Split Transfer ports ?
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The best thing to do is remove the divider or you can enlarge both channels and add a 3rd boost port along with matching windowed piston...
Just know that windowing the piston in relation to the boost port will enhance bottomend torque....The more boost ports you grind the more torque you can make..
Taking the tool based engine totally apart and blueprinting the crankcase aswell as the cylinder to crankcase youll enhance velocity and reduce turbulence...
In 2 stroke you want velocity and you do not want Turbulence...…..Velocity makes power...Turbulence robs power...…..
Sharp edges inside the crankcase causes turbulence...……..Sharp edges need to be rounded and polished..
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Fantastic. I bought a stock 49cc engine today im going to strip this one and blueprint , port it. My cylinder has a 1 boost port but no window on that side of the piston.The best thing to do is remove the divider or you can enlarge both channels and add a 3rd boost port along with matching windowed piston...
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Just know that windowing the piston in relation to the boost port will enhance bottomend torque....The more boost ports you grind the more torque you can make..
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Taking the tool based engine totally apart and blueprinting the crankcase aswell as the cylinder to crankcase youll enhance velocity and reduce turbulence...
In 2 stroke you want velocity and you do not want Turbulence...…..Velocity makes power...Turbulence robs power...…..
Sharp edges inside the crankcase causes turbulence...……..Sharp edges need to be rounded and polished..
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So for my application a few more ports would be better?
What cutter do you use to cut these boost ports in the cylinder?
I will be using my Bridgeport. Also what is the best cutter to cut the window in the piston I was just going to use my Endmills for Aluminum?
How High in the piston do I cut the window?
And if I add 2 more boost ports in the cylinder do I cut 2 more ports in the piston or just cut a long horizontal window in the piston to match it ?
Do you use better crank bearings and crank seals?
Thanks again Mike
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one wide boost port keep the window small and away from the ring gap so you dont get blow by when you pump up the compershon if your going to a full circle crank your going to need to balance it to a somewhat reasonable balance factor and add some pathes so the bearings dont get oil starvation are you going to run VP 105 or Juice
I think I have someone that can balance the crank for me. Where would I add pathes to the bearings in the bottom end? I might just run the standard crank if the FC crank is problematic.
I run VP94 ETHANOL Free mixed with Castor 927 now in my RC's but if I have to run VP105 that's not a problem I will definitely get some.
I want to set my squish around .030" - .035" will I need the VP105 if so do you have a part number for the fuel? I don't see any VP105 on there website.
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I use a carbide barrelcutter on a Dremel and drill my holes in the piston by hand in my hand with a glove literally holding it..……….I chamfer and debur with a deburring tool aswell as 2000/4000 grit sandpaper and jewelers files.
I do all my work with a hacksaw,dremel,handfiles and sandpaper also 18v cordless impact gun and drill in my hobbyroom on the benchtop as it helps keep down costs over time as cylinders and pistons are very expendable and the more theyre modified the lesser they last...
The amount and type of 2 stroke oil used dictates that too..
A bone stock engine has a service life of 120hours when used as a tool based engine.......When used on rideables and modified I cut that in half off the bat and its usually pretty accurate..
So depending on how you modify the cylinder each and every subsequent cylinder after that will also need to be equally modified aswell...…
For my pocketbikes I had a whole slew of extra engines already built sitting on the shelf all built ready to rock n roll as anything can happen and ruin these small engines fast..
When you start getting over 200psi the heat generated from using gas no matter even if its VP the engine will run hot unless tuned fat and tuning 2 strokers fat doesn't make power and screaming revs....
Tuning a 2 stroke on the edge of being too lean does and that generates a lot of heat like I said and when that happens those open transferport cylinders expand hugely and compression starts to drop off staving off power...
When that happens its time to tune the engine to run on alky/methanol mix or stick a basegasket under it to get it in the .038"-.040" range so youre able to run the VP and tune to temps....
A stock engine is built with .062-.065" of squish stock with a compression ratio of roughly 8:1...…...Anything under .050" is gravy...…..
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Crank balancing is easy if the stock engine is matched right when built by the Chinese kids in China...
40mm cylinders with 40mm 10mm piston pin require an IE-40 crank to start with...…...
44mm cylinders with 10mm piston pin needs a IE-44 crank...……
44mm cylinders that have a 12mm pin needs a IE-44 HD crank
You match the parts right youll be matched for bone stock and pretty ready to run then you use a balance bar rail type setup and then you have the option of using a digital scale to prove it out to make sure it falls within proper %age after you modify the piston with windows which ultimately lightens it too but if engine is matched good when the Chinese kid initially built it then it isn't overly critical...
Its not rocket science and another way to keep costs down too in this cheap hobby...
One thing you'll want to steer away from is any form of FCC as the FCC reduces volume inside the crankcase and it also reduces the amount of fuel that reaches the transferports too....
These engines are a way different type of animal compared to a 2 stroke MX engine as the atomized mix must be fed through two crankweights with a mixing stick in the center creating a bottleneck..
If you had a crankcase like this....A FCC will become very beneficial....
Good Luck
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You need off the line power and revs,,,,Modifying the clutch can do that just fine if you want to maintain the higher revs....The more boost ports you add the more the revs reduce but the torque goes up....
Its like the same difference between a SBC and a BBC...………..
Yes I use Timken brand deep groove bearings 35mm x 15mm x 11mm and SKF or STIHL 25mm x 15mm x 5mm low drag crankseals...Theyre way better quality than the cheap Chinese rubber seals...…..
The Chinese seal is on the left and the SKF in the center and Stihl on the right...
This is what I seal the engine up with....
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For the question on the piston and hole placement...…
Alls Ill say is buy about 5-6 of them and use your judgement...……
Best replacement pistons are the better quality pistons and rings used for STIHL/Husqvarna engines
As you can see this is just 6 months of pistons that were run through 3 different bikes.
All are modded differently....
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Once you start getting into crank mods that's when balancing gets a lil involved utilizing a drilpress and molten tungsten...……
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Alls Ill say is buy about 5-6 of them and use your judgement...……
Best replacement pistons are the better quality pistons and rings used for STIHL/Husqvarna engines
As you can see this is just 6 months of pistons that were run through 3 different bikes.
All are modded differently....
Once you start getting into crank mods that's when balancing gets a lil involved utilizing a drilpress and molten tungsten...……
I have build many 2 stroke Dirt Bikes but never had to do many mods on them Built many SBC back when I used to drag race the 1/4 mile but this engine is a different animal as you say so all this info is much appreciated. Do you have part numbers on the wrist pin bearing and Pistons from Husky/Stihl that fit a 44mm bore? Again Thank you very much for all the info.Crank balancing is easy if the stock engine is matched right when built by the Chinese kids in China...
40mm cylinders with 40mm 10mm piston pin require an IE-40 crank to start with...…...
44mm cylinders with 10mm piston pin needs a IE-44 crank...……
44mm cylinders that have a 12mm pin needs a IE-44 HD crank
You match the parts right youll be matched for bone stock and pretty ready to run then you use a balance bar rail type setup and then you have the option of using a digital scale to prove it out to make sure it falls within proper %age after you modify the piston with windows which ultimately lightens it too but if engine is matched good when the Chinese kid initially built it then it isn't overly critical...
Its not rocket science and another way to keep costs down too in this cheap hobby...
One thing you'll want to steer away from is any form of FCC as the FCC reduces volume inside the crankcase and it also reduces the amount of fuel that reaches the transferports too....
These engines are a way different type of animal compared to a 2 stroke MX engine as the atomized mix must be fed through two crankweights with a mixing stick in the center creating a bottleneck..
If you had a crankcase like this....A FCC will become very beneficial....
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Good Luck
I'm going to put the FCC to the side and open up the engine I bought when I get and look to see what crank I have then order parts that I need my Cylinder says 44TM78 om one side and C9 on the other.
Ill attach a pic of the cylinder and circle the part im talking about that will need to be removed or ill jig it up and turn it on my lathe. Is this normal to have to do this to get the squish closer to what I want? Another ? What are the holes in the piston next to the wrist pin ?
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You need to remove about .060" ( 1.5mm ) off the top of the cyld where the compression cap sits with the round copper head gasket, which brings the piston to the top of the cyld. Then you need to raise and shape your exhaust port to the right height. My favorite cyld has hogged out transfer ports and one .600" to .700" wide upper port.
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I completely understand about shaving the top of the cylinder but With this cylinder if I just took .060” off the top it would not allow the head to sit any lower because it hits where I circled in my pic. I was wondering if that was normal or was this cylinder not machined correctly ? Either way I will machine it off
Because this is going in my RC Monster Truck I want more torque than high revs so I’m going to do what CAM2 has suggested.
What is the anti parachute mod and the turbo crank mod do you do this while balancing or do the crank mod and then balance ? Thanks again Mike
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CAM2 knows all about this stuff and so much more. Can't go wrong with his advice, he has helped me so many times. Head should not sit that low, put a 45 degree angle on the cylds shelf edge and inside the head OD where it meets that will give more drop. That's how I got the Polini 80mm clutch housing on my 39cc clone Polini W/C engine.
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i whouldent think you whould anti para mod the piston with a boost port if your boosting you want to send it all up the boost port.
after your finshed moding calculate your balance factor drill tap in weld in tungston to the counter balance on the crank is the best way or add it to the flywheel thats easy to tape and die some bolt steal in the aluminum.
i whould run all the fins on flywheel to get the most cooling so you can run it for a longer time without over heating ...
after your finshed moding calculate your balance factor drill tap in weld in tungston to the counter balance on the crank is the best way or add it to the flywheel thats easy to tape and die some bolt steal in the aluminum.
i whould run all the fins on flywheel to get the most cooling so you can run it for a longer time without over heating ...
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