Camshaft Top End Rattle

Anyone got any other ideas.

Have you tried using 2 valve cover gaskets to see if the noise changes. It doesn't seem normal for the chain to rub on either side of the rubber block in the middle of the valve cover. It's almost like the cover is pushing down on the chain in the middle...Just a thought.....Billy

Bump...... What progress have you made on this Don?

Not much Ian, as I have the tank off, going through the panel beating, priming, undercoating, painting, etc. procedure.

It will be remembered in the last post that I had ground the rub marks on the inside of the valve cover away with a rotary grinder. So I have removed the cover again and checked for any chain marks on the inside of the cover and there were not any. That's good, but does not help me with the noise problem though. I hate it when you can't tell where the noise is coming from.

I rechecked all the tappet clearances and they are all between .06 and .1mm when cold.

I rechecked the ignition timing (I have points) because when I initially set the ignition timing I had to rotate the base plate as far as it would go to the left of the slots to get the timing spot on. It was out slightly, but not much, so I just nudged the base plate a couple of degrees to make it spot on again. Don't know why the base plate is not in the central position as it should be. Maybe it's to do with the after market points not being manufactured to factory tolerances.

I rechecked the cam chain for tightness and it seems to be OK. As soon as the crank nut is rotated the exhaust cam sprocket rotates immediately. All seems well there. The tensioner seems to be working OK. I can't see any reason why there would be any slack in the cam chain. Maybe it's not the cam chain, what else could it be?

I cannot hear any scraping or grinding sounds when I rotate the motor by hand. I thought maybe it was the chain rubbing on the chain guide screwed inside the lower crankcase half. This happened to Brian (Bwringer) apparently he replaced the screws on this guide once and the heads of the screws were a bit higher than originals and were grinding on the crankshaft when it was rotated. He had to split the cases again. But I don't have this problem. The noise only appears to be at idle.

Anyone got any other ideas.

[49er]

Bump...... What progress have you made on this Don?

Thanks Ian for the prompt reply.. I will do as you say and get another video. I might even remove the rubber dampers in the head and valve cover and see if that makes the noise more pronounced. Thanks again for the reply.

[49er]

Don, I've had a listen to your 2 video clips above. It doesn't sound like the cam end float knock that I experienced on my 850. Mine sounded more like a hollow knock similar to that made when a big end bearing had failed on a plan bearing (shelled bearing) engine.

If you could do another video clip lowering the idle down to 900 rpm and snap open the throttle occasionally, to say 4000-5000 rpm, this might help diagnose the problem.

At .016" end float, you should do the repair anyway. The stock clearance should be around .0015" for both cams.

Your cam cover has chain guide rubbers that may be damping the knocking sound, compared to my 850 which is fitted with an idler sprocket instead of the rubber guides.

Cheers
Ian

I removed the valve cover and ground the area where the chain had left marks on the cover previously. I used a compressed air mini grinder for this task.





I then refitted the cover with a new gasket after doing some minor adjustments on the valve shims to make sure they were all correct.

I then took the bike for a good run and was disappointed to find that the noise was still there in the motor as evidenced in the following two videos.

http://s226.photobucket.com/albums/dd105/donclifton/Engine%20Noise/?action=view&current=P1000314.mp4

http://s226.photobucket.com/albums/dd105/donclifton/Engine%20Noise/?action=view&current=P1000315.mp4

I then removed the valve cover again and there was no evidence of the cam chain marking the inside of the valve cover in any way.

So running out of ideas again. Any comments on the noises in the last two videos will be appreciated. If there are no suggestions then I will be looking at doing the cam end float modification as there is about .030" end play on each camshaft.

Another possibility which I have not pursued yet could be the tacho drive in the valve cover, maybe too deep a mesh with the camshaft skew gear (unlikely, but must must look at every possibility).

The other possibility, because I am running out of ideas and getting desperate, is that when the cam chain tensioner came apart the loose chain may have ripped some rubber off the rear cam chain blade and the chain is rubbing against this or a metal part of the blade, but I cannot look inside to see what is happening down there without removing the head. What are your collective thoughts on this? I looked at the old rear blade that I pulled out during the rebuild and it does not look like the rubber would come off this blade very easily.

Thanks for any advice that can be given.

Another thought (that's three now) I had was the way that I did degree the cams in when I was setting the motor up.
The factory specs give the lobe centres as Exhaust 103 and Intake 106. According to RAY this is back to front as to how the cams should operate. Apparently the exhaust should have the larger lobe centre number to gain better cylinder scavenging.
When I first installed the 650 cams I checked the lobe centres to see what position they were at before I slotted the cam sprockets and started to degree them in. The figures that I came up with was Exhaust 103 (exactly as it should be) and Intake 108, 2 degrees more than it should be.
On advice from RAY he said it would be best for more torque to degree them in at Exhaust 106 and Intake 104 degrees. So this is what I did, which means it is the other way round from the way they were degreed before as stated by RAY.
The actual final figures which I achieved were Exhaust 106.625 and Intake 105 degrees.
Could the fact that I have reversed the way the cams were set up originally be causing this noise/problem or does it have to be something hitting/rubbing/dragging on some other part of the motor?
All replies appreciated.

Vacuum sync out of balance won't cause noise like that Don.

Maybe try running the engine without that cam chain guide? Since you are using a 650 head, and that model didn't use the guide, than maybe you don't need it?

Thanks Ed. I need to remove the valve cover to see if there are any tell tale signs of chain rubbing on inside of cover, so when that is checked I will remove this chain guide if I can. Might be difficult though with the cams in place. Might need to remove carbs and tensioner to achieve that.

[Nessism]

Vacuum sync out of balance won't cause noise like that Don.

Maybe try running the engine without that cam chain guide? Since you are using a 650 head, and that model didn't use the guide, than maybe you don't need it?

Another thought that I have had (that's two in one day) is that when I was rebuilding the motor I bench synched the carbs and I fully intended to do the highest idle mixture adjustment and then a vacuum synch. but seeing as the bike was idling so good and responding to throttle with heaps of really smooth power on the road I never really got around to doing those two tasks.

Does anyone think that if the vacuum is off on one or more of the carbs that could be causing this noise in the motor?

My 650 doesn't use this central cam chain guide, was this part of the 650 head you are using or did it come from your 550?

Are the diameters of the cam gears nearly identical between the 550 (30 tooth) and 650 (34 tooth)? There may not be enough clearance with bigger gears.

Somewhere I had heard that idling is hardest on the cams since they are moving so slowly and the chain will jerk more with each valve opening. It just be that there isn't enough clearance to use the 550 valve cover.

One last question, did you use new 650 cam chain guides in front and back? I ran into a situation where the cam chain was excessively worn from worn out guides and poor cam tensioner. It made some nasty sounds as it came in contact with valve cover. It did this around 2000 rpms not idle.

Other than this tick, sounds pretty good in videos.

Ed, I am using the GS650E camshaft sprockets which have only 30 teeth, the 650G motor has the 34 tooth sprockets.

I am using the central chain guide from the 550 and looking at all the 650 fiches I see that none of them use this chain guide. Although the 650 head is cast/machined for the chain guide to be a positive fit in the head. It is a perfect fit as can be seen by the picture. Also the original 6/550 conversion done by Nerobro & Skreemer shows a picture of the head with the chain guide fitted, so they apparently used it without any consequences.
That is interesting to hear that the 650 does not use the central cam guide in the head. Does your motor use the cam guide in the valve cover which is positioned above the chain?

I used a new cam chain, a new cam chain guide (the one at the rear) and the other one was in really good condition so I re-used it.

I removed the valve cover over the weekend and ground 30 thou. from it for extra chain clearance. I checked the cam timing, I re-did the valve shims, a couple were off so I replaced them. I checked the cam end float which I reported earlier.

I started the bike and took it for a ride today and the noise is still there when the motor is fully warmed up.

I now need to remove the valve cover again to see if there are any chain marks on the inside of the cover where the chain may be touching during operation.

I just wish it was a bent valve or something I could just go ahead and fix. Instead of having this noisy motor and not knowing what it is. Very frustrating.

I thought you had a 650 head and cylinders?
How does the 650 valve cover not fit and the 550 cover does?

Even the 550 had three different valve covers and gaskets. Check the fisches, they changed mid '81 I believe.

Thanks wally, I will check that. Where is the arrow that you speak of.

Here is a better picture Wally. And I agree it does look close, I will have to check that when I get home from work. Well spotted.



Thanks

My 650 doesn't use this central cam chain guide, was this part of the 650 head you are using or did it come from your 550?

Are the diameters of the cam gears nearly identical between the 550 (30 tooth) and 650 (34 tooth)? There may not be enough clearance with bigger gears.

Somewhere I had heard that idling is hardest on the cams since they are moving so slowly and the chain will jerk more with each valve opening. It just be that there isn't enough clearance to use the 550 valve cover.

One last question, did you use new 650 cam chain guides in front and back? I ran into a situation where the cam chain was excessively worn from worn out guides and poor cam tensioner. It made some nasty sounds as it came in contact with valve cover. It did this around 2000 rpms not idle.

Other than this tick, sounds pretty good in videos.

I thought you had a 650 head and cylinders?
How does the 650 valve cover not fit and the 550 cover does?

Tom there was a change in cylinder head design halfway through the 650 run. Sometime in '82 I believe. Suzuki added an extra valve cover bolt to the front flange around the cam chain area to stop oil seepage. They did it on some of the bigger motors too I believe. I have the earlier head on my motor and the spare cam cover is off the later version of the 650 motor so a couple of holes do not line up.

If you check the microfiches on Alpha Sports you will see the obvious differences. Or look at "650 valve cover" on EBAY to see the same differences.

[tkent02]

I thought you had a 650 head and cylinders?
How does the 650 valve cover not fit and the 550 cover does?