Author Topic: Noisy engine 400/4  (Read 513 times)

Offline sc29

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Noisy engine 400/4
« on: May 27, 2022, 02:38:31 PM »
My 400/4 seems to have developed this knocking at tickover. I was just about to try and adjust the cam chain, following some instructions I'd read about removing the bolt above the cam chain tensioner bolt and pushing a screw driver in to do the work of the springs, and I couldn't remove it.  My socket extension wasn't long enough so I need to get a longer one if I'm going to do that.

Anyway, before doing that I convinced myself the noise wasn't the cam chain. It seems to come from that area under the carburettors. I just wondered whether anyone had any ideas what might be causing it and whether it needs a major overhaul. Here's a link to a recording I made https://youtu.be/ENf3vm9v_BE

Offline paul G

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Re: Noisy engine 400/4
« Reply #1 on: May 27, 2022, 02:59:58 PM »
I would try a Carb balance first  ;)
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Offline Johnwebley

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Re: Noisy engine 400/4
« Reply #2 on: May 27, 2022, 03:02:51 PM »
Most of the sohc bikes rattle at tickover,

Normally it is clutch rattling,

Check the tappets, plugs,

And see about synchronise the carbs

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Offline McCabe-Thiele (Ted)

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Re: Noisy engine 400/4
« Reply #3 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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Offline sc29

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Re: Noisy engine 400/4
« Reply #4 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.

Offline Johnwebley

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Re: Noisy engine 400/4
« Reply #5 on: May 27, 2022, 03:16:49 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.
Let us know what area you live in,

Maybe someone close has the kit to sort the carbs

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Offline Nurse Julie

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Re: Noisy engine 400/4
« Reply #6 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?.
« Last Edit: May 27, 2022, 03:29:59 PM by Nurse Julie »
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Offline sc29

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Re: Noisy engine 400/4
« Reply #7 on: May 27, 2022, 03:43:19 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.

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.

Offline sc29

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Re: Noisy engine 400/4
« Reply #8 on: May 27, 2022, 03:55:01 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?.
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.




Offline Nurse Julie

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Re: Noisy engine 400/4
« Reply #9 on: May 27, 2022, 04:03:23 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?.
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.
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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Offline McCabe-Thiele (Ted)

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Re: Noisy engine 400/4
« Reply #10 on: May 27, 2022, 04:58:10 PM »
I did not hear the whine in the first video but can hear it in the second one now NJ has pointed it out.

What rpm is it doing at idle an extra 50-100 rpm might make it sound a lot better?
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Offline sc29

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Re: Noisy engine 400/4
« Reply #11 on: May 27, 2022, 06:27:33 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.
Let us know what area you live in,

Maybe someone close has the kit to sort the carbs

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I'm in North Hampshire Hook area if anyone can recommend an expert around here.

Offline royhall

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Re: Noisy engine 400/4
« Reply #12 on: May 28, 2022, 07:36:16 PM »
Run it in neutral until you hear the rattle, then pull the clutch lever in. Does it change the sound?
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Offline 400 Cafe Racer

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Re: Noisy engine 400/4
« Reply #13 on: June 03, 2022, 04:15:12 PM »
Hi sc29,

That idle performnce sounds very erratic to me, more like 2 to 3 cylinders doing the work rather than 4. This would cause an oscillation effect on the crank speed and aggravate both timing chain and clutch assembly. (A bit like shaking a tin full of nuts and bolts, rather than just carrying them carefully)

As NJ says, its best to go through all your core settings, ign timing, tappets etc, etc, then make sure the carbs are syncronised correctly, and mixtures correct so that all cylinders are doing equal work at idle. This will smoothen out tickover and make for cleaner performance throughout the range.

Just my observations.

Let us know how you get on. ;)

Dennis

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