Would a balanced crank help me get above 8600 rpm?

[extremeodd]

I'm running a zeda motorsports 'poor boy' motor https://zedamotorsports.com/collect.../copy-of-new-zeda80-super-stock-r-engine-only with a stock carb and an MZ65 pipe. I've noticed that the motor cannot get past 8600rpm, it's not cutting out or 4 stroking, that just happens to be where the revs stop both while riding or stopped with the clutch in. At this point it is vibrating VERY hard, enough that causes the choke to close (I've since removed it) and has caused the needle housing/jet to fall out in the bowl once. The vibration starts around 6-6500 rpm and gets stronger and stronger until 8600 rpm. The motor is very securely mounted so I know its not that causing the vibration.

Would this be an issue with an unbalanced crank, or is this a potential limitation of the stock carburetor?


Moderators Note:
Please be aware that Zeda Motor Sports and Robert Bianchi have nothing to do with Zeda itself which is a manufacturer of Zeda Motors in China.
A reputable vendor of the Zeda line of motors can be found at bicycle-engines.com

 

[JerboaJohn]

sure it can help for some more revs, mostly it will smooth things out. there's a few things that can add more revs. reduce the reciprocating mass along with balancing - the rod can be polished, and a couple grams can be shaved from the piston. good needle bearings for top not the stock ones..
couple other tricks I could tell but then I'd have to kill ya lol. yeah stock NT doesn't let near enough air in above like 5000rpm. big gains there, too.
do you have machine tools?
when I pull my 48cc and put the big bore jug on, I'm going all out on it. same deal, just my piston is smaller than the zeda80. theoretically I can get more rpm out of it than a 47mm piston

 

[JerboaJohn]

just a side note,, I don't believe the hype from zedamotorsports. to make money they exaggerate all claims. fully ported jugs aren't cheap. lots goes in to porting. time = $$. they aren't showing you the internal view of ports they supposedly worked. their piston is just drilled to be done fast

Moderators Note:
Please be aware that Zeda Motor Sports and Robert Bianchi have nothing to do with Zeda itself which is a manufacturer of Zeda Motors in China.
A reputable vendor of the Zeda line of motors can be found at bicycle-engines.com

 

[Spare_Parts]

I just got an email showing that piston lol. Might do something similar though haha.

Balancing a crank can help with rpm but needs supporting mods.

 

[gary55]

Well he advertises it as fully ported, And (supposedly) all his new engines have 3 holes drilled for balancing, so if this is the case a larger carb. 18mm or abv. Should get you where you want to be. It may even begin vibrating less as you get above 8500. No way to know for sure without looking inside and trying the carb. upgrade.


Moderators Note:
Please be aware that Zeda Motor Sports and Robert Bianchi have nothing to do with Zeda itself which is a manufacturer of Zeda Motors in China.
A reputable vendor of the Zeda line of motors can be found at bicycle-engines.com

 

[Spare_Parts]

Just pulled my engine apart and unless he is doing more it is balanced to the rod. No balance factor. Literally checked it 10 minutes ago

 

[Street Ryderz]

I'm running a zeda motorsports 'poor boy' motor https://zedamotorsports.com/collect.../copy-of-new-zeda80-super-stock-r-engine-only with a stock carb and an MZ65 pipe. I've noticed that the motor cannot get past 8600rpm, it's not cutting out or 4 stroking, that just happens to be where the revs stop both while riding or stopped with the clutch in. At this point it is vibrating VERY hard, enough that causes the choke to close (I've since removed it) and has caused the needle housing/jet to fall out in the bowl once. The vibration starts around 6-6500 rpm and gets stronger and stronger until 8600 rpm. The motor is very securely mounted so I know its not that causing the vibration.

Would this be an issue with an unbalanced crank, or is this a potential limitation of the stock carburetor?

Robert isn't very bright and misleads customers all the time.The stage 2 engines are ported and may have improved balance the early ones didn't,Most of what you feel is the stock cdi being to advanced making it run lumpy, Also the MZ 65 pipe doesn't rev past it's peak very well and yeah it's usualy 9k or less stock.


Moderators Note:
Please be aware that Zeda Motor Sports and Robert Bianchi have nothing to do with Zeda itself which is a manufacturer of Zeda Motors in China.
A reputable vendor of the Zeda line of motors can be found at bicycle-engines.com

 

[gary55]

Just pulled my engine apart and unless he is doing more it is balanced to the rod. No balance factor. Literally checked it 10 minutes ago

Which of these cranks did yours look like left or right?
View media item 61765

 

[Spare_Parts]

Which of these cranks did yours look like left or right?
View media item 61765

The left but the holes are filled with jb weld and it is not welded.

 

[Spare_Parts]

Is this a thing now? The crank's are practically flywheels then.

The cranks are flywheels. That's why the cheeks are so thick.

Is what a thing now, balancing a crank? No. You see it more because more people have been doing it and more companies are advertising it. Been part of engine building since the start.