Vintage Dirt Bike Q & A

Hi all,
according to my book the Ignition timing on a CR125 (1978) is 18 degrees BTDC am I wrong or does that equivilate to 2mm
my beast still isn't quite right and I'm getting rather P****** of with it!!!

cheers for any info

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

My '74 Honda manual lists the CR125M timing as 18 degrees BTDC, but the '76 manual shows 22 degrees, which I think is also correct for the '77 and '78 models.

18 degrees is 1.52mm BTDC
22 degrees is 2.26mm BTDC

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Thanks Ray,
I've come to the conclusion that the timing is not correct on my bike. been up and down the scale with slow jets just cant get a quick throttle response from idle, warm or cold with or without choke.......no air leaks!! it must be this new ignition i've installed gonna try the old one and compare then the difference after that don't have a clue!!

cheers Lad
Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!

Malcolm,

Was the bike running well before the ignition swap? I really hope it's not the ignition, it seems like an excellent unit.

Are you still using the modern 33mm Keihin? You might want to try one of the original 30mm carbs with stock jetting (140 main, 45 slow jet - this jetting should also work OK in the 33 to start with) if you haven't already, just to eliminate it as a suspect Also, what slide does the 33mm have? The slide can make a real difference in throttle response, but that might be a change better made later, once everything's running fairly well.

I went back over many of your earlier posts, and I still can't figure out if this is a rich or lean condition... is the plug wet? Does the bike blubber / four-stroke / smoke a lot when you give it throttle (rich), or does it bog out with kind of a snoring sound (lean)?

Also, if you can put the choke on with the motor warm and it still runs, something's definitely running wicked lean.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

malcom, if you are interrested in the whole manual send me a pm with your adress.

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80 CR250Ra
80 CR250Ra
78 CR250R
80 CR80
82 Bultaco Sherpa 340
78 Bultaco Pursang 250 MK12
76 Bultaco Frontera 370 MK10
76 Bultaco Alpina 250
73 Bultaco Lobito 125 MK6
76 Suzuki RM125A
90 Kawasaki KX250

Hi there Ray and B-joe,......it's been a while

haven't done anything yet!!! been fiddling with other projects however......now the weathers cooling off i'll be in my shitty shed full of shit sorting this and other headaches out. Thanks for the info though gonna try the old system again if that cures it then I'll take another look at this new system

Regards Malcolm

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1976 Yamaha TY80 X 2, 1977 Yamaha TY250 X 2, 1976 & 1978 Honda CR125 Elsinores, 2013 Harley Davidson 48 Special.
Range Rover Vouge Black Edition, a Little Smart four two and a shed load of other shit!!