Bbr 4 stroke 49cc eng limits

humpley

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Don't want to over stress motor I way 200 lbs what's a good range for eng.temp and rpms.this week motor can't seem to carry me up a hill how can I tell when it's being over burdened is temp and rpm an indicator what's too hot and max rpms or a sign eng can't carry the load.thanks just don't want to burn up motor carrying 200lbs up hills🤤
 
Don't want to over stress motor I way 200 lbs what's a good range for eng.temp and rpms.this week motor can't seem to carry me up a hill how can I tell when it's being over burdened is temp and rpm an indicator what's too hot and max rpms or a sign eng can't carry the load.thanks just don't want to burn up motor carrying 200lbs up hills🤤
What is your gearing right now? you may need a bigger sprocket, but know an engine that size will need assistance from the rider unless you have crazy low gearing.

RPMS are limited by the governor, so unless you monkey with it, you'll never over-rev it.

Temps I'm not sure, but it's force air cooled, so unless you try to climb a dune in the desert, you shouldn't have to worry about temps.

You'll burn out your clutch before you roach the engine.

Just keep an eye on oil.
 
You shouldn't need to worry about engine temp unless you are putting a heavy load (steep hill) on the engine. On a 4t oil temp is way more important than head temp. Pil temp should not get close to 300 degrees.
 
Don't want to over stress motor I way 200 lbs what's a good range for eng.temp and rpms.this week motor can't seem to carry me up a hill how can I tell when it's being over burdened is temp and rpm an indicator what's too hot and max rpms or a sign eng can't carry the load.thanks just don't want to burn up motor carrying 200lbs up hills🤤
Strange, I'm 250lbs, live in the mountains of Tennessee, my bike weighs 100 lbs and pull 200 lbs trailer up 30% grade hills for a total of 550 lbs. The engine is a 4 stroke, 1.6 hp 33cc Robin Subaru.

I can do this because my bike is a shifter.

20230219_194143.jpg
 
Thanks for answer my bike is 21 speed(me I'm not fit with heart problem need motor as help up hill)the motor is friction roller no gears.i don't know about a govner that's why I have tach to avoid over rev,do you know what the govner's max rpm is.i tried to spin up the motor on a lift got it up to 7300 rpm just about gets the wheel moving with no load.do you know ,say if I was on flat grownd what the rpms should be and what the govnrs set at thanks verry much .also besides the govnr is there a way to tell im straining motor.
 
Thanks for answer my bike is 21 speed(me I'm not fit with heart problem need motor as help up hill)the motor is friction roller no gears.i don't know about a govner that's why I have tach to avoid over rev,do you know what the govner's max rpm is.i tried to spin up the motor on a lift got it up to 7300 rpm just about gets the wheel moving with no load.do you know ,say if I was on flat grownd what the rpms should be and what the govnrs set at thanks verry much .also besides the govnr is there a way to tell im straining motor.

I'm going to help you. I too have heart issues and live in the mountains of Tennessee. Posting pictures of the bike will help. Let's start with some basics.

What kind of engine do you have?

What is the total weight (bike + rider)?

What size tires are on the bike?

What grade of hills are you contending with?

Does the tach rpm drop significantly when going up the hills?

Answer these 5 questions then I can give you a course of action to take.
 
It's all about the drove ratio. With such small engines you have to make compromises to achieve your desired results. You could install a smaller drive roller on your friction drive. This will give you more torque, but less wheel rpm relative to engine rpm, thus reducing top speed.

To add to Jerry's list of questions, what is the current drove roller diameter?
 
It's all about the drove ratio. With such small engines you have to make compromises to achieve your desired results. You could install a smaller drive roller on your friction drive. This will give you more torque, but less wheel rpm relative to engine rpm, thus reducing top speed.

To add to Jerry's list of questions, what is the current drove roller diameter?
Smallest drive roller 0.93" and 29" wheels gives you the lowest reduction ratio of 31\1. For a level ground top speed of 19 mph.

However, if the total weight is around 270 lbs and the hills are over a 20% grade a reduction around 40\1 is needed with some pedal assist to keep from burning up the clutch.

Idle speed is recommended at 2800 rpm on these engines. Clutch engagement is around 4000 rpm. Max torque is at 4500 rpm. If at full throttle you can't maintain 4500 rpm then you need to provide more pedal assist.

You don't have a 21 speed bicycle. What you have is 21 shifter combinations; some of these are redundant ratios. Your bike is a 3x7 drive system. This is how a 3x7 gets shifted:

1(1-4)
2(2-5)
3(4-7)

For 12 sequential non-reduntant ratios. All gears are easy to use when the terrain is within the ratio range. If a gear is too easy or to hard to comfortably maintain a cadence of 70-90 it means you're in the wrong gear or you've exceeded the gearing range. For example: in 1(1) but still to hard to pedal up hill or in 3(7) and too easy going down hill.

The good news is you can now select the best ratio to help provide pedal assist to maintain 4500 rpm when going up hill.

Take off gear 1(1) for starts going up hill. All other starts use (2).
 
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