Hey guys quick question, I live in southern Indiana and im going to taylor park, colorado july 24. 9000' plus evevation is what Im told. Bike is a 13 and has RB head mod and carb rework. What have you guys had luck with out there jetting wise? Ill take a few different sizes with me for back up but Id like to have the bike jetted before we leave hone. Thanks
300 jetting advice for colorado??
- Thread starter andykr87
- Start date
General consensus (after a quick google) seems that a 165 main jet will get you by from 8000 to 13000, which can happen easily. I think the top of American Flag Mountain is 13.8k, if I remember right.
If you want to dial it in perfect then you'll need a pile of needles, pilots and mains and spend your entire trip messing with it.
When I was at Taylor Park I ran a 168, N3EJ (lean even up there on my 2000) and a 38 pilot. I'll say the pilot and main were acceptable but that fat needle interfered with definitive results. When I go back, I'm going to try a N3EW which I have on hand or order an NEDW because I am in love with the Suzuki needles. With this set up my bike didn't smoke a bit.. not even a little, so probably not a good thing.
Having said that, from what I gather the newer bikes with the AS2 carburetor might benefit from a leaner needle so the J diameter could be right on the money. I have to go at least one step richer on needle diameters due to my older carb design.
If you're looking for quick and dirty, I'd drop the needle a slot or two (depending on your current elevation?????) and go to a 165 on the main and call it good. Your pilot will be fat but that never seizes motors.
If you want to dial it in perfect then you'll need a pile of needles, pilots and mains and spend your entire trip messing with it.
When I was at Taylor Park I ran a 168, N3EJ (lean even up there on my 2000) and a 38 pilot. I'll say the pilot and main were acceptable but that fat needle interfered with definitive results. When I go back, I'm going to try a N3EW which I have on hand or order an NEDW because I am in love with the Suzuki needles. With this set up my bike didn't smoke a bit.. not even a little, so probably not a good thing.
Having said that, from what I gather the newer bikes with the AS2 carburetor might benefit from a leaner needle so the J diameter could be right on the money. I have to go at least one step richer on needle diameters due to my older carb design.
If you're looking for quick and dirty, I'd drop the needle a slot or two (depending on your current elevation?????) and go to a 165 on the main and call it good. Your pilot will be fat but that never seizes motors.
frankinberg
Platinum Level Site Supporter
Col jetting
I have 2 300 gasgas with rb head and carb mods I run 42 pilot 175 main jd blue needle in the 2nd clip from the top good up to 12000' in summer
I have 2 300 gasgas with rb head and carb mods I run 42 pilot 175 main jd blue needle in the 2nd clip from the top good up to 12000' in summer
coopernicus
Platinum Level Site Supporter
I have a '14 300 with an AS2, "stock" head (it was replaced under warranty before it was started), stock carb, stock pipe/silencer, Mylers radiators, and stock 48T rear sprocket. I went to Taylor Park last year about that time running pump gas, number 8 slide, NEDW on second clip, 48 pilot, 168 main, air screw about 1.5 turns out, and map switch on "sun mode". It worked great but extended clutch work up hills after waiting for the riders in front to "clear" did get it to spit a couple of times so I would say it was a touch lean in the mid range. Frankinberg is very meticulous with his jetting so if you match his configuration (2011 300 with RB Mods, AS1, and 51T rear), use his specs as he has the best running bikes. Right now, I am running the NEDH instead of the NEDW since I am riding lower altitudes and I went to a 49T rear sprocket. As for other things, it will rain at some point in the afternoon and get cold when it does so something waterproof (or close) and warm dry gloves in your pack. Bring more fluids and some calorie dense food as your body will burn a lot trying to get used to the altitude. Also, please note that Colorado had plenty of snow this year and the trails will not be open for some time. Your dates should be fine but snow melt may linger later in the season than normal!
Eric
Eric
Can I buy just that blue needle from JD or will a suzuki needle work as well?
Ok, The group we are going with has been there a bunch so we are in good hands. It cooper bailey and his dad from texas plus a few others. They are hardcore some ive gotta get my big girl panties on for sure. Im an A level enduro rider so im looking forward to the challenge and trails.
frankinberg
Platinum Level Site Supporter
Just remember with the rb design carb mod your jetting is a lot richer than stock I live and ride in Colorado don't go with the standard jetting you will be way to lean I have 5 gasgas bikes mine are all dialed in if you can find a jd blue needle you will love it
With RB designs carb kit you have greater sensitivity on the air screw - I think stock setting is like 3/4 turns out with his mod. You need to ask what the air screw setting is for the RB design carb setup in colorado. Start out with same idle screw setting as well - (how many turns "out" and it should not be 'coil bound').
You will be able to adjust bottom end for very large altitude changes just turning air screw on RB designs carb setup.
Also - with some needles (and some that work very, very well) you run a richer pilot along with it.
jeff
You will be able to adjust bottom end for very large altitude changes just turning air screw on RB designs carb setup.
Also - with some needles (and some that work very, very well) you run a richer pilot along with it.
jeff
I would like to hear some thoughts on this. I have done this to many bikes successfully.
coopernicus
Platinum Level Site Supporter
You know, I really did not want to believe that going up on the pilot at our altitudes would help but it does. I conducted repeated tests with and without RB mods on a 250 and 300 using multiple needles. Surprisingly, on my 250, the best low end was with a 52 pilot (AS1), an N1EE needle, number 8 slide, a Boyesen Rad Valve with carbon reeds, local tuner head mod, and the reed spacer removed. It jumped off the bottom as strong as a 300 and then fell flat on it's face due to the rich taper and could never tune it out. I believe the lesser atmospheric pressure at our altitudes will not "pull" enough fuel at a given RPM through a pilot jet (remember, it is all about orifice size, pressure, atomization, and timing of the atomized fuel getting to the combustion chamber). A larger pilot gives it access to more fuel to offset this weaker vacuum in the carb. The end result is that a larger pilot does work at higher altitudes.
Eric
Eric
This was done in Denver? You're only 500 or so feet higher than me and I'm running a 42 pilot.. That is the fattest I have, I believe. Time to pick up some more jets and see what happens. Although the 50cc less displacement of the 250 could probably have a measurable difference on how strong a vacuum it generates.
I have no intention of having a carb mod done, but I won't be surprised now if a fat pilot gets me hopping along even faster than before.
I'm curious, if several step ups are taken, if I end up back on a W diameter needle to get a better transition coming off of the pilot. I know after going up and down from the 172 main the NEDH and 172 are very happy together so I'd hate to start over on all that.
Anyway, didn't mean to hijack, but this definitely provided some interesting insight.
Last edited:
adriano.ro
New member
Removing reed spacer,gain some quick response,torque? Where do you feel more difference,bottom,midrange...? I have 0,5mm one.
coopernicus
Platinum Level Site Supporter
I had the carb mod and I don't think I would do it again. Please remember that all bikes will differ a little if they are the same configuration. Additionally, we don't have much riding at Denver's altitude as we tend to ride at 9000 feet +/- 2000. I ride with Frankinberg and our bikes our tuned and geared differently. We differ most with pilot and main but I ran the JD Blue needle most of the time on my 250 with a 50 pilot, #8 slide, and 165 main.
Eric
coopernicus
Platinum Level Site Supporter
The only difference that I was able to feel was on the bottom as soon as I opened the throttle and nothing more. I called it "improved throttle response" but I would not say it made any difference anywhere else in the powerband.
Eric
Zman
Platinum Level Site Supporter
While the specific jetting suggestions may be close, you need to remember all bikes are slightly different and you need to jet your specific bike for the riding conditions. I am pretty sure your base jetting is different from other bikes so you need to work from your base line.
Assuming similar riding temperature ranges, I have found that dropping the pilot and main jets 1 size worked well for 6 to 9k ft worked well and drop 2 sizes and drop the needle one clip for 9K to 13K+. After you reject you will need to adjust your idle and idle mix as well.
Regarding the question on increasing the pilot size. It helps compensate for a weak vacuum signal like many GG engines have with large squish and big 38mm carbs on 200 cc and 250cc engines. If you already have the squish and carb mods done it should work out well as indicated above.
You can also help increase the vacuum by adding a little ignition timing.
Assuming similar riding temperature ranges, I have found that dropping the pilot and main jets 1 size worked well for 6 to 9k ft worked well and drop 2 sizes and drop the needle one clip for 9K to 13K+. After you reject you will need to adjust your idle and idle mix as well.
Regarding the question on increasing the pilot size. It helps compensate for a weak vacuum signal like many GG engines have with large squish and big 38mm carbs on 200 cc and 250cc engines. If you already have the squish and carb mods done it should work out well as indicated above.
You can also help increase the vacuum by adding a little ignition timing.
