New top end

DAMIEN1307

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Dserna said:
DAMIEN1307 you said the reed would help with low end?

ONLY IF you have the 80/66cc type motor, then these are the things you would need in order to not only fix your motor with a new jug etc. but to also modify it to use a reed valve...I am also assuming that your head is not damaged and hence reusable if you also get a new head gasket since I did not see a picture from you showing the underside of the head.

Be sure that you also have the appropriate bottom of the jug gaskets as well, I am not a believer in re-using old gaskets.

You will need a windowed piston for this to work for a reed valve.
If your present piston has these measurements as close as you can measure it, this one should work.
Why this windowed piston doesn't include the bearing as well is anyones guess why not...lol.

47mm diameter
45mm height
Type B high wrist pin


If your motor setup is an 80/66cc motor, you would also need this needle bearing for the piston rod that goes over the wrist pin when assembling the piston to the piston rod...


And IF you have an 80/66cc motor setup, this jug below already has the reed valve I use with my BoFeng carburetor...The stock NT carburetors will work with this reed valve as well.


NOTE:
If some of our well known members could chime in and tell us all if the bottom end on a 49cc motor is the same as the 88/66cc motor, then these recommendations should work as well...I just dont know the ins and outs of the 49cc motors to know if there is a difference in stroke which i believe is 38 versus the 40 that the larger motors are, and if there is a difference in low or high wrist pin position...Best to wait for one of them to chime in before ordering anything that might not work with your setup.

It would also be a good thing to know if your intake and exhaust ports measure either 38mm or 40mm by measuring from the center of one stud to the center of the other stud...This would also give us an insight into what motor you might have as well.
 

TheWizzerd

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Its a 47mm piston, so is most likely a 66/80cc. The 49cc are 44mm I believe.

Most 47mm jugs "should" work fine as long as you match the exhaust stud spacing. I am unsure if it varies much these days, but at one time years ago there were 2 different exhaust stud spacings. Intake doesn't matter as much as you are replacing with a reed and can buy accordingly, or the G2 I linked will work with either spacing. Preferably make sure its 40mm spacing though.

Chances are a pretty common bone stock 47mm jug will work for you just fine. But dont be totally surprised if you get one that something is off preventing you using it with your bottom end if your engine is some years old.

Like Damien said.... get new base and head gaskets too.... and you may consider an "aftermarket" head while you are at it. They are not expensive and some of them do indeed perform a bit better and offer better cooling than the stock head. There are a few that are crap though.

Also, when fitting a reed to your cylinder, you may need to file the intake mating surface flat to ensure a good seal. It is common for them to leak there if you do not.
 

Nickt919

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His pic shows a zae50 rod on pg 1
it may be a low hole piston needed

There’s so many combinations of 38 or 40 mm stroke .. high hole… low hole.
It can get quite confusing.
 

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TheWizzerd

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His pic of the piston where you can see the side a bit, and the hole location appears to be a low hole to me. Could be wrong as its not 100% clear, but seems to be.
 

Dserna

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What cc size motor do you have???...Is it what is called an 80cc motor, which in reality is actually the 66cc motor by American measurements???
Yeah I'm trying to figure out the port area of all ports now to determine the size carb I'll need. I made a quick crude port map and used a port calc. To determine what still would have to be taken off. It's a half breed, 38 mm stroke, 85 mm conrod, type a piston (not sure of exact name). Once I get it all figured out I'll make a new post with exact information. I was just being lazy earlier because I'm tied up with a lot of different work and all my stuff is packed or unpacked and not sure where it is because I just moved into a new place. I wasn't expecting this to happen so I'm in a scramble to get the bike back together. I've just been having to renovate the house I'm renting, working full time, and doing trade work on the side so estimates, meeting people and figuring out material. But I sat down today and had to refresh my memory on major and minor bike details. I appreciate all your guy's help
 

Dserna

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His pic shows a zae50 rod on pg 1
it may be a low hole piston needed

There’s so many combinations of 38 or 40 mm stroke .. high hole… low hole.
It can get quite confusing.
Thank you so much. It's a low hole piston
 

Dserna

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Its a 47mm piston, so is most likely a 66/80cc. The 49cc are 44mm I believe.

Most 47mm jugs "should" work fine as long as you match the exhaust stud spacing. I am unsure if it varies much these days, but at one time years ago there were 2 different exhaust stud spacings. Intake doesn't matter as much as you are replacing with a reed and can buy accordingly, or the G2 I linked will work with either spacing. Preferably make sure its 40mm spacing though.

Chances are a pretty common bone stock 47mm jug will work for you just fine. But dont be totally surprised if you get one that something is off preventing you using it with your bottom end if your engine is some years old.

Like Damien said.... get new base and head gaskets too.... and you may consider an "aftermarket" head while you are at it. They are not expensive and some of them do indeed perform a bit better and offer better cooling than the stock head. There are a few that are crap though.

Also, when fitting a reed to your cylinder, you may need to file the intake mating surface flat to ensure a good seal. It is common for them to leak there if you do not.
I was planning on getting a better head, for cooling and a good squish band. I found one for around 60$ on Amazon I think might be good.

The engine isn't too old and I split the case to check all the bearings and clean out debris. I might balance the crank since the case is split and I'll be matching the transfer ports when I get the new jug. That's what I was worried about though getting a new jug and it being garbage.

I had a 48 cc that the plating was chipping so I bought a new cylinder and it was complete garbage when it came. I always make new gaskets from gasket material I get from ace hardware. But I had to double gasket the case on the 48 cc, not sure if I'll have to do it on this one.

I always buy the copper head gaskets too but I planned on getting a new one just so everything is fresh and proper when I get it back together. I was expecting the conrod to be different on the 66 than the 48 but they're the same, I was pretty surprised.

I'm not sure if I'll need an offset reed because of space. I use an offset intake now. I just figured since I destroyed the top end might as well do it right and get the reed if it will make a difference on power. I just have all the jets for the nt carb but I'm sure I'll need a bit bigger carb I just didn't want to get a pos and then the wrong jets. I'd rather get a better carb because it'll be better for tuning I've just been using the nt and speed carb the whole time and didn't know if I could take the time to learn all about reeds and new jetting.

I have a clone carb but that thing is garbage so I didn't want to just get anything. I use to come on this site all the time a couple years ago but life got busy and I only needed the bike for a 5 minute bike ride to work. Now I have a 45 minute bike ride and I knew taking on the trip daily was risky.
 

TheWizzerd

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You may be better off just getting one of these, doing the necessary port cleanup, and drop a Bofeng carb on it. Then you would have a pretty strong engine


Cheap as beans right now with the coupon.

Already comes with a decent head (but not ideal squish, its the standard 47mm head on a 49mm jug/piston....easy fix, but seemingly do fine as is for some, unless you deck the jug and need the clearance)

Would spend less, a lot less fiddling around.

Those are what Karl Snarl prefers, and mine had been doing great after the port work. Its the strongest minimally modified engine I have had, and super smooth.

They are decent straight piston port, but you can window the piston to add the reed setup I linked.

Much better option than rebuilding what you have IMHO, and you have everything you need without question for around $120 with a BoFeng, or another $20 for the Bofeng reed setup I linked.

A reed wont really "add power", but it can improve the low end torque a bit. However I honestly think that its mostly due to the intake tract length that does it in this case more than the reed itself. But its a cheap, simple, neat, bolt on way of extending the intake without a bunch of hoses and uglyness.

You dont need a "bigger" carb. The NT or the BoFeng (much better option) run great on a G2 reed. The BoFeng comes with a 70 jet, and very likely will not need to be changed. The needle settings and taper seem to be adequate for 90% of engines with the Bofeng.

The reed set I linked comes with the offset intake you will likely need running a G2. In fact it comes with 2.


That engine and that reed/carb/filter set at around $140 total is hard to beat for the money.
 

Greg58

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The 48cc engine has a 40mm bore, the 66-69cc has a 47mm bore, the difference being the 66cc has a 38mm stroke and the 69cc has a 40mm stroke. The strange thing is both stroke length engines can use the same type of piston, confused yet? I have a 2014 38mm stroke GT5 type clone that uses the high pin piston, I also have a 2021 40mm stroke engine that also uses the high pin piston.
 

Greg58

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When working on older style 66cc engines you will have trouble finding a cylinder with the correct port timing unless you find some really old stock, I've got three different cylinders I've checked the timing on using my 38mm stroke, all would need a lot of port work just to match the original cylinder.
 
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