Beta Jetting

[Saffa]

I'm in the UK running standard UK gas 95 octane.. I don't see how this chart can be correct all around the world when there is such a difference in gas like compared to USA

[GMP]

With my 10%+ ethanol fuel at sea level the chart is about right, maybe a hair rich but OK using the stock series needles, so I doubt your lean unless your fuel is worse. Check if your PV is adjusted out too far, that will make it open fast and hit harder off the bottom.

[garrett]

I had a chat with a fellow at JD Jetting to clarify a few points from their info sheet. He told me the Beta (or maybe all 2 strokes) has little vacuum off idle so the bikes need to jetted a bit richer down low, which is why JD provides a 38 PJ compared to the 35 that comes stock. He went on to say this lean condition disappears quite quickly as the throttle is opened and why they pay special attention to their needle tapers. He also told me the Beta is quite tolerant of altitude and that I should use 15 degrees Celsius or 59 F as a baseline from switching from the blue needle (rich) to the red, (lean) needle. He also said, OR if I wanted a little bit more of a snappy response I could leave the red needle in, so I went with the blue for the break in, and will switch to the red once spring arrives. I also took the carb off and checked the float level and it was set to close at horizontal from the factory.

Garrett

[GMP]

While the JD needles are the answer in some bikes, in the Beta its not really neccessary. The dias are far apart between the Blue and Red, and there is no 1/2 clip option if needed.

[garrett]

Hi Glenn

When do you start changing jetting for temp? All other things being equal, that is. I realize there are humidity and fuel issues.

Garrett

[GMP]

If your running the stock needle family the chart is not bad as a guide. With the Suzuki needles, NEDJ in mid spring to mid fall (60s) and NECW when cooler. One up on main and adjust air screw. The NEC* is leaner longer off the bottom so you need to be aware of lean symptoms when it cools off. This is just what works for us on the 300s here, but it should be close.

[nevermind]

The NEC* is leaner longer off the bottom so you need to be aware of lean symptoms when it cools off.

Can you iterate a couple/few of those symptoms for us un-educated tuners?

[Clearvu1]

A lean condition on the bottom will cause the engine to run hot and idle poorly. The bike might surge then die when you try to ride off, but that's extreme and more likely due to an air leak. If the bike needs to have choke in order to idle properly when fully up to temp it's lean. Unfortunately, the best way to fine tune your engine is to read your plug, and often. Get a new plug, install it, run the bike up to temp at idle to very low rpm. Maybe ride around the shop in 1st to 2nd gear at low rpm until fully warm, then pull the plug. If it's dry and discolored it's likely too lean and needs a bigger pilot. Now, get another plug and do it again at low to mid rpm. Look at the plug, if it's wet you're rich and need to drop the needle or try one with a leaner taper like the NECJ referenced by GMP. My personal experience with the '16 250RR is that it's almost impossible to get dangerously lean on the bottom. With the stock 35 pilot (pretty lean to begin with) and the stock needle in the 2nd position (also a lean setting) the bike was just a little blubbery (rich) off idle, a condition I could not tune out with the air screw. I'm at 600' asl and riding in 65-85 temps. With the stock jetting the bike did run hard and I felt a need to turn the PV in to make the hit less abrupt. After reading some of the jetting threads here and elsewhere I decided to try the NECJ, I even had one in my tool box. I used the middle clip position (3rd) and made no other changes. The blubbery condition is smoothed out and the bike carburates smoothly from idle to open throttle now. It's subjective but the mid might be a little more tame than before but the bike still makes plenty of power. I've actually turned the PV back out to add a little hit back into the engine. For me the NECJ has improved the engines performance, especially at lower rpm, which makes the bike more manageable in tight and technical riding. It still scares the hell out of me at WFO so I don't need anything more there. The 300s react differently then the 250s and may not produce the same effect.

[nevermind]

I tried the NECJ and various size pilot jets and it was always annoyingly blubbery off the bottom. I've got my float set as close to perfect as I can get it. I just put a NEDK in a few days ago and with the 35 pilot and two turns out on the air screw, the blubbering is almost all gone. My plug pulls have always shown the mixture to be way fat. Now that I have 20 hrs and 230 miles on it, I want to try and lean her down until I start to see lean symptoms. Thanks for your descriptions, I'll watch for the things you mention.

FWIW, I ride at 10-60' above sea level with very high humidity all the time, usually no lower than 60% and sometimes as high as 95%. Even with today's chilly air, humidity is at 73%. I heard the NHRA drag racers talking about Density Altitude and started studying up on what they were talking about. Using the DA calculators, my adjusted altitude is usually right around 3000' above sea level. Anyone else bring constant, high humidity into their jetting calculations?

[GMP]

Typo in my last post, it's NECJ in summer not NEDJ. NEDJ is 1/2 clip richer. It's humid here in summer but the J dia works well at 0-1000'. If it's lean on the dia and/or pilot it will hang idle, and possibly knock on decel.