Strange noise/vibration.BSA A7 1960

[BSA500]

Sometimes(ok most times) the is a vibration & noise from the drive side. Its sounds just like trying engage a gear without using a clutch. Vibration felt through the left footpeg and usually only at 50 mph. Anybody had this(it has done this for years)

[Billybream]

Could be the cush nut on the crank hitting the primary crankcase outer cover.

[BSA500]

Checked in the past and no metal filings etc and the vibration/noise does seem to come from the clutch/gearbox end. And only at about 50 mph. Most strange.

[Klaus]

Ok 50 mph is 4 gear, is the noise louder by asscelleration? Sounds like a brocken teeth in the gearbox.

[Sluggo]

Can be any number of reasons, Primary issues such as chain whip at certain RPMS/Speeds, worn thrust washers at back of clutch basket, bad clutch basket bearings or wear, clutch basket issues
(Go away when clutch lever pulled?)  loose end nuts or not fully seated on either end of mainshaft?   Worn bushes in trans?

(Klaus has a valid point about 4th gear final drive being a important clue)  These issues can be challenging to nail down.  Especially when you do your own work and know intimately all the little bits and pieces.  Some call this "Knock-itis" and many a man has fallen to paranoia and rants chasing down real or perceived issues with noises and vibration like this.  Some go off the deep end when after repeated tear downs the cause still is not found or determined. (Toys in the attic)

I have a family friend who spent a career working for several local Auto dealerships and much of the latter half of his career was customer service and complaint resolution.  Patient and philosophical guy. 

"Well, it makes this horrible clatter and the whole car shakes  but it only does it going downhill and going over railroad tracks and most of the time only when turning left,. It did it a couple times turning right but that was a long time ago,.  And most of the time its when its raining, when its dry out it doesnt seem to do it.  When my husband drives it he has not had it happen at all which is just totally weird right? Am I right? What is with him anyway...? So, he just thinks I am crazy so thats why I brought my friend Becky with me today, she heard it too!"

I know a few people that motor about blissfully ignorant of this stuff and in some cases things go horribly wrong and catastrophic failures (You did not notice that your oil light was on and there was smoke coming out?) but some seem to just do quite well ignoring any such noises or symptoms and it all works out.

[JulianS]

Could be that some part or parts of your bike starts to vibrate in sympathy at 50 mph in top causing the problem.

Make sure everything is tighten up and tinware does not touch anything where it should not.

Make sure the drive side foot rest is not touching the primary chaincase sometimes the clearance here is limited.

[BSA500]

My own feeling is wear in the gearbox bushes. This is an area I have not gone into for many years. Things like the clutch basket,primary chain etc have been replaced in recent years and this vibration and noise(a noise which can heard/felt while doing 50 mph) has remained constant. I must admit I have never replaced the layshaft bushes ever(over 20 years of ownership) only the mainshaft ball bearing a few times  .
 I think this winter the gearbox needs attention. I did swop to a c12 cluster a few years back.

[Topdad]

ermmmm.... poss ride at 48 mph or 55mph ??  .\seriously the biggest improvement on the transmission I ever have noticed was after I refitted the gearbox when SRM had reground the layshaft and fitted a new bush to suit as well as the first gear pinion ,made a hell of a difference. 

[BSA500]

Doing some extensive testing and I can confirm this only happens in top gear at about 50mph. Not while doing 50 in third  . Couldn't quite get to 50 in second but the vibration was interesting.

[Klaus]

When you going faster in top gear it seems to vanish?
I remeber my shot worn slevegearbushes distroyed mainbearing or a brocken teeth. Time to split the box and see what happened.

cheers Klaus

[BSA500]

I have had issues with sleeve gear bushes before. Winter rebuild is on the cards.

[BSA500]

Well noise/vibration may have another reason. Sounds/feels like the big end has gone on the drive side. It even clanks when its turned over by hand. Bugger

[muskrat]

 

[BSA_54A10]

As Sluggo has already mentioned this can be all in your mind or could be happening in all gears but masked by engine noise or vibration.
Isolating is a long slow methodical process.

You will need a long section of road where you can do a lot of testing.
Basically you have to ride the same section of road several times at the same speed in different gears ( don't try doing 50 in 1st ).
Then the same engine speed in all gears.
Take a pocket book and pencil and write down the results of each run and you will need to do every combination at least 3 times.
An open face helmet is also good as it will allow more engine noise to hit your ears.
Before you start, check all of the mounting bolts for tightness.

Over the years I have seen all sorts of things cause these types of problems but the most frequent are loose mounting bolts followed by damaged chains, one of the reasons why I like to run multiple chains.

If you do not have a tacho, go on line or to a mower shop & get a "Tiny Tach" which are made for stationary engines, self contained and pick up is a wire that gets wrapped around a HT lead . This will make running at constant revs easier.

[BSA500]

Before the latest issue, which so far is a really really loose small end, the bike consistently vibrates/grinds/screeches at 50 mph in top gear only. No argument its coming from the gearbox and horrible vibration through the left footrest. Now the engine has to come out so will the box.