Jetting Recommendations

[Greg]

Hey guys. I am looking for some jetting advice.
I do not expect to get the right jet on the first shot. I just want to be in the right ballpark when I go to fire up my BBK.
Oh, also, I'm being extremely cautious to try to avoid what happened to Benny's kit over in the 2 stroke forum on SD.
Here are the particulars.

Jonway YY50QT28A, 50cc 40QMB minarelli
Autotech355 47mm BBK
Stock expansion chamber/stinger type exhaust
Free flow air filter
stock reeds
stock carb - made by TK Japan

My stock main jet is 68
I bought: 6mm DelOrto compatible jets in sizes 75/78/85/88

Any good educated guesses on where to start?
I can't decide.
Murphy's law will probably dictate that I will need an 80 jet because they didn't have that size when I bought them.

PS: Anybody looking for jets? I got these jets from sherryberg188 over at the bay. A buck a piece, I ordered two of each. So it came to $8.00 with free shipping from Singapore. They came airmail and took 8 days to get here. They had bigger jets, but no 70, 80 or 90.

[90GTVert]

Welcome to the forum!

Since you are going to be using a free flow air filter, I'd probably start with the 78 or 85. That's not really an educated guess though, just a guess. Without the new air filter I'd guess somewhere between stock and the 75. I've never ran a 70cc with a free flow filter so these guys will probably have better advice from their experiences. I know 190mech has the same kit, not sure what filter and jetting. I used the stock 70 main jet with the stock filter in mine and it was actually a little rich.

One note on that stock pipe, it may or may not work much like a real expansion chamber pipe. 2strokd cut a similar pipe apart and found lots of sound deadening things in there. If you have the ability to cut and weld metal, you may wanna take a look in there... assuming you are willing to increase sound levels to possibly get more performance. May not be a dramatic improvement in performance though.

That is a good deal on jets. Thank you.

[Greg]

Thanks Brent.
I did find it funny to see Noob next to my name. LOL
I have been on SD as Gsfromct for over a year now, just finally signed up here.
On a side note, I hope you are feeling better and pretty much back to normal since your accident.
Just goes to show you what can happen if you don't secure your load.
Those idiots!
Now, back to jets. I'm sure it is better to be too rich than too lean.

[shiftless]

I have 200+ miles on an autotech 47mm kit I recently put on my Beamer with no issues
I started with an 80 main, stock pilot in the stock mikuni 32:1 premix
I stepped up to an 85 and the plug read was a lil rich (I feel safer that way)

[90GTVert]

Thanks for the well wishes gs.

Sorry Skip, didn't mean to forget you. I think after seeing those Stage 6 and other name brand parts you added I was thinking you had added a different kit.

[Greg]

Skip, how is your Beamer breathing (type of air filter and exhaust).
Also, what did you start out as for your stock main?
Thanks
Greg

[shiftless]

MRP 70cc - 100cc pipe

Stock airbox with the snorkel removed
My mikuni had a 70 main stock

It breathes well ( I guess )
Gas mileage isn't great

[Greg]

Sweet pipe.
Right now, I plan on running stock exhaust to try to keep it on the sleeper/quiet side.
I'm sure in the future that will change for me as I'll want to squeeze out more performance.
Since my stock exhaust is more restricted, I'm thinking I should start with the 78 main jet.
Since I got my jets, I'm ready to put the kit in and re-jet. This 20 degree weather is not inspiring me.

[drawkward]

Yeah man I can't wait until spring arrives so I can work on the scooter all day long.

I'm interested in how the 78 main does. I was surprised that your not going to start richer than that, since you already have the jets anyways. Ya know, just to be safe.

Keep us posted, and good luck.

[Greg]

Well, my thinking is that I'm still restricted by my stock exhaust. If I were putting on a performance pipe at the same time, I would start at 85 or 88.
I have read that going to a free flow air cleaner does not require as much of an up-jetting as is needed when a new pipe goes on.

[Greg]

Well, an update for anybody interested.
I installed my big bore kit today with stock exhaust and uni filter.
The uni really gives the scoot a nice deep low end growl.
I basically seated the rings by idling for 30 minutes, but hitting the gas periodically.
At the 30 minute mark I turned the scoot off and checked the plug which looked fine. The I re-torqued the head and exhaust.
I started it up and ran it another 5 minutes.
I then took it for a ride. I bogged pretty bad at WOT with the 78 jet.

I then put in my 85 jet and took another ride. The bog is gone.
So for now I'm running the 85 main jet. I don't know if it will stay because it is 40 here today and usually my minimum riding temp is 50.
When it warms up I may need to lean it out a little.

[2strokd]

Cool, glad its running well ;D.
Yea a 78 seems a bit lean for a free flow.

[Greg]

Thanks!
Well, here is an update on my tuning.
The 85 jet took away the bog, but the scoot still felt rather flat at WOT.
Kinda hard to explain, except less throttle off the line seemed to produce more crisp power, but WOT didn't add to the power.
I honestly thought, so what's the big deal? This BB kit is running slightly better than stock 50, but I was unsure and thought, maybe my CVT tune is not where it should be and I wasn't getting max power to my wheel.
I did a plug check after a WOT run up a long hill. Plug still looked a little lean (not white, but light brown).
So I put in my 88 jet. This unleashed a monster!
Holy Fricken cow!
The long big hill I just went up with the 85 jet, I was doing 15 mph. Now, with the 88 jet I'm doing over 25.
At the top of the hill where things flatten out, I hit 45 quickly and backed way off. Normally this scoot goes 45 on a bigger downhill.
I cannot believe the difference from 85 to 88.

[2strokd]

Amazing huh ;D? Im glad your getting it dialed in better and better.
Makes you feel good when you get that sweet tune .
Take mental notes of how it runs with what so you can better tune in the future. And remember only one change at a time is always best.
Swweeet deal! I love hearing of unleashed 2T power ;D ;D ;D

[90GTVert]

That's exactly why I will spend time testing with jets in small increments once I get close. I write down my speeds (and RPM if I have a tach hooked up) from landmark to landmark (my driveway to a road or a sign or mailbox, whatever). Always try to do things quickly for the same wind etc... if you want the best results.

If I were you, I'd try a 90 just out of curiosity. You might end up back at the 88, you might see more improvement. If you're tired of tuning, it sounds like you've got it pretty close at least so no worries either way. Glad it's come to life for you. ;D