That mysterious cam chain tensioner on a 85 NH CB 650

[MaklooN]

Hello everyone,
Is the cam chain tensioner on a 1985 Honda CB650SC NIGHTHAWK 650 really self adjusting?
I've read that the cam chain tensioner spring tends to lose some of its tension, allowing some cam chain noise after a while.
I've also noticed a couple of posts here where people wrote or asked about manually adjusting the tensioner but no real information was provided as to how to do it on this particular Nighthawk model.

My question is... does anybody know if the cam chain tensioner on a 1985 Honda CB650SC NIGHTHAWK 650 can be adjusted manually and if so how?

Thanks in advanced for any help provided.

Cam chain tensioner schematic for a 1985 Honda CB650SC NIGHTHAWK 650

[JordanA]

No.  The 1985 Cam Tensioner cannot be adjusted like the SOHC versions (1980-82 650's, I believe).  It is "self Adjusting" and meant to be maintenance free, but after a while it can develop some slop and rattle.  Once this occurs, it can be a few things:

- Stretched cam chain (means you've got to split the cases)
- Worn out tensioner/tensioner spring (means removing valve cover, oil piping, cams, etc... not as bad as it sounds).
- Worn out guide surfaces (the cam chain guides have rubber on the chain side of them that can harden over time, especially with high temp situations like overheating and constant high revs).

It is all doable with the right tools (inch/lbs torque wrench and ft/lbs) and a good walkthrough or factory service manual.  I recently was sent a write up about this complete with pictures.  I can forward it to you if you'd like.  It was a life saver for me!

[MaklooN]

Thanks for your help.
I just got a hold of a Clymer manual for my model bike and I will try to go through the steps.
Hopefully the spring is faulty or the guide is worn out, although if it turns out to be the chain it will do me good to open the engine and take the opportunity to learn and do extra maintenance.

Again, thanks for your help.

[FirstCavArmyVet]

No.  The 1985 Cam Tensioner cannot be adjusted like the SOHC versions (1980-82 650's, I believe).  It is "self Adjusting" and meant to be maintenance free, but after a while it can develop some slop and rattle.  Once this occurs, it can be a few things:

- Stretched cam chain (means you've got to split the cases)
- Worn out tensioner/tensioner spring (means removing valve cover, oil piping, cams, etc... not as bad as it sounds).
- Worn out guide surfaces (the cam chain guides have rubber on the chain side of them that can harden over time, especially with high temp situations like overheating and constant high revs).

It is all doable with the right tools (inch/lbs torque wrench and ft/lbs) and a good walkthrough or factory service manual.  I recently was sent a write up about this complete with pictures.  I can forward it to you if you'd like.  It was a life saver for me!

Would you mind sending that to me if you have time? Email is pimpdaddytanker@yahoo.com

[Zugzug]

If your going to go thru the trouble of getting the adjuster off to replace it or replace the spring you might as well replace the chain while your there. Replacing the chain is the easy part. Just think how bad its gonna suck to put everything back together to find out the chain is stretched and needs to be replaced also.  Trust me, I know...

[hppants]

Is the 650's chain designed like the 700s?  I mean, do you either split the case and keep the chain in one piece, or split the chain and reinstall with a master link?  Neither one appeals to me, or I would have done it on mine a long time ago.

[JordanA]

Is the 650's chain designed like the 700s?  I mean, do you either split the case and keep the chain in one piece, or split the chain and reinstall with a master link?  Neither one appeals to me, or I would have done it on mine a long time ago.

Yes, those are your only two options.

FirstCav, I'll try to find the writeup.  My email has become severely cluttered over the last few months!

[zippy]

is the cam chain basically the same across all models or are there significant differences? i was lookin into doin this on by cb450.

[JordanA]

I would assume that they're difference, since the motors of of different size and shape. 

[fishmeister]

The chain splitter and replacement link are of such design that the link is attached in a permanent manner and not like a typical master link that is removable. Word has it with the right setup they don't come apart.

I have seen it done, but can't testify to it's longevity. I believe it is a solid fix.

http://www.z1enterprises.com/default.aspx
http://www.motionpro.com/images/documents/08-0058.I8-0058.pdf


Link was/is also available from Honda....they too use this method.

[fishmeister]

If your going to go thru the trouble of getting the adjuster off to replace it or replace the spring you might as well replace the chain while your there. Replacing the chain is the easy part. Just think how bad its gonna suck to put everything back together to find out the chain is stretched and needs to be replaced also.   Trust me, I know...

Good Advice....BTW, there are also two guides and a slipper that are polymer lined helping reduce chain noise. The tensioner alone won't completely eliminate noise if these other parts are worn.

[zippy]

so to replace all the pieces, i guess i need to take off the head to get into the engine to reach the guides? its fairly easy to get the chain replaced itself but the hell is gonna be gettin to them guides, slipper, tensioner etc. unless anyone has an easy way of goin bout it.

btw, anyone got a link to a place where i can get a cam chain, tensioner and guides for a fair price? the bike shop closest to me wants over $200 for that stuff only not including shipping costs which they want to tack on an additional $75. . also thinkin bout replacin the valves but then im gonna get into lapping and such and i dont have the time for all that

[fishmeister]

http://nighthawk-forums.com/index.php/topic,3439.msg39306.html#msg39306

Gammer tried....not sure of his outcome tho...

It's not the easiest job to do I will tell you. Cam timing and other mysteries can rear their ugly heads to the inexperienced.

But there is Bumblebee's patient step by step instructions that require more patience than I have in the explanation aspect.

[zippy]

http://nighthawk-forums.com/index.php/topic,3439.msg39306.html#msg39306

Gammer tried....not sure of his outcome tho...

It's not the easiest job to do I will tell you. Cam timing and other mysteries can rear their ugly heads to the inexperienced.

But there is Bumblebee's patient step by step instructions that require more patience than I have in the explanation aspect.

lol, sounds like something i would do. anyhoo, where is bumblebees page? its so dam hard to find anything of his in all that jumble of other posts he has. do we have a "Bumblebee's remedies for everything" thread?

[fishmeister]

Not sure about his posting, if there was one....you might have to bribe him into helping. Do you have the official honda service manual yet?
http://www.repairmanual.com/motorcycles/1985/27/0/431/1306

[zippy]

Not sure about his posting, if there was one....you might have to bribe him into helping. Do you have the official honda service manual yet?

i wish. seems like everyone wants the price for its weight in gold round here, that is, if they have em in stock at the time since it varies from day to day. sounds like a crack dealer tryin to sell his goods. "oh, we are the only one who has that book", or "you would be lucky to find that, wait , i think i can get you one". you know the bs stories shops can give you and seems like every one round here do that. who ever hear of payin $69.95 +tax & shipping? i even got sick of the one place i thought was halfway decent says stuff is unavailable when i just found 5 of the 6 items (stated as unavailable by a "dealership") i need on that z1 site. and it was cheap to boot. they (the shop) did have a carb rebuild kit, for $112. found the same thing on z1 site for $21.19. looks like the exact same kit they were tryin to sell me:

this one is supposed to be for a CX500 (78-79). looks exactly like the kit they tried to sell me and an awful lot like whats in the carbs i have on my '85 CB450SC.

[fishmeister]

You must learn to reference and search for such parts successfully grasshopper. Look alike don't cut it, matching part numbers do.

http://www.cyclepartswarehouse.com/fiche_select.asp

[zippy]

oh, i understand that. i know parts can be interchangeable on some models. the air cut valve they sold me was not the right one. they sold me this one:

this is the actual part number called for on the cyclepartswarehouse site (VALVE SET, AIR CUT
16048-443-901  (replaces 16048-429-771)) but it is all wrong for my carbs

Air Cut-Off Valve Set Honda GL1100 CB900 CB750 GL500 CM400
KL18-2795
OEM: 16048-429-771 16048-429-671---



after goin on and lookin further, this is the valve i actually have in the carbs:

Air Cut-Off Valve Set Honda CB1100 CB1000 GL650 CX650 FT500
KL18-2796
OEM: 16048-KB7-901


the one with the bulbous head wouldn't work since it didn't fit the hole and since they would not accept returns on "special order" items, i had to grind the bulb of the head of the one they ordered for me and very carefully, using my digital calipers to ensure proper diameter, ran a extra fine rotary stone around the shaft till i got the same diameter as the original and then using the depth gauge portion of the caliper, cut the shaft to length. runs like a champ now. no problems at all, other than its a cold natured bitch now but during the warm months, its fine. ya know, after looking thru all the carb parts, i wonder if i actually have the stock carbs or if they were swapped out at some point.

[JordanA]

Zippy, did you ever get some help on the cam chain replacement?  I've got a write up for the 1983-1985 CB650SC if you think it'll help.

[zippy]

actually any help is better than no help at all. even if it isnt the exact same thing, it can get me a general working knowlege of what i'm gonna be doing rather then goin in blind. it would be appreciated. drop me a line jmelectronics@netscape.com

[aeropenguin]

Hey folks,
I realize I'm reviving this thread from the dead again but just wanted to see if Jordan still has those files for the 1983-85 CB650SC cam chain tensioners, or if anybody he sent them to might have them.
My bike is making a distinctive cam chain rattle when I close the throttle quickly. As a local bike shop explained to me, it's the slack on the the front of the cam chain rotating around the crank shaft and then slapping against the cam chain tensioners and/or guides on the rear of the chain. Or something like that. Not sure if I can do anything about this or how much work it would be. I'm not splitting the cases on this thing, but I'm down for pretty much everything else!
Thanks for the help!
Misha

[olNick]

New member here, and greetings to all,

Penguin, FWIW, I just replaced the spring in the tensioner in my 83 650 and the noise was totally cured. Mine also rattled on throttle close. I could not believe how much the original spring had lost its tension.
Got the spring here...

http://www.cmsnl.com/products/spring-tensioner_14514me5010/


regards,
nick

[Laminar]

Hey folks,
I realize I'm reviving this thread from the dead again but just wanted to see if Jordan still has those files for the 1983-85 CB650SC cam chain tensioners, or if anybody he sent them to might have them.
My bike is making a distinctive cam chain rattle when I close the throttle quickly. As a local bike shop explained to me, it's the slack on the the front of the cam chain rotating around the crank shaft and then slapping against the cam chain tensioners and/or guides on the rear of the chain. Or something like that. Not sure if I can do anything about this or how much work it would be. I'm not splitting the cases on this thing, but I'm down for pretty much everything else!
Thanks for the help!
Misha

Join the Yahoo Nighthawk group, they have them stored in the "Files" section.

[aeropenguin]

Holy smokes, batman! I didn't get a chance to get around to this until just now, and did a google search for the issue again. I find this thread, and not only are there replies I wasn't aware of, but some of the best advice I've ever gotten!

Nick -- I'm really happy to hear that something just so simple as replacing the spring can make the problem go away. I already bought replacement springs from McMaster-Carr which should be direct replacements, except 10x stiffer so that can't hurt (with the rattle at least). If that's all I need I'm going to be really happy!

And Laminar: you may have just saved my life with that pointer. I joined the group and lo and behold, there were those files. With those in hand the job should be a breeze. I'll follow along in Clymer too just in case.

One question though, and I would really appreciate any help you guys can give with this. I rode the bike around a little more and after the engine warmed up, the rattle got a lot worse -- in fact it's pretty bad even at idle. Do you guys still think replacing just the springs should do it, especially considering how much stiffer than stock they are? The entire tensioner unit is not sold anywhere anymore (and would be too expensive if it was), so the only other thing I can get is the cam chain slipper piece (14510-MJ0-000, $48 shipped on Ron Ayer). Considering the rattle is pretty bad even at idle, does this mean I should for sure replace the slipper, is it "optional," or should I wait until I pull it out of the engine and inspect it to know if it's worth ordering another one of? If so, what signs do I look for to know if I should replace it?

I know you guys are thinking "you might as well replace it all while you're in there!" but after I figure out how to get in doing it again won't be an issue, but right now cash is. I just want the thing to run well.

Thanks again for all the help.

Best,
Misha

[danthesk8er]

Hello,

I have been having an issue with my chain tensioner since a few days after I changed the oil in it. It rattles on acceleration right around 2000rpm. I saw this post and I'm so glad I did. I ordered the replacement part 14514-ME5-010. I'm hoping it will get here in a few weeks since it was ordered from the UK. I ordered three of them because the minimum order was 10EU. If you need one please let me know. I'm going to try to sell the extras on ebay since there are none for sale on there. Thanks for the wonderful thread here. Hopefully this will fix my problem. I'll reply again when I receive and install the spring.

Thanks,

Daniel