I think I'll start at the carburetor and work my way into the engine I took off the carburetor and already see a problem the intake manifold is blocked a bit by some kind of gasket sealer things typical to these engines this is why I never run one right out of the box...
For the first mod I'm going to do the petcock delete this mod helps feed the fuel to the carburetor the petcock is highly restrictive and after modifying the engine it will definitely starve for fuel all I do is take a 1/8 drill bit and drill all the way through the petcock.
The wide mouth carburetor mod this mod helps with flow and cuts down on turbulence that slows the air intake down I just grind away at the mouth of the carburetor and then smooth it out with my Dremel and some sandpaper.
You definitely have to rejet the carburetor after doing this mod...
If you go in to deep and mess with the slide area the carburetor is ruined doing anything to the back side of the carburetor is also a bad idea.
I wouldn't want to forget to open up my float bowl 🥣
The old carburetor is a little different then the 2019 carburetor that I have I bent the forks so the float shuts the fuel off just right before it over flows it might over flow and I'll have to readjuste it but I want to make sure I maximize the amount of fuel the bowl can hold
Spent a little time slightly changing the tip angle of the needle then polished it by gently putting it in my drill and spinning it with a rag with mother's metal polish then I raised the needle up by putting the E clip on the bottom slot (not pictured) on the slight chance the stock jet might work ( probably not but there is a chance) then I put the carburetor all back together.
I opened up the intake manifold so the fuel can charge properly through the reeds then I carefully rounded all the edges off the back side of the Reed plate you should not have any rubber on this side then I laped the intire plate flat ( this part is stamped and sometimes will have a warp to it ) then I de flashed the Reed stop shortened the tips just a tad and changed the Reed stop angle a bit so the reeds can open a little farther
Took off my pull start wow it came with a aluminum starter pawl that's cool
And I got the flywheel with the long fins that's cool more cooling I'll remove 6 fins to lighten some of the rotational mass
What's not cool is they did not thread the holes used to remove the flywheel I'm going to try and pop it off but I might have to cut into the 20$ budget and buy a metric tap and do it on the engine or thread it with the american standard taps I have will see how this is going to go...
I did it it's pretty obvious how I did it by the pictures but what I did is I heated it up as hot as I felt comfortable getting it with a plumbing torch ( glue starting to smoke ) used a flat bar and applied as much pressure as I felt comfortable putting on it then I gave it a whack on the long bolt I threaded into the crank!!!
Well I decided to work on it a little bit more in my main concern is the crank bearings the crank bearings always feel smooth when there in the case and you spin them with your finger they do not show their true colors until you take them out 😜 use Dawn dish soap and rinse them in the sink once you do that you will feel the grittiness... The bearings that came in my engine are CCE 6202/P5 I did a search on Google and found them on Alibaba for 2$ eatch good ones SKF from Napa are almost 8$ eatch that's a lot of money if your budget building plus my engine is brand new never been run so I'm going to attempt to smooth these things out and I'll tell you how
First get the bearings cleaned out really good with Dawn dish soap Rock them back and forth under the running water experience the grittiness as you roll the Chinese bearings.
Step two get the mother's mag wheel metal polish just dry them off a little bit you want a little bit of water still left inside then pack in the wheel polish.
Now it's time to spin them up I use the air compressor if you don't have an air compressor you can use your Dremel tool with the buffer wheel on high you will notice the mother's polish starting to turn black that's how you know it's working.
Spray in some WD 40 spin them some more
Go back to the sink and rinse them out with dish soap again
How do they feal? If they still feel gritty repeat these steps until they start to smooth out.
Once they feel good soak them in gasoline and shake them and make sure you get all the Polish out.
Spray WD-40 inside of your polished bearings and put them in a Ziploc bag so nothing gets into them.
This method will improve the stock bearings they're never going to be as good as premium bearings but every little bit helps
It's time to figure out my balance factor so I know how much I can take off the piston and crank shaft counter balance without converting my rotational horsepower into vibrational horsepower for today's challenge I mean crank stand we have 2x Rice-A-Roni the San Francisco treat and 2x paper mate pens
Time to calculate the balance factor
Weigh the connecting rod small end
Weigh the total reciprocating Mass
( that's the piston, rings, wrist pin, wrist pin bearing and wrist pin keepers with the connecting rod end )
17.54 + 87.05 = 104.59
now you have to make a balance stand out of anything that you happen to have available to you 😉 notice I just use some food boxes out of the pantry and a couple ballpoint pens taped to the top of them.
Set the crankshaft connecting rod set onto the stand then make a hook out of a paperclip hang it onto the wrist pin end hang random nuts and bolts and things onto the paper clip until you can turn the crankshaft and it will stay in its place in any position.
This is going to be your hung weight
Now what you do is is add the connecting rod weight to the hung weight
17.54 + 13.51 = 31.05
Now you take this number and devide it by the reciprocating mass
31.05 / 104.59 = .29687
Now move the decimal over two places for
This is bad news for me the realistic goal would be 45% with 50% being optimal to achieve that I would probably have to take a lot out of the piston and the wrist pin and add some tungsten to the crankshaft counterweight then fine tune it on the flywheel but this is a budget build so what I'm going to do is I'm going to go ahead and modify the crankshaft counterbalance lighten and change and modify the Piston skirt and add some windows then I'll reweigh everything and fix it on the flywheel by drilling holes threading and JB welding in slugs of steal bolt
That balance factor is insane.
Mine isn't much better though on the 12mm engine. I've got 39%.
I've already lighten the piston.
I haven't lighten the wrist pin yet.
But that's not gonna change the balance factor by much unfortunately.
unfortunately it's the luck of the draw it's pretty obvious that the Chinese don't give a crap about the balance factor it looks like mine has a abnormally thick wrist pin I also know that when they make the Pistons they like to throw a lot of brass and other junk metals into the vat making the Piston heavy further throwing off the balance factor
I'd love to get a genuine Robin/Subaru NB411 to compare to these HuaShen copy cat engines
Yes it seems like that.
It would be a fun comparison.
My 40mm engine got a balance factor of 45 but I haven't lighten the piston yet.
But if I take of 2 grams it would just get a balance factor of 46%.
How bad are the full circle cranks? 10mm wrist pin.
Drilling some holes and fill with epoxy would make the fcc better. But if it's to much off it won't be good anyways
Budget builds are most likely on everybody's mind. The real question is what did you buy this engine for originally?
You can blow most of your budget just on the purchase. I understand that you're basically just cleaning up and balancing the motor. With just labor and time and no other parys incolved.
You could buy one of these motors for $100 not put any money into it or sometimes you can pick these motors up for $40 and you're in the golden Zone for anything you want to do, no other parts or replace some very important items.