Timing idler pinion noise

[bsa-bill]

a little point here.
I assume most are talking about a toothed belt, these do not need to be drum tight to drive.
There are however some belt kits with a V belt, they do have to be a bit tighter than the toothed variety, I had one of these and gave it away, the new owner seems to get on alright with it

[Dynamo Regulators Mike]

Some of the timing type belts are 10 mm. The Dynamo Regulator Belt is 15 mm uniquely.
The slack with 1/2 turn on our wide belt would be huge, and it would probably touch the casing.

[bikerbob]

Well today I slackened the belt until it had 1/2inch up and down play took the bike for a run and the noise is still there, so it is not belt tension that is causing the noise. The next thing I am going to try is removing the belt then put the case on with just a few bolts and start it up and see what happens with a cold engine you can just hear it but it gets a lot louder when the engine is hot. The noise is definitely coming from the idler pinion area nowhere else.

[duTch]

 Bob, when I put mine back together with the Belt conversion, I had a hassle with the idler pulley rubbing on the bottom of the intermediate (inner?) casing. Maybe yours is similar but not until it gets hot as per previous suggestions of expansion. Maybe pop the big pulley and look for signs?

 For the record, the instructions in my SRM kit state "the belt must be easily twisted through 90º". I think it also works out  about 1/2" slack midstroke.

[bikerbob]

I removed the belt drive belt and idler pulley put the case back on started the bike and the noise is still there, so that eliminates any problem with the belt drive. Took the inner case off removed the idler pinion and inspected it found 2 teeth marked as photos also some previous owner has ground  the end of the  shaft that goes into the crankcase for what reason I do not know only maybe 1/32" ground off the end. I hesitate to say this is the problem but can find nothing else.

[muskrat]

G'day Bob.
Don't we luv previous owners
I'd say the grinding was needed to rectify a burr/mushroom caused by "not so" gentle persuasion to get the pinion off the shaft. It should be a light press fit centered between the two grooves on the shaft. Slight miss-alignment of the dynamo pulley's can be rectified by pressing the pinion one way or the other on the shaft. The damage to the teeth would have been caused by the use of a hard wedge between the pinions to lock the pinions to remove the cam or crank nuts. Look for same on the cam or crank pinions. This may give you noise, the shaft won't.
There's probably heaps of them out there, here's one on fleabay  http://www.ebay.com.au/itm/BSA-A7-A10-Idler-cam-pinion-gear-great-condition-B967-/331299548153?hash=item4d22fdebf9:g:crUAAOSwnDZT-TP5
Cheers

[bikerbob]

Thanks for that info Muskrat I did check the cam and crank pinions but can find no damage to either so have put it all back together now and will look out for pinion on ebay or maybe at an autojumble.

[olev]

I've just received a SRM belt drive (slipped in while brexit was hammering the pound) and am a bit surprised by the instructions:
"then pack the cavity with grease to help lube belt and keep it cool. This is important!"
are people running their belts dry?
It seems immoral to chuck a handful of ugly axle grease onto such a pretty thing.
cheers

[bsa-bill]

It seems immoral to chuck a handful of ugly axle grease onto such a pretty thing.

depends on the stuff the belt is made of, my new car's timing belt runs in oil, got a life of 150,000 miles,  provided the belt can grip then any lube will keep it cooler

[duTch]

 It's a bit of a diversion from the original post, but I'll add on anyway; I bought a SRM conversion, but the belt only lasted just over 6K miles. I thought I'd tensioned it as per instructions but maybe I had it too tight and it shredded bits of steel fibres, and finally stretched, so as per previous posts^^^^, I've backed off the new one a bit. It's only done ~2.5K miles since then, but seems ok. I haven't run either in grease or oil or anything- totally dry.

  Original belt; Synchroflex AT5/420 x 10mm  Gen 111 (steel reinforced)
 Replacement; Optibelt     AT5/420 x 10mm   (Polyurethane)- current   
 I've last week bought a new spare same as current one (except 'made in Ireland' ), so see how it goes.

 I bought the last two from the local bearing supply shop, they have to get them in and not as cheap as I'd like, but waddafarque, I have a spare-*dunno*