Talking of torque

[49er]

Well, the months of procrastination and planning have finally come to an end.
Today, I put 40kms on my 850 rebuild using the controversial "Motoman" bedding in process. The early results are very encouraging.

My motor had only 76,000kms on it when I stripped down the top end.
It had many PO's and had been stored for a number of years. At idle, excessive camshaft endfoat was causing rattling/knocking sounds similar to that of a big end knock. On inspection, the endfloat had increased to .005 in on the inlet and .006 in on exhaust.
One bore had a major score mark running down most of the stroke area. I made two decisions. Bite the bullet, rebore and fix that dam annoying endfloat knock.

For a road bike, when you have to rebore, go as big as you can without having to resleeve the bores. With this in mind, I decided to custom a set of 71mm, 10.5 to1 pistons. By going up 2mm in diameter, I could retain the minimum wall thicknesss of 2mm on my standard sleeves. The increased CR and capacity should give more punch through the entire rev range.
I have replicted the standard piston weight with the new pistons to maintain the balance of the motor. :-D

The endfloat was reduced by changing the thrust surface from the cam bearing end faces on the head, to the matching bearing caps. These cap ends are not in contact with the cam thrust rings, but are well supported and dowelled, ideal for precise machining and moderate loads.
These bearing caps were machined back 3 mm in the shape of a half moon, slightly bigger than the cam thrust ring. Ali spacers were sized and fitted to reduce the endflat to .0015 in for each camshaft.
No repair work was required to the old thrust surfaces on the head as they are no longer in contact with the thrust collars.
The advantage of this system is that some 30-40k further down the track, new half moons can be machined to reduce the wear that has occurred over that period, at a relatively low cost.
While the motor was apart, I reground the cams to standard specs, replaced the cam chain, the cam chain tensioner slipper, the idler, tacho drive seals, cam chain tensioner seals, plus cleaned and re-kitted the carbs.
On those quiet nights, I cheered myself up by polishing some ali covers and fins.
The valves were in good nick, so they just got a clean, re-lap and a set of new guide seals. The guides and valve stems had minimal wear. I guess this is the advantage of having buckets with an OH valve configuration.
After setting up the carbs and checking the ignition timimg, I squeezed a small shot of fuel into #1&4 pots before screwing in the spark plugs. I know this is cheating, but they fire up first pull of the rope every time this way.
The only adjustment that I made to the carbs while the motor was warming up was to the idle speed knob, before blatting off out into the countryside. I was surprised how quickly the effect of the rings sealing could be felt on the acceleration/deceleration sessions.
It looks like there will be little or no re-jetting changes required.
Standard ignition timing and advance is working well with no detonation. I'm running 98 octane pump gas.
The increase in torque, now has the clutch letting loose in 3rd,4th and 5th gears. I will renew the springs and check the condition of the discs.
I plan another 160km session tomorrow. After that, I will complete another 200kms before doing the fine tuning. The carbs have only been bench synced, but the engine is pulling cleanly through the lower to upper midrange and idling evenly.
Did I tell you I love these VM carbs.
I have taken some pics of these mods and will post them when they have been scanned.
Cheers

[tomcat24551]

If I understand you correctly, you're saying that what limited the endfloat of the cams was the bearing faces cast into the head--not the sides of the bearing caps, right?

But you have figured out a way to add a half-moon spacer to the side of the bearing cap to take up more clearance between it and the cam's thrust ring. How did you do this? What holds the spacer in place?

I have been wishing someone could come up with a solution like this for 20 years at least! Please let this board know if this works. I know you've got the engine buttoned up now, but if you take the cam cover off in the future, pictures of your modifications would be greatly appreciated.

Sounds like everything you did to this engine was well thought-out. Please let us know if the endfloat knock is cured and how the break-in process worked.

Many thanks

Tomcat

[49er]

Tomcat
The machining went like this.
I decided to reduce the ovality in the camshaft bearings, without having to go through the costly and arduous task of line boring. I used some plasi-gauge to measure the wear and then skimmed .002 in off the cap mating faces. Before I did this I used the existing surface as a datum to lightly re-surface the bolt hole faces so they could be used as the datum for the cap re-surfacing. After re-surfacing of the caps, they were coated with bearing blue. I then bolted them down with the camshafts and established the tight areas that needed hand scrapping. After they were scrapped and scrapped and scrapped, the caps were paired up face to face and bolted to a dummy shaft to allow easy machining of the 3mm deep groove. This groove produce a half moon in each cap that was slightly higher than that of the mating thrust rings on the camshafts.
Each cap was then fitted up and the distance from the groove face to the thrust rings was individually measured. Care was taken to ensure that the cams were still correctly aligned/centered to each other.
Individual half moon spacers were then machined to the precise figure that allowed a total of .0015 in thrust clearance for for each cam. The half moons are held in place by precisely mating to the cape grooves and the bottom bearing mating face. The cam thrust rings trap the spacer from the other end. There is about .5 to 1mm of spacer protruding clear of the end cap groove, so there is no way it can fly out of it's possition. If the spacers were to wear rapidly, there would be a reversion back to the existing thrust surface on the head and that annoying clatter would resume. There is no way that these spacers can come free. I was going to locktite them to the caps, but decided that it would be easier to replace them if they weren't glued in.
I have machined a small chamfer on the internal outer curve of each spacer to ensure a precise fitment of the spacer to the cap groove. Also, oil may sqeeze between the mating face and the cap to take up any eventual wear and increase the time before the process needs to be repeated. Hopefully, as they wear this oil cushion will form and reduce the possibility of that knocking sound returning for some time.
Incidently, if anyone has their motor top end apart, strip out the valves and sit your cams into the bearing surfaces in the head and test the endfloat. You will be amased at the clunking sound that is heard when sliding the cams back and forward against each of the thrust rings. This noise is magnified when the cam covers are installed on the motor.

After the first 40kms, there is no cam knock, so it looks promising.
I have taken some film pics of the pistons and the cam mods. I just need to have them developed and scanned. I haven't lashed out on a decent digital camera as yet.

I will keep you posted as to the breaking in results. I believe that Motorman has done his homework too.
Cheers
Ian

[Dink]

Following with interest

Dink

[BadBillyB]

Way to go Ian, I was having this same problem with my 79 1000L model. Hope the fix lasts forever....I bought my L model brand new in 1980 and noticed that after a good warm up, at idle only, there was a distinct knocking noise. Being under warranty, I took it back to the Suzuki shop and told them something was wrong....They heard the noise and disassembled the motor for inspection. They found nothing....I was furious...Well a year or so goes by and I have the head off for some performance work and I saw marks in the cam chain tunnel area where the back side of the cam sprocket flange (on the cam) was rubbing the cylinder head. The knocking (hammering) had also worn some material from the area of the cylinder head just below the cam caps. The end float was probably in the neighborhood of around .040" or more. Not seeing an easy fix, I just releived the area on the cam where it was rubbing inside the cam chain tunnel....Didn't want aluminum scrapings falling into the bottom end.....Figured my motor was made on Monday, but apparently it was an engineering flaw from the factory......Nice fix, Hope it lasts.....Very nice of you for posting this repair .............BadBillyB

[49er]

Thanks for your info BadBillyB.
I have only managed another 70kms on the motor since my last post. Wimped out on some bad weather.
Still no sign of that cam knock though, but it's early days yet.
A small trace of oil smoke was just visible when the motor was reved to 5000rpm after arriving home from the last run. There's still a bit of bedding down to be done yet.
I need to look at the clutch before venturing to far from home though. Uprated springs, or new discs, or both?
Thanks for your interest Dink.
I will keep in touch with progress.
Cheers
Ian

[tomcat24551]

Back to the cam knock, Ian:

Were you able to identify any possible cause for the excessive endfloat?

I wonder if one or both of the cam chain sprockets is not running perfectly perpendicular to the cam's plane. This would cause a wobble as the cam completed a revolution. When the idler sprocket up top would try to keep the chain running straight, the cam might be pushed from side-to-side causing the cam thrust rings to hit the bearings cast into the head.

Or maybe the cam chain was unevenly worn at some point on its run, somehow leading to excessive whipping from side-to-side as it traveled over the sprockets. Also, I wonder how much side-to-side play existed in your idler sprocket.

Maybe something wasn't true down on the Crank sprocket? Or is it just the fact that valves may be actuated at one end of the cam at a different time than they are at the other end of the cam causing some side-to-side thrust?

Anyway, now that you have physically stopped the valve gear from doing what it liked to do, I wonder what, if anything, is likely now to prematurely wearout or break because of your fix. Any thoughts on this?

This was a real tour de force piece of work, in my opinion. I'd like to think I could make the same modification to my bike, but I'm not a machinist. So I'm just trying to find out as much as I can just to fully understand the problem. If it wasn't for the knock (which can be damn embarrassing!), my bike wouldn't need anything, so I am naturally reluctant to remove the head right now if this problem could be fixed any simpler way.

If your modification works long-term, it would be great if you could do a presentation on this website with pictures and how-to, similar to what's been done in the VM carb rebuild piece located in the "In the Garage" section.

Thanks for your interest in helping me get educated. Sorry to be so long-winded.

Tomcat

[Dink]

Would it be an idea to make the "bushes" in bronze??

Dink

[49er]

Tomcat

From my early investigations to this noise I determined that in my motor the cam chain idler was probably misaligned, causing the chain and cam sprockets to load up the thrust surfaces on the head. I say probably, because it is near impossible to check the alignment with the cam sprockets when the idler is mounted in place. The housing design encloses around 65% of the sprocket and is pressed steel. It fits very close to the cam cover which makes it difficult to fabricate a substitute without major cam cover mods. I did check the mount hole alignment with the cam axises and found it to be ok. My old idler had wear on the teeth on the right side of the sprocket. The pivot(rivet) had some axial wear and the sprocket had excessive endloat inside the housing and had been slapping both sides of the housing. When you slapped it agressively back and forth it made a knocking sound similar to that which we all hear at idle. I checked the chain for signs of wear and tight spots but couldn't find anything. The chain appeared to be in good nick for 70,000kms. I also checked for any cam sprocket runout but they were ok. I thought that I had found the cause of the knock and proceeded to modify the idler by replacing the shaft and making up teflon spacers each side of the sprocket to take up sideplay and quieten things down. This didn't fix the knock, so I looked closer at the camshafts, in particular, the thrust area.
When the cams were pulled, I noticed that the cam bearings showed signs that the cams had been whipping under load/rpm and that the trust rings had worn light grooves in the trust surfaces on the head. I don't know what the factory endfloat figure was but calculated that it should have been in the vicinity of .0015 to .002 ins. I believe that you need to elimenate the idler all together, like they did to the later GS models, to completely fix this problem. The cams would need to be re-timed and the chain length and/or the tensioner system be modified.
The other two things that probably cause some side movement of the cams is the tappered wear pattern on the cam lobes caused by the cam whip and in two cases, the mis-alignment of the lobes to the centre of the cam buckets. One lobe was 2.5 mm off center. This last cause is a casting error on lobe positions of the cams.
By the wear pattern on the bearings of both cams realitive to each other, the idler is influencing the direction of the whip of the cams. The loading has occurred on the side closest to the idler in both sets of cam bearings.
I proceeded to modify the caps and fitted a new idler and regound the cams.
I wonder whether the automatic cam chain adjuster has enough range of adjustment to cope with the expansion of the motor under hard working conditions. If it doesn't, the load would increase in the idler and cam sprocket areas.
Time will tell whether the idler misalignment was a contributing factor.
Cheers

[49er]

Dink
I did mull over the idea of using either cast iron or bronze, but wasn't sure of the wear consequences in relation to the cast thrust rings. I didn't want the rings to wear instead of the spacers. At least with ali, I know the rings aren't being excessively worn. You don't want to be building up the thrust rings with weld at a later date.

[BadBillyB]

It was always my impression that the heel of the cam in conjunction with the lobes slightly offset from the center of the bucket would cause the bucket to rotate in its bore. This would keep the cam lobe from wearing a "ditch" into the adjustment shims....My 78 GS1000 motor knocked basically from day one so I would chalk it up to poor machining in either the head or the cams....I suspect the maching was a hit or miss kind of thing...If you get a "knocker", the end float will progress at a fast rate.......If you have a nice tight end float from the factory you may never have an issue......Ian, I can picture exactly what you did to fix this issue and wish I had thought of it back in the day when it became a problem for me. The back of the sprocket flange had become my "thrust" surface......Tomcat, is your knocking only at low idle rpms ????........BadBillyB

[tomcat24551]

"Tomcat, is your knocking only at low idle rpms ????........BadBillyB"

Yes, usually at 2000 RPM or less. Worse at around 1100 RPM, with noise reducing as RPMs increase towards 2000. But there's more. It is definitely heat related.

When my '79 850 engine is stone cold at startup, it's quiet as a mouse. But then as things begin to heat up, a rythmic, knocking noise (usually knock, knock, knock--knock, knock, knock) becomes audible. The hotter the engine gets, the louder and more pronounced the noise becomes--until it gets to, say, about 3/4 of full operating temperature, then the noise begins to gradually go away. When the engine is full hot, the noise will be all but 100% gone. If the day is hot enough and I've been riding long enough, it'll be completely gone.

But when I stop for 10-15 minutes and restart after its cooled down a bit, I get that rythmic knocking again, sometimes so strong I can feel it in the handlebars. (If I'm riding in a group, I usually let the Hogs and V-twin riders start their bikes first and guess what? Nobody notices the noise and everybody's still admiring my bike, heh, heh.)

I have noticed, as have others on this Forum, that sometimes the knocking can be made worse by leaning the bike over to one side or the other.

I've also noticed that it looks like the sides of the cam bearings were "machined", (or so I thought) in a half-moon pattern, but that must be where the cam thrust collars have contacted that area, causing the noise.

This noise started when the bike had about 16,000 miles on the clock and has slowly gotten worse. I originally thought it was cam end play, but didn't know how I could verify it. I thought the wear areas on the cam bearings were intentionally machined there by Suzuki. Later I thought it was a piston pin knock or a piston with a cracked pin boss. But you can hear it best with a stethoscope around the exhaust area of the cam cover, so thanks to Ian, I'm back to the endfloat diagnosis. I've let a lot of dealer mechanics listen to the noise with their diagnoses ranging "clutch basket rattle" to "too much valve lash", etc, etc. Really? That's why I don't trust service departments with my motorcycles.

To my knowledge, no one has put the thought and work into solving the problem to the extent Ian has. I'm really following this closely. If I could solve this problem and get some brakes on this machine, I'd have a really good, refined ride.

Tomcat

[49er]

Tomcat

My 850 used to do exactly the same as yours does. From a cold start the engine would be smooth and quiet. As it got to the normal running temperature the knocking sound would become quite audible. When running in normal air temperature and moderate revs the sound at idle was horrendous. How do people sell these things when they sound like that?
If the bike was thrashed/worked hard, the noise at idle was gone.
I believe that when the engines are cold the thicker oil around the bearings and cam thrust rings acts as a cushion and prevents the knock. As the engine warms up, the oil film thins and the ali expands faster than the cast cams, the endfloat increases until it becomes audible. I'm sure that poor design and machining in this area have created this problem.
Now here's the scary part. :shock: When the engines are worked hard, I think that the expansion rate of the block and cylinders is that great that the cam chain tensioner is unable to cope with the increase, so the chain actually tightens and increases the load on the idler and cam sprockes. The tension is sufficient to stop the cams from floating. That's my suspicion after examining my wear patterns on the cam bearings and the idler.
Once the engine cools down to normal operating temps the sound returns.
My next mod will be to increase the flat section on the tensioner rod to allow for slightly greater automatic adjustment.
Hope I haven't scared you all now.
Cheers
Ian

[49er]

Time for another update.
I now have 550kms on the rebuild. No cam knock, Yeeha.
The engine feels and responds great. My only concern is the oil rings don't seem to have bedded down yet. #1,2&4 are stilll slightly sooty and #3 has slight wetting above the thread of the plug. Oil consumption isn't great though. It just may need more kms to seal properly.
When following me, my brother tells me its drawing some oil on severe deceleration (down hill). That extra CR seems to be hindering the bedding down process. It certainly makes life a lot easier when braking though.
There is strong axial torque of the bike to the right under hard acceleration in top gear, and then the clutch breaks loose.
Has anyone fitted barnett clutch kits to the 850 motor? Are they suited, or would it be overkill?

[Doctor Shifty]

Following with interest

Dink

Hey Dink, are you still following? I thought I shook you off somewhere up above Bellingen. :-)

Kim