[SOLVED] Feedback on purchase/jetting/install for going to 70cc BBK

[245luigi]

Installed the BBK this past weekend. Install went fine with 0 issues! The bike started right up on its first turnover. While I had everything apart I went ahead and installed the new intake manifold. I did not use the supplied carbon fiber reeds as another like owner on the forum stated all they did was cause trouble.

With the one change at a time mentality I have left the stock carb and airbox on the bike (for now) with no modifications except for going from 86 main jet to 95. I got the bike to idle although it idles really high right now (2600 rpm rather than 1850). In theory, how should the new bbk affect the idle and air screw settings relative to my previous set up? Not looking for exact turns but something along the likes of "the idle screw would come out and the air screw would go in". Should I go up an idle jet size? Currently it has a 35 IJ, I have 38 and 40 on hand.

I live in the city so I did all the work at my parents house over thanksgiving and they have kindly allowed me to leave it there. I tuned the bike so it could at least move without issue. Engine has been run ~1.5 hrs total in the 2000 - 6000 rpm range (varied). Im going to break in the engine as much as possible with the stock airbox and carb, then put on the dell'orto 19mm with holes in stock airbox, then finally open filter.

Its a work in progress....

For the interested some photos of the install
http://imgur.com/a/FbcOs

Note after I put the new piston on the connecting rod I got so excited and forgot to take pics for the remainder of the install

[JJJoseph]

Current gameplan is to change the cylinder and intake manifold as I suspect it will be easier to change the manifold with the whole bike apart.

The intake manifold is easy to remove/change.  It just takes 15 minutes with the seat pan out.  I'm not sure if your new manifold will mate with the stock carb.  If it doesn't match, don't sweat it, just put the stock manifold back.  The hard part is ahead of you, trying to tune it so it doesn't overheat at WOT.  Hint: add 10ml oil per litre of gas to the gas mix while running in your new cylinder.  Try not to boot it for the next 500km or so.  It's tempting, but resist the temptation :-)

[245luigi]

Already put in the new manifold and it was made by kymco so mated perfectly

[245luigi]

Over this xmas break I have had access to the scoot again. Theres about 2.5 hrs on the engine and maybe ~ 10 miles. Having trouble tuning the dang thing! Best Ive gotten with the stock carb (16mm) and airbox restrictor/collet out (no holes in airbox) is a constant 1500 rpm Idle. Id like to get it to 1850. I have gotten the "base idle" to be 1850 but is has a "secondary idle" at 2500rpm. Meaning if it idles at 1850 and i give a little 1/8 throttle rev the rpms will come down and "hang" at 2500 for a couple seconds then return to 1850. My 1500 rpm idle is clean and crisp.

I will place my 19mm carb on the bike once i feel the engine has broken in. Do you guys think having this tiny carb on it right now is preventing me from getting to my 1850 rpm goal?

For my 1500 rpm idle im at 2 7/8 turns out on the idle screw with a 38 pilot (1 step up) and 1 1/4 turns on the air screw. I have a 40 pilot in my possession too.

[245luigi]

I wanted too add that when the bike starts cold ie autochoke on, the bike idles at about 1900 just fine until it falls to 1500 one the bike is warm

[ophelia]

You have the hanging fast "secondary idle" when blipping the throttle, a symptom of a lean idle circuit. I think you may need to turn the air screw in a quarter or half turn more. Past that, you may need to swap a larger pilot jet in and start back again at 1.5 turns out. The ideal setting range is roughly between 1 and 2 turns.

[LoveMyKymco]

When upgrading a 2-stroke, just do one thing at a time as others here have suggested.  The Kymco 2-strokes are similar to the Honda Dio, so I can suggest that you switch the jug but leave the stock carburetor except for changing the main jet from a #75 to a #90.  You can add a tuned pipe at this stage, and 9:1 gears perhaps, but that's about it.  Then ride it carefully for 500 miles or so to break it in, sticking to the original top speed.  You'll have enough fun with the increased acceleration.  The main problem with running 2-strokes at WOT is that (unlike 4-strokes) they can quickly overheat and melt the piston.  Then you have to start all over again.  This is NORMAL when tuning/racing 2-stroke scooters & dirt bikes.  You're trying to go as fast as you can WITHOUT melting a hole in the piston. But sometimes you miscalculate.  A Cylinder Head Temperature gauge is useful, more useful than plug chops.

Please dont take advice from this guy. Your engine is NOT a honda clone, it is more of a minarelli clone but not exact. It is in fact a HORIZONTAL not vertical engine style. The honda style is vertical (up and down not long ways) unless youre getting into super dio af35 styling and this engine is not that. Ive said it before and Ill say it again, if you dont know what youre talking about dont chime in with sage like advice thats incorrect and misleading.
Haarek gave you some great information and I would follow it.
thesurgeonistherobot is also correct in that your "secondary" idle is from a lean mixture, on the stock like carb the mixture screw is usually capped off thanks to EPA regs. You can drill a small hole and use a screw to remove it if it hasnt been done yet.
More than likely you have an air leak somewhere tho. I would lightly try to turn on the intake bolts and maybe the cylinder bolts, then check for a great connection to the carb. Always make sure to have a perfectly clean mating surface also when installing those intakes. I personally like CF reeds over fiber glass ones but I also change my reeds often.
Sounds like your like is on the way to being liked more!

[245luigi]

So I have in fact checked for air leaks and have found none. I have tried going in 1/4 turn on my stock carb (I removed the cap a couple months ago). I havent touched the bike since I last updated so now im starting to forgeth what I did. I do remember that the bike idles low (1500) and for the life of me cant get it to come up. Next time im home to work on it hopefully itll be warmer so its not acting so funny either.

FYI I have to stock carb (16mm) and stock airbox (no holes but intake collet is removed). Setup OK?

Love this new torque!

[LoveMyKymco]

I would just get the 19mm fitted and tuned rather than doing this tuning also. If no leaks and its hanging up then its pilot circuit is too lean and you have a larger pilot jet so you can just pop that in there and see how it goes. Also I clear out the cylinder in between pilot jet swap. Usually a good mid throttle running for 20-30 seconds will clear it out. Then as it idles back down I adjust the idle and mix. The Malossi cylinders like to flow some air for sure.

[245luigi]

Ya I have the 19mm carb sitting in the shed with the bike. No open air filter at the moment though. Maybe if I just go a head with that my woes will disappear.

[JJJoseph]

Please dont take advice from this guy. Your engine is NOT a honda clone, it is more of a minarelli clone but not exact.

Don't listen to this guy, he doesn't have a clue what he's talking about.  You should never take advice from anyone who says they know it all like this blowhard does.  As you can see, he's not even sure what kind of engine it is, so how can you trust anything he says?  He's probably not even aware that you can use Honda Dio parts in most 50cc Kymcos, even the 4-stroke models.

[LoveMyKymco]

I do know what his engine is you turd its a mina clone, but not exactly a mina due to the slight upward degree of the cylinder. I also would like to make sure that he doesnt buy a single piece of honda parts for it since it is based off a yamaha design.
JJ is a moron, tried and true.

[LoveMyKymco]

Don't listen to this guy, he doesn't have a clue what he's talking about.  You should never take advice from anyone who says they know it all like this blowhard does.  As you can see, he's not even sure what kind of engine it is, so how can you trust anything he says?  He's probably not even aware that you can use Honda Dio parts in most 50cc Kymcos, even the 4-stroke models.

Im going to guess this guy doesnt know me at all, do some research on what Ive done for this forum and others before you try to say anything. Im a Goliath of information. He just doesnt get that that engine in the like isnt at all a honda based engine. I currently have 2 like engines on my shelf right now. Oh wait is he going to put up another pic??? Oh wow he must not have them or Know anything about them since he has pics of them.



Heres a link to my photobucket so you can look at what a real deal scooter guy does.
http://s1305.photobucket.com/user/lovemy2strokes/library/?sort=3&page=1

[Vivo]

LoveMyKymco is a guru here...tried and true... 

[Frustrated2]

Wow..I'm excited for you too Luigi. How did the install go? I'm a newbie here and really starting to pick up a lot of interesting tips. I read somewhere else on this site about someone installing a bbk. How much did that kit cost you?
I'm in two minds at the moment. Tinker with my old Kymco or simply upgrading my bike to a newer one. It's really hard to find bits and pieces over here. Japan that is.
So have you installed the kit yet?