SOHC.co.uk Forums > CB350/400
Noisy engine 400/4
Johnwebley:
--- Quote from: sc29 on May 27, 2022, 03:13:21 PM ---Thanks. I was just looking into carb balancing. I was told once most of the noises are cam chain or carb balancing. Doesn't look I can balance the carbs myself. Looks like I'll have to take it somewhere.
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Let us know what area you live in,
Maybe someone close has the kit to sort the carbs
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Nurse Julie:
Give the engine a full service 1st, including setting tappet gaps and then have carbs synced. To be honest, it doesn't sound to bad, they can all rattle a bit like a bag of spanners at low revs, especially when the engine is cold and even more so if the engine hasn't been regularly serviced, has done high mileage, has been thrashed or needs an engine overhaul. If you bring the revs up to about 2k rpm, does the noise go away?.
sc29:
--- Quote from: McCabe-Thiele (Ted) on May 27, 2022, 03:11:56 PM ---I would also check the timing for 1/4 & 2/3 as a starting point then go for Pauls suggestion on carb balancing.
I don't like the idea of pushing down from the top cap bolt of the tensioner sytem unless it will somehow move a partially seized horseshoe. I agree it does not sound like the cam chain more of an inbalance between the cylinders at low revs.
More experienced members might add to the possible cause of the noise.
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Thanks I'm veering to some sort of timing or carb issue. Seems like the noise is some sort of "inbalance" issue. It's a lot quieter when it revs.
sc29:
--- Quote from: Nurse Julie on May 27, 2022, 03:27:13 PM ---Give the engine a full service 1st, including setting tappet gaps and then have carbs synced. To be honest, it doesn't sound to bad, they can all rattle a bit like a bag of spanners at low revs, especially when the engine is cold and even more so if the engine hasn't been regularly serviced, has done high mileage, has been thrashed or needs an engine overhaul. If you bring the revs up to about 2k rpm, does the noise go away?.
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Here you go. Another video from the other side with it revving a bit. https://youtube.com/shorts/KYLy1Kbj1YI?feature=share
I don't go that far on it and it does get service occasionally. I took it for a service last summer because of the noise and I think it came back worse.
Nurse Julie:
--- Quote from: sc29 on May 27, 2022, 03:55:01 PM ---
--- Quote from: Nurse Julie on May 27, 2022, 03:27:13 PM ---Give the engine a full service 1st, including setting tappet gaps and then have carbs synced. To be honest, it doesn't sound to bad, they can all rattle a bit like a bag of spanners at low revs, especially when the engine is cold and even more so if the engine hasn't been regularly serviced, has done high mileage, has been thrashed or needs an engine overhaul. If you bring the revs up to about 2k rpm, does the noise go away?.
--- End quote ---
Here you go. Another video from the other side with it revving a bit. https://youtube.com/shorts/KYLy1Kbj1YI?feature=share
I don't go that far on it and it does get service occasionally. I took it for a service last summer because of the noise and I think it came back worse.
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There are a couple of strange noises that need investigation, the rattle and that whine. I know it's really difficult to hear what's going on with a mobile phone video though, as the sound reproduction isn't good.
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