Tachostrobe / Metro carb type / Vim is rubbish

Answer: it's on a tag plate at the top of the carb. Which says MAC10050blahdeblahdeblah.

Great. It's not one of the carbs listed in the HBOL. Now what the f*ck do I do??

The 10003 has an AEK, the 10043 has an AEK, the 10050 has an AER. IIRC the higher the letter, the richer the needle. So I'd go with the AER bing a rich needle, which means you can run a little more advance (in theory, I think), which would fit in with it being 10 BTDC.

At least that's my guess, though frankly the couple of degrees more or less in either case should hardly be critical, when you consider tolerances get a bit sloppier with age and carbs aren't the most accurate devices...

it is 10 degrees at 1500, vacuum disconnected

mrcheerful

Cheers, that's really helpful. Out of interest where did you get that from?

autodata, they list two variations of 8 or 10 degrees for the carb version, so if it starts pinking on 10 knock it back to 8

mrcheerful .

Just make sure you don't blow the engine first.

Unless it is a race engine then 2 degrees will give no problems, the worst would be minor pinking, but I would very much doubt he will even get that. I have run engines with up to 36 degrees of initial advance with no long or short term problems.

Personally I doubt whether his timing is even a speck out, but you never know till you check.

mrcheerful

Set knob so small marker points to desired rpm on 4 cyl 4 stroke scale. Connect to number 1 plug and with engine running hold trigger in, adjust idle to stablise dark line seen in prism.

It's a wonderously simple device. It has a length of spring wire that vibrates, the frequency of vibration is set by turning the knob to adjust the length of vibrating wire. The end of the wire casts a shadow on a double prism at the side of the strobe. When engine is running at correct rpm, strobe flashes at a rate that makes the shadow become still and both images line up.

Note: Because it work on frequency, harmonics 1x, 2x, 3x etc of the desired rpm will also stabilise the image. If you can't tell 1500rpm from 3000rpm by ear you may have a problem.

-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!

Sounds like a wonderful gadget from before the age of digital everything!

Calibration might be a problem, though?

the best one I ever saw was a thing like a tuning fork, you set it to the required speed, you stood it on the engine and when it vibrated to max swing the engine was at the preset rev number. optical rev counters were the first practical ones for car use that I came across and of course the old faithful lathe type rev counter, I used that a little while ago to check the idle speed on a diesel.

mrcheerful

Never needs calibrating. Scale and pointer on side just measures free wire length like a 6 inch rule, you don't calibrate them. Losing the scale would be an issue. Only other reason it would need calibration is if someone opened it up and changed the wire somehow, changed length by cutting it, or made it heavier by soldering or crimping something on.

Frequency of vibration of a length of wire is due to law of physics.

's a little bit more complex as instead of single mass at the end oflightweight rod it's the distrubuted mass of the wire. If that lawchanges or stops working we are all very truly screwed cos it meansthe Devil just stole the rule book from GOD and rewrote it, orscrambled it, or burnt it (possibly the same day Hell freezes over).Or the Earth has been hit and swallowed whole by a wandering BlackHole or some other equally cataclysmic space time warping event.-- Peter Hill Spamtrap reply domain as per NNTP-Posting-Host in header Can of worms - what every fisherman wants. Can of worms - what every PC owner gets!

It's a little bit more complex as instead of single mass at the end of> lightweight rod it's the distrubuted mass of the wire. If that law> changes or stops working we are all very truly screwed cos it means> the Devil just stole the rule book from GOD and rewrote it, or> scrambled it, or burnt it (possibly the same day Hell freezes over).> Or the Earth has been hit and swallowed whole by a wandering Black> Hole or some other equally cataclysmic space time warping event.> --

Or it's a spring wire with some internal static stress, or it cracks slightly or oxidises.

> It's a little bit more complex as instead of single mass at the end of>> lightweight rod it's the distrubuted mass of the wire. If that law>> changes or stops working we are all very truly screwed cos it means>> the Devil just stole the rule book from GOD and rewrote it, or>> scrambled it, or burnt it (possibly the same day Hell freezes over).>> Or the Earth has been hit and swallowed whole by a wandering Black>> Hole or some other equally cataclysmic space time warping event.>> --

So, are you saying that rust is the equivalent of a black hole?

>> It's a little bit more complex as instead of single mass at the end of>>> lightweight rod it's the distrubuted mass of the wire. If that law>>> changes or stops working we are all very truly screwed cos it means>>> the Devil just stole the rule book from GOD and rewrote it, or>>> scrambled it, or burnt it (possibly the same day Hell freezes over).>>> Or the Earth has been hit and swallowed whole by a wandering Black>>> Hole or some other equally cataclysmic space time warping event.>>> --

Err no, but it'll massively affect the resonant frequency of your spring, it'll be heavier & less stiff.

..or it fatigues, or gets a layer of gunky oil residue on it from being satin the garge for years, or...

satin the garge? WTF am I on about?

sat. in. the. garage.

I'll get me coat.