Minibike running wrong not going faster

[Minibikeproblems]

Ok so you have the hemi 26lb springs correct? Sounds like a nice combination. What color is the spark plug.

I’ll have to check at around 2:30 I’ll take it out and show a picture, I’ve been running autolites on all my engines and projects for years now and they have never failed me yet.

 

[Minibikeproblems]

I’ll have to check at around 2:30 I’ll take it out and show a picture, I’ve been running autolites on all my engines and projects for years now and they have never failed me yet.

I’m also now moving on to a 4.4:1 ratio on my tires I’m hoping that will get me up there to 70mph

 

[Minibikeproblems]

Ok so you have the hemi 26lb springs correct? Sounds like a nice combination. What color is the spark plug.

 

[ole4]

Hard to tell on that plug but it does not appear to be running lean. 4.4 :1 may still hold you back. See if a 60 tooth or 72 rear sprocket will fit your rear wheel. You can get a inexpensive digital tach off Amazon. The mod 2 cam is a long duration cam. Your target rpm for peak hp is near 7000 rpm on a 212.

 

[Minibikeproblems]

Hard to tell on that plug but it does not appear to be running lean. 4.4 :1 may still hold you back. See if a 60 tooth or 72 rear sprocket will fit your rear wheel. You can get a inexpensive digital tach off Amazon. The mod 2 cam is a long duration cam. Your target rpm for peak hp is near 7000 rpm on a 212.

i have a 72 tooth sprocket it’s the one that comes stock with it but the thing is I want to be going atleast 70mph and on the 72 tooth one I only go 42mph what do you think I can do to achieve that 70mph while still being able to keep the ability to wheelie

 

[ole4]

You are correct but it will get to 40MPH in a hurry and it would be easy to tell if your motor setup is good as it should be able to get to the 7000 rpm mark if all is ok. (you will need the tach) Then you can start reducing the ratio. Once you get to a point where the RPM is dropping then you know you went too far. It takes a lot of power to get to 70MPH not sure if that is possible with your combo. Remember you have traded off low end power for high end power with that long duration cam. That may be why the stage one works well with your type of gearing as it would have more low end torque. On my drag bikes some are 8:1 ratio with a Torque converter. I run a bigger rear tire. If you have the 72 tooth it would be a useful experiment to try it once you get the tach. You would also need a longer chain.

 

[Minibikeproblems]

You are correct but it will get to 40MPH in a hurry and it would be easy to tell if your motor setup is good as it should be able to get to the 7000 rpm mark if all is ok. (you will need the tach) Then you can start reducing the ratio. Once you get to a point where the RPM is dropping then you know you went too far. It takes a lot of power to get to 70MPH not sure if that is possible with your combo. Remember you have traded off low end power for high end power with that long duration cam. That may be why the stage one works well with your type of gearing as it would have more low end torque. On my drag bikes some are 8:1 ratio with a Torque converter. I run a bigger rear tire. If you have the 72 tooth it would be a useful experiment to try it once you get the tach. You would also need a longer chain.

Ok I will try doing that and if it’s possible what do you think is the best cam available that’s not over $150 so I can get up there to the 70mph mark

 

[ole4]

Before you start changing more stuff first work with what you have to get it running the best it can. Then you can decide if it's enough power or not. Mod 2 has a lot of duration but low lift so one future mod would be ratio rockers. Also the stock head will be a limiting factor although some of the newer 27/25 heads w 5mm valves do a decent job.

 

[Minibikeproblems]

Before you start changing more stuff first work with what you have to get it running the best it can. Then you can decide if it's enough power or not. Mod 2 has a lot of duration but low lift so one future mod would be ratio rockers. Also the stock head will be a limiting factor although some of the newer 27/25 heads w 5mm valves do a decent job.

Ok I will look into those when I get the tachometer and perfect gearing

 

[Minibikeproblems]

Ok I will look into those when I get the tachometer and perfect gearing

 

[Minibikeproblems]

Before you start changing more stuff first work with what you have to get it running the best it can. Then you can decide if it's enough power or not. Mod 2 has a lot of duration but low lift so one future mod would be ratio rockers. Also the stock head will be a limiting factor although some of the newer 27/25 heads w 5mm valves do a decent job.

I have received the tachometer and it told me I made a whopping 8500 max rpm’s I’m still waiting for the gears to arrive is it supposed to hit 8,500?

 

[ole4]

How did it get to 8500? I hope you were not free reving it

 

[Minibikeproblems]

How did it get to 8500? I hope you were not free reving it

Can you explain what free revving it is please? I was slowly climbing up and down on certain rpm’s and then decided to do a top run and slowly climbed my way to max and it registered 8500 rpm’s or so

 

[MJL]

I don't recommend those speeds either, but you are going to do what you are going to do so here are my thoughts: Have you checked other factors? Are your bearings smooth? Are your wheels balanced? Does your brake drag at all? What do you weigh? Are your tires inflated for minimum rolling resistance? Are you tucking in as much as the other guys? Headwind/tailwind? All of these things matter when you are at the very limits of the engine.

 

[ole4]

Free reving is when there is no load on the motor.

 

[Minibikeproblems]

I don't recommend those speeds either, but you are going to do what you are going to do so here are my thoughts: Have you checked other factors? Are your bearings smooth? Are your wheels balanced? Does your brake drag at all? What do you weigh? Are your tires inflated for minimum rolling resistance? Are you tucking in as much as the other guys? Headwind/tailwind? All of these things matter when you are at the very limits of the engine.

My bearings are smooth my wheels are balanced my brakes don’t drag i weigh 180 I’m running 5 psi on the back and 9 psi on the front for wheelies I’m not going as fast as other guys and idk about heading and tailwind

 

[Minibikeproblems]

Free reving is when there is no load on the motor.

Then yes I was free revving but gears come next Sunday

 

[minibikin']

My bearings are smooth my wheels are balanced my brakes don’t drag i weigh 180 I’m running 5 psi on the back and 9 psi on the front for wheelies I’m not going as fast as other guys and idk about heading and tailwind

That's light on air pressure if you're trying to get MPH...

 

[Minibikeproblems]

That's light on air pressure if you're trying to get MPH...

Well I’m trying to maintain a good amount of grip

 

[Minibikeproblems]

Free reving is when there is no load on the motor.

Ok so I have a 53 tooth on the back and it makes me run absolutely perfect I love it so now my question is turns out I have a mod 2 cheater cam and now I’m wondering if I should put the 22lb springs back on because the engine still feels like it’s under a lot of load and it’s a lot quieter than what it used to be so should I put the 22lb springs back in?