My 1979 CB750 had the same noise. I read your suggestion and discovered the three bolts on the flywheel were loose and two were backed out! I tightened them and noise gone. I owe you a steak diner.
Dude thank you so much for making this video. I'm really new to owning old DOHC hondas (mostly post 2000 crotch rockets) and had the same noise driving me crazy on my cb900c for a week. Finnaly came across your video and went to the garage to check my bolts before riding to work and they were like half way backed out. You saved my bacon. Thank you.
Hey, thanks for posting this video. I had the same noise and it has had me puzzling. I thought it was the timing chain and thought I'd probably have to fit a new chain, but after seeing your post I went and tighten the flywheel bolts and 90% of the noise is gone. Now all it needs is a carb tune. Thanx bra!
I have a 1980 cb750f and mine had the same noise. I fixed it by taking the left side cover off and there are 3 silver bolts that come lose over time when the engine gets in a low idle. I beloved this is a common problem with the 750s. I just took them out and put just a touch of "lock tight" on them and haven't had a problem since. I really hope this helps!
Kevin Adams: Dude, I just read your comment, went and checked mine and sure enough, my 3 silver bolts were loose too. Tightened them up and that fixed it. Thanks for commenting. I was told it was the primary chain adjuster, or stretched chain, which didn't sound right, since the rest of the engine was tight! Thanks again, your comment saved my ass alot of work!
Andrew Margesons: I was devastating when I heard that noise, and thought I was going to have to get into the engine, thank goodness it was just those bolts, couldn't believe it.
It is the exact problem I had it is on the starter flywheel. It will be as others have said. 3 bolts have worked themselves loose. It’s under the left front ignition cover
Just tuned the carbs, adjusted the cam chain tensioner and tightened the three bolts on the starter gear freewheel, and 90 % of noise disappeared. A tiny clutch rattle at idle and some faint cam chain/valve rattle is all thats left! Easy enough to pop the left cover (timing cover) with the 8 mm bolts and bam there it was. easily tightened the 12 mm bolts attaching the freewheel to the starter gear sprocket. A small amount of oil behind the cover is normal. Go and try it to buy it!
Hey again. I cleaned the carbs out, and it turns out there were some gunk in the idle jets. Now it's much better, and it'll idle. But it still has some mysterious knocking at 1400 and below. I'm trying to get a wrench that's able to reach the bolts for adjusting cam chains. and getting my carbs synced soon. Hope that'll fix it. Other than that i absolutely love my bike.
I had the same type of noise. When I pulled in the clutch most of the sound was gone. When the clutch was not pulled in the noise came back. So what I did was to change the whole clutch to another one and then the noise was gone. In my case the wheel that holds the clutch on place was flexing to much and making this sound. In your case I don´t know but you can also check the starter clutch (you have to remove the bottom oil plate) and then you get acces to the cogwheel (the Torx-bolts can be loose).
That is a clutch problem you describe, that is when the rivets, holding the basket to the gear rattle loose. Also when the springs in the clutch basket rattle loose. The baskets are easily rebuilt better than new. Falcon make kits to rebuild them
the pods were there when I bought it. dont know if it has been rej-jetted. Søren- try to adjust the idle screw under the carbs, it will make her idle on higher RPMs so that idling works even when cold. although idling will be higher when hot. it helps to synch carbs also. but hard to synch when not idling:) good luck!
I say Cam chain too. same sound mine was making, had to replace the tensioners, then it was minimal afterwards. it goes away at high rpm but loud at idle
WOW 93,792 miles and time for a timing chain tensioner adjustment. It is located to the rear of the head, behind an access panel. I wonder how many miles are on the great running Honda CB750F now ?
The old saying is true. The mind will see what it wants to see. My evaluation was not accurate. This bike is a European model. The home architecture and style. The helmet construction in the video. This bike really has 58,279 miles when you convert kilometers to miles. Still a great running bike, even compared to new models.
Glad i found your video. I just bought a similar bike, and it's got some rattle. When i give it some throttle it dissapears. I suspect either cam chain, clutch or those screws you mentioned. also gotta sync carbs. Unfortunately i can't get mine to idle properly when it's not completely heated up. It's good when it's hot though.
my bike sounds just like this now... but checked those 3 bolts and they were tight... did timing chain.... still fucking loud!!!!!!! sounds like its mostly the clutch now...
It is hard at a distance that engine I don't believe is running on all four. Feel your exhaust pipes and see if one or two are not getting hot. Let me know and I will take you further, that is not one issue you have there
Hi One pipe has been cooler all along. No 2 exhaust. I just rebuilt and did valves last year. Carbs have been synced as well. Now considering to change ignition cables but I’m worried that compression is poor in no 2 even after valve job.
If the compression is not within ten percent, first check your valve clearances before you pull the head. Try and do a leak down test, not a compression check, look it up on u tube, that will tell you. Also check your coils resistance on the cylinder, also check, inside the valve cap, under the little brass screw is a resistor, these things if you are not sure are all on u tube. I am and have been a mech for 45 years so it easier for me but see how you go. Come back if you need more help
Could you be more specific on what you did under the timing cover? and what bolts you tightened. perhaps just point me to where you found the solution? many thanks!
My 1984 Honda vf700c sounds exactly like this! Omg! Ive been dying to find a video of someone with the same sounds! You can check my video for the sounds but, did you ever get it fixed? And what was the problem??
im completely new to this bike.... is there anywhere online that shows how to do what your talking about? been riding it 2 days now and its getting a good bit louder!
Cam chain tensioner. I had exactly same issue and sound. I just changed it on my Honda Phantom TA200. 10$ for tensioner and 10$ for service. Looks like Honda can make only good car engines and fail motorcycle engines. Almost every Honda bike having this shitty problem.
My 1979 CB750 had the same noise. I read your suggestion and discovered the three bolts on the flywheel were loose and two were backed out! I tightened them and noise gone. I owe you a steak diner.
Dude thank you so much for making this video. I'm really new to owning old DOHC hondas (mostly post 2000 crotch rockets) and had the same noise driving me crazy on my cb900c for a week. Finnaly came across your video and went to the garage to check my bolts before riding to work and they were like half way backed out. You saved my bacon. Thank you.
i too have a 82 cb900c ill have to see as well my bike has a knock right now
Hey, thanks for posting this video. I had the same noise and it has had me puzzling.
I thought it was the timing chain and thought I'd probably have to fit a new chain, but after seeing your post I went and tighten the flywheel bolts and 90% of the noise is gone.
Now all it needs is a carb tune.
Thanx bra!
👍
I have a 1980 cb750f and mine had the same noise. I fixed it by taking the left side cover off and there are 3 silver bolts that come lose over time when the engine gets in a low idle. I beloved this is a common problem with the 750s. I just took them out and put just a touch of "lock tight" on them and haven't had a problem since. I really hope this helps!
Kevin Adams: Dude, I just read your comment, went and checked mine and sure enough, my 3 silver bolts were loose too. Tightened them up and that fixed it. Thanks for commenting. I was told it was the primary chain adjuster, or stretched chain, which didn't sound right, since the rest of the engine was tight! Thanks again, your comment saved my ass alot of work!
Hey just letting you know that i had the same problem thank you very much such a ez fix
Andrew Margesons: I was devastating when I heard that noise, and thought I was going to have to get into the engine, thank goodness it was just those bolts, couldn't believe it.
i will have to check this too when i take my bike out of storage i have a cb900c making the same noise
THANK YOU VERY VERY VERY MUCH. I had the same noise, I found your comment with Google, I fixed it !
My 3 bolts were loose too. THANKS !!!
It is the exact problem I had it is on the starter flywheel. It will be as others have said. 3 bolts have worked themselves loose. It’s under the left front ignition cover
its always nice to hear you found the solution to the problem!
Just tuned the carbs, adjusted the cam chain tensioner and tightened the three bolts on the starter gear freewheel, and 90 % of noise disappeared. A tiny clutch rattle at idle and some faint cam chain/valve rattle is all thats left!
Easy enough to pop the left cover (timing cover) with the 8 mm bolts and bam there it was. easily tightened the 12 mm bolts attaching the freewheel to the starter gear sprocket.
A small amount of oil behind the cover is normal.
Go and try it to buy it!
Hey again.
I cleaned the carbs out, and it turns out there were some gunk in the idle jets. Now it's much better, and it'll idle. But it still has some mysterious knocking at 1400 and below. I'm trying to get a wrench that's able to reach the bolts for adjusting cam chains. and getting my carbs synced soon. Hope that'll fix it. Other than that i absolutely love my bike.
You have 2 different sounds. Other one is stretched cam chain, or cam chain guide to be tighten. Other sound is valve shims.
I agree MV, definitely cam chain. well known on kz for slapping. lovely smooth engine when alls tightened and shims spot on
Also note that freewheel can be cracked. Look for lines along the edges where the sliding cylinders are( 3 of them)!
GLHF
Had the same noise on my 79 CB750 and I replaced starter. That resolved the knocking noise
My knock was the screws behind the thing you time it with they were lose we tighten them and it stopped and now it sounds great
I had the same type of noise. When I pulled in the clutch most of the sound was gone. When the clutch was not pulled in the noise came back. So what I did was to change the whole clutch to another one and then the noise was gone. In my case the wheel that holds the clutch on place was flexing to much and making this sound. In your case I don´t know but you can also check the starter clutch (you have to remove the bottom oil plate) and then you get acces to the cogwheel (the Torx-bolts can be loose).
should have dumped the bike and kept the clutch.
That is a clutch problem you describe, that is when the rivets, holding the basket to the gear rattle loose.
Also when the springs in the clutch basket rattle loose.
The baskets are easily rebuilt better than new.
Falcon make kits to rebuild them
the pods were there when I bought it. dont know if it has been rej-jetted. Søren- try to adjust the idle screw under the carbs, it will make her idle on higher RPMs so that idling works even when cold. although idling will be higher when hot. it helps to synch carbs also. but hard to synch when not idling:) good luck!
I say Cam chain too. same sound mine was making, had to replace the tensioners, then it was minimal afterwards. it goes away at high rpm but loud at idle
WOW 93,792 miles and time for a timing chain tensioner adjustment. It is located to the rear of the head, behind an access panel. I wonder how many miles are on the great running Honda CB750F now ?
93792 Kms back then. Now after a top end rebuild and cafe racer remodel its a good bit beyond 100 000 km. fantastic machines!
TT T CBs have 2 timing chains.one in the front and one in the back of the head.
The old saying is true. The mind will see what it wants to see. My evaluation was not accurate. This bike is a European model. The home architecture and style. The helmet construction in the video. This bike really has 58,279 miles when you convert kilometers to miles. Still a great running bike, even compared to new models.
Glad i found your video. I just bought a similar bike, and it's got some rattle. When i give it some throttle it dissapears. I suspect either cam chain, clutch or those screws you mentioned. also gotta sync carbs. Unfortunately i can't get mine to idle properly when it's not completely heated up. It's good when it's hot though.
It could be your cams slapping the valve shims. Do a valve adjustment. Clearance should be .005
My 81' 750FB is making the exact same noise.....I'm going to play around with it this coming week. If I need help i'll know where to find you :P
piston-cylinder GAP icreased with age. bad problem but solveable...
Carb sync!
my bike sounds just like this now... but checked those 3 bolts and they were tight... did timing chain.... still fucking loud!!!!!!! sounds like its mostly the clutch now...
It is hard at a distance that engine I don't believe is running on all four. Feel your exhaust pipes and see if one or two are not getting hot.
Let me know and I will take you further, that is not one issue you have there
Hi
One pipe has been cooler all along. No 2 exhaust. I just rebuilt and did valves last year. Carbs have been synced as well.
Now considering to change ignition cables but I’m worried that compression is poor in no 2 even after valve job.
If the compression is not within ten percent, first check your valve clearances before you pull the head.
Try and do a leak down test, not a compression check, look it up on u tube, that will tell you.
Also check your coils resistance on the cylinder, also check, inside the valve cap, under the little brass screw is a resistor, these things if you are not sure are all on u tube.
I am and have been a mech for 45 years so it easier for me but see how you go.
Come back if you need more help
Another thing is one carb could be slightly blocked, to sync the carbs only equaliser's out the vacumes
Could you be more specific on what you did under the timing cover? and what bolts you tightened. perhaps just point me to where you found the solution?
many thanks!
mine does the sound only at around 3000rpm till around 4-5000 rpm.Can it be the bolts?
My 1984 Honda vf700c sounds exactly like this! Omg! Ive been dying to find a video of someone with the same sounds! You can check my video for the sounds but, did you ever get it fixed? And what was the problem??
im completely new to this bike.... is there anywhere online that shows how to do what your talking about? been riding it 2 days now and its getting a good bit louder!
hahaha just posted video of a bike i wanna buy doing the same thing.... think ill try to tighten them up.... if it goes away... IM BUYING IT!!!!
See my other video for solution!
Eyvind Johansson
Check clutch
th-cam.com/video/eB1s7vivu6s/w-d-xo.html had exactly the same , fixed with the clutch dampeing kit
loose crankshaft. Fill crankcase with bananas and noise will quiet right down.... then BOOM!
Cam chain tensioner. I had exactly same issue and sound. I just changed it on my Honda Phantom TA200. 10$ for tensioner and 10$ for service. Looks like Honda can make only good car engines and fail motorcycle engines. Almost every Honda bike having this shitty problem.
Primary chain inside the block.
Chain comand
Hi, do you run a jet kit to make it run smooth with pod filters? Thx, Jan
My bike does the same thing
I bought it! ill try this out tomorrow! btw can you post link to the forum?
sounds like a.cb750!!
Mine got exact same noise did you ever solve it?
see my other video. loose flywheel bolts under timing cover was the most obvious sound. But I believe I have other problems too.
Its Clutch problem!!!
I put cb 750 rc42 engine to my cbx 750, sounds quite nice: th-cam.com/video/xYrCQnnOBOA/w-d-xo.html You could also swap the engine for newer?
I heard your sound and its def the same. Did you manage to get rid of it?
out of tune carb