| Beans Stock Air Box Mod |
Pictures and Text provided by Greg (Forum member BEAN210)
| So, you want to improve the performance of your ACE 750, but don’t have $200 to drop on a Thunder Air Kit? If so, this mod is an inexpensive and very effective solution. |
|
Here is the list of goods you will need for this mod: 1. Previously re-jetted and re-piped ACE 750 2. Replacement K & N filter element for the ACE 750(PN# KNF-HA-7500 $38.50) 3. D134(front) and D138(rear) main jets available from Dynojet @ (800)992-4993 4. Dremel tool with grinding & cutting bits, or a sharp knife and sand paper |
| The first step in this process is to remove the stock air box from your ACE 750. Follow the first TWO instructions on Blacktop’s Rejet page to complete this: |
|
Diagram 1 shows the stock air box with the snorkel and cover still attached, right off the bike |
|
Diagram 1
|
|
Diagram 2 shows the airbox in stock configuration. The snorkel is still in place. |
|
Diagram 2
|
|
Diagram 3 shows the snorkel removed (it simply pops out) |
|
Diagram 3
|
| Diagram 4 is the opening created by removing the snorkel. Some people have done no further modification to the box, installed 128(rear)/124(front) jets along with a Dynojet Jet Kit (required for the new slimmer needles), and had good results. Since were going to open up the carbs, lets get all the power/air we can! |
|
Diagram 4
 |
|
Diagram 5 shows the pattern scribed into the air box. This raised rib is the pattern to follow when marking inside of this rib between 1/8″ and 1/4″. The accuracy of this is not critical, as the base of the filter will actually become the new opening. |
|
Diagram 5
 |
|
Diagram 6 shows the Dremel bit I used. You can also use a good sharp utility knife, making small cuts and get the same results. BE CAREFUL. |
|
Diagram 6
|
|
Diagram 7 shows the new opening. Think of the original opening in the snorkel (appr. 1″x1″). The new opening is 6-8 times the original size! |
|
Diagram 7
|
|
Diagram’s 8 -9-10 shows the final sanding and cleanup of the filter. Diagram 8 is a picture of the Dremel bit used for cleanup. |
|
Diagram 8
 |
|
Diagram 9
 |
|
Diagram10
 |
|
Diagrams 11, 12 & 13 show the areas that I removed after I put the modified air box back on the bike and noticed how obstructive they were. All you need is a sharp knife to score one side, wiggling back and forth until pieces snap off. After removing the exterior obstructions, clean and sand any little slivers or loose plastic that may break off later and enter the engine or filter. Now is a good time to give the air box a hot bath. Clean all debris and dry with paper towels. |
|
Diagram 11
 |
|
Diagram 12
 |
|
Diagram 13
 |
| Diagram 14 shows the filter in its new home. Notice that the stock filter opening is slightly smaller than the modified air box opening. Not a problem. The K & N filter opening is larger than stock and can actually be trimmed (it has a rubber base) to fit the opening perfectly-which I did. |
|
Diagram 14
|
| Diagram 15 shows the filter in place. I drilled two 1/8″ holes and installed screws to hold the filter in place. This is important because the portion of the air box that held the filter in place has been removed. Actually, the cover holds the filter in place, the screws just position it until you can get the cover on. If you have the K & N filter, you can use two 1/8″ x 1/2″ long rivets. This allows you to slide the rubber-based filter on and off the rivets and not have to remove the air box to clean the filter. |
|
Diagram 15
|
| Diagram 16 shows the finished product, ready to mount back on the bike. |
|
Diagram 16
|
| After completing this mod, rejetting with the D134(front) and D138(rear) is a MUST. Refer to Blacktop’s Rejet page for instructions: A few more suggestions:
1. I used the above jetting and the bike is running very well. 2. Make sure to adjust the air mixture screws, mine are turned out to 3 1/4 turns. 3. After all this modification and wrenching, I suggest getting the carbs synched. 4. I strongly suggest the k&n filter. I have no experience with the UNI filter and for that reason only can’t recommend it. Toddo is going to use the UNI filter and post his results. |
