MB Dev Timing Disc - Am I missing Something?

[davla]

I bought a nice shiny metal timing disc made by MB some time ago, although can't remember who I actually bought it from. Am I missing something but when I went to use it today to work out TDC I found it's too big in diameter? It's totally useless!

[bike grim]

Yeah, I bought one of those a few moths ago. It's about 20mm too big in diameter isn't it? Just used my old one instead and hoped that one day I would find out the reason it's bigger.

[bookertmgs1]

Did exactly the same and now stored safely in the useless box. Bought a Cambridge Lambretta one which is perfect size and is fit for purpose.

Call me old fashioned but I’d have thought being the right diameter was a basic requirement?

[Knowledge]

I heard some reasoning about bigger being more accurate (half a degree), but I don't see the advantage if you have to remove the engine mount to use it.

I then I heard another tuner say that it was impossible to measure "half a degree".

Yes, Camlam disc is good, but now I have bought an incilinometer and I am going to play with this instead.

[dickie]

Bigger is more accurate but only if you know when to determine the starting point for measuring; which I don't to be honest. Is it as soon as you see the top of the port? When you can pull out a 0.1mm gauge?

0.5mm is about 2 degrees on an exhaust port and that's about as accurate as I get.

I think it matters to them what knows what they're doing proper.

[HxPaul]

Bigger is more accurate but only if you know when to determine the starting point for measuring; which I don't to be honest. Is it as soon as you see the top of the port? When you can pull out a 0.1mm gauge?

0.5mm is about 2 degrees on an exhaust port and that's about as accurate as I get.

I think it matters to them what knows what they're doing proper.

The way I do it.I find TDC by putting a piston stopper in the plug hole,I turn the flywheel in one direction and mark the mag housing,then I turn the flywheel in the other direction,I mark the mag housing and exactly between the two is TDC.I time mine at 17 degrees BTDC,using a timing disc.

[coaster]

If you want accuracy you should ideally us a dial gauge on the piston crown, I did it both ways, dial gauge to find tdc and mark degrees on the mag housing. Then put head on and used positive stop to find TDC and degree disc to check timing marks and they matched near as damn it.

[rossclark]

I heard some reasoning about bigger being more accurate (half a degree), but I don't see the advantage if you have to remove the engine mount to use it.

I then I heard another tuner say that it was impossible to measure "half a degree".

Yes, Camlam disc is good, but now I have bought an incilinometer and I am going to play with this instead.

Your iPhone has a built in inclinometer - swipe the compass left - I was just thinking you'd need to find a way to make a bracket that fitted onto the centre nut and could hold the phone.

[coaster]

I heard some reasoning about bigger being more accurate (half a degree), but I don't see the advantage if you have to remove the engine mount to use it.

I then I heard another tuner say that it was impossible to measure "half a degree".

Yes, Camlam disc is good, but now I have bought an incilinometer and I am going to play with this instead.

Your iPhone has a built in inclinometer - swipe the compass left - I was just thinking you'd need to find a way to make a bracket that fitted onto the centre nut and could hold the phone.

I have one of those brackets, bought off a guy on Face Book. It's just an L shaped bracket with a large hole in one side with a grommet fitted that is a push fit into the thread for the extractor. Works, pretty very well but I'm pretty sure I don't have a compass app I downloaded a free app called 'Handy Level' which is a spirit level and does the job just fine

[rossclark]

I thought the Compass was standard with IOS?

[coaster]

I thought the Compass was standard with IOS?

I haven't got it on any of my 3 IOS devices But the Handy Level app is free anyway

[modster79]

On my two iPhones, not on my iPad

[Knowledge]

Interesting that since this thread started, Mr B has been posting on Facebook about his own timing disc. There have been a number of comments about the disc from users, and several mentions of the disc being too large.

MB states that size equals accuracy.

[modster79]

I’ll mention that to the wife

[bike grim]

Yes Martin, he reckons we should use a straight edge from the disc to the mag housing to mark the timing marks. Good job I’ve got 3 hands. I suppose he sees the disc being used More for port timing than setting ignition timing. Therefore the larger the disc the more accuracy.

[a-teamlambretta]

Can't you use the disc as is and use a bit of wire tied on to your motor and used as a pointer on the disc, then use have both hands free to use your other main lambretta tools, your lump hammer and cold chisel to make your marks on the mag housing??

[bluebob]

saw this advertised on fb,but luckily read this post before I ordered.will get one that fits instead.cheers