Vintage Dirt Bike Q & A

Haven't stopped by here for a while, but in the mean time I've managed to aquire a 78 CR250 and an 80 CR250, both bikes were missing the needles out of the carb slides. (amongst other things.) I see needles are discontinued from honda, and I haven't seen any aftermarket carb kits, anyone know where to buy one?

Thx
Hans

You might try some old dealerships that may have some old stock on their shelves. Western Hills Honda in Cincinnati or Bob's Indian in Etters, PA come to mind.

http://www.westernhillshondayamaha.com

http://www.bobsindian.com

The latter is quite old-fashioned and may not be willing to mail parts as I don't even think they accept credit cards.

Hans,

Here's what little I know about these carbs' needles.

They are Keihin N427-48-xxx 66mm needles, with the last 3 digits being a three-letter code (taper 'A'/straight length 'L1'/straight diameter 'D'). These are available from http://www.motorcyclecarbs.com, but it's not quite that simple.

Here are half-assed specs for the three I have (number is stamped below the clip grooves):

271302: D .0988", long L1, mild taper (leanest) '76 CR250M 36mm
271006: D .0983", short L1, mild (dual?) taper (medium) '76 MR250 34mm
271309: D .0972", long L1, heavy taper (richest) '73 CR250M optional 36mm

The problem is that even if you're able to figure out exactly what needle you need (and believe me, it's not easy), not all of the letter code combinations are still available from Keihin, and if the straight diameter isn't fairly close to the OEM spec or otherwise doesn't match well with your needle jet, the bike may not even start. For example, the closest replacement needle for the 271309 needle above may be a N427-48-BGA; it's not available, and even if it was, the 2.465mm diameter doesn't even show up on the chart, although it does on the N427-46 57mm needle chart. N427-48-DCA and -ECA needles are available, but may end up as expensive toothpicks if the length and taper don't work for you. I believe some of the Honda needles were OEM-only as well, as the L1 and D specs are off the ends of the Keihin replacement charts.

Your best bet would be to try and find a needle on eBay. I got one recently along with the slide and spring (apparently it's pretty common to remove a carb for sale and leave the slide etc. on the cable).

All this is assuming your carb looks like the one in the picture.

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

EDIT.

http://rapidshare.com/files/248642897/Honda-Keihin-Sudco_Needle_Comparison.pdf

I captured the Honda information provided and attempted to map it to the parts available from Sudco for the Keihin PE 36mm round slide carb. This missing variable at this point is to know the measurement of L1 from the stock needle (because it is not clear what this is from the owners manual or parts catalog). I am interpreting this as the distance between the top clip groove and the start of the taper on the needle. Why is this important? Because for each combination of diameter and taper, Sudco provides 2-3 needles each with a different L1. I would go for the middle 38.15mm needle.

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

Thanks for that needle info! I didn't realize they went with the bigger needle/jet in '78, that sure opens up possibilities with the available needles.

I wonder why they abandoned the power jet in these carbs? All the ones I've seen have the outside passages in the casting, but only the '73 (I believe) has the undrilled openings in the mouth, and the MR250 carb seems to be the only one that has everything drilled out and functioning.

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 for all the info, I did find a 28D in my parts box, and it's running with that, but the 28D isn't on any of the charts I have. I'll try ordering from Sudco.

Is the needle the same for the '80 ?

Thx
Hans

....

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

from the 80´s manual

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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