gearing 44t to 36

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CR500AF

New Member
May 20, 2012
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Ontarieo
Here are the specs on my engine 66cc

ported 2mm higher 2mm wider ex
2mm lower 2mm wider in

4mm deep by 6 wide boost ports in between the transfers and intake, going as high as the transfers

piston skirt cut to match the intake

no base gasket

head has bin lathed to remove the flat spot in the combustion chamber to allow the piston to come up farther (acting as a stroker crank and real swish

port mached everthing

stock carb

with a 44t im getting a 100% Honest gps 57-61 kph (the rpms stay the same but the speed changes from 57-61 kph at wot I think up hill down hill and wind have something to do with this

I bought a 36t of ebay in hopes it would make me be able to start it with less effort or in the wet, the conpression is at 197psi with not base gasket and i head has bin modded to let the piston come up farther with out thouching the head.

I scard that my engine won't have the balls to get the bike moving with a 36 form a dead stop tho.

my 0-5% speed power is nothing,would not make it up a hill and my 5-95% power is twice of my friends stock HT

one more thing i want to know is im doing appox 37mph with a 44 on 26s

what would be my rpm ?

and apox what will be my top speed with a 36t at my max rpm


sorry for so many qustions and blabbing

usflg
 
ocho ninja

ocho ninja

Member
Jan 14, 2012
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San Jose, CA
I could answer a couple of those questions.
I did the same swap a while back for my bike, went from 44 to 36.

It was a good swap. Good speed and kept my rpms down, however I did lose starting acceleration

It will also make the bike slightly harder to start.

My bike was stock besides expansion chamber, and ported intake manifold and it did fine hauling my big 250 lb a$$ around town on a 36t sprocket.
 
C

CR500AF

New Member
May 20, 2012
78
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Ontarieo
ocho ninja said:
I could answer a couple of those questions.
I did the same swap a while back for my bike, went from 44 to 36.

It was a good swap. Good speed and kept my rpms down, however I did lose starting acceleration

It will also make the bike slightly harder to start.

My bike was stock besides expansion chamber, and ported intake manifold and it did fine hauling my big 250 lb a$$ around town on a 36t sprocket.
Click to expand...
im 150lbs.

i know i have to go faster to start but i was thinking the it would be easyr to turn the engine over with a 36t.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Venice Motor Bikes said:
I like to use 40T sprockets on my bikes... It gives a little more top speed & still has good power going up hills. :)
Click to expand...
Ditto, and you shouldn't expect the bike to go from a dead stop without a little pedal assist. It's not a motorcycle. You have pedals; use them, to give your clutch a little help and a longer life.

Tom
 
X

xenodius

New Member
May 23, 2012
150
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Spokane, WA
your magic number for a 36t is 180.587 * speed in mph = rpm.
For example, to go 37mph you would need 6680 rpm.

For your 44t, the magic number is 232.153 * speed in mph = rpm.
37 mph = 8590 rpm.

I think my math is correct, I tried to simplify things. 181 * mph = rpm for 36t, 232 * mph = rpm for a 44t. 211.36 * mph = rpm for Venice's 40t sprocket. =)
 
C

CR500AF

New Member
May 20, 2012
78
4
0
Ontarieo
xenodius said:
your magic number for a 36t is 180.587 * speed in mph = rpm.
For example, to go 37mph you would need 6680 rpm.

For your 44t, the magic number is 232.153 * speed in mph = rpm.
37 mph = 8590 rpm.

I think my math is correct, I tried to simplify things. 181 * mph = rpm for 36t, 232 * mph = rpm for a 44t. 211.36 * mph = rpm for Venice's 40t sprocket. =)
Click to expand...
Im sorry to ask again but what would my speed be if i had this set up

26''
32t
8600rpm
 
X

xenodius

New Member
May 23, 2012
150
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Spokane, WA
Haha, well, I'll stick to the one I have for now-- matches the rest of my bike. For a 36t, take those rpms and divide by magic number to get speed in mph. 47.62mph in this case.

Edit: maybe the rest of my bike needs to change? =)
 
C

CR500AF

New Member
May 20, 2012
78
4
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Ontarieo
xenodius said:
Haha, well, I'll stick to the one I have for now-- matches the rest of my bike. For a 36t, take those rpms and divide by magic number to get speed in mph. 47.62mph in this case.

Edit: maybe the rest of my bike needs to change? =)
Click to expand...
well i hope i can get at least 45mph if i was to gusse asssuming a stock ht makes 2hp @ 5500rpm then mine would make about 3.5-4hp @8000rpm


my weight is 150lbs and the bike will be 100% 7005 alloy with alloy rims,forks,bars.........

and if that dose not do it then il get the sbp pipe when the chrome ones comes back in


anyways thank you for your help
 
G

goofyfoot2001

New Member
Aug 16, 2012
75
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South Carolina
These engines are doing no where near that kind of RPM. I believe it's probably under 2000. Here's how I calculate with my 29" tires.


Drive Sprocket Teeth 12
Rear Sprocket Teeth 44
Tire Size In. 29
PIE 3.14

Gear Development In. 24.83
Gear Development Ft. 2.07 (How many ft you travel per each engine drive gear turn)

RPM Estimate 1200

Speed (mph) 28.3113818182 (This is about my top speed from this formula: Speed (mph) = gear development (ft.) X rpm X .0114

.0114 is the EXACT RATIO = pitch/(2*PI*radius) = 0.011459155
 
The_Aleman

The_Aleman

Active Member
Jul 31, 2008
2,653
4
38
el People's Republik de Kalifornistan
goofyfoot2001 said:
These engines are doing no where near that kind of RPM. I believe it's probably under 2000. Here's how I calculate with my 29" tires.


Drive Sprocket Teeth 12
Rear Sprocket Teeth 44
Tire Size In. 29
PIE 3.14

Gear Development In. 24.83
Gear Development Ft. 2.07 (How many ft you travel per each engine drive gear turn)

RPM Estimate 1200

Speed (mph) 28.3113818182 (This is about my top speed from this formula: Speed (mph) = gear development (ft.) X rpm X .0114

.0114 is the EXACT RATIO = pitch/(2*PI*radius) = 0.011459155
Click to expand...
Please stop spreading around your flawed math. You completely forgot the 4.1:1 reduction built into the motor.
 
C

CR500AF

New Member
May 20, 2012
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Ontarieo
tests have bin done and the top speed on a slight up hill (IE if you put a pop can down it would roll slowly)

no wind


74kph and but im having a slight spudder at max rpm so with some time 76 most likey be top speed

il say once tuned i will be able to say my bike dose an honest 75kph

power wise i did not loss much if any

it runs smother with more load

i now feel im pushing the limits of bicycle parts and no longer feel safe on my bike

I now understand that a 36 is unsafe and a 48 is about the fastest a bike sould ever go

but im keeping my 36
 
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