What a difference a Chain Makes....

[Kev M]

... A TIMING CHAIN that is... specifically one that's not stretched half a tooth and slapping and clacking as soon as the bike is warmed up.

Well, the rest of the parts arrived yesterday (BIG UPS to Bob'S BMW... I ordered them the day before, but I guess they only had one state to go to get to me!).

Sooooooo, I got home last night and went to it.

Wound up having to almost remove the entire exhaust system thanks to the balance pipe preventing me from removing the timing cover. Managed to keep it all together and pull out the header pipes, hanging the assembly by one clamp on either side of the bike.

I'd already pulled off the diode board, stator, rotor, and ignitor a day or so before.

THANKS BMW for making a stock timing chain with a master link... took about 2 seconds to get that off!

The timing marks SUCKED, almost looked like the one on the camshaft sprocket was penciled on by hand (and it wasn't even completely straight).

Sure glad I thought to buy all the little pieces like the chain guides, plunger and MOST importantly the plunger spring.

The master link is a god-send, and a PIA.... since putting it back on is a bit of a beatch, but no biggie, I put a rag in the opening to the oil pan to prevent loosing it in the sump (good thing I did too ;)).

Well, about midnight I fired her up and I noticed 2 things.

1. The timing chain was MUCH QUIETER....
2. Now those valves sound a lot louder, LOL :D


A quick test ride and a timing adjustment later and it was off to bed...

A couple hours after that and it was time to ride (to work)...

I must say, I know it is probably MOSTLY mental, but the bike just felt happier (could also be that half a tooth out of mechanical timing it was due to chain stretch).

I loved coming to a stop and not hearing the clack,clack,clack,clack slap of the chain!

Well... Jenn will get to ride it tomorrow and I'm sure she'll love the difference too.

And as we all know HAPPY WIFE = HAPPY LIFE!

Ride safe,

Kev

[Braddog]

Not a timing chain, but once my valves were adjusted, they were a tad bit noisier, but everything was "happier" as you said.

It's great that Jenn's getting used to all the little clicks, clacks, and thunks that come with an old airhead.

[BMWRich58]

...also check the clearence in the rocker arms! That could also produce a "clack" very simular to an out of adjusted valve.
One more thing over looked,is the exhaust system.
Yep, even a small exhaust leak that "ticks" under acceleration,will giving the impression that valves or rockers need adjustment. New alumiunum sleeves fitted between the header pipe (front of engine/cross over) and the exhaust ends to mufflers, and new "donut rings" beneath the exhaust nuts will seal and quiet the exhaust system "big time".

[Kev M]

Originally posted by Braddog
Not a timing chain, but once my valves were adjusted, they were a tad bit noisier, but everything was "happier" as you said.

It's great that Jenn's getting used to all the little clicks, clacks, and thunks that come with an old airhead.


An engineer and BMW freak I've known for years has an expression...

"A tappy valve, is a happy valve"

I'd rather set it to the loose side of spec than to the tight side, I'm not trying to eek out the last hp out of anything I ride.

So I don't mind em making a little noise, as at least I know I'm not about to burn on that way.

As for Jenn, she constantly amazes me. She picked this bike out on her own and she loves it, quirks and all. She's performed all of the maintenance on it so far (up until the Timing Chain, which I'm sure she would have helped on if not for her first major exam of the year... a 2 1/2 hour written exam on Anatomy, Histology, Radiology and Primary Care, PLUS an hour long Anatomy Practical in the Lab :eek )... So while she studied her ass off, I did a little wrenching for her...

Anyway, looking forward to riding with her some this weekend (as soon as she's over the post exam hangover)... :)

[Kev M]

Originally posted by BMWRich58
...also check the clearence in the rocker arms! That could also produce a "clack" very simular to an out of adjusted valve.
One more thing over looked,is the exhaust system.
Yep, even a small exhaust leak that "ticks" under acceleration,will giving the impression that valves or rockers need adjustment. New alumiunum sleeves fitted between the header pipe (front of engine/cross over) and the exhaust ends to mufflers, and new "donut rings" beneath the exhaust nuts will seal and quiet the exhaust system "big time".

Ahhh yes, all excellent points... thanks for mentioning them.

As for the rockers, I suspect they're fine as the valves were quiet when we bought the bike (3 out of 4 were a bit too tight when we check clearances)... and we knew the chain was making noise when we bought it (and I MEAN IT WAS MAKING NOISE)...

We used a rubber hose as a stethescope to make sure it was coming from the timing cover and NOT the crank/con rods...

Compression was good (enough) and the noise was definitely in the front of the motor... with 50k or so miles on the original chain it was an educated guess that the chain was the culprit and the fact that the timing marks seemed to be off by 1/2 a tooth supported that prediction. But most of all the fact that the noise is now GONE tells me for sure we did the right thing.

The pipes are in great shape... though I did NOT replace the donuts, they looked good enough and I don't see or feel any evidence of leaks by the exhaust flanges (or at any of the pipe clamps/crossovers etc).

Lastly, as I said the valves were set (or worn) too tight and the current click,clicking is to me the healthy sound of valves that are set properly (or to the loose side of properly).

It sounds like a happy airhead to me.

[Kev M]

Maybe I should start a new thread for this question, but since it's a follow up to the timing chain let me ask it here.

The Clymer and Haynes manuals were sorta mostly useless, except where the Haynes manual told me about using a 6mm thick 40-50mm long shaft and the rotor retaining bolt to push the rotor off the end of the camshaft (very cool)...

But they didn't warn me anything about matchmarking the rotor (which I sorta did, but didn't do well enough).... and both their timing procedures differed from the owners manual and from each other.

So I put it all back together, I have no way of performing a static timing check so I start it to check it out mechanically. Well, I TRIED to start it, but the first time it really didn't want to fire... it would stumble and not really catch... a little backfire or two... eventually I got it started and even after it warmed up it would die on me if I let the rpm drop...

IT SOUNDED to me like timing was a little too retarded... sooooooo I removed the front cover, loosened the bolts on the igniter and rotated it a good bit counterclockwise.

Made all the difference in the world started right up first touch of the starter (which it always has since we bought it with the bad chain)...

Anyway... I'm still a little uncertain how to dial in the timing more exactly AND since this very rought SWAG adjustment I'm noticing that the idle rpm has gone WAY UP... well sorta... it will idle in the 1500-2000k range IF I CHEAT and let the clutch out slightly while in gear and stopped or slowing (using the clutch to slow the motor down)... however if just come to a stop while riding and pull in the clutch it will usually idle at about 2.5-3k...

My guess is that idle speed is now being pushed up a little by too advanced timing.

Does anyone here concur or have another theory.

the carbs were rebuilt right before we bought the bike and they seem perfectly balanced, though they MIGHT have been tuned/set to a bike that was slightly off mechanical timing and I guess they MIGHT require adjustment to reset the idle, but I'm thinking the only things I touched were the timing chain and igniter soooo I should probably start with a better timing adjustment.

The owner's manual doesn't give a static or idle speed timing check, they only give a check of lining up the Z mark on the flywheel with the center of the timing window at 3500 rpm, the one confusing part was they said to connect the timing light to the RIGHT cylinder igniton wire???? This seemed back/assward to me??? Do they really mean the right cylinder when sitting on the bike?

Any other tricks/tips before I try to dial it in a little better????

thanks in advance for any advice.

Kev

[Kev M]

OK... nobody with any ideas?

Update, I made a very slight adjustment this morning, rotating the ignitor a little bit clockwise (seeming to better line up my original matchmarks).

We THOUGHT it did the job, as the idle was down this morning, in the 1500 rpm range. But Jenn said that as the day went on it creeped up a bit.

About a 100 miles later it was oftem running high again.

I could try a further adjustment, but otherwise I think it will be time to look at the carbs. Any ideas???

[sgborgstrom]

Kev-
Use a dynamic timing light. Just get the ball in the middle of the window (or slightly below per some shade tree mechs...) at full advance and button things up.

Yes, adjusting your timing will alter the idle speed. Once the timing is happy and your valves are set properly you need to adjust the carbs to the right idle speed and do a good synchronization. You want to be quick about the synching and/or use a high velocity fan to provide some cooling for the motor. Get the bike close to normal running temp before doing the carb adjust...

Steve

[Kev M]

Originally posted by sgborgstrom
Kev-
Use a dynamic timing light. Just get the ball in the middle of the window (or slightly below per some shade tree mechs...) at full advance and button things up.

Yes, adjusting your timing will alter the idle speed. Once the timing is happy and your valves are set properly you need to adjust the carbs to the right idle speed and do a good synchronization. You want to be quick about the synching and/or use a high velocity fan to provide some cooling for the motor. Get the bike close to normal running temp before doing the carb adjust...

Steve

Thanks for the reply, but

Couple of questions if I MIGHT.


1. Which wire for the timing light (left or right cylinder). I thought left, but I'm pretty sure the service manuals/owner's manual disagreed and at least one said RIGHT????

2. Carbs were rebuilt and synched a couple months ago (right before I bought it)... but of course with the bad timing chain. However, although the adjustment with regards to the chain might be a bit high or low for idle speed, I don't see how it would affect synchronization???? Either the butterflys are opening together or they are not right? I've got some balance sticks, so I CAN check em. However, it's been nearly a decade since I've done that on an airhead??? Are there vacuum ports on the carbs to which I attach??? Where are they?

3. Are there idle/main JETS or idle/main mixture screws on these carbs. I.E. is mixture adjustable or fixed. Again, I figure if it IS adjustable, PERHAPS the carbs are set up for the old stretched chain and they need a tweek. However, if fixed, I'm much more concerned with the timing.


Of all these, I'll check and set the timing again first and see what it does.

Is my logic correct that BECAUSE the engine when mechanically slowed (using the clutch and brake) to 1500 rpm will STAY at 1500 rpm and not go back up to 3000 on its own, I believe that it is NOT a mechanical carburetor adjustment issue.

Because, if it was a mixture or amount of idle air issue, the engine would return to 3000 rpm on its own once the clutch/brake were released.

Does that make sense???

Thanks again for the reply and anything else you might be able to answer/indulge me with.

Kev

[sgborgstrom]

Kev-
It's all about timing....
With the new chain your ignition is firing at a different point in time than it was before. The systems (carbs, timing ,valves) are all individually adjustable but relate to one another. I would suggest looking at this:

http://www.airheads.org/index.php?Technical%20Tips+Synchronizing%20Carbure tors

and surfing around the airheads.org site while you're there.

Idle mixture screws are under the carbs, next to the float bowls, vacuum ports are horzontal, sticking out to the left or right side of the carb depending on which side of the bike you are standing on.

Make sure the butterfly plates were installed correctly, it is easy to install them ever so slightly "off" in the throat and this will screw up any chance of ever getting the idle right.

Since the hole for the timing port is on the left side, I use the left spark plug cable.

Steve

[Kev M]

Originally posted by sgborgstrom
Kev-
It's all about timing....
With the new chain your ignition is firing at a different point in time than it was before. The systems (carbs, timing ,valves) are all individually adjustable but relate to one another. I would suggest looking at this:

http://www.airheads.org/index.php?Technical%20Tips+Synchronizing%20Carbure tors

and surfing around the airheads.org site while you're there.

Idle mixture screws are under the carbs, next to the float bowls, vacuum ports are horzontal, sticking out to the left or right side of the carb depending on which side of the bike you are standing on.

Make sure the butterfly plates were installed correctly, it is easy to install them ever so slightly "off" in the throat and this will screw up any chance of ever getting the idle right.

Since the hole for the timing port is on the left side, I use the left spark plug cable.

Steve



Thanks again Steve, I've read most of the stuff on Airheads.org, but they did not have any instructions about timing.

So using the left plug wire was not wrong, I'm wondering if this bike uses a waste-spark system, guess I should check under the tank to see if there are two or one primary circuit(s)...that would tell me.

So, it's time to break out the carb balance sticks... ok, but again, first I want to make sure the timing is honestly set correctly. Once I'm sure about that, then I'll mess with sync as necessary.

Thanks for the info.

Kev

[dlearl476]

Kev, I don't know what bike you're working on as it's not in your sig, but I'm getting a R75/5 back on the road and my mechanic friend suggested I install new "heavy duty" advance return springs. It helped a lot. Don't have the part number handy as I'm at work, but a dealer should be able to help. And I think it's perfectly normal for your idle to be off now after ignition work. Don't worry, adjust. I think you'll find that with the ignition all correct and your new timing chain, you'll be turning the idle mixture and speed down significantly because it's all up to proper spec.

[Kev M]

Originally posted by dlearl
Kev, I don't know what bike you're working on as it's not in your sig, but I'm getting a R75/5 back on the road and my mechanic friend suggested I install new "heavy duty" advance return springs. It helped a lot. Don't have the part number handy as I'm at work, but a dealer should be able to help. And I think it's perfectly normal for your idle to be off now after ignition work. Don't worry, adjust. I think you'll find that with the ignition all correct and your new timing chain, you'll be turning the idle mixture and speed down significantly because it's all up to proper spec.


Hmmm sorry, thought I had put it in the opening post.

1981 R65...

So we're talking about an electronic ignition (no advance spring).

Nonetheless, I haven't been sweating this in the slightest... I've been a little puzzled by the contradictions in the serivce manuals. And I've been lazily hoping that the timing adjustment alone will do the job. I'll still make sure the timing is REALLY dialed in before I mess with the carbs, but If I've got to sync and adjust I'll do that too.

Don't get me wrong t he bike is running like a top right now. The slightly high idle is the ONLY problem, and it is not horrible, but something I'd like to dial in.

Thanks for the words.

Kev