Vintage Dirt Bike Q & A

I just got a '79 CR250 Elsinore... What mixture should I use for the gas/oil? 20:1? 32:1? I run my old 2-stroke outboard at 32:1. Don't like to smoke any more than I have to, and I've never had any trouble with it. What do you guys recommend? What did Honda call for originally? Thanks!

My Clymer manual specifies 20:1 for all CR M's and R's 1973-1980. I have read some articles that seem to think that 32:1 is fine for all 2 stroke bikes. This is based on the advances in 2 stroke oils. I stick with 20:1 and get a little smoke until warm, but the plug reads fine.

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Steve Amling

1976 CR 250M
1980 Yamaha DT100G
1980 XR 200
1981 CSR650

http://www.maximausa.com/technical/oilmigration.html
...based on this I run Maxima synthetic at 32:1.

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

50:1 with castrol rs2 or motul800
no problems in 17 years

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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

The richer the oil mixture, the leaner the fuel mixture is(more oil and less gas in each intake stroke). So, it it more likely for you to have lean burn problems,and overheating problems at 20:1 mix ratio than at 32:1, 40:1, or 50:1. I have run Golden Spectro 2 cycle for over 30 years and never had a problem at 50:1.
OriginalDirt

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74 AMPI CZ125
73 CZ400
73 CZ250 Basket case.
72 SherpaT 350
75 Montesa King Scorpion
72 Rickman 125 Enduro
70 Honda CL70
72 Honda Z50
00 DRZ400E Baja'd

Well I ran it today at 20:1. A little smokey when you gas it but not bad at all. Less oil smoke would be nice, but maybe more research first. For now I'll stick with what Honda reccomends.

The bike wasn't running 100%... Kinda bogged a bit more easily down low and took a bit to get into power band sometimes. Sometimes starts 1 kick, other times take 3-4. Gotta thoroughly go through the bike.

My recently finished restoring my 79 KX250 and it ran a little sluggish at first but after running a couple of gallons of fuel through it the power band really came together.

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Terry Moody #48f
3x 74 Honda CR250M Elsinore
74 Honda XR75
73 Honda QA50
78 Yamaha YZ125E
78 Yamaha YZ250E
78 Yamaha YZ400E
79 Kawasaki KX250
79 Honda CR250R
79 Suzuki RM400
80 Honda CR125
2x 83 Honda CR480R
98 Kawasaki KX250