Rattler 110, Keihin 26mm carb update

[boyjeenyus]

After trying a few different carb options, I landed on the Keihin PE-26 for around $50 on ebay from China...it came after a few weeks as ordered. This one connects with the NCY intake (which can be bought for around $30 these days). For those considering this mod, a few things to make your life easier:

-I'd assume that anyone using the NCY Intake on the 110 will need to grind/Dremel a longer grove in the intake to clear that body pivot bar thing. I had to remove a good bit of material to make it fit. It's still a little tight, so I may eventually shave away the cross bar where it's touching the intake a bit as well.
-it IS possible to get enough pull out of the stock throttle cable set up and continue to use the oil pump. You do have to take off the floor panel and access the splitter for the throttle cable up near the front. Then I used a dremel to sand down the "stop" on the case so that the swiveling piece could go farther (all the way to the side of the case) when the throttle is pulled, then sand down the stop AND the corner of the swivel so that it will relax farther in the other direction when the throttle is off as well...when I only did the first part, I wasn't able to get the slide to open all the way--there was always 1/8-1/4" of the top of the carb slide opening blocked. Then I loosened the throttle cable adjustment at the handle bar all the way, and tightened up the adjustment on the cable under the seat to the carb a good bit. Now it'll open and close all the way with the stock cable set up.

I'll probably end up with a main jet at 128 or so...I've been waiting until I got the carb to open all the way for final testing. I'm currently at 125 and was reading slightly lean on my new plug WOT chops...we'll see how it chops now that it opens properly...still feels and sounds a little lean to me at 3/4 - WOT. I'm can also see that the oil pump's cable will be a little more slack until 1/4 throttle and above. That combined with this carb pumping more fuel/air than the stock one means that I'm adding a cap of 2-stroke oil to each tank of fuel to be on the safe side.

The good news is that this mod makes the bike FAST and FUN. I can cruise around on flat ground at 50mph at 1/4 throttle and can beat most other cars on the road to 35 from a dead start. Top speed is somewhere above 60mph, but I'm waiting to really push it until I get the jetting correct. I doubt that I'll do much more modding to this scoot--it's now everything I want. I'm already using a pod air filter. Definitely the best $80 or so that can be spent improving the Rattler 110

Thanks to everyone here who answered my questions, both on the forum and in my messages. What a fun ride!
Stephen

[viney266]

Nice job!

Yeah, the carb really is a cork on the 110. Remember, a little rich is better than a little lean! Nice work.

How is the noise level with the open carb filter?

[boyjeenyus]

When I got this bike, it had a pod filter on the OEM carb, so this isn't any louder than that. Definitely louder than the stock air filter.

As to jetting, I'm up to a 140 main, which still feels a hair lean. I wonder if I'm maybe getting the wrong jets? I'm gonna keep wrenching, but so far, it's so fast that I rarely end up at 3/4-WOT anyway
Stephen

[boyjeenyus]

OK,
I'm up to a 145 main Jet, which is still probably a bit rich. There's a noticeably BOG as I go from 1/2-3/4 throttle, then it'll kinda "catch up" and run stronger if I push through to WOT. 140 still showed lean (totally white electrode to the base) on a WOT new plug chop. 150 felt super-rich and covered the entire electrode, so I'd guess that I'll land at 142 or 143, whichever is available. I have a few general jetting questions:

-ever since I've been above 125, I've felt some kind of bog between 1/2-3/4, which then pushes past to better as I approach WOT... It feels as though there's something not right as it transitions from needle to main jet. I've messed with needle height a few times, but this seems to persist--would swapping the needle itself maybe solve my issue?
-I'm using a "new-plug, engine hot, WOT for 20 seconds uphill, kill the engine, cut the threads off of the plug after, inspect electrode" method for determining main jet sizing. Is this the best method, or should I go back lower on the main jet where it seemed to ride better and ignore the WOT electrode?

It's riding well now, and doing what I want, but I hate to ride an un-tuned engine....it feels like wasted fuel and performance can't be good for it!
Cheers!
Stephen

[B02S4]

Yes, the needle profile could make a difference.

Too lean, & a 2T does not want to accelerate.
Too rich, & a 2T won't accelerate.

To me, hesitation or brief stutter is "lean", & an "8 stroke" bog is rich.

[boyjeenyus]

I've been traveling, but I'll try the method described in this article to determine if maybe my needle diameter or taper is off:

http://www.shiny-red.net/guides/keihin- ... r-jetting/

I'll report back as I tinker a bit
Stephen

[boyjeenyus]

Hey there. I've been traveling a good bit and spending time working on my CL350 rebuild, but I finally got around to researching and ordering some new needles to play with. It's finally tuned right (or at least it feels right to me). The stock needle had no markings on it, but with Keihin's help, I guessed what it was. I then ordered a few leaner needles to play with. First one I tried feels great. It's a GFK size in the middle clip position.

I had been experiencing a slight bog between 1/8-1/4 throttle, then a bigger one between 1/2-5/8 throttle. Both of these felt like "rich bogs" to me--sputter and struggling to run smoothly at those spots in the throttle whether accelerating, decelerating, or trying to cruise. I pulled the main jet (as described in the article linked above), and it would only run to about 1/2 throttle at all, then stall with the stock needle. It should apparently be able to run to 3/4 throttle with no main jet if my needle is correct (apparently). This new leaner needle smoothed out my throttle through the entire range. In my test ride, I could accelerate, decel, or cruise at any throttle position without any bogs, and it's a smooth feel. I may play around a bit more later, but for now I'm very happy!
Over and out, thanks for all the suggestions!
Stephen