Author Topic: Easy CB750 cam chain tensioner adjustment idea--what do you think? (Read 21782 times)

Holden · « **on:** June 13, 2011, 09:41:00 AM »

I'm not a mechanic, so I wanted to run this by the people who know a lot more about this than I do. Here is my idea for adusting the tensioner on my CB750K4:

-Loosen the tensioner set bolt,
-With the bike in a higher gear and on the stand, turn the the rear wheel,
-Use a small screwdriver inserted in the back of the tensioner to feel the movement of the tensioner rod (without applying pressure to the rod),
-Find the point at which the rod extends forward the most and tighten the set bolt.

I'd appreciate input before doing this. (I have to admit that I don't really understand setting the engine to TDC +15 degrees.) Is this a good, if not ideal, way of setting the tensioner?

strynboen · « **Reply #1 on:** June 13, 2011, 09:51:22 AM »

are you doing an 550.

..350 and 400 can be done done dynamic..but 550 and 750 are static..adjusting the chain..think not you can destroing anything..
just not push..on somthing..let the spring do the work..
pull the plugs..and turn the engine over with that bolt on egnision plate..its easyer then turn the wheel

EDIT got vrong..750 can be done dynamic..then it only 500 and 550..who are static done

Holden · « **Reply #2 on:** June 13, 2011, 09:54:32 AM »

Quote from: strynboen on June 13, 2011, 09:51:22 AM

are you doing an 550...350 and 400 can be done done dynamic..but 550 and 750 are static..adjusting the chain..think not you can destroing anything..
just not push..on somthing..let the spring do the work..

Good point--I edited the post to include the specific model.

Skunk Stripe · « **Reply #3 on:** June 13, 2011, 10:01:08 AM »

I don't know about the k4 but I doubt it is much different from the K8 for the tension unit. The manual for the K8 says to start the bike and set it while idling.

MCRider · « **Reply #4 on:** June 13, 2011, 10:14:20 AM »

Quote from: Holden on June 13, 2011, 09:41:00 AM

I'm not a mechanic, so I wanted to run this by the people who know a lot more about this than I do. Here is my idea for adusting the tensioner on my CB750K4:

-Loosen the tensioner set bolt,
-With the bike in a higher gear and on the stand, turn the the rear wheel,
-Use a small screwdriver inserted in the back of the tensioner to feel the movement of the tensioner rod (without applying pressure to the rod),
-Find the point at which the rod extends forward the most and tighten the set bolt.

I'd appreciate input before doing this. (I have to admit that I don't really understand setting the engine to TDC +15 degrees.) Is this a good, if not ideal, way of setting the tensioner?

To me, that's significantly more difficult than simply removing the points cover, turning the engine to the right point (which is the point you are finding by trial and error turning the wheel) set the adjuster, put the cover back on and you're done.

To respond to your confession. 15° ATDCC is found thus: Remove the #1 intake tappet cover (you'll have it off setting the valves anyway, if you're doing a tuneup); rotate the engine by turning the nut on the ignition; watch the #1 intake tappet go down, then back up. Now watch the spark advancer pass the T for 1-4, continue to the left side of the spring post. That's 15° past TDCC. Set the tensioner and button up. Very quick and clean.

MCRider · « **Reply #5 on:** June 13, 2011, 10:28:26 AM »

And to be clear as there was some confusion. This is just for CB750 only. All other CB/4s do it some other way.

Skunk Stripe · « **Reply #6 on:** June 13, 2011, 10:39:04 AM »

Do you do it that way or with the bike running? I do it while idling and it seems to work very well.

MCRider · « **Reply #7 on:** June 13, 2011, 10:40:55 AM »

Quote from: Skunk Stripe on June 13, 2011, 10:39:04 AM

Do you do it that way or with the bike running? I do it while idling and it seems to work very well.

The CB750 must be done with the engine Off. SS What bike do you have?

Skunk Stripe · « **Reply #8 on:** June 13, 2011, 10:44:57 AM »

cb750 k8, manual says to do it while running. Honda shop manual btw.

MCRider · « **Reply #9 on:** June 13, 2011, 10:49:24 AM »

Quote from: Skunk Stripe on June 13, 2011, 10:44:57 AM

cb750 k8, manual says to do it while running. Honda shop manual btw.

Wow, that's news to me. I'm open for explanation.

I looked it up on a parts fiche and they are the same tensioners. My K2 to your K8. I can't see how setting it while running could work. Though I guess it wouldn't hurt anything.

Skunk Stripe · « **Reply #10 on:** June 13, 2011, 10:52:45 AM »

I have the 78k/f manual and the 69-78 manual and both say to do it with the engine running.
I do not have my 78k/f manual right now but the 69-78, you go to page 279 I think, in section 3-7.

MCRider · « **Reply #11 on:** June 13, 2011, 10:56:44 AM »

Quote from: Skunk Stripe on June 13, 2011, 10:52:45 AM

I have the 78k/f manual and the 69-78 manual and both say to do it with the engine running.
I do not have my 78k/f manual right now but the 69-78, you go to page 279 I think, in section 3-7.

I don't have an official Honda manual. My Clymer's 69 to 77K & F says to do it static. I'm open to learn.

MCRider · « **Reply #12 on:** June 13, 2011, 11:47:34 AM »

Apologies to Holden for jacking the thread. To address his issue, I'd rather do it dynamic than turning the rear wheel.

DYNAMIC! Yes, after a quick round of discussions, I see that dynamic will work, obviously many of you must be doing it if that's what the Honda manual says.

Let it simmer to an idle, loosen the bolt, tighten it back up and you're done. Can't get easier.

But lets speculate. the static method allowed for and invited abuse. Once the position is attained, the shady tree mechainc can shove something up the butt of the tensioner and make it really tight. It'll be quiet, but it will hasten the wear on the roller and chain.

My bet is that Honda in an effort to curb this enthusiasm, began suggesting the dynamic method. Even if you shove something in the back of the tensioner, the spinning chain would not allow anyone to overload it, or at least not as much. I'd love to get a pre-K? Honda manual and see if they were recommendiing the static procedure on the earlier bikes. Then in later print dates, retrofitted the dynamic procedure onto the early bikes.

I still prefer the static method, done properly, without the extra zeal.

And I learned something today.

Holden · « **Reply #13 on:** June 13, 2011, 12:02:02 PM »

Thanks to all for the replies and discussion.

I got the clymer manual in the mail today and followed its instruction and picture (figure 33) to set 15 ATDC. Haven't started the bike yet (have a few more things to do on it), but it wasn't hard. I didn't open the tappet cover because I'm waiting on new tappet cover o-rings for this 37 year old bike.

Is this preferable to dynamic? Should I re-do it after I start the bike? (That might be a premature question...I guess I should wait to hear how it sounds...)

MCRider · « **Reply #14 on:** June 13, 2011, 12:26:59 PM »

You need to confirm that you are at 15° ATDCC for Cyl #1. The second C means compression. You might be at ATDCO which is overlap. The most slack is on the back row of the chain when #1 is set at ATDCC. The only way to know is the test I outlined, pull the intake cap and watch the tappet. Its complicated to talk about, but in real life its a snap.

I think the Clymer mentions use #1 at ATDCC but doesn't discuss how to confirm that's where you're at. You could stick your screwdriver in your hole, as you know you can feel the chain get tight and loose, and turn the engine thru to TDC 1-4 again, and see if that's giving you more slack.

I prefer static to dynamic, but that's what I was raised with. After setting at least a few hundred, I only learned today that the CB750 could be done with the engine running and I may warm up to that idea.

climbingaz · « **Reply #15 on:** June 13, 2011, 12:34:40 PM »

I'm in the middle of fiddling with mine right now. I had the airbox off the bike to do some work on the carbs and figured I'd adjust the tensioner while I had the extra room to work. Got the bike running on choke, idling okay, and then loosened the bolt about a half a turn. Then I heard the "clackity-clackity-clackity" and said $hit! Apparently the internal mechanism was stuck. After doing a little research, I also found that some of the springs weaken with age and aren't strong enough to push back on the chain with enough force.

So I loosened the 3 bolts that hold the tensioner to the motor and took it off the bike. Sure enough, the mechanism seemed a little "stuck"...wasn't moving freely. So I took it apart, cleaned it up a bit and will mount it back on the bike this afternoon and give it another try.

If it doesn't seem to work with the motor running, I'm pretty sure the old spring is the culprit. I've got to assume that after 30+ years that spring is bound to loose some of it's pushing power. Then I guess I'll resort to the static method.

BobbyR · « **Reply #16 on:** June 13, 2011, 12:46:08 PM »

Quote from: Skunk Stripe on June 13, 2011, 10:52:45 AM

I have the 78k/f manual and the 69-78 manual and both say to do it with the engine running.
I do not have my 78k/f manual right now but the 69-78, you go to page 279 I think, in section 3-7.

I have the Honda factory manual for my K8 and Stripe is right it says adjust the tensioner with the engine running at idle.

Stripe could you confirm that the back of the tensioner housing is not open, so we can't insert anything in the back to either see if it adjusts or loosen it if it is stuck.

MCRider · « **Reply #17 on:** June 13, 2011, 01:17:57 PM »

BobbyR: The micro fishy indicates its the same part number as the earlier ones, so it should have the access push hole as well.

climbingaz · « **Reply #18 on:** June 13, 2011, 01:47:25 PM »

My K8 has the access push hole.

Skunk Stripe · « **Reply #19 on:** June 13, 2011, 02:04:56 PM »

Not home but I do not remember have a hole in the back. There is an indent but no hole.
I do not that crud builds up in though housing and it makes the rod stick. If the rod sticks, you can't do it statically either as the rod does not move.
When I pulled mine off, I sprayed cleaner in there, simple green I think, and nothing leaked out of the back of the housing.
I am inclined to say that you should not be able to push anything into the housing on a K8.

MCRider · « **Reply #20 on:** June 13, 2011, 04:10:27 PM »

Quote from: Skunk Stripe on June 13, 2011, 02:04:56 PM

Not home but I do not remember have a hole in the back. There is an indent but no hole.
I do not that crud builds up in though housing and it makes the rod stick. If the rod sticks, you can't do it statically either as the rod does not move.
When I pulled mine off, I sprayed cleaner in there, simple green I think, and nothing leaked out of the back of the housing.
I am inclined to say that you should not be able to push anything into the housing on a K8.

As i am currently assembling mine for my project, I am intimately aware of their construction at least for the K2 and the parts microfish indicates it's the same for the K8. The plunger bar is a machined fit in the hole of the housing. I mean it is very tight, less clearance than a valve in a valve guide. It also has an oil seal inside of the housing. To get grime in from the outside would be something most foul, though I'm sure someone could do it. The plunger will hang up under certain circumstances. The access hole allows one to determine if its hung up as the movement of the end of the plunger is very noticeable, no movement would be a sure sign of a problem..

SS check yours when you gt a chance, I may learn something again.

Cuts Crooked · « **Reply #21 on:** June 13, 2011, 04:23:22 PM »

Weird!!!

I just tried to adjust my cam chain tension, in my K8 with the engine idling.....Got the clackity/clackity noise immediately!

Shut her down and did it the old fashioned way......sounds good again! $:-\$

Go figger!

While I had the plugs out, to help find TDC + 15, I looked at em.......nice tan color!

MCRider · « **Reply #22 on:** June 13, 2011, 04:32:47 PM »

Quote from: Cuts Crooked on June 13, 2011, 04:23:22 PM

Weird!!!

I just tried to adjust my cam chain tension, in my K8 with the engine idling.....Got the clackity/clackity noise immediately!

Shut her down and did it the old fashioned way......sounds good again! $:-\$

Go figger!

While I had the plugs out, to help find TDC + 15, I looked at em.......nice tan color!

That's what I would have guessed would happen. The spring on the plunger bar was never meant to be strong enough to push against a flailing cam chain. It would just lightly push the plunger into the roller holder. I accept it, but i don't get it.

Taking the plugs out will work, you'll see bits of the valves on overlap, (I think) and none on compression. And helps in turning the engine over with the nut on the ignition. Quite a resistance with the plugs in.

climbingaz · « **Reply #23 on:** June 13, 2011, 05:29:29 PM »

Ok, just got home and went out to the garage to finish my adjustment. I decided to do it "dynamic" with the engine running. When I got it to an idle, I loosened the bolt a half turn but the tensioner didn't really "auto-adjust". I still heard the clackity-clack. I then took a small screwdriver and gently pushed in the rod from the access hole until the engine sounded good and then tighted up the bolt and locking nut. The amount of force I had to use to push the rod in with the screwdriver was very minimal. Hope that helps!

Cuts Crooked · « **Reply #24 on:** June 13, 2011, 05:30:50 PM »

Quote from: MCRider on June 13, 2011, 04:32:47 PM

That's what I would have guessed would happen. The spring on the plunger bar was never meant to be strong enough to push against a flailing cam chain. It would just lightly push the plunger into the roller holder. I accept it, but i don't get it.

Taking the plugs out will work, you'll see bits of the valves on overlap, (I think) and none on compression. And helps in turning the engine over with the nut on the ignition. Quite a resistance with the plugs in.

With the windshield in place I can't get a good look down the plug holes, so I put a plastic soda straw in #1 and watch it when it comes to the top of it's movement, I check the timing plate, if its at TDC I turn the motor just enough to make the straw start to drop.......and VIOLA it's there!

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Author Topic: Easy CB750 cam chain tensioner adjustment idea--what do you think? (Read 21782 times)