Questions and problems after 50cc to 80cc upgrade

[andrewf]

Hey,

First of all, hello. I'm new here, though I've been lurking around for quite some time.

Now, to the point.

• The sound of my ag50 engine doesn't seem to be "continuous". What I mean by that, instead of a normal "pop" sound on every rev, sometimes there is another sound - kind of knock, as if the engine was choking on this exact rev. It happens randomly, but as far as I can tell only when the engine is on idle. In one minute I can count as many as 8-15 of such discontinuities.
  
  I have to confess that I didn't change carburetor jet yet. May it be the case?
  
  Also it's probably worth mentioning, that scooter got noticeably louder after this upgrade (It's hard to say exactly how much louder as it's the first time this year to run my scoot and it's right after 80cc upgrade).
• Another thing bothering me - should I change the crankshaft to the reinforced one (not sure if it's the right word) or will the stock one handle 80cc?
• I can't start my scoot using the electric starter. I have to say that rotating shaft by hand got pretty tough on compression phase. Is it because of 80cc or something is wrong
• Is using stock jet on 80cc any harmfull for the scoot?
• Is there anything specific I should be paying attention to after 80cc upgrade?

I know that probably some of those questions have been already answered on this forum, but I couldn't find it, and the terrible search engine isn't helping.
I'll try to record previously mentioned "knock" sound to make things easier.

[blue]

You should go a size up on the carb.and yes you should do the grank. And after a rebuld like that dont ride full throtle tell after the frist 100 miles or so.it does need some kind of brack in time. A bigger jet might help but the next size up in carb is better.I went from a 18mm to a 20mm after a 70 cc big bore.becarefull to much for the stock crank might just do you in. Good luck.

[andrewf]

Okay, so I've managed to fix the discontinuity issue and loudness issue by tightening the exhaust-engine connection and changing the gasket there.

As for the crank... I really would prefer not to change it as it seems to be a load of work. I would like to know if it is really absolutely necessary and if anyone tried running stock crankshaft with 80cc. Right now I'm on 4500 miles and so I think that most parts are in a good condition.

Thanks for the advice blue

[JJJoseph]

As for the crank... I really would prefer not to change it as it seems to be a load of work. I would like to know if it is really absolutely necessary and if anyone tried running stock crankshaft with 80cc. Right now I'm on 4500 miles and so I think that most parts are in a good condition.

You don't need to change the crank. The same crank is used in 50cc / 80cc/ 100cc models around the world.  If you bought your same scooter in India it would have 80cc and the same crank.

[motman]

I would agree, no need to change the crank at all. I would run a #88 main jet to see if there are any gains to be had, it won't do any harm.