more top end speed after run in

4wdingman

New Member
Aug 26, 2008
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Coffs Harbour, Australia
will my 70cc happytime motor gain more top speed after run in cauce i have done 50km and it can only get up to about 40km?? Could it could be cauce i am not getting enough air into the carby?
Thanks
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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I have had kits that ranged from 25 mph (40 kph) to over 35 mph (60 kph).

A lot depends on the engine, which intake it has, how well the ports are matched, what type of muffler, ect.

Most all of them can be made to run 50-60 kph with a little work.

Break-in does help, but I think a lot of it is due to "tweaking the engine and components" during the break-in period.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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You'll get a little more power and maybe speed if you go to 24 to 1, or even 30-32 to 1 synthetic oil.

How's the break-in going? Has it picked up any speed yet?
 

Spunout

MB Builder Extraordinaire
Jul 21, 2008
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coventry, RI
blog.360.yahoo.com
i noticed a big difference in out-of-the-box power, between bushing and bearing motors.

bushing motors were quick from the start, but bearing motors dont achieve total power until you're into the third tank.

its a new motor. everything's tight, and the rings havent seated yet.
 

4wdingman

New Member
Aug 26, 2008
69
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Coffs Harbour, Australia
well when i first got it, it had a bit of power but no top speed so i drilled some holes in the carby filter cover and that made a bit of a different to the top speed but it seems to be not getting enough air.
Like when i ride i can put it full and it will get up too a speed and then the exhaust will make a vibration noise and it just wont go no more.

Thanks
 

Dave31

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Staff member
Mar 1, 2008
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Aztlán, Arizona
Have you checked your motor mounts? It is possible the fuel is foaming in the carb due to lose mounts or excess vibration.

:-||
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
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Sound like it is going into a four cycle when it "gets there". Try a leaner carb setting. (one notch up on the needle.)
 

old motorbike

New Member
Sep 21, 2008
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So far, new (16:1) it reached 28 mph with 44 tooth. After a few hundred miles, 24:1 with a shift kit it has gone 36 mph with a tail wind.lworider1
 

4wdingman

New Member
Aug 26, 2008
69
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Coffs Harbour, Australia
thanks all I put the needle up one spot and she run's great it will top out at 40km and i am still running it in just a questiom. how much oil should i use, i am using 25-1 and blowing the smallest bit of smoke but the motor get real hot do you think i should go to 20-1??


Thanks
.wee.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
63
up north now
Yes, if you use synthetic, you can use that much oil.....not really needed though and make sure you are not running lean due to the high oil content.
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,843
236
63
up north now
thanks all I put the needle up one spot and she run's great it will top out at 40km and i am still running it in just a questiom. how much oil should i use, i am using 25-1 and blowing the smallest bit of smoke but the motor get real hot do you think i should go to 20-1??


Thanks
.wee.
I will bet a dollar that if it's hot, and you go to 20:1 it will get hotter and make a carbon-y mess.

The reason is simple. More oil=less gas in the fuel to air ratio. Going from 24:1 to 20:1 will make the engine run leaner, and if it's already running hot, it WILL run hotter.
 

slipdrive44

New Member
Dec 3, 2008
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Tucson
More oil should not necessarily make the engine run hotter. Alot of the heat comes from friction.
Also the actual extra amount of oil from 24-1 to 20-1 should not have a noticeable effect on leaning out the engine especially if it is high quality two stroke oil designed to mix cleanly with gasoline.

Some oil when mixed will make the gasoline murky, but I use Bel-Ray Si-7 synthetic racing oil and the gas turns to look like blue Gatorade, very clear and light.

Personal Experience: Using a high quality synthetic oil will reduce smoke output to near zero.

I run 20 to 1 in my 80cc with Bel-Ray Si-7 and you cannot even see the exhaust. even not moving holding WOT
Furthermore I have tuned the engine to hit 40mph, my speedo top speed tells me 42.1 peak, this seems like a result of reduced friction and it does not get very hot.
 
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Dave31

Moderator
Staff member
Mar 1, 2008
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Aztlán, Arizona
I love the Bell Ray...I recently switched to Lucas semi-synthetic because its cheaper. So far I am liking it for the price.