Ham Can Airbox

I have a MK3 and want to fit the ham can airbox. I have a pre Mk2a battery mount/box that I know will do the job, but a hard look at the Mk3 battery mount/box appears to have the two lower captured nuts in the right place and the frame has the hole for the "spacered" upper mount already drilled. I like the extra battery space of the Mk3 batter mount/box.

Will the ham can bolt in?

I will also be fitting a pre Mk2a left side cover and see that the Mk3 battery box does not have the lower side cover mounting stud (like the pre Mk2a battery boxes do), the frame is drilled for the upper side cover mounting stud, has anyone done this conversion? difficulties?

Mounting the "ham can" airbox to your bike isn't that difficult. You would need to remove the ignition switch bracket off the rear air filter plate. Also you would need to modify the battery tray by installing two captive nuts just inboard of the existing captive nuts. This is what I did with my Mark IIA tray (basically a Mark III with the added Dzus bracket).

I riveted in two aircraft type nut plates. However, there are press in, weld in, braze in, etc. options as well.



The air filter assembly will bolt in just fine with those two modifications. The top of the airbox mounts exactly like a Mark III and the lower part of the air filter sits a little farther back than originally designed. However, it's not even noticeable to the eye. If anything it makes the air filter easier to remove and replace.

Fitting a pre-Mark IIA side panel may be a little more involved. You would have to remove the tool box portion of the side panel. Then I think you could put a tab on the bottom of the side panel that mimics the Mark III side panel to hold the rubber mount that fits between the Z plate and the frame.

I had a problem with my Mark IIA when I replaced the air filter assembly with the ham can style filter. The battery is not well supported and it fell over when braking hard on a steep downhill. I added an extra strap to my battery tray to help secure the battery.This may not be a problem with the Mark III because the battery is physically larger than what was in my Mark IIA. Also the battery wiring could possibly help hold the battery from falling over on a Mark III.

This is a picture showing the extra mounts for the battery strap:



One last thought for the pre Mark IIA side panel, I machined an aluminum spacer that fits around the Dzus stud retainer. It's held on with two set screws. The rivets that hold the Dzus S-spring on the side panel need to be replaced with flush rivets for this spacer to work. My thinking is that this spacer gives a more stable platform for the side panel and it reduces any side load stresses on the snap ring. I have yet to test this idea. I am still using my Mark IIA side panels on my bike.



I hope some of these ideas help.

Peter Joe

Many thanks Peter Joe!

My original plan was to use a pre Mk2a battery box which drops right in and has all the right captured nuts and geometry for the ham can and the side cover. I asked the question because I was trying to avoid a Li battery to make up for the smaller battery platform.

I am grateful for the pictures and your knowledge as they show the Mk2a/Mk3 battery box is NOT as compatible as I was hoping. I will go back to plan "A" and learn about Li batteries, they sure are light.

Any one out there have experience with what is the smallest maintenance-free AGM battery that can kick a Comeau or CNW starter and can provide sufficient ballast for a 180 watt 3 phase charging system??

Li?

RoadScholar said:

I will go back to plan "A" and learn about Li batteries, they sure are light.

Click to expand...

Going back to plan "A" by using the pre Mark IIA battery tray is by far the easiest method to go especially since you have the pre Mark IIA side panel to go with it.

As far as battery size is concerned, I believe you can fit an 850 Mark III size battery in the earlier battery tray without any real problem. The pre Mark IIA battery tray is designed to work with two - 6 volt batteries wired in series for police bike use so there should be plenty of space for your purpose.

To top it off you can keep the tool box in the side panel along with the plastic tool tray.

Peter Joe

I have a 20ah battery sat on my earlier type battery shelf. That is after i shortened the shell by an 1/8 of an inch at both ends to.

toppy said:

I have a 20ah battery sat on my earlier type battery shelf. That is after i shortened the shell by an 1/8 of an inch at both ends to.

Click to expand...

Was this a LI battery? In any event how did you shorten the battery without creating issues with containment/cooling?

RoadScholar said:

toppy said:

I have a 20ah battery sat on my earlier type battery shelf. That is after i shortened the shell by an 1/8 of an inch at both ends to.

Click to expand...

Was this a LI battery? In any event how did you shorten the battery without creating issues with containment/cooling?

Click to expand...

Oops dam predictive spell does it again. I shortened the battery SHELF not the shell.
Its a standard size 20ah rated sealed gell battery which is mounted upright an held with long cable ties. It drives the Alton Ekit starter and the relay for this sits above the battery. If i remember correctly its 89mm wide 155mm tall and 173mm long. The shelf was shortened to by cutting ends off an rewelding them back on to give a little more clearance for fitting air filter without so much of a struggle and like wise rear mudguard. Though they did fit anyway but i wanted to try an make removal of filter a bit easier if i could (you cant go any more or filters two clamping bolt foul frame). The mounting for battery tray are still in same position and the side panel with built in tool box is also used as is side mounted oil tank. There are 4 micro relays a blade fuse type fuse box with 6 fuses the flasher unit (in it standard position) and Alton relay and the battery all in the space. It is a close fit but everything is accessible with removing anything else once you have removed the side panel.