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Honda Carburettor needles
givemethebighammer - 9/1/07 at 11:36 PM

Has anyone got any information about honda carburettor needles?

The Blackbird uses needles marked as J5FZ
The Fireblade uses two J5FS and two J5FR

I can't find any info anywhere about how these numbers relate to L1 length, taper etc or how they relate to the standard keihin part numbers available from people like Allens Performance.

ReMan - 9/1/07 at 11:47 PM

All four needles in the fireblade dynojet kit are the same?

givemethebighammer - 10/1/07 at 12:01 AM

evening Col, up late too!

I found some info that says certain models of fireblade (and blackbird)also jet cyls 1+4 differently to 2+3, but only by a small amount, something like 1+4=142 and 2+3=140. I guess it is the same thinking as the different sized trumpets to spread the powerband?. I know about the needle thing because I picked up some fireblade needles from a bloke who had fitted dynojet ones. I have tried measuring them with the vernier to see how the differ from the blackbird ones but I can't see any real difference. It must be subtle.

Surrey Dave - 10/1/07 at 09:45 AM

found this chart , could be useful.

http://www.motorcyclecarbs.com/Keihin_PJ_PWK_Jet_Needle_Size_W52C495.cfm?UserID=395580&jsessionid=7e30314441168422117833

are you fine tuning with the LM1 etc?

it would be a miracle if any of the bike carb original needles worked out spot on for a different engine setup , I've found that even very small changes on keihin /mikuni carbs make a difference.

On my GSXR carbs the original jets where 112 on the outer cylinders and 115 on the inner cylinders , I assumed this was to do with the fact that the inner cylinders would probably run a little warmer , the intakes are the same length on the GSXR.

[Edited on 10/1/07 by Surrey Dave]

givemethebighammer - 10/1/07 at 10:53 PM

quote:
Originally posted by Surrey Dave
found this chart , could be useful.

http://www.motorcyclecarbs.com/Keihin_PJ_PWK_Jet_Needle_Size_W52C495.cfm?UserID=395580&jsessionid=7e30314441168422117833

are you fine tuning with the LM1 etc?

[Edited on 10/1/07 by Surrey Dave]


Thanks Dave I already found the above link and it doesn't have any relevance to the honda codes. I'm not really fine tuning, more just playing really. I do have a slightly rich spot just off idle, not enough to cause the engine to bog down. In fact if I didn't have the the LC1 I wouldn't have known it was there. Like I said I got a box of needles and jets for a fiver from a bloke who had upgraded his fireblade to a dynojet kit and was going to bin the old parts and the remains of the dynojet kit he hadn't used. My thought were that perhaps needles from a smaller bike might have a different taper etc on them. As it is I can't tell the difference between the blackbird ones and the fireblade ones even though they have different part codes, hence this post.

thanks

Surrey Dave - 11/1/07 at 12:33 PM

I think the needle jet is relevant to just off idle as the top portion of the needle is parrallel , although I believe also that the point at which the needle goes from parrallel to tapered is higher or lower for different needles.

I guess needle jets would be expensive and probably not worth the hassle if it is not noticeable when driving