Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: El__burro on June 02, 2018, 11:37:55 AM
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Good day, i am trying to check wether or not i have a serious problem.
When the engine of my k2 is running I can hear a rattling noise (from the primary chain?) that goes away when i pull the clutch.
Its not very loud or worrying but i wouldn't like it to worsen. I've tried to adjust the cam chain (Clymer manual page 48) via the tensioner but didn't improve it.
Any other way to assess the problem?
thanks
el__burro
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Usual cause is carb balance, or lack of it! You need a set of vacuum gauges to set them up properly, but don't even attempt it until ALL other service items are done, plugs, points, timing, clean oil to the correct level. The CB750 engine will always seem agricultural next to a modern bike, but sorting carb balance can minimise that rattle/clatter.
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does overall sound like carb balance they are noisy when out of sync, do that first before anything else
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Good day, i am trying to check wether or not i have a serious problem.
When the engine of my k2 is running I can hear a rattling noise (from the primary chain?) that goes away when i pull the clutch.
Its not very loud or worrying but i wouldn't like it to worsen. I've tried to adjust the cam chain (Clymer manual page 48) via the tensioner but didn't improve it.
Any other way to assess the problem?
thanks
el__burro
Sent from my SM-G935F using Tapatalk
Any chance of a video to hear this noise or you could look up member Yozzer, he had the same problem & put as video on here.
if you have adjusted the cam chain then that should be fine...for those who are not sure how to do the cam chain
here is a short video to show hot to adjust the cam chain properly.. [good video]
https://www.youtube.com/watch?v=8841eO5tvro
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Hi, I also have this problem. It sounds awful at tickover ( in fact it's embarrassing). I pull in the clutch and it more or less disappears. My clutch grabs when the lever is almost fully out so I thought it might be the clutch ? That was on its way out. I've just reset the timing ( static) which was out , so at least it now starts on the button ( before I could be there 2-3 minutes waiting for it to fire). I will now reset the cam chain, I may have to consider rebalancing the carbs as many say the rattles and bangs are as a result of imbalance). I hope it's not an issue with the primary chain as I assume that's a strip down job ?. I will keep you posted as I progress.
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Carb balance is often the cause of rattles at tickover on the Honda fours. Carb balancing needs to be done AFTER all other service items, tappets, camchain, ignition timing etc, with the engine warm and the correct oil level. It will make a big difference when it's been done.
Sent from my X6pro using Tapatalk
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Yep mine sounds like an empty can of bolts at the moment just saving the pennies to take it too
These guys. http://d-mengineering.co.uk They can fine tune it, then it's time to put the smiles with the miles on!
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I wonder if we can define the difference between a rattle and a clatter ?, I would describe mine more as a clatter - certainly if the indicated revs are around a 1000. If I up them a little to 1500 it seems to be less noticeable. I actually question the accuracy of the tacho in any case as running it adj my Suzuki 4, even 1500 rpm read, sounds less than 1100rpm on my Suzuki!. I read on the forum that a replacement clutch with one of the plates having a wider tab ?????. Not sure if this means anything to anyone, I assume the wider tab means that the plates won't clatter from side to side as much ?. I guess in the first instance a carb resync is advisable and take it a step at a time. I've set my static timing & cam chain as per the video,does anyone have a decent link to a video or paper on setting the dynamic timing with a strobe ?.
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Yep mine sounds like an empty can of bolts at the moment just saving the pennies to take it too
These guys. http://d-mengineering.co.uk They can fine tune it, then it's time to put the smiles with the miles on!
Saving pennies to go to D-M Engineering.. :o.. Mate you will need lots & lots of £'s....DM are the best in the business for the sohc engines but very minty !
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I think I'll use them as a last resort. I dived into the classic bike scene expecting and wanting to learn a bit more about them. So far it's quite enjoyable solving the issues. I hope I can progress to changing the clutch toward the end of summer and get the carbs balanced. If it needs more intervention then I might have to rely on someone who knows what's what as I'm sure I don't have the knowledge as yet to strip it down - hopefully it won't come to that.
What I have noticed after doing the static timing and the cam chain adjustment is the bike fires up much better. On tickover it clatters until you pull in the clutch ????? - clutch or primary chain ????. Also when riding in any gear you can hear what I can only describe ( hopefully it's an understood term) the drivetrain working. It's less noticeable say above 3-4 k rpm. I am not sure if this is normal for a bike of this age (k6) or if it's symptomatic of something worn ????. As the k6 is new to me I am on a steep learning curve.
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The noise will quieten greatly when the carbs are balanced, the noise is caused most of the time by the carbs being out of sync, so it idles uevevenly, causing the clutch/primary chains to clatter/rattle. If the noise almost vanishes pulling the clutch in, 99% of the time it's carb balance issues.
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Thanks for that, carb balance next on the list after a quick check of other service issues.
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Yep mine sounds like an empty can of bolts at the moment just saving the pennies to take it too
These guys. http://d-mengineering.co.uk They can fine tune it, then it's time to put the smiles with the miles on!
Saving pennies to go to D-M Engineering.. :o.. Mate you will need lots & lots of £'s....DM are the best in the business for the sohc engines but very minty !
Would not say they are the best in the business but, someone has to pay for all their advertising and trade stands ;D ;D
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Yep mine sounds like an empty can of bolts at the moment just saving the pennies to take it too
These guys. http://d-mengineering.co.uk (http://d-mengineering.co.uk) They can fine tune it, then it's time to put the smiles with the miles on!
Saving pennies to go to D-M Engineering.. :o .. Mate you will need lots & lots of £'s....DM are the best in the business for the sohc engines but very minty !
Would not say they are the best in the business but, someone has to pay for all their advertising and trade stands ;D ;D
Who is the best in the business then Trig? ;)
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I think I'll use them as a last resort. I dived into the classic bike scene expecting and wanting to learn a bit more about them. So far it's quite enjoyable solving the issues. I hope I can progress to changing the clutch toward the end of summer and get the carbs balanced. If it needs more intervention then I might have to rely on someone who knows what's what as I'm sure I don't have the knowledge as yet to strip it down - hopefully it won't come to that.
What I have noticed after doing the static timing and the cam chain adjustment is the bike fires up much better. On tickover it clatters until you pull in the clutch ????? - clutch or primary chain ????. Also when riding in any gear you can hear what I can only describe ( hopefully it's an understood term) the drivetrain working. It's less noticeable say above 3-4 k rpm. I am not sure if this is normal for a bike of this age (k6) or if it's symptomatic of something worn ????. As the k6 is new to me I am on a steep learning curve.
On both your bikes [yours & el-burro's] It does sound like its the clutch, which rattles a bit normally until you pull it in, & perhaps as others have said if the carbs are out of sync that's making it sound worse ...but don't expect this bike to be smooth & silent like a gold watch, they are not the quietest of engines even when totally rebuilt, but should not be noisy.
...I set my idle speed at 1100rpm & it will sit there nice & steady when warmed-up & I do get a little bit of clutch noise until I pull it in.
my bikes engine has done 2600 miles since rebuild & I have not had to have the carbs balanced again yet.
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Hopefully will be associated with the clutch. I am going to purchase a clutch pack I think from David silvers and replace at the end of the season. I will also acquire a Morgan Carbtune to do the carbs once everything is set up. Certainly an interesting learning curve - I haven't touched a bike since the 70's as mine have all been new , I've had this about 3 months and spent more time tweaking than I have sleeping !.
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Hopefully will be associated with the clutch. I am going to purchase a clutch pack I think from David silvers and replace at the end of the season. I will also acquire a Morgan Carbtune to do the carbs once everything is set up. Certainly an interesting learning curve - I haven't touched a bike since the 70's as mine have all been new , I've had this about 3 months and spent more time tweaking than I have sleeping !.
Good luck with it...rather you than me ;)
I enjoy cleaning & looking after my bikes & riding them obviously...but I am not a huge tinkerer...I leave that to the experts....
I watched most of the rebuild of my Honda & when I saw the engine stripped down in a million bits all over the work bench I shivered & went cold at the thought of even trying to do that myself.. :o
PS.. I am capable of putting fuel in & changing the plugs & oil...you know the easy bits.. ::)
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You would be surprised how many people can't put oil or plugs in let alone change them. :o
I will tackle small engines but anything else would take me an age to strip and build.
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Hopefully will be associated with the clutch. I am going to purchase a clutch pack I think from David silvers and replace at the end of the season. I will also acquire a Morgan Carbtune to do the carbs once everything is set up. Certainly an interesting learning curve - I haven't touched a bike since the 70's as mine have all been new , I've had this about 3 months and spent more time tweaking than I have sleeping !.
Hi Paul
I have a Morgan carbtune that you are welcome to borrow if & when you need it...not used it myself yet ..sold the bike it was intended for and the current one is in bits at the moment! 😬
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Appreciate the gesture, that's what makes this forum great in my opinion, people are genuinely helpful with their time and equipment, I hope I can do similar as my knowledge increases. Only issue on the Morgan - mine arrived this morning !. Never mind if either fails we know where we can loan one. Thanks for the gesture though - much appreciated. I just ordered a spoke torque wrench also so if anyone needs one give me a shout !, oh and also a Gunson - you never know you might be able to teach me how to use all ths stuff !