OS 9B needle.

[Ian Inverarity]

I have just received an OS 9B which I am going to fit to my K-90. It was supplied with a needle on the carb. I do not use radio needles, and already have an OS 9B remote needle for the carb. Is there anything wrong with the needle fitted to the carb? Can I simply use that?

Ian.

 

[Hammerhead]

I think that the needle on the carb is much easier to use than the O.S. remote needle. I know a few people that use the remotes, but only because of the convenience of refueling. You can set it up where you don't have to remove cowling. to get to it. O.S should have supplied you with a needle horn for a third channel that you can put on the carb needle with a grub nut. Works great. I have used the remote needle myself, but I have always felt more comfortable with the carb needle. That is my 20 yen. Oh! By the way, If you are going to use it on a K90, you will need to reduce the throat of the intake manifold to match the opening in the bottom of the carb. You will need to machine a collar. Epoxy it in. You will also have to troth the case of the carb and bring the bolt holes in a little.

I would go ahead and epoxy the carb onto the block and bolt it on.

If you need to take it off, just heat it up.

Hammer

 

[Hammerhead]

One more thing. I run my 9B with the needle 1 and 1/3 turns out.

Break your K90 in at about 2 and 1/4 turns out.

Hammer

 

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New they cost about ten dollars in US currency. I'll buy it if you don't need it.

 

[Ian Inverarity]

Hammer,

Thanks for the info, I will use the needle on the carb! 8) I have only been using remote needles because the carbs I have been using do not have needles. The motor is well and truely run in, I dont have to worry about that! ;D

I was going to flare out the bottom of the carb rather than adding a sleeve to the K-90 drum housing.

Ian.

 

[Hammerhead]

Hey Ian! When you flare it out, could you show me a pic of how you did it? I might try it next time.

Hammer

 

[Ian Inverarity]

Hammer,

I did it today, I used a drill which had been ground to have a 60 degree included angle (Much steeper angle than a normal drill)and put a large chamfer on the bottom edge of the hole. I then did a small bit of grinding with a dremel and a little polishing with a cratex tip. Of couse this does not perfectly match in with the drum housing of the K-90, but it is not too bad.

I also lightly polished the barrel of the carb so that it operates a bit smoother.

Unfortunately I dont have a digital camera so I cant show you a pic. I want to get a digital camera, but the sort that I want, say a Nikon Coolpix 5700, is a bit to expensive for me yet!

Ian.

 

[Hammerhead]

Let me know how it works. If it works good, I would like to get the extra baggage out of my intake manifold, too.

I think I get the picture from your explanation.

Hammer

 

[Hammerhead]

Hey Ian! You know how the intake of the 9B is kind of blocky?

I was wondering what you think would happen if you flared it.

Have any ideas?

Hammer

 

[Hammerhead]

Oh! I just remembered something. If you run the 3rd channel directly to the needle, you will have to use some thin, perhaps 1mm or less

piano wire. If you use really heavy stuff for the push rod, the vibration will break the needle. They look tough, but they break easily.

Hammer

 

[Ian Inverarity]

Hammer,

I am not going to use the third channel on the needle, my third channel is tied up with radio tabs at the moment!! But I would have thought that using the needle directly would not give enough adjustment?

The intake of the 9B is not very nice. I have designed a venturi to fit mine, but have not been able to make it due to problems with the CNC lathe.

I think failing that, if the stock inlet was cut a bit shorter and a generous radius put on the end it would be a big improvement on the stock shape.

Ian.

 

[TimD]

if the stock inlet was cut a bit shorter and a generous radius put on the end it would be a big improvement on the stock shape.

Ian.

I'll second that! Cutting up a perfectly good (and expensive) carb is not easy though!

 

[Ian Inverarity]

Tim,

Exactly! ;D Hence the add-on that I have designed! Once the stock venturi is cut it would be hard to make an adaptor to fit if you wanted to change it, so my preference is for an add on venturi!

However, if worst comes to worst, cutting the carb is my next option.

Ian.