Asking Norm 'cause I couldn't find it anywhere else

M

MM7

New Member
Norm,

Just a couple of quick questions, as I couldn't find the answers by going thru the thread.
I have a 49cc set-up that I want to change over to 66 cc. Maybe I'm just too cheap but I do not want to just simply replace the engine (about the same $s as a full kit?!). Is it just a matter of changing out the jug and piston? Keeping the old bottom end from the 49 cc unit? As I research the matter I am running into things such as F-80 type J vs. F-80 type D on the 80/66 cc engines with no explanation as to the difference. Only difference I could see (old eyes) was in the wrist pin diameter.
Does the stroke change between the 49 cc and the 66 cc? Thereby requiring a con-rod change?

I would love for you to tell me that all I had to do was change out the piston and the jug (not counting all the associated tweaking that will be needed) but that is probably just wishful thinking on my part.

Looking forward to your response.
Thanks Guy!
Matt (or MM7)drn2
 
MM7 said:
I have a 49cc set-up that I want to change over to 66 cc. Maybe I'm just too cheap but I do not want to just simply replace the engine (about the same $s as a full kit?!). Is it just a matter of changing out the jug and piston? Keeping the old bottom end from the 49 cc unit?
Click to expand...
It is not possible to change a 49 cc engine to a 66 cc.

For one, the cylinder studs are further apart on the 66 cc cases and are
8 mm

Sometimes being cheap will cost you more in the long run. :)
 
Not Norm here, and interested in what he has to say about this. But I would guess changing a 48cc to a 66cc is gonna be a no go. It seems suppliers are selling 48cc and 66cc bottom ends and crankcase body's , which would seem to indicate there are differences, otherwise I would assume they would only sell one type if they were exactly the same. I think the head studs on at least some of the 48cc motors are different than on the 66cc.
That said, perhaps its not impossible, but you definitely need to start out at least knowing exactly what flavor motor you are working with, as parts can vary even among the same size motor...
IMHO (from what I read) there isn't a huge difference between the 48cc and the 66cc motor output power, and I have read that the 48cc motors may actually be more balanced and smoother, (never owned one though) so I would probably just stick with the 48cc that I have.
Are you lacking power and/or speed right now?
 
I am NOT Lord Vader, either... :-)
but I agree w the above fellows.

Many people have suggested the 48cc motors just might be better balanced.

Best to pursue increased hp with a xpipe, porting cleanup, better carb, and perhaps higher compression. ...imo...

Actually, best to go with a morini, or a 4 cycle motor if you really want more.
then you will have something.

Best
rc
 
Pure and simple for me to answer. I've not done it.
But you maybe able to, you will need a mill and lathe for boring cases and the cylinder studs if they need moved or the holes enlarged. It would involve a lot of machining.
The only way I see doing it is to have all the parts on hand, but then that would cost as much as a complete engine kit, or close to it.
If you want a cheap way to larger engine best bet and less headache is buy a larger engine. You can or used to be able to buy just an engine from some of the engine vendors.
I have no knowledge on what interchanges with which engine.
 
I want to say thanks for the responses from everyone. It does look like I will have less headaches if I just get the 66 cc engine, otherwise trying to make the smaller motor do the job is going to be "too many moving parts".
Again, Thanks Everyone!!
Matt/MM7
 
Guys,

Another thought occured to me (sounds dangerous- me thinking): the 49 cc jug I am running at present has the cast iron sleeve inserted into the bore, why could i not just take it around the corner to my local "speed shop" and get those fellows to just bore it out to fit the larger piston??? Kind of like the 'hot-rodders' do.
My trouble with my little 'china girl' is she will not pull off the line. I have an expansion pipe I installed as well as I have piddled around with the carbs jets and needles until I got a combination she seems to like fairly well. She just seems to have no torque, be it off the line or at a point near top end. There comes a point where even if I give her a higher gear for more speed she has not got the torque to keep her RPM's up and starts to bog down until I shift into a lower gear. (which is OK by me cause once I get around 40 mph things seem to flash by awfully fast. makes my b_tt pucker)
What I dream of getting her to do is pull away from a stop sign quickly and allow me to safely merge with traffic; then get up to 35 - 40 mph so I don't have irate motorists whipping around me cause I'm goin' "too slow" and getting in thier way to the nail salon or hair salon. (you know -critical things) The young blonde in the black BMW is the worst, like bikes have no right to be on HER road.
I may be asking just too much from this 49 cc set-up I have and I may just have to accept it the way it is. Doesn't mean i have to like it and doesn't mean I'm not gonna try to find an answer to my builds' drawbacks. You guys know what I mean? So any help/suggestions will be mucho appreciated.

Thanks for listening to me rant,
Matt(MM7)
Here are some Pics of what I have.

022.jpg

026.jpg
 
MM7 said:
the 49 cc jug I am running at present has the cast iron sleeve inserted into the bore, why could i not just take it around the corner to my local "speed shop" and get those fellows to just bore it out to fit the larger piston??? Kind of like the 'hot-rodders' do.
Click to expand...
I have had a few of those sleeved 50 cc motors which have
the carb bolted right on the back of the head and I have one
left that had the liner bored off center and at an angle.

If you had the liner bored out to fit a 66 cc piston there would
be very little left and the part of the liner that goes down into the
case would be totally removed as it is the same size as a 66 cc piston.
 
if you bore it it you will ruin the liner if they can bore it enough to get the piston in to it also i dont know if the piston will fit on the rod because i bet its a smaller rod and if you change the rod then also the crank and that means machining for the larger crank and the bearings for it its not worth it also they will charge you a minimum of $60 just to bore it not worth it no matter how you look at it just buy another kit and use this as a spare motor or look for another bike to put it on

another thing is it sounds like you dont want to ride it like a motorcycle which isnt going to happen without some serious performance parts and modding
cant realy not peddle on one of these even with a 66cc as far as i have seen and its not good for the motor
 
JonnyR said:
also i dont know if the piston will fit on the rod because i bet its a smaller rod
Click to expand...
You bet wrong as the 50 cc rod is the same size and the gudgeon pin
is the same size too and at the same height but I already explained
in the post above that the 66 cc piston is too big to rebore.

I actually have the parts here so i'm not guessing like you. :)
 
i dont have the parts so i was guessing you where correct.
i only have 2 66cc engines a Grubee paper weight (GT-5) and my flying horse which i ride all the time i said screw it if im going to buy one get the big one

but i don't condone experimentation on a good running motor
 
Everyone,

It is playing out that it would be smarter and fewer headaches to do;
1) Just ride the 49 cc & expect to pedal a little... or
2) Get the 66 cc and expect to pedal a little..

I guess those chinese engineers actually do know what they are doing when they design these things..:p....thanks for everyone's response,

Later!
Matt(MM7)
 
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