[Kimjon]

Hi, I'm new to this. Joined last week and have been reading as much i can to learn more. I'm in New Zealand and information is hard to come by over here.

Now looking at the way the reeds face/open in the 49cc cag motor, to me it almost looks backwards? The crank rotates against the opening, the air/fuel has to come out and around the reed stop. Well at least that's how I see it???

I've done the following:

1) flipped the reed 180°, I'll use a walbro pumper/diaphragm carb.

2) milled the screw holes deeper, and the top off the reed block for clearance on the crank.

3) milled a slight angle on the bottom of the reed block, this changes it's position in the case to closely follow the crank counterweight, and will also allow the reed to open slightly further.


So; is any of this a good idea, or have I got it all arse about face?

Any input welcomed, thanks
Kim

 

[Kimjon]

FYI: I'm putting the motor on an old Go-ped Bigfoot.

It was missing the motor, and had definitely seen better days. So I don't feel to bad cutting it up and changing it up a bit. Once I finish the welding I'll paint it in 2K car paint.

I've followed as much information on porting as I could glean off this forum. And made the expansion chamber up out of an old one that I cut up, and added in bit more volume.

Photos attached:

 

[CAM2]

Hi, I'm new to this. Joined last week and have been reading as much i can to learn more. I'm in New Zealand and information is hard to come by over here.

Now looking at the way the reeds face/open in the 49cc cag motor, to me it almost looks backwards? The crank rotates against the opening, the air/fuel has to come out and around the reed stop. Well at least that's how I see it???

I've done the following:

1) flipped the reed 180°, I'll use a walbro pumper/diaphragm carb.

2) milled the screw holes deeper, and the top off the reed block for clearance on the crank.

3) milled a slight angle on the bottom of the reed block, this changes it's position in the case to closely follow the crank counterweight, and will also allow the reed to open slightly further.


So; is any of this a good idea, or have I got it all arse about face?

Any input welcomed, thanks
Kim

If you flip the reedplate you have to flip the intake aswell as you alreadyknow. If you plan on running a pumper carb youll be alot better off.............

The idea seems sound but with the way the pulses bounce around the crankcase you never know til you try it out...

 

[EPR]

throw them tin reeds in the trash, go on eBay, search, 49cc 2 stroke pocket bike parts, look for carbon fiber reeds for 8 to $10 USD. They have parts sellers direct from China w/ free shipping, might have to wait a few weeks,so I plan ahead, lol. The exhaust, hard to fit a scooter, w/a big belly exhaust, i would add a big pipe between the to big cones, 3" ??? Shorten the head pipe if you can, 3/4" ID at the head port to 1 1/2" ID at the start of the cone and shape the whole thing to fit.

 

[Kimjon]

Cool, thanks for the replies.

I ordered some cf reeds last night, strangely enough I find some locally for about $15USD that I'll get overnight.

 

[Kimjon]

The Chinese eBay order for the carburetor kit came with the wrong manifold. A week's worth of daily emails going back and forth amounted to no satisfactory solution.

Out of frustration I made my own out of the one they sent me and the factory one put together.

Think it should work... I brought the port for the diaphragm into the main body of the manifold to get some crank case pressure from the reed flutter...hopefully that works?

 

[Kimjon]

Couple more pics, here. What do you think, will this port provide a pulse?

I'm just not sure on it been on the other side of the reeds? But from photos I've seen on here of the aluminum version, it appears to operate the same way?

 

[CAM2]

Everything looks good to me....The intake adapter will work...If you use a WT series carb youll need to JB Weld the pulse hole in the drop area so there isnt an airleak.........

Only thing im intrigued to find out how much you have changed the timing of the reeds initial start of opening in relation to the transition between the upstroke to the downstroke motion to the crank counterweights and whether reed flutter at high rpms will hapen........

Thrse engines are designed for power tools like power augers,,trash pumps and generators......

The case pulses differ from a euro style engine where the reeds arent battered full on by the downstroke pulse like the chinese engine design........

 

[Kimjon]

Thanks for your feedback Cam2. I'll post an honest outcome when it's back together and (hopefully) going.

I've attacked the lower cases with the Dremel to help it flow better. Next I'll port the cylinder barrel and set squish.

I'm really enjoying learning about these motors. I've always had gopeds, but most performance was "bolt on" with hybrids and a wee bit of port matching.

Thanks for all the input.

 

[CAM2]

Thanks for your feedback Cam2. I'll post an honest outcome when it's back together and (hopefully) going.

I've attacked the lower cases with the Dremel to help it flow better. Next I'll port the cylinder barrel and set squish.

I'm really enjoying learning about these motors. I've always had gopeds, but most performance was "bolt on" with hybrids and a wee bit of port matching.

Thanks for all the input.

You're Welcome ...I'm always into what youve done here...it's like a science....lol

I'll be awaiting the results of the test....Do you have any results of a bone stock setup?

It seems the GoPed is pretty well planned designed and built....the exhaust looks killer...

One thing you'll learn is without altering gearing you can only gain so many extra mphs but you'll gain top speed in the blink of an eye with some serious pull.....

 

[CAM2]

ADA makes a pretty killer 4 petal reedblock pumper carb setup that works pretty deecently....you may want to check it out.....

 

[Kimjon]

@CAM2 I have been building the motor alongside the goped, so I don't have a baseline unfortunately.

It's more the challenge of building/learning about these motors that's driving me at the moment. I picked up the motor for about $10USD... it was full of water from been left outside, but luckily the oil in the fuel mix basically saved it. A quick wipe down and it looked ok to use (I'm replacing the gaskets, oil seals and bearings).

I do have a heap of these cag motors on other projects I've made (49cc; mobility scooter, kids gokart, drift trikes and stock mini dirt bikes), but I've only played with the exhausts to get more power...the rest is stock. I guess it's a natural progression to want to learn more and start porting etc.

I started on the top end and port matched the exhaust port to my pipe. I haven't changed the timing of the port yet as I'm not sure what numbers to use, need to do a little more research first.

Im an absolute beginner with porting, but if i make a mistake - I'll just put it down to the cost of education.

 

[Kimjon]

I brought a bulk lot of parts last night on the New Zealand equivalent of Craig's list (trademe) for about $60USD...I'm stoked as NZ doesn't have a pocket bike scene going on here like you guys have, so performance parts are hard to find here...or else we have to buy online and pay huge shipping costs.

Looks like there's some good stuff in the box? For $60USD I think it's worth the risk to buy and worry about the exact value later? Guess I'll know when it arrives next week.

 

[CAM2]

I brought a bulk lot of parts last night on the New Zealand equivalent of Craig's list (trademe) for about $60USD...I'm stoked as NZ doesn't have a pocket bike scene going on here like you guys have, so performance parts are hard to find here...or else we have to buy online and pay huge shipping costs.

Looks like there's some good stuff in the box? For $60USD I think it's worth the risk to buy and worry about the exact value later? Guess I'll know when it arrives next week.

You got a heck of a steal my friend looking you in the face....A huge deal and a half....

You'll find the FCC doesn't work as well as the stock crank...

 

[EPR]

Killer deal, buy it now, lol.

 

[Kimjon]

Awesome! Yip, brought it.

So full circle cranks aren't very good? Do they take up to much crank case volume?

 

[CAM2]

Awesome! Yip, brought it.

So full circle cranks aren't very good? Do they take up to much crank case volume?

Yes full circle cranks diminish too much volume where you cannot feed the cylinder as well as you can with a stock or heavy duty crank...

If the case was designed like a euro engine the FCC would be a huge performance improvement

I found that the higher the power the harder it is to balance the tune.....if you tuned it to start fast and easily topend power will suffer....and if you tune it for topend you'll need to blip the throttle to keep it running and from fouling the sparkplug as well as have difficulty firing it up initially without using a heat gun to heat the cylinder

I ran one cylinder with ..030" of squish...ported it pretty aggressivly,,ran it with a 40mm piston/cylinder,,stock 10mm pin crank with crank pin tigwelded to the counterweights... super lightened piston,,28 grams of balanced ballast weight added to the flywheel,,ADA 4 petal reedblock with 19mm tillotson carb and custom exhaust pipe....it free revved with chain attached to rearwheel at 16,100rpms....loaded it hit 13,700 with my 200lb *** on it....

 

[Kimjon]

Wow! That's a good effort cam2.

Would the fc crank work if I calculated the difference in volume between the fc and stock cranks, then made a spacer block to put between the case and reeds, to add that difference in volume back again?

Or is the mass of the crank also another issue that creates the next problem?

 

[Kimjon]

For the 49cc cag, is there a go-to in terms of a solid performer. Guess what I'm (probably been a bit cheeky asking) trying to find out, is there a known set of port timing figures and sizes for port area/s that I should be aiming for with this motor?

Once again; any help our guidance will be greatly appreciated, as I'm trying to avoid mistakes by asking those with more knowledge than myself.

 

[CAM2]

Wow! That's a good effort cam2.

Would the fc crank work if I calculated the difference in volume between the fc and stock cranks, then made a spacer block to put between the case and reeds, to add that difference in volume back again?

Or is the mass of the crank also another issue that creates the next problem?

Here's an easy way to explain it..

As the stock style crank counterweights spin in the crankcase it creates a way for the fuel mix to be pulled and pushed throughout the crankcase ...

In the FCC environment within the same crankcase the fuel being pulled into and pushed throughout has to flow through the center of the crank and feed the topend solely on the engines velocity while being battered by the crankrod..

In the 44mm cylinders you'll see a notch in the cylinder above the exhaust port..this is a manual compression releif notch...

Couple the diminished area to feed fuel into the transfer ports and diminished velocity at high speeds due to the compression releif notch you'll gain no more power than taking a stock 1 PC 40mm cylinder and adding a 3rd port to it and reassembling without a basegasket...

EPR has a build thread going down with a billet set of cag cases that are identical to the euro style engines.....look how the crankcase is designed...

The fuel flows straight from the carb through the Reed's and directly into the transfer ports on merit alone due to the fact they're built between 15-17:1 which enhances velocity to make power...Very little mix makes it through the crankcase on a euro style engine......

I've built dozens of engines all different ways and have tons of comparisons...

Sometimes what seems logical isn't always what's better especially when it comes to Chinese made stuff...