Topic: NASTY engine-noise (Sound file included)

[mrbreeze]

 

[ofreen]

My opinion is that the carbs being out of sync may exacerbate the rattle, but that sounds like way too much slop.  My computer speaker isn't exactly hi-fi, but there sounds like a loud metallic slapping noise there.  Like something hitting a case. Have you tried putting your hand on the case to see if you feel something that corresponds with the noise? Even if a carb sync quiets it down, I reckon I'd drop the oil pan and check out the screen and look up in there.  I'd do that anyway if I wasn't familiar with the bike just to see what's what.

[Bob Wessner]

Haven't had the occasion to try it, but I've read that if you put a screwdriver tip at various places around the engine, with your ear pressed against the handle, you can at least isolate where it is coming from. 

[DarkRider]

same can be done with a dowel..or a stethoscope.

[ic455]

Not to scare ya, but I have heard a similar sound in a '92 Nissan v-6 (it was the timing chains) unfortunately, it was let go until the long chain snapped and took out the left valve cover    no real similarities between the two, I know, but it does kinda give the mental image of the cam chain slapping around until you blip throttle raising the rpm and centrifugal force stops the slapping. 
Curious to see the actual cause

[Jonesy]

Haven't had the occasion to try it, but I've read that if you put a screwdriver tip at various places around the engine, with your ear pressed against the handle, you can at least isolate where it is coming from.

This trick works very well. Or, you can use a mechanic's stethescope:

[Sam Green Racing]

Nice one Dr Dan.

[Bob Wessner]

I'm sure it would work. I wonder how many of us have one.

[scunny]

those stethescopes are good, I got one when I got sick and tired of playing mr twister trying to get my ear on the screwdriver end in tight places.
re your noise problem, if it's a loose cam chain it will tend to be quite as the revs build or the motor is put under load then rattle like hell when the throttle is released.

[Hop on a Honda]

Horrible sounds

[Hop on a Honda]

Very nasty indeed.
My CB 750 had a very similar sound The Number 4 Cam shaft bearing  (LHS) was  dry and was grabbing and then SEIZED UP. I did however have a Nak Nak nak sound in the top end
The oil was not getting to the bearings nor the tappet shafts.
Pull the inspection ports and wipe clean the insides then start motor and look for oil mist from the insides.
Replace them run the motor at say 3000RPM then remove them again and inspect for oil residue in the caps. This will virtually give you a quick idea IF the cam & tappet shafts are getting lube oil if any at all.
A strong light will tell if the cam and  springs etc are dirty with black crap.
I ended up rebuilding the engine Only the Cam and top end tappets were R/S.
I managed to save the motor.
When I removed the sump the sump itself  and the strainer was full of  bits from a very worn cam chain adjuster slipper and the two wheels were bald .
The cam chain slipper and rollers  are more the suspect in my humble opinion
BTW Bike is great.
Dave Australia.

[750goes]

Just to ease the tension you must be feeling - mine sounds similar at low revs, but it does reduce a bit with the clutch pulled in...and IF the bike has not been ridden in a few years, a thought could also be the clutch plates are a bit dry from lack of oil...

The noises in my bike have gradually reduced over the last few months, so I think apart from the carb sync routine, getting some more oil through the clutch will help a bit...

plus the obligatory tappet adjustments, cam chain adjustment etc...etc.....you got any spare sidecovers for that bike particularly the left and right ??, I could be tempted to relieve you of them if the price is right ??

[MadDogMcq]

Thank you to everyone who's helped with this topic - all that remains now I guess is to do the carb-cleaning-tuning and re-evaluate after that's complete. You guys have been a big help - I'll update you at the weekend.

Tom

PS : I love gadgets, so I want one of them there Stethescopes!

[bryanj]

Carb tune is THE LAST service item on the list!
Adjust/replace points and do timing,
Adjust valve clearances,
adjust camchain,
change oil and filter,
THEN adjust carbs.
if your email address is shown i will send you a how to on cam chain adjustment that works.

[bryanj]

Change thw plugs also then email me direct for the how to. I'll be in Bury this weekend but a bit busy with family to get over to do it for you

[mcpuffett]

hi mad dog, my 750 f1 sounds like that , pull the clutch in and it goes away and also lift the revs and it goes away  definatley full tune up over due  , i do have a set of vacuum gauges  but i have never used 'em yet , good luck with the 750, mick.

[Terry in Australia]

Mate, do as Bryan suggests and give that F1 a good tune first, don't buy the morgan yet (good kit though, I've got one) just use a piece of wire to synch your slides and double check your cam chain adjustment, most blokes stuff it up.

You can check your primary chains without ripping your engine apart, just remove the sump plate and you can access the chain, then just push the chain up, any more than about an inch of movement, and it's toast.

Sorry about your lack of friends and your mothers disdain for you, but don't let that get you down, your cricket team has similar problems, but that doesn't seem to have affected their performance! Cheers, Terry.

[spitfire]

Hi Mad Dog,
               Nice looking bike, looks just like mine did when I bought it in 1976 (P reg as well), that standard silencer (muffler) did not last long on mine as it reduced the ground clearance quiet a bit (it's still in my garage).
What was the bike running like before it was laid up ? If it was OK then it sounds like something has deteriorated while in storage, sticky clutch, gummy carbs (mine were so gummed I could not move the twistgrip).
Or more serious if you started it up without changing the oil or pressurising the oil system, that is turning it over with the kill switch in the off position until the oil gets to the bearings, you may have had metal to metal contact on start up.
However, as the guys have said do a full service on the bike before you give up or reach for the tool box.
The screw driver trick really works in isolating the problem area, used to use it a lot as I'm a cheapskate !

Cheers

Den

[MadDogMcq]

Too late - The CarbTune is ordered. It will be a great tool to have in the garage anyway and if there's anyone near to Bolton who wants to come and use it, you only have to ask.

From David Silver I have ordered new plugs, points and condensors. Also bought a new tensioner (to be on the safe side) and an oil-pan gasket in case the pan has to be removed further down the line to look at the primaries. Finally, I've ordered 4 carb-repair kits because even if the service sorts out the rattle, the carbs will always benefit from a refurbishment.

BryanJ has very kindly emailed me with some good tips and I'll be taking a closer look at the weekend.

And thank you Terry for your concern over my relationships and cricket team 

Great place, this SOHC club!

[Bob Wessner]

Finally, I've ordered 4 carb-repair kits because even if the service sorts out the rattle, the carbs will always benefit from a refurbishment.

I assumed the same a couple of years ago. When I examined and compared the kit parts to the originals (primarily the needles and float valves) I found differences in the taper of the needles and the float valve spring tips were very stiff compared to the stock valves. On closer examination, you may find the hard parts just need a good cleaning and nothing more. At the very least, compare parts carefully. As suggested by someone here, I used a drill bit gauge to check the needles. That's how I found the profile difference. The kit needles would have resulted in a richer mixture at the higher throttle openings because they were noticeably more slender as the profile moved toward the tip. Anyway, ended up using virtually all the original hard parts after cleaning and reassembling.

[Jonesy]

I love gadgets, so I want one of them there Stethescopes!

They are available at most auto parts stores for around $14.00. (I got mine on the clearance table at the local hardware store for $7.00!  )

[MadDogMcq]

To be honest Bob, I too was a little concerned about using Keyster kits that I was sourcing from an American company because I thought there might be some slight differences between US and UK. Since I have now ordered them directly from a UK company, I'm less concerned but I will still take heed of your warning and check the dims when the bits arrive.

Thanks.

[Crusty_Butt]

That sound reminds me of the times I made mistakes adjusting my valve lash. One time I adjusted them on the exhaust stroke, ha ha ha. One time I forgot to tighen one of the adjusting nuts.

That sound is too much of a hammering sound to be clutch rattle, but its hard to tell for sure hearing it over the computer.

You will definitly need that carb balancer, so no regrets on that purchase.

Good luck.

Bret

[andy750]

The Keyster carb kits are ALL made in Singapore (I believe) so it wont really matter if you buy them from a UK or US company. Id go with Bobs suggestion of re-using the hard parts after a good clean. However Ive also had success with Keyster carb kits on my K4 so no complaints here.

Good luck and keep us posted.
cheers
Andy

[Jonesy]

As I said earlier, I've had luck with most of the stuff in the keyster kits except for the jet needles. New ones are still available from Honda.