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Discussion Starter · #1 ·
Good day all,

I'm in trouble .. I need a new set of needles for my carbs .. New OEM needles say they are different, but one needle is no longer available. Just my thoughts. Can I use the same needles on the two carbs?

Any advice from someone? Don't want to spend few hundreds for used crabs..
 

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No. Front and rear cylinders have different needles because they don't work under the same temperatures. If I remember well, I believe even the emulsion tubes are different. I started buying used carbs years ago, just for spares... ;-)
 

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Discussion Starter · #3 ·
No. Front and rear cylinders have different needles because they don't work under the same temperatures. If I remember well, I believe even the emulsion tubes are different. I started buying used carbs years ago, just for spares... ;-)
So, you have spare needles to sell for me :)
 

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I beg to differ, how can the temperatures between the cylinders be different. With an air cooled engine yes, but a water cooled engine with a water pump, the temperature variations are not going so big as to affect the carb jetting.
One of my cylinders was actually running richer than the other, so i ordered a new needle to match the leaner cylinder and voila, both cylinders run the same. So the answer is yes, you can run the same needles and from memory the emulsion tubes are the same, but i will try and find my notes on this.
Just curious Andrius why you think you need new needles. Are they visibly worn or bent (how!!)?
Before messing with needles etc, have a look at a spark plug (either one) from each cylinder and check the colour. They should both be a chocolate brown colour ( refer to pics on the web if not sure). If the needles have worn this will always result in a richer mixture, causing the plugs to be black.
Note: the plug check should be done after a good blast or a normal run and stop the engine without letting it idle for too long. If either of the plugs is black, check the carbs choke mechanism is closing fully, not sticking and the plunger seat is not damaged allowing fuel to leak past. Other things to check are the float chamber needle valves (not a bad idea to change them anyway) to make sure they are not leaking but also the float height as if this is too high, also allows the fuel mixture to be richer than it should.
Hope all this helps, but it is most important to check out what IS ok before jumping to assumptions as to what is wrong.
You dont state what problems you are having and the reasons for you concluding the needles require replacing.
What model, year and mileage is your AT as it all helps in the diagnosis!
FYI, I built race engines for years, dyno testing etc and am a bit of a carb expert having had a lot of experience with re-jetting, choke sizes emulsion tubes etc. Also if you want to make your AT pull full throttle from 1500 RPM (YES!!) and be the bike it always should have been, check out my posts about altering the ignition map (somewhere on this site !)
 

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Having done a bit of checking, the needle i replaced was the front cylinder, with the rear needle part # 16027MAY620.
However both front and rear needles are available from a UK company Rugged Roads where i bought mine. The needles are a bit expensive, but what bike parts aren't!
The link to their XRV pages :

Doing a part # search may also find other non Honda dealers who have parts.
 

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Discussion Starter · #6 ·
I got new needles, one part number shows same code from honda cbr f2 model, problem is when my bike warm rpms stays high, after some time it calms down, my mister carb guru says its needles fault.. bike mileage is about 300kkm..
problem is my needles sliding “bushings”are worn out
 

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I am not sure your MR Carb knows his arse from his elbow!

If the needles are worn it will result in a richer mixture as it is allowing exra fuel to pass from the jet hence the different needle profiles. This does not raise the rpm with the throttle closed as that is taken care of by the idle circuit and throttle stop screws. Do the plug check i suggested and it will tell you about the main jet and needle condition AS A MUST!!
Not sure what you mean by your 'sliding bushings' the orifice the needle slides in to?
If you have an erratic idle (high) this is usually caused by the throttle butterfly shaft? bushes being worn so the butterfly does not close in the same place allowing more air to pass, hence the higher rpm, then settling into its closed position so slowing down. I have seen this problem many times. If you try to adjust the idle down with the throttle idle screw, it may calm down, but then stall (stop). Try moving the throttle shaft up and down (on both carbs) with the engine running, if the rpm changes then that is you problem. It is difficult to repair this so usually the most sensible fix is a replacement carb body.
As the engine has done so many Km, this is more likely to be the problem as a single carb per cylinder is subject to more severe pulsing than a carb feeding multi cylinders and the butterfly shaft and bearings ( usually just a drilling in the body, no actual bearing) have a higher rate of wear.
Attached picture shows what i mean by the throttle butterfly (just to be clear).
I presume you have examined the rubber diaphragms for holes as a matter of routine.

Hope this helps!
 

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Revs hanging high can also be due to air leaking past the inlet rubbers, don't discount sticking choke cables.
As said, hanging revs isn't due to worn needles or emulsion tubes - that would cause a rich midrange.

Sent from my SM-A320FL using Tapatalk
 

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Discussion Starter · #9 ·
No air leaks, allready checked several times, i replaced allready needles for a new ones, but don’t feel any better..
 

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Unfortunately i did think you have wasted your money on new needles, perhaps send the bill to your Carb Guru !
Have you tried the throttle shaft wiggle as i have suggested as i would place a healthy bet that that is the problem, based on what you have said. If you cant make much of a difference you best remove the carbs, separate them and check each shaft as it may only be one that is furthest from the throttle cable end that is causing the problem.
With constant depression carbs like these, SU's, Stromberg's and many Japanese makes, an erratic tickover of higher revs slowly lowering, can only be caused by excess air leaking past the butterfly. Unless the idle mixture is excessively rich, an air leak between the carb and engine will make the idle mixture too weak and the engine will stall. Likewise if the choke plungers are open or leaking, the idle will be lumpy and cant be corrected by adjusting the idle mixture screws. I know this because one of my choke plunger seats was wrecked (see attachment) and required a tricky repair!
 

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Discussion Starter · #11 ·
Ok, i see i must to inspect all again, from butterfly’s and choke. Will get a free time some day..
 

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Discussion Starter · #12 ·
Ok, just took off the carbs.. few pics of the plugs
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Automotive tire Motor vehicle Automotive design Automotive fuel system Hood
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Looks like butterfly assy has no movement , but i will try to inspect today later on..
 

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The first pic plug looks like its running a bit rich, whereas the second pic looks a little lean but thats ok. Presumably you know which cylinder each plug came from. I would suggest changing the needle and main jet of the rich cylinder to that of the leaner cylinder. Depending on the year of your bike, the main jet are as follows (according to my manual):
1990 -1992 front 118, rear 122
1993-1995 F 118, R 120
1996 ---- F&R (my AT) 115
However, before changing the jets etc it is vital that you check the carb floats to make sure they are not porous and the float needle valves to see if they are leaking. Replacing these whilst they are still available may be sensible due to the age of yours. Lastly check the float height and adjust if required, hopefully you have a workshop manual (Haynes?).

Both plugs show burnt oil deposits probably due to the high KM's but keep a check on the oil level and consumption.
None of this will cause a high engine idle. though.
If the throttle butterflies spindles have negligible movement thats great news, so the air leaking is elsewhere.
Just an obvious thought, have you checked the throttle cables are free AND properly adjusted as they are a dual pull system. You could try running the engine with them disconnected and just operate the carb spindle cam manually, to see if the idle speed problem still exists.
What year is your AT as the carbs vary somewhat depending on year.
 

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Discussion Starter · #14 ·
I didn’t mention, both plugs from same cylinder.
I installed old main jets, they are 115. And yes, we like to burn oil, nothing abnormal. She takes what’s se needs :)
It’s time to find repair manual, because never had or used it.
 

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A manual is a 'must have' when doing Carburetor or engine work. Strange how the plugs look so different from the same cylinder. Did you give the bike a journey before removing the plugs? What do the rear cylinder plugs look like?
 

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Discussion Starter · #16 ·
Its from rear cylinder.
Found something interesting today again

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rear cylinder choke hole been with paper inside ..
 

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Is the choke hole seat or choke plunger damaged as this may be the previous owner trying to block off the port. It should look like my previous photo (repair in place).
Its amazing what you find when you really look at everything on the carbs, which is why it is necessary to make sure everything is ok before changing needles jets etc.
 
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