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

[scdmarx]

Sure sounds like the spring is not keeping up.

 

[mcgovern61]

I would agree! The good news is, even if that is the source of the knocking, it appears that it can knock like that for a very long time before anything is damaged. I know for fact that I ran my '81 engine for 2 years with that knock at 3k on up and ran the engine up to an held 6k on the highway all the time! It was noisy, but keep running fine otherwise. The shape of the rocker followers is very forgiving considering these cam lobes.

I wonder if there is a test to see if the valve springs are actually worn out? (This is beyond my paygrade)

 

[joedrum]

theres no doubt in my mind that the cams honds cut were crude period ....no top knoch work going on here at all ....its all a timing thing made up with of various factors ....from looking at the cams ....if you have a flat spot on top of the cam or where ever on the taller lobe area is nothing more than the cam telling you on that picticulure lobe where the landing spot is no more ...

it was idiotic for honda to to assume that these crude cams were going to wear in smooth somehow .....to a point you can use this logic ....but it cant be 80% of the machining proccess....and i disagree about outcome ....i think that a lot of total failure blamed on timing belt breakage was first broke here and then the belt ...most of them probably.....

i know machinery in not a textbook way but in a continuess operrational way .....it makes sense to me now why my 79 1000 never had this problem and never made noise ....78-79 cams are as mild as the 1200 cams and milder than 1100s.....the springs are proably the same but the forces on ths springs were much less ...i always wonder why it was so much more quiet than other wings in general....but i strongly think if your wing is making noise it needs to be fixed or your new timing belt might break :smilie_happy: :mrgreen: right after the valve is suck.....i read somewhere on thompson 1100 that the cam was broke right in half

so it would be neat if someone could figure some replacement springs this is big ....maybe dan can figure something out at the head shop :mrgreen:

:mrgreen:

 

[scdmarx]

Yes there is a way to test them, and any head repair shop "should" be capable of doing so.

There is a measured height spec. And it should measure "just so high" @ "just so many pounds of perssure" as the spring is being compressed. Metal fatigue from use will weaken the spring, allowing float. On the other hand, too much pressure (the wrong spring for the application) will start pounding the valve into the seat. Shimming the spring will compensate for the loss, but it's not the right way to repair it and at best it will work for a while to buy some time. Might be just the ticket for a mild application where new parts are not that readily available. Keep in mind the reason for the weak spring is metal fatigue. It's never gonna be the mighty spring it once was. Also, shimming takes up space, bringing the spring just a little closer to coil bind.

 

[dan filipi]

Just got back from the head shop.
I brought over 3 cams for him to look at, all have the typical wear/defects we've been talking about here.
Interestingly he said all 3 cams are not that bad, that the wear they show would cause a reduced power.
This is what I found out.

I pointed out how some lobes are not smooth all the way around. He said that is wear and showed me if holding it in the light just right you can see a flat spot and sure enough I could.
He said they were originally machined so when you run your finger around it you should feel smooth without any ridges, dips, or flat spots.

I described the knock, he says no way a knock would come from the cam area, lifter tap yes but not a knock.
Not what I wanted to hear.

I showed him how it looks like the follower leaves the surface then impacts the cam on the low side.
He agreed it's doing that but said again that would not cause a knock.

I told him I put a good low mileage cam in from a 1200, that the knocks seems to have gone away on that side.
He said that could be due to something else like better cylinder pressures because the valves are opening as they should.
The worn cams could be causing a differing uneven pressure which might cause loose rod bearings to knock.
I said A Ha! That could be it!

So let's see, where we at with this thing.

He said they can grind the cams to whatever spec we want, within the limits of the cam of course.

What do you guys think of this so far.

 

[joedrum]

i think he confirms what ive been saying about the cams and whats going on .....but the reason its getting uneven pressures is due the valves not staying with the cam when running there floating ....thats to kind a word ....no there hammering like a jack hammer ...valve stems being hit with the strike of the cam ...trama trama bang bang ....he might be right on rod bearing but if you get the trama running valve trane up to snuff its got to lessen the stress of running out of balance so to speak and quit hammering the rod i would think :mrgreen:

 

[dan filipi]

...but the reason its getting uneven pressures is due the valves not staying with the cam when running there floating ....thats to kind a word ....no there hammering like a jack hammer ...valve stems being hit with the strike of the cam ...trama trama bang bang ..

Hammering is what I thought and told him but he said the noise would be like a loose tappet, tap, tap not a dull knock.

 

[joedrum]

on my bikes im leaning towards the reality that the springs have to be address ...iguess right now shims .....thats probaby going to lead to more evidense of glides and stem damage ....maybe ill try not look at it and just shim them .....as ron says cheat the tension up...and see how good i can get it the to follow the cam

for me im going to run the more aggressive early 1000 cams and ive got to get it valves under control ....if we could buy upgrade springs like we can progessive for the shocks ...we would just buy the springs and put them on ,true and polish the cams up and be done with it running outside the cam profile ....the cams im running have got to be the most stressful .....

thats what i want for chistmas new springs that will work on my bikes :whistling: :ahem: :mrgreen:

 

[dan filipi]

Parts fiche says springs are available, About $7 each but I bet dollars to donuts a shop could match them up for 1/2 that price.

 

[joedrum]

help me show me where :smilie_happy: :smilie_happy: :mrgreen: this would be the best machinical move we could make :beg: at least know where and and maybe specs so we know what were looking for :yes: :mrgreen:

 

[scdmarx]

I told him I put a good low mileage cam in from a 1200, that the knocks seems to have gone away on that side.
He said that could be due to something else like better cylinder pressures because the valves are opening as they should.
The worn cams could be causing a differing uneven pressure which might cause loose rod bearings to knock.
I said A Ha! That could be it!

It's a theory, but easy for me to buy into because I don't know what's causing the noise. Also easy for me to buy into because I have always associated the "tapping" and "ticking" noise with the top end, and the "solid knocking" noise with the bottom end. To tell you the truth, I don't think I've ever "heard" valves floating. Maybe that's because it happens at higher RPM's when there is a lot of other noises going on. But I would really expect it to be a ticking and tapping noise if I did hear it. I like his theory of odd ball cylinder pressures making the bottom end say "ouch". And the better cam making it run quieter sorta backs that up.

I've been thinking about this most of the day. I have a few questions that I'm not sure how to ask. First, I'm just a little surprised to see this on an OHV engine. I mean it's not like the cam has to deal with the reciprocating mass of flexing pushrods and all that.
Are the 1000 & 1100 solid adjustment valve trains an engineering flaw? Were they cutting corners to save manufacturing costs? Or is this mostly a "lack of maintainence" and-or "improper valve adjustment" and-or "incorrect luricant" issue that has taken it's toll over the years?
Another thing I'm questioning in my mind is doesn't the 1200 have hydraulic lifters? Could this have a cushioning effect on the cam, or would this just be more slack that has to be taken up within the time frame of the event (opening/closeing cycle of the valve)? (why is the 1200 cam in better shape?)

Hmmm.....so many questions, and so little pizza left.

 

[joedrum]

i realy like the solid valve head and its cushioning is the springs but the springs are obviously not up to the job ....the 1200 and 78-79 1000 cams have the quickest open time and less lift reducing the loads on the cams and springs ....both things you said about hydrualic valves seems to be true ron :mrgreen:

 

[dan filipi]

Just to clear up that 1200's do not have hydraulic lifters, they have hydraulic adjusters.
The hydraulic adjuster may cushion the impact the rocker has on the valve and cam but the cam I have that's in good condition could be simply from a low mileage 1200.

 

[mcgovern61]

Also easy for me to buy into because I have always associated the "tapping" and "ticking" noise with the top end, and the "solid knocking" noise with the bottom end.

Have you looked at the video of my '81 noise? I kinda thought it sounds like top/middle noise? Almost like it comes from just under the cams inside the head but mimicks valve taps like a stuck rocker on a push rod engine.

Are the 1000 & 1100 solid adjustment valve trains an engineering flaw? Were they cutting corners to save manufacturing costs?

Same question I asked!

Hmmm.....so many questions, and so little pizza left.

Pizza sound good! :clapping:

 

[AApple]

How many times have youse guys told us that an out of synch carb can cause a knock noise like a rod? IF the cam(s) are not opening the valves correctly, you will have differing cylinder pressures, leading to the same noise, no? The piston don't know WHAT caused it to not speed up properly...just that something did.
Valve float is what happens when the valve slams back down onto the seat. It actually will bounce back up/down a couple of times. Float only occurs at higher rpms. Float is not because the cam is causing the rocker to open/close too fast/slow. The backside of the cam can be worn, and allow the lifter/follower to slam back down onto the cam, but this happens so quick(and at a higher rpm than just idle) I don't think it would be something you could actually hear. If it was audible, it would be more of a tick, like a loose rocker adjustment, imo.

And...a hydraulic lifter set-up is much different than a solid set-up. A solid set-up requires a certain amount of clearance between the cam and the rocker, or lifter. A hydraulic set-up requires no clearance, in fact, they require a certain amount of pre-load, and the lifter does act like a cushion, and therefore you should have no valve/lifter noise.

That's my story, an I'mma stickin wid it! :mrgreen:

 

[dan filipi]

Say Joe, I don't understand why you say the springs are not up to the job.

All we have are theories so far, no definite source of the knock, although some pretty good leads.
If anything is to blame so far for bad engineering or quality is the cams themselves. I think they should be in better shape.

I think the next step for me is to install 2 good cams with good springs and rockers then run it.
If the knock is gone then we'd be one step closer to figuring out what caused it.

Now I just need to round up 2 good matching cams or a good 1200 right.

 

[thewhiterhino]

Say Joe, I don't understand why you say the springs are not up to the job.

All we have are theories so far, no definite source of the knock, although some pretty good leads.
If anything is to blame so far for bad engineering or quality is the cams themselves. I think they should be in better shape.

I think the next step for me is to install 2 good cams with good springs and rockers then run it.
If the knock is gone then we'd be one step closer to figuring out what caused it.

Now I just need to round up 2 good matching cams or a good 1200 right.

Look at these.
https://cgi.ebay.com/ebaymotors/HON...otorcyclesQ5fPartsQ5fAccessories#ht_674wt_943


https://cgi.ebay.com/ebaymotors/84-...orcyclesQ5fPartsQ5fAccessories#ht_2234wt_1169

 

[dan filipi]

Hmm, $30 for matching cams. Should I go for it?

 

[slabghost]

Jump on it! If it works as theorized there may be a lot of us hunting a deal like that.

 

[mcgovern61]

Hmmmm....$30 is cheap!

I am in a pickle for testing anything because my '81 engine is on the floor and I do not have any way to reconnect it for testing. The cam theory is plausible to me (for what it is worth, but I am not an engineer or even a good mechanic, just a wrench turning parts changer).

Dan....if you test the 1200 cams and it quiets down, then I would consider doing the same for my '81 engine. If it does not make the difference we are anticipating, then I will open up my '81 and split the halves to check bearing tolerances to either put to rest the lower end is worn out, or it is not the origin of the knocking. (We were going to open it up at some point anyway, but if it is the cams, I'd rather not split the case and have to spend $150 for a gasket kit to close it up again.)