my first case reed project

Ebay "phbg needle" kits only

The fine tune will cost more than the carb but with original parts... good night i have to go aerodynamics test tomorrow or today...

mrfubs said:

im still new to tuning and all of the specifics like upgrades to a carb to make it better and such, what is a AU style atomizer? and yes i am making a case reed engine

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AU style is for reed valves and four stroke engines. The end of the said atomizer that sits in the carb, ''bore air channel'' is shaped for this type of air pulse.

The other style is for a two stroke with no reeds.

Here's a question to the OP... What are you doing about blocking off (& filling the old intake port) in the side of the cylinder???

Filling that up will do more for reducing the inside volume of the case than stuffing the case will.

I would hope that anyone doing this much work on a chinagirl would go ahead and run a moped jug for the better port options available and FAR better quality.
foureasy led the way....let's see someone take up the torch!

yeah.. I read all the way thru Foureasy's post and I'm really impressed with his work and the engine's performance... I'll definitely be looking to put one of those moped jugs on mine as soon as I can spend money again... I'm in the middle of opening up an auto shop so I can't spend too much until I know all my expenses are covered... hopefully I'll be up and running in 2 to 3 weeks.

Nothing wrong with that... A lot of people have got some really good power gains with the stock jugs. i'm sure you can get well past the 5hp mark pretty easy with your case inducted setup, and still have good street manners.

I gotta say, if you want to experiment freely and try silly things without breaking your bank, the china dolls are perfect! If you know your stuff, the cylinder can easily be ported far beyond it's stock capabilities and the sky is the limit with what you can try if you have the chops.
The single limiting factor in my opinion would be the spotty chrome lining.
But hey...For $30-35 bucks replacement cost, short service life is not as big an issue.

True, but there are some killer jugs out there that are all cast iron and others that are of mugh higher quality nikasil plating that can be adapted with a little cutting and welding to match up the tansfers... You can still make serious power with the China Girl jugs, but, you're right about them not lasting because of the sketchy at best nikasil plating.
The easiest adaptations of course are the ones that have the same bolt pattern, but if ya gotta weld and cut anyway, even that shouldn't hold someone back from making some real power from these engines... I saw what Foureasy did with his and that was impressive, but this one with the Hebo jug is insane... Now I want to look more into that setup...

I remember back in the early 80's, I was 12 years old and I was looking for a better dirtbike and I was at this little shop over here, the guy was trying to sell me this little tiny Italjet 50 saying how fast it was etc... I thought he was crazy because the bike was so tiny, but then I read an article about it in a motorcross magazine and that bike was cranking out 13 hp, then I was kicking myself for not asking my parents to buy it... You'd be lucky to find one of those still running now because they didn't make very many and not too many people knew about them, but they would easily keep up with a KX60 or RM60 back in the day.
Then fast forward to about 2005 and Blata has a 50cc pocketbike making nearly 20 hp with a top speed of 60 mph. You can still find them on ebay if you're lucky

I'd recon you'd need to go water cooled to get any where near 20HP.
But 10 HP air cooled is obviously possible. Probably 12 or 14 would be the absolute limit?

maniac57 said:

I gotta say, if you want to experiment freely and try silly things without breaking your bank, the china dolls are perfect! If you know your stuff, the cylinder can easily be ported far beyond it's stock capabilities and the sky is the limit with what you can try if you have the chops.
The single limiting factor in my opinion would be the spotty chrome lining.
But hey...For $30-35 bucks replacement cost, short service life is not as big an issue.

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I definitely agree here, these cylinders can be had for about $25 each or less so they're great for experimenting on. I get mine from ebay seller boygoesfast because he sells the cylinder with a piston and rings for $25 and shipping is about $10 so $35 for the cylinder and a new piston with rings to my door isn't bad at all. His jugs have the larger intake port that's angled a little less steep with the slanted transfer ports. As far as quality goes, I had to shave off .009" from the deck before it was perfectly flat with no low spots, but the nikasil plating was a nice .010" thick, how well it's bonded I don't know yet, but it's definitely nice and thick. You do have to cut out the nikasil that overhangs past the ports tho and re chamfer the ports but that's not too hard to do with a pencil grinder and some diamond coated burrs. The nikasil is also really smooth so honing the cylinder before running it might be a good idea as well to get the rings to seat properly.

Now for aftermarket jugs, I'm still very impressed with the performance of the Hebo. I was watching other youtubes where others were using these on their scooters and the power and sound is just amazing... Lots of power wheelies when it hits the pipe. I'm definitely gonna get a few of these to play with as soon as my money is free'd up so I can spend some of it. I gotta hold onto as much of it as I can right now until I get my shop opened up then it'll be fair game. The Puch Athena jug also makes wicked power on these bottom ends, but don't sound as good as the Hebo or make that kind of rpm.

I got a table top lathe over here and pulled my original crank to check it and it was over .020" runout, then I used the prybar method to true the crank and the flywheels were way off so bad you could see them moving back and forth in the lathe as it spun.
After this I used some channel locks and closed the flywheels back to where they were somewhat true spinning and isolated each crank half to bend each snout until the runout was under .002".
What I've found out is that the cranks are pressed together at the crank pin but they're not pressed in as tight as you'd think, most likely the interfearance fit is too loose from the factory so after the crank is trued by prying on the flywheels, you can actually separate then or they'll actually move on the pin. The fix is to simply weld the pin to the flywheels so you want to be sure you have a good bottom end bearing in there before welding the pin.
Once the pin is welded in place, there's no going back so you also want to be sure that the flywheels arelined up as perfectly as possible, and you have a good bottom bearing on the crank pin, and that the flywheels are as parallel with eachother as possible. Once these are set, you can weld the pin.
After the pin is welded onto the flywheels, you can then put the crank back on the lathe to true it up either by bending the snouts or tweaking the flywheels if the runout is minor. Then after this is done, you can cut the outer edge of the flywheels to get them true as well as the sides. You can also turn a small amount off the bearing surface areas to allow the bearings to slide over much easier, a slight resistance is good, but it shouldn't be so loose that the bearing just slides right on. You can also correct the bevel on the gear end if the gear is sticking out too far and not fully engaging with the clutch gear.
Once all this is done, then you'll be ready to balance the crank and it'll be ready to reinstall with a LOT less vibration.

The reason I say to weld the pin is because if you can correct the runout by just moving the flywheels by hand, it'll be true, but under the stress of higher torque and rpm, it'll just move again after installed. Welding the pin does make it impossible to replace the low end bearing, but when cranks are $25 or less it's justifiable if you get a few thousand miles on it before needing replacement. Welding the pin is not uncommon when building up a high performance Harley or Buell because the same thing, the pressed in crank pins are more stable than the bolt on pins, but they will move with the added torque and inevitable vibrations you get with a single cylinder or V twin. the weld can easily be done with a TIG welder without overheating the beraring and you should be able to weld all the way around the pin in one pass before the whole thing gets too hot.
I've also made up an aluminum block that's milled the same size to fill in the gap in the flywheels for reassembly, this combined with getting the bearing journals to where they'll slide over with a lot less force will keep the crank from bending during reassembly.

I would also pay more for a true crank if anyone was selling them, I've done one of mine and there is a lot of work involved to get them true, and to make sure they stay that way during assembly and after the engine's been run hard.

For the Hebo cylinders, the cylinder reed configuration is definitely the easiest way to do the swap, a little case stuffing might be needed tho, but going case inducted isn't that hard to do by putting the reed block right behind the cylinder between the case bolts at the base. There's also a LOT of room underneith the engine to add a reed block if it doesn't interfear with mounting the engine, and it's possible to even mount a reed block on the side of the case on the gear side, but the flywheel may block off the intake flow too much if you went side mounted.