NEEDLE VALVE SET REPLACEMENT
Reason for changing the STOCK needle float valve set
I own a 2000 Silverado, and love this bike. Shortly after I had the bike broken in, I decided to see what our rides could do flat out. Well at just under 100MPH, the bike stuttered a bit and began missing. I attributed that to the “REV LIMITER” kicking in. To make a long story short, this spring, still with the same bike, but now with Samson Shogun 2 ¼ inch full pipe system and Küryakyn twin velocity breather, perfectly jetted, I seemed to be hitting that so called REV LIMITER earlier. This caused me to investigate this problem further.
After sacrificing ride time and some cash, using my own ride as test vehicle … You can read the post to follow the history;
Here is the conclusion. Our Mikuni 40mm CV type carburetors have a 2.0 flow size needle valve set. This corresponds to 2.0 mm hole size, which also equals a 200 DynoJet size. Once you add up all the orifice sizes that fuel leaves the bowl from and compare it to the only entrance size of the needle set, you find that the MAX inlet capacity is just a bit under sized to the MAX consumption limit. Most will never run there ride in this situation, therefore will never “starve” the bowl. But, anybody who’s modified there bike requiring increasing the fuel capacity to the engine, i.e. larger jets, should strongly consider replacing the needle valve set of the carburetor bowl. We re-jet the carburetor to make sure our fuel mixture stays correct, in order to maximize the performance and to NOT lean out the engine and endanger it, but we forget another component in the fuel delivery system, maybe as important, if not more, the needle valve set!
Ah yes, as a BONUS, if you swap the needle valve set with this larger one, the fuel pump becomes unnecessary! That’s right, you don’t need it anymore.
I would like to also mention and give a special thanks to Joel (Odo) Parker for his help and assistance in double testing and confirming the test results.
#2.3 13370-07F00(Suzuki p/n) (old p/n 13370-19E00)
#2.5 13370-08F50(Suzuki p/n) (old p/n 13370-08F00) ← This one recommended.
Yes these are Suzuki part numbers, but or carbs are manufactured by Mikuni, who also also makes carbs for Suzuki and this needle valve will interchange with ours. The 2.5 is recommended for running with NO fuel pump.
Note: Depending on your bike set up, carburetor bowl access may require you to remove your carburetor from the engine.
1. Shut off the tank fuel petcock and then drain the carburetor bowl. Remove your air filter, if required, to gain access to the bowl (float chamber) of the stock carb. You may need to loosen the carb heater (item 2) with a 10 mm deep socket, in order to swing the electrical ground tab (item 1) out to allow the cover to come off.
Bottom View of Carburetor
2. Remove the 4 holding screws.
Bottom View of Carburetor
3. Remove the float holding screw (arrow). Be careful not to drop the pivot shaft (item 2), it can slip out easy. Be very careful NOT to loose the needle that will come out with the float assembly tab. Carefully put the float away making sure NOT to damage, scratch or bend the TAB on the float assembly.
Floats Reference, Bottom View
4. Remove the needle valve body by removing the retaining screw first. The brass valve body will not fall by itself, you will have to pull it out with needle nose.
5. Moistened the o-ring on the NEW needle valve body with a light oil or Vaseline. Carefully push it in the carburetor. Fasten in place with the retaining screw, DO NOT OVER TORQUE! Snug is good enough.
6. Reinsert the float assembly with the new needle. It should slide in easy, do not force or fight with it. DO NOT OVER TORQUE the holding screw for the float shaft.
7. Re-install the bowl cover making sure both o-rings (item 1) are in place and not damaged. Again, tighten the bowl cover holding screws snug; do not over torque as you may strip them. You may want to get 4 NEW M4-.7mmx10mm screws, depending on the shape of the ones you have. If you’ve already rejeted your carb, you probably have already changed out the stock Phillips head screws.
8. I would recommend, especially if going pumpless is desired, to remove the plastic screen mesh in the gas inlet spout of the carburetor. Remove hose (item 1-PIC 1), screw in the spout (PIC 2) a small wood screw until snug, and then pull it out with pliers, with the plastic mesh. Reconnect the fuel line.
Fuel Line Into Carb
Fuel Spout on Carburetor
9. THIS IS THE MOST IMPORTANT PART, make sure to set the bowl level correctly, as per Mr. Tidy’s procedure on the Road Star Clinic;
If you’ve removed your carburetor from the bike, it may be just as easy to set the float bowl right on a bench (or kitchen counter as I’ve heard some do, lol), with water. You want the fuel level distance to be anywhere within a 2 mm gap from the bowl seem down, on a level standing carburetor.
This is the recommended setting for 99-03 Road Stars ONLY. 04s and higher have their float level set higher than the mating surface. If you have an 04 or later model, check the service manual for correct float level settings.
“Float level can be too high or too low and that effects any, or all, jetting parameters. A high fuel level richens the mixture and a low level can lean it.” – Extracted from an article here on the Clinic by Ken "The Mucker" Sexton.
10. Once done, don’t forget to tighten up the heater, BE VERY CAREFULL not to over tighten. The heater is hollow and made of brass, it can snap very easy! Snug is enough.
EDIT NOTE: If you are going pumpless, route the fuel line carefully away from the cylinders to avoid line melting. I used the spring wrap from the stock fuel line and wrapped it from the carb up to the petcock. The important thing here is to make sure the spring wrap covers the part of the fuel line that could potentially come in contact with the cylinders.
You are now done! Enjoy the ride and ride as hard as you want, you will no longer get stutters at WOT (wide open throttle) as the fuel can now enter the bowl at a MAX rate slightly higher than the MAX demand from it!
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|Using the Griz inlet valve|
Written by HoseDog, on 08-16-2013 17:03
I am using it(may have been the first to do so) with cap vented & stock petcock. Have SpeedStar pipes, air & jet kit. Did have to raise the float level a little higher than stock, but now runs great under all throttle conditions.
|better neele valve|
Written by compman, on 12-05-2012 23:28
The needle valve from a 660 Grizzly part number 5KM-14190-30-00 has a higher flow rating of 3.0 and is the only one that I found won't starve the motor on an extended high speed run. The Suzuki part with the 2.5 rating starved on mine even without a fuel filter and the vent in the gas cap removed. Once I installed the bigger needle the problem went away, I even have the higher 4800 rpm rev limiter on my 2003.
|Gas Leak Related|
Written by Ready2roll, on 07-11-2012 08:54
Hi. I have had my 2000 Roadstar for about 1000 miles. I did not know it had a fuel pump system when I bought it. Don't like the "leave you on the road factor" so have been looking on the web for a solution. Recently, after a 50 mile ride, my bike started to leak fuel out of the nipple on the carbon cannister of the AIS system(california model). The leak would not stop. The bike would also only start if I gave it full gas (like it was flooded). Anyway, I removed the AIS system (another acticle on this site), the bike ran but still started the same way and would not idle properly and eventually stalled out. I poured some carb cleaner in and went for a good ride. Seems to work OK now...I think that some bad gas caused all my problemsbut at least I am ride of this system.
MY REAL QUESTION is, after reading on the fuel pump removal, do I need to do a rejet of the carb and gas cap venting for the bike to run without a fuel pump. In other words, what are the minimum steps I need to take to run without a fuel pump. I don't feel I need more flat out perfomance (rejetting) and I am confused with the gas cap venting as the tank is already vented. I was just going to remove the fuel pump, reconnect and see what happens but I thought I would put the question out to someone who may know, first. Hopefully someone out there has done a simply fuel pump extraction. Thanks.
Written by pastornj, on 06-11-2012 19:56
No, I haven't vented the cap as the stock vent tube is routed cleanly and working and I don't relish the idea of smelling gas through the cap. My current setup works great with the fuel pump mounted under the front of the tank, filter inline, float level set to '04 level.
Written by Gram, on 06-08-2012 20:11
Did you vent your fuel cap? That's probably betters than a high flow petcock. I know a lot of people that have done this mod, but all vented their fuel caps.
|not a perfect solution|
Written by pastornj, on 06-08-2012 14:49
We tried this - using the large fuel valve from a Grizzly and found that it worked well except in 3/4 to wide open throttle situations. I could literally feel the bike running out of fuel at sustained open throttle settings. Reinstalled the fuel pump - under the gas tank this time, and all problems vanished. It seems that unless you install a high flow petcock this solution isn't really viable.
Written by Fiddlekop1, on 05-02-2011 07:47
I have a 07 RS 1700 and at times while cruising at around 65 or 70 mph I hear a sound like i've open up the throttle giving that deeper air intake "bogg" sound. Im wondering if this is normal or a problem. Any help would appreciated
Written by kc0106, on 04-06-2011 13:56
pump gone good riddance looks great runs even better it was easy too thank you so much i'll tell more later getting back on the bike now
|NEW OWNER OF ROADSTAR|
Written by mikey mac, on 03-25-2011 19:42
FOUND YOUR WEBSITE TODAY,LEARNED ALOT.THANKS.MIKEY.
Written by ricardoroadstar, on 10-19-2010 06:58
If I go Pump less, where do I install the carburetor choke nub??? I'm going STAGE IV
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