Finally got the Mack Mag built!

[Kpi890]

I know lots of people hate these boots bottles and I’m not trying to use it for a performance upgrade but here is the description on BikeBerry website for how the boost bottle works. Wouldn’t this solve my issue of the fuel reversion into my air filter? From the description this is the exact issue that is causing my problem.


How does the boost induction kit work?

As the engine draws fuel and air in through the carburetor on the intake cycle, the spark plug fires this mixture forcing the piston down and forcing a small amount of leftover air/fuel back into the the carburetor. As the air and fuel mix is forced back through the carburetor and intake manifold, it causes a double rich mixture which can result in a rough idle and hesitation. Primarily, the leftover air/fuel mixture, already burnt from the previous cycle which provides little or no oxygen, is cycled back to the next intake cycle resulting in bogging/ sluggish throttle response.

To take advantage of the leftover air/fuel mixture, the Boost Bottle kit provides storage for this "pre-atomized air/fuel mixture" or the leftover air/fuel mixture, leaving the intake cycle fresh and unburnt. As the piston makes it next cycle and draws a new fuel and air supply into the cylinder, the "pre-atomized air/fuel mixture" that is stored in the bottle returns to the engine as a burst, forcing the atomized fuel into the engine. In result, the boost bottle provides a "boost"or supercharge effect in engine performance.
This boost bottle works best at lower and mid-range rpm and when you are on & off the throttle. The advantage is that it brings up the horsepower and torque in the bottom of the rpm range, to mid-way through the power band (eliminating bogging).

 

[FurryOnTheInside]

I don’t quite understand how to do this? Do you have pictures of how to do this?

I think it will become obvious as you do it and it will be very easy. You just need to watch the piston go up and down as you turn the engine over by rotating the rear wheel. Mark zero with some tape on the engine case when you see the piston skirt begin to open the intake, and then read the figure when the skirt finally shuts off the intake completely.
@Street Ryderz kindly provided us a link to a nice degree wheel you can print out. Or just Google it of course. SR would be able to tell you the figures, what normal intake duration is and what is ideal, or you can find them with the forum search.
I can't remember and I don't want search right now... Packing for a trip.

 

[Kpi890]

I think it will become obvious as you do it and it will be very easy. You just need to watch the piston go up and down as you turn the engine over by rotating the rear wheel. Mark zero with some tape on the engine case when you see the piston skirt begin to open the intake, and then read the figure when the skirt finally shuts off the intake completely.
@Street Ryderz kindly provided us a link to a nice degree wheel you can print out. Or just Google it of course. SR would be able to tell you the figures, what normal intake duration is and what is ideal, or you can find them with the forum search.
I can't remember and I don't want search right now... Packing for a trip.

Okay I see what you’re saying... and once I find the degrees what will this show as far as the fuel reversion?

 

[FurryOnTheInside]

I know lots of people hate these boots bottles and I’m not trying to use it for a performance upgrade but here is the description on BikeBerry website for how the boost bottle works. Wouldn’t this solve my issue of the fuel reversion into my air filter? From the description this is the exact issue that is causing my problem.


How does the boost induction kit work?

As the engine draws fuel and air in through the carburetor on the intake cycle, the spark plug fires this mixture forcing the piston down and forcing a small amount of leftover air/fuel back into the the carburetor. As the air and fuel mix is forced back through the carburetor and intake manifold, it causes a double rich mixture which can result in a rough idle and hesitation. Primarily, the leftover air/fuel mixture, already burnt from the previous cycle which provides little or no oxygen, is cycled back to the next intake cycle resulting in bogging/ sluggish throttle response.

To take advantage of the leftover air/fuel mixture, the Boost Bottle kit provides storage for this "pre-atomized air/fuel mixture" or the leftover air/fuel mixture, leaving the intake cycle fresh and unburnt. As the piston makes it next cycle and draws a new fuel and air supply into the cylinder, the "pre-atomized air/fuel mixture" that is stored in the bottle returns to the engine as a burst, forcing the atomized fuel into the engine. In result, the boost bottle provides a "boost"or supercharge effect in engine performance.
This boost bottle works best at lower and mid-range rpm and when you are on & off the throttle. The advantage is that it brings up the horsepower and torque in the bottom of the rpm range, to mid-way through the power band (eliminating bogging).

I find Jaguar's explanation of how it works much more believable, and his recommendation on when it is appropriate too.. Which is with a reed valve, and the "bottle" reflects the pressure wave created by the reed valve closing. Nothing to do with reversion of the actual intake flow. Not really a volume thing so much as pressure, and forcing more a/f into the case at the moment the reed begins to open.
It would have to be a tuned length and volume and the right header and all that stuff, and none of the boost bottles you can buy are like that.


You can probably stop the filter getting too wet by adding a snorkel between the filter and carb. But the filter being wet isn't the cause, it's the symptom. Healthy engines don't have to breathe through a snorkel (or use a boost bottle) lol

 

[FurryOnTheInside]

Okay I see what you’re saying... and once I find the degrees what will this show as far as the fuel reversion?

It'll show whether you have too low intake port so it stays open too long.. or perhaps it's a mismatch of the piston type and cylinder causing the same. Who ported this cylinder?

 

[Kpi890]

It'll show whether you have too low intake port so it stays open too long.. or perhaps it's a mismatch of the piston type and cylinder causing the same. Who ported this cylinder?

It’s a stock Zeda80 kit as far as the engine is concerned. And with the snorkel I see how that would keep the filter from getting wet but wouldn’t the fuel still sit in the “elbow” of the snorkel? The hardest thing right now is trying to find the correct jet size. Because the reversion of the fuel into the filter causes the bogging and 4 stroking once it’s wet and is trying to draw air in it’s actually drawing in air mixed with fuel from the soaked filter. I could run the bike without any filter and jet it perfectly. It’s once I put a filter on it it starts to bog on throttle when the filter soaks up the reverted gas.

 

[Kpi890]

It’s a stock Zeda80 kit as far as the engine is concerned. And with the snorkel I see how that would keep the filter from getting wet but wouldn’t the fuel still sit in the “elbow” of the snorkel? The hardest thing right now is trying to find the correct jet size. Because the reversion of the fuel into the filter causes the bogging and 4 stroking once it’s wet and is trying to draw air in it’s actually drawing in air mixed with fuel from the soaked filter. I could run the bike without any filter and jet it perfectly. It’s once I put a filter on it it starts to bog on throttle when the filter soaks up the reverted gas.

I’m going to assume a Lightning CDI wouldn’t fix this issue would it? I ask because I have one sitting aside and haven’t tried it on this bike yet.

 

[Kpi890]

Well here’s an interesting post! https://motorbicycling.com/threads/modded-boost-bottle.58291/page-2

Basically he taps into the intake and installs a one way check valve that allows him to dump the fuel reversion as it heads back towards his carb... he says it worked great to smooth out his low and mid range rpm. Not a performance mod per say but one way to deal with the reversion.... maybe I’ll give it a try!

 

[Street Ryderz]

All piston port engines spit back fuel,They have no choice when the piston climbs (intake stroke)it creates a vacume below it to fill the case with a/f mix then as it decends (power stroke) it's also now pushing that a/f mix that was just pulled in up the transfers but also out the intake because the intake window is still open and there are no reed valve to stop that reversed flow.So having a partialy saturated air filter is quite normal but freshly cleaned or new with only short run time on it would not restrict enough airflow to change the setup! Those carb's used to claim they were self tunning some how? I don't really know what they mean by that but I find they do tend to run rich! Also when setting up a carb there is loaded lean condition that fools some tunners,That being when the engine see a certain amount of load it cleans out and runs great then as the load comes off at higher rpm it goes back to being rich!Some tunners will use this condition to their advantage where as input is given and load is present the engine cleans up and runs strong until unloaded again then the rich signal helps with cooling at fixed high rpm's.So if your jetting is rich enough to 4 stroke at the top but cleans up getting there it's just a tad too rich!this degree wheel works great just size it to fit a old cd or anything you want and your good to go!

 

[Kpi890]

All piston port engines spit back fuel,They have no choice when the piston climbs (intake stroke)it creates a vacume below it to fill the case with a/f mix then as it decends (power stroke) it's also now pushing that a/f mix that was just pulled in up the transfers but also out the intake because the intake window is still open and there are no reed valve to stop that reversed flow.So having a partialy saturated air filter is quite normal but freshly cleaned or new with only short run time on it would not restrict enough airflow to change the setup! Those carb's used to claim they were self tunning some how? I don't really know what they mean by that but I find they do tend to run rich! Also when setting up a carb there is loaded lean condition that fools some tunners,That being when the engine see a certain amount of load it cleans out and runs great then as the load comes off at higher rpm it goes back to being rich!Some tunners will use this condition to their advantage where as input is given and load is present the engine cleans up and runs strong until unloaded again then the rich signal helps with cooling at fixed high rpm's.So if your jetting is rich enough to 4 stroke at the top but cleans up getting there it's just a tad too rich!this degree wheel works great just size it to fit a old cd or anything you want and your good to go!

Okay thank you! I think I’m following what you said. The tough part right now is trying to jet it correctly. If I jet it with the air filter on it gives me false readings because it gets soaked with fuel on my low and mid rpm range. So should I jet the carb correctly with the filter off and go from there or should I jet the carb with the filter on? It’s just hard to tell where I’m at since the filter soaked with reverted fuel is proving rich conditions but I’ve got a 61 jet in it and if I run it with the filter off it I can really open it up with rpms ranging in the 9,000’s. I’ve the filter is put back on I’ll maybe see a 7,300 rpm range at the highest?