring. It is there to keep the valve and the outer spring vibrations in check, but it does also add to the total spring seat pressure(s). I see no reason to believe the application on a motorcycle engine would be any different. The inner springs do tend to loose tension, or "flatten" quicker than the outers, due to the design...most of the inner springs are flat wound, or wound from flat stock.

 

[mcgovern61]

Knock-knock....who's there??? As I try to dig in and determine the cause of my '81 engine knock and follow this thread with all of the great information here, I can add at least this much for consideration:
*My '81 engine is a high mileage engine (169,000 miles)
*noisy on start up until oil pressure is up (2 seconds)
*sounds like it detonates when throttling hard (seems as though this was a carb problem)
*knock/rapping begins after engine is warm (thinner oil?) and doesn't start until 2800-3200 RPM and continues through higher RPM
*knock/rapping will happen either no load or while under load (although it cannot be duplicated automatically by just increasing RPM)
*Engine operated flawlessly at all RPM's otherwise and was operated by me for 4000 miles at all RPMs and loads without a problem
*Engine did not run hot
*Compression when hot - 160's for all 4 cylinders

Additional findings:
*cams are showing wear on the cam lobes (consistent with other GL1100 cams)
*#3 intake springs real easy to compress, all others seem normal
*when pistons at just past TDC - push hard and no play is found in lower bearings
*pistons seem tight with no excess play in skirt
*I measured the cylinder bore on all 4 and they are all at 75mm as per original spec with no areas showing warpage or wear other than a area in #1 cylinder that looks like water was in there at one time
*the carbs were leaking when the engine was in service and I don't wonder if there was too much gas mixing in
*The vacuum advance is working correctly and will hold vacuum (also not stuck and moves freely)
*After correcting the carbs, they were installed on the swapped in '83 engine which does not knock (wish I had tried to check them on the '81 before pulling the engine)
*The engine seems to be in good mechanical condition otherwise, no clutch slipping, good power, no smoke
*I did find that the front cam shaft oil seals were leaking (which I now believe was the main source of my unfound oil leaks)
*After a test of the oil pressure was performed and the bike leaned over while at 3000 RPM, there is a significant oil pressure drop and it started knocking/rapping (even when straightened back up).
*Have not been able to check the scavenger pump inlet yet (no tool to remove the clutch nut), but I did check the oil pickup screen and cleaned it (still knocked afterward)

 

[dan filipi]

Everything you listed is a duplicate of what I've done and the noise characteristics to a T!

At this point I think we can narrow the possibilities to cam and/or springs and on mine I'm certain it is over advanced because when it's hot under load sometimes I'll get ping and when starting hot I'll get the tell tale "click" (detonation/ping) noise typical of over advance.
I have not ruled out a detonation knock. Not sure what has to be done to do so.

I have tried premium gas and octane boosters, no change.

I've had the case split, main bearings look good. Although they do show some signs of wear they are within spec as checked with plastigauge. I did not mike the rod bearings but they all felt tight. Maybe this is next?