What would be the first aftermarket part I should buy?

[Gavin67]

I have bought a used 2009 80cc ported engine that is in great condition and hasn't even been broken in yet (it is fully broken in now) for $165 a month ago. I had to get rid of the stock antique carburetor since it was having leakage problems so I switched it out for a high performance carb. Everything else is stock and I have a 44 tooth sprocket. The max speed with the engine is 35mph anything over that the engine sounds overworked, it hits 15-18mph with slight throttle so I was thinking about getting a smaller sprocket to put less stress on the engine and give it a higher top speed.

How can I get an idea how much of a higher top speed I will get with a lower sprocket (36T or so) also knowing how much torque and acceleration will be lost?

Besides possibly getting a smaller tooth sprocket, what other aftermarket parts should I consider getting first to increase the performance?

 

[FurryOnTheInside]

.........

How can I get an idea how much of a higher top speed I will get with a lower sprocket (36T or so) also knowing how much torque and acceleration will be lost?

Besides possibly getting a smaller tooth sprocket, what other aftermarket parts should I consider getting first to increase the performance?

Arithmetic.
(44/10) ÷ (10/36) = 1.222
35mph x 1.222 = 42.777mph
Assuming that you have sufficient power to get up to the same RPM.

(10/44) x 36 = 0.818
So it leaves you with about 82% of the torque.

I got a 42t rear sprocket (actually a mountain bike front sprocket) and a (1/8") #410 bmx chain (KMC Z510HX), and narrowed my front 10t sprocket to 0.120" to fit the chain. Not all rear sprockets will fit #410 chain without modification, and very few drive sprockets will.
I would have got the 11t drive sprocket if shipping cost to where I live wasn't so ridiculous. I think they are a great idea for anyone who lives in USA or Canada and wants to use the lightest possible chain. They increase speed (and chain speed) about 10% but at the same time decrease chain load by about 10%

Before getting into increasing power I would improve the cooling by getting a nice big cylinder head with lots more surface area.
The MZ Miami ("R" head to fit my eBay engine) head that I got was worth the international shipping cost, and in the USA would be basically too affordable to not get.

 

[crassius]

top speed depends more on rider weight than anything else

 

[FurryOnTheInside]

top speed depends more on rider weight than anything else

OP said his engine is revving it's nuts off at 35pmh with the 44t.
So he should lose weight and that will help how?

So besides being off topic I'm pretty sure that your statement is actually false. At speeds over 35mph on smooth paved level ground, the drag from air resistance is the main force to overcome. Weight is more of an issue in acceleration, braking and turning.

 

[6blueoval9]

Everytime i hear about a ported engine it makes me smh wondering what was actually done.

Porting requires some know how and its not just making ports bigger as many think and mistakenly do to the cylinder...its possible this porting performed by whoever could be hurting your performance especially without a good exhaust .just keep that in mind.

35 mph on a ported 66cc motor with a 44t gear doesnt sound all that great from the start..maybe im missing something as to how the older motors were designed or perform but its not un common to hit 40mph today with no performance work done and proper gearing.

I wouldnt say weight was keeping you from more speed because it doesnt matter about the weight..more weight just means it takes longer to reach your top speed not keep you from reaching it.

Did you do anything to tune the carburetor or just throw it on and forget about it?

How does your plug read?

If you are using a 44t i would try 40t before trying a 36 unless you want to pedal the first 25 yards to get you going at a snails pace.

Just my .02 cents.

 

[FurryOnTheInside]

Everytime i hear about a ported engine it makes me smh wondering what was actually done.

Porting requires some know how and its not just making ports bigger as many think and mistakenly do to the cylinder...its possible this porting performed by whoever could be hurting your performance especially without a good exhaust .just keep that in mind.

35 mph on a ported 66cc motor with a 44t gear doesnt sound all that great from the start..maybe im missing something as to how the older motors were designed or perform but its not un common to hit 40mph today with no performance work done and proper gearing.

I wouldnt say weight was keeping you from more speed because it doesnt matter about the weight..more weight just means it takes longer to reach your top speed not keep you from reaching it.

Did you do anything to tune the carburetor or just throw it on and forget about it?

How does your plug read?

If you are using a 44t i would try 40t before trying a 36 unless you want to pedal the first 25 yards to get you going at a snails pace.

Just my .02 cents.

Older engines were badly balanced, RPM was limited by horrendous vibration. I have drilled a 15mm deep hole (measured about halfway in the cone shaped hole bottom) using a 3/8" tungsten carbide bit (3/16" for pilot hole) in each crank weight either side of the connecting rod. This did not require splitting the crankcase, so it was easy, although I didn't get it perfect, but for using a crappy cordless drill not bad I think.

Modified Happy Time crank

• FurryOnTheInside
• Aug 24, 2017

Not perfect but better "balance" than it was when stock! More Happy Time less Crappy Time. ;)

 

[6blueoval9]

Well, im glad im starting in this current market of motors lol...who knows what another 10yrs will bring.

 

[crassius]

OP said his engine is revving it's nuts off at 35pmh with the 44t.
So he should lose weight and that will help how?

I remarked that weight is a factor to be considered before changing anything. If his weight is OK, it will allow him to drop the tooth count on rear sprocket without losing top speed (and possibly gaining speed) - fat folks can't do that.

 

[FurryOnTheInside]

I remarked that weight is a factor to be considered before changing anything. If his weight is OK, it will allow him to drop the tooth count on rear sprocket without losing top speed (and possibly gaining speed) - fat folks can't do that.

I'm sorry if I sound argumentative. It's far too nice a forum for any of that. I do disagree with the idea that top speed is related to weight but I don't want to argue about it. *peace*

 

[crassius]

I'm at 150#, my friend is at 265# - we race down a long street & I win - we swap bikes and race back & I win. I don't find anything in that to argue about.