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Author Topic: [1982 Honda CB125s]Camchain tightening procedure - need advice  (Read 427 times)

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Hi to all,

I have a CB125s and recently while riding I noticed a lot of noise coming from the head and determined that the cam chain might be a bit loose causing the sound. I know the valves are alright as those were tightened to spec recently.

I have a Clymer manual and it specifically indicates that there is a different procedure for the 1970s CB125s and for the 1976 onwards CB125s.

The pre 76 ones can be adjusted cold, you just remove the plastic cover from the bolt, remove the top plug bolt and then loosen then re-tighten the adjustment bolt. However for the 76+ models it asks that you turn on the bike, let it get warm, get to idle at 1300 and then do the adjustment while the engine runs and to not remove the plug bolt completely as oil will spurt out.

Here's the problem : The 1982 CB125S does not have a tachometer and so the manual says you should use a portable tach to set it to 1300 idle.

I am trying to figure out if I can adjust the cam chain exactly as done in this video:


I want to avoid buying a portable tach (they seem to be 100-125 dollars for wireless ones that sense the pulse from the coil) to do this adjustment...

I figure it should be possible if done like in the video but I don't want to make the situation worse....

Thanks for reading.

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #1 on: Jul 04, 2018, 13:08:52 »
Hmmm well I wasn't able to get some advice elsewhere or here which is fine so I guess I will attempt to adjust it by ear.

I figured it would be horribly inaccurate but I have no hope of installing a tach so I will find the best youtube vid of a similar bike idling at 1300 and try to match it with mine then do the cam chain adjustment.

\_(ツ)_/

Online trek97

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Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #2 on: Jul 04, 2018, 13:37:27 »
I put one of these on my 72 CL100.  Not great, but it will get you in the ballpark of 1300rpm.
Its got a battery built in.  So just wrap the single wire around the plug wire about 5 wraps close to the coil. Secure w a piece of tape.

https://www.ebay.com/itm/Digital-Engine-Tach-Tachometer-Hour-Meter-Inductive-for-Motorcycle-Motor-SM/302754258178?epid=1946925043&hash=item467d8f5d02:g:~wEAAOSwHNxaCVIC
« Last Edit: Jul 04, 2018, 13:39:47 by trek97 »

Offline jpmobius

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Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #3 on: Jul 04, 2018, 13:49:13 »
You should be fine following the video, assuming your bike is like the one shown.  The exact rpm used in the manual is not that critical.  The engine just needs to be running slow, but fast enough to be running smoothly.  The reason is to allow the side of the chain where the tensioner is to be as slack as possible so that all of the slack can be taken up when you adjust the tensioner.  In the video, this is achieved by having the cam positioned where the valves are not pushing back on the cam and creating slack on the opposite side of the chain.  If you want to follow the video, it would be a good idea to put a wrench on the crank and apply pressure in the direction of running to ensure the non tensioner side of the chain is tight.  Hold pressure on the wrench and adjust the tensioner.  There is another benefit to the video, which is manually exercising the spring loaded tensioner mechanism because they often stick.  Moving it manually through its travel a few times will scrape away any varnish that may hang the mechanism up ensuring the proper tension is achieved.
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #4 on: Jul 05, 2018, 12:04:58 »
Thank you trek97 and jpmobius, I greatly appreciate the replies.

Trek, that's a cheap piece so that's definitely an option. Since I posted a friend of mine has given me a tach but I had no idea how to install it and was beginning to look into that. I think I'll be good with your instructions.

jpmobius, yeah I was thinking of doing what he did in the video with pushing down the mechanism using a screwdriver to make sure it's not stuck. I'll do my best to get an idle close to 1300, at least my bike has no trouble idling so I won't have to fight it.

Okay I think I will be trying this on Sunday. I will try to take videos to post here of before and after so it can be more useful for people who stumble upon this thread in the future.

Thanks

Offline TheCoffeeGuy

  • Posts: 642
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Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #5 on: Jul 08, 2018, 10:49:37 »
+1 on jpmobius
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike
1982 Honda CB650 Chopper light

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #6 on: Jul 09, 2018, 10:49:13 »
Hi everyone,

Okay so on Sunday I got to the bike, unscrewed the top cap of the adjuster nut and tried to use a screwdriver to push the mechanism down. It wasn't budging and I felt like if I pushed any harder I might do some damage so I decided to leave it. Unsure if it is stuck....

I then turned on the bike, got it warm and drove it around a little bit, came back and got it to idle no problem. Not sure if it was 1300 but it was a steady good idle you will hear it in the video.

I loosened the nut a lot...felt like it was almost about to come out of the engine so I then re-tightened it.

I have a really shitty torque bar thing that is in mKG and the cylmer manual was saying to adjust to 12 lb-ft. I did the conversion which is close to like 1.6 mKG so I torqued it to about that and it was indeed tight.

However there is no difference in sound. The engine is still making a loud chattery noise. I had previously done a valve adjustment on this bike too and it was in spec. I'm a newb so there's a chance I completely fucked it up but I made sure to check the valves 3 times in a row making damn sure the adjustment nut on the valves was fully tightened and then re-checked to ensure I didn't screw up the gap by doing that.

So yeah I'm wondering what could be causing such noise and if my engine will grenade while I'm riding because of it.

The GOOD NEWS !!!! however is that I took the bike for about 25 minutes driving around town and it did not reproduce the condition causing me to do this adjustment in the first place. I had a problem where if I was in 3rd,4th or 5th and quickly decelerated to a stop the engine would cut out. Right after the adjustment I tried to reproduce that many times and it did not stall and seemed to idle much better.

So victory?

I had promised to film a video pre-adjustment video and a post-adjustment video and did do that. I am only posting the post-adjustment video because I listened to both and I can tell you they are 100% the same in terms of sound nothing has changed.

Please remember my bike is a project and is incomplete if you're feeling the urge to point out things like a missing front fender :P

https://streamable.com/flhvi Please let me know if this link doesn't work I will re-upload if that is the case.

« Last Edit: Jul 09, 2018, 10:51:24 by RoyalRider »

Offline TheCoffeeGuy

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Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #7 on: Jul 09, 2018, 22:22:06 »
did you put a wrench on the crank bolt and put tension on it to take up the slack on front side of the motor to leave skack on the the tensioner side of the chain?
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike
1982 Honda CB650 Chopper light

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #8 on: Jul 10, 2018, 10:05:43 »
CoffeeGuy,

I did not...I only followed the clymer manual instructions which doesn't require you to remove the cover or keep torque on the crank bolt. I thought I would get lucky but you're right I need to do it again and remove the cover to see if I have actually adjusted anything.

I was weary of opening that side of the engine again but now remember that it can be done without losing much oil so it shouldn't be a problem. I will do it again and take a video again and see if I can actually get it to adjust.

Thanks

Offline RoyalRider

  • Posts: 64
  • 2010 Royal Enfield Bullet 500 - 1982 Honda CB125s
Re: [1982 Honda CB125s]Camchain tightening procedure - need advice
« Reply #9 on: Jul 10, 2018, 10:14:18 »
Just to make sure I don't newb out and screw it all up.

I assume by crank bolt you mean this bolt here right ? (Not my engine just a pic from the internet) https://imgur.com/a/N7ZZFvr