Camshaft tensioner adjustment "knocking chain"

[RAdam]

I have a 81 cb750K with 60'000kms on it. my first bike and when I bought it just a couple months ago there was a knock in the engine that the seller told me was just the camshaft chain which it is i believe. I didn't think it was a big problem as it only knocked while idoling and i didn't now any better. I have a friend with the same bike in much better condition and his doesn't rattle or knock.  I tried the suggested adjustment method prescribed in the Crymer's manual with no change....still the rattle/knock.

 We just went on an 800kms trip and I have noticed that the knock is potentially getting worse after a long ride and I'm hearing it more at high speeds so I'm wondering

A) Is this something I can fix if the adjustment method isn't fixing it? I'm not afraid to open it up and try even though i'm a newbie tinkerer...

B) is this doing internal damage which will eventually cause more problems or is it just an inconvenient irratating problem that won't have any real impact.

 the bike was cheap and ridden hard and put away wet but it seems like a strong runner and I did just ride it for 3 days straight so.... I want to fix it up and I just want to know if this is going to be worth it or if it will cost me more than its worth.


thanks for your help:)

[Lucky 1]

Better fix it before all the metal filings go through all the bearings and oil passages.
60,000 miles it could need new cam chain tensioners.

[TOOLS1]

There are two things that could be causing this. First is the carbs out of sync. This will make the engine sound like it is going to fly apart at idle, but quiets down as you throttle it up. Second there are 3 bolts on the rotor on the left side of the crankshaft that tend to come loose. Just pull the cover off the left side, and you will see the 3 bolts. If they are loose, put some Locktite on them, and tighten them up.
TOOLS

[seestheday]

If TOOLS recommendations don't work, can you post a video?  It could still be a loose cam chain, especially because you're starting to hear it at high speeds.

Try what TOOLS said first though, because those are much easier/cheaper fixes.

60K kms/37K miles isn't that much for one of these bikes.  I have 92K kms/57K miles on mine and it runs like a champ.

If the rest of the bike is in good shape I would say you should at least open it up and see what is wrong.  Don't pay a mechanic to do it though.  Do it yourself.

Some possible things wrong:
- worn out A cam chain tensioner (fairly easy to replace, but requires pulling the engine)
- worn out B cam chain tensioner (fairly easy to replace, but requires pulling the engine)
- worn out B cam chain (fairly easy to replace, but requires pulling the engine)
- worn out A cam chain (a little more complicated, requires either splitting the case or cutting the A cam chain)

Lots of great resources here to help you along if you're willing to read/learn.  As long as you have some decent hand tools and are willing to invest a little in some specialized tools that aren't too much money you will be able to do it yourself.

[RAdam]

Thanks guys.

  I will check those suggested fixes starting from the easiest to the hardest. I assume to get into the engine to diagnose the problem aside from the carbs in any case requires pulling the engine? 

  I wanted to do this anyway to clean everything up and paint the frame/swing arm although not until the winter. Can any of this be done over a weekend or two by a newbie. I have tools and am keen for the challenge but I don't want to cripple my bike worse than it is and I'd also like to be able to keep riding it until the fall. 

  I would attempt cleaning syncing the carbs one weekend. Is there a carb cleaning for dummies reference that might be of more help than say a service manual? And Do I need to buy a kit or new parts to do this procedure? 

Thanks so much

Sent from my iPhone

On 2013-07-23, at 9:09 AM, "seestheday [via Honda CB750'S]" <[hidden email]> wrote:

If TOOLS recommendations don't work, can you post a video?  It could still be a loose cam chain, especially because you're starting to hear it at high speeds.

Try what TOOLS said first though, because those are much easier/cheaper fixes.

60K kms/37K miles isn't that much for one of these bikes.  I have 92K kms/57K miles on mine and it runs like a champ.

If the rest of the bike is in good shape I would say you should at least open it up and see what is wrong.  Don't pay a mechanic to do it though.  Do it yourself.

Some possible things wrong:
- worn out A cam chain tensioner (fairly easy to replace, but requires pulling the engine)
- worn out B cam chain tensioner (fairly easy to replace, but requires pulling the engine)
- worn out B cam chain (fairly easy to replace, but requires pulling the engine)
- worn out A cam chain (a little more complicated, requires either splitting the case or cutting the A cam chain)

Lots of great resources here to help you along if you're willing to read/learn.  As long as you have some decent hand tools and are willing to invest a little in some specialized tools that aren't too much money you will be able to do it yourself.

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[seestheday]

By "the weekend" do you mean that you have an entire weekend to dedicate to it, if so then yes there are a few things you can do in that time.  If you are like me and have a kid to play with, dinner to make, a lawn to mow, etc. then no a weekend won't do it .

There is an absolutely fantastic carb cleaning manual that you can download for free, and if you're going to clean them I recommend just getting the full kit from Randakk, it'll make your life a lot easier.  That said, I wouldn't do a full carb cleaning just yet.  Start with just syncing them.  From the sounds of it you aren't having fuel delivery issues, so cleaning the carbs won't help with the knock.

Syncing the carbs will take you an hour or two if you're really slow.

To sync them you'll need a carb sync tool (e.g: http://www.carbtune.com/ - you need the 4 column one), and a tool to make turning the screws easy (e.g. http://www.carbtune.co.uk/carbtool.html).  You will also need either a long fuel hose so you can set your gas tank up high and run the fuel hose to the carbs or it could just be a small vessel you make (heck an old 2L plastic coke bottle would work if you could get the hose to seal well).

There are plans on the internet on how to make your own carb sync tool if you have lots of time and want to save money, and you can get away with not having the specialized tool to for turning the screws with locknuts, it just takes longer (I am very happy I bought mine).

You can also do your own search to find some cheaper models than the carbtune.  I ended up getting that one so that's why I linked to it.

[RAdam]

ok thanks a lot.

  I will get those tools and give my first carb sync a go. fortunately I can probably find at least a full saturday or sunday to try as I don't have kids yet;) not too far off though and I do look forward to having a garage were my kids can hang while I'm tinkering on the bike one day!

 couple more questions if you guys don't mind......

1)Do you have a link for the carb cleaning pdf that you mentioned?

2)Can you suggest a good company/product for front brake pads and steel braided brake line to purchase for this bike?

3)All the electrical wiring and rubber hosing on my old bike are crusty and cracked. I found a Carb hose kit on Amazon but Is there a rewiring/wiring housing kit for these bikes? Like if I wanted to pull my engine eventually and re paint everything and clean it up with some new parts and new rubber....the old wiring and housing and the lot would still look old and crappy. what's the best way to achieve that clean "restored bike" look with the controls and wiring?

thanks guys.






 

[icerigger]

Here's the link to the carb manual.

http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revF.pdf

Like Sees said, if the carbs haven't been rebuilt in the last couple of years you'll probably need all new rubber. I too recommend the Randakk kit.

But first try to sync them. It's amazing what a racket one carb being out can make.

[TOOLS1]

Cycle-X has the carb sync gauges at a very reasonable price.
TOOLS

[RAdam]

Thanks for all your help guys, can't wait to dive in! That carb manual is very comprehensive. Just gotta wait for the tools to do the job get here.

Cheers! 

Sent from my iPhone

On 2013-07-23, at 10:42 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

Cycle-X has the carb sync gauges at a very reasonable price.
TOOLS

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