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Valkyrie tank conversion

Like many Magna owners I was unhappy with the gas tank capacity and, following the lead of a few others, decided to proceed with adapting a Valkyrie tank. The Standard and Tourer models have a 5.3 gallon tank, and the Interstate has 6.9 gallons capacity; I used a Standard tank. The project is finished and following are photos with the Valkyrie tank and the Magna tank, with and without bags, so you have a good comparison of the change in appearance. Unfortunately, many of the “work in progress” photos were unusable but a few were salvagable and are included here.

I separated the Magna tank bottom section (pan) from the top section (shell) by cutting the shell just above the welded seam on the outside and I separated the Valk halves by cutting the pan just above the seam along the inside. This yielded two pieces (Mag pan and Valk shell) with the double-thickness seams from each tank (better for welding) intact.

I removed the vent chamber from the Magna pan and left the vent chamber attached to the Valkyrie shell; I left about three inches of the 1/8” steel tubing attached to the fitting on the Mag pan and the chamber on the Valk shell. I used a piece of ¼” copper tubing with one coil to form a line between the fitting and chamber, junctions are silver soldered. If I were to do this again I would use 1/8” copper tubing and use two ¼” copper pieces, about one inch long, to form the junctions. This would reduce the tendency of the ¼” tubing to sag when hitting bumps and then vibrating against the pan. I still have to slip in a shim to fix this annoyance.

The next step was to tack the shell to the pan in a few places to determine the shape of the filler pieces needed to close the gaps between the pan and shell at the front and rear (sides are a perfect fit). I made templates (1/16” mountboard) for the filler pieces and cut pieces of metal from the discarded Magna shell and then formed them using a ball peen hammer and a piece of 3” diameter steel bar. This was my first attempt at this procedure; I now have a hell of a lot of respect for the craftsmen who used to form entire automobile body parts using only hammers, bucks and dollies.

Formed filler.

The next steps were welding the components together, grinding the welds smooth, leak testing, re-welding the pinhole leaks, grinding, leak testing, coating the inside with Kreem just for assurance leaks wouldn't develop later, filling the dents in the used Valk shell and filling the areas where the filler pieces were added. This was followed with sanding, priming, filling light scratches, priming, sanding, priming, sanding, finding paint and locating a painter.

Side view, welded.

Side view, both tanks.

Bottom view, finished tank.

This seemed like a good opportunity to measure the capacities of the stock Magna tank and the new “Valkna” tank, following are the results (temp was about 60° F).

Notes on Magna tank capacity

01/08/03. Measured gas after fully draining (including shaking) and reinstalling petcock. Total capacity, fuel halfway up filler neck with bike on sidestand is 3.7 gal. Hits reserve with 1.0 gallon remaining, can get .78 gallon out on reserve setting which means .22 gallon is still in the tank but won't come out under normal conditions.

Range is 2.7 gallons from Full to Reserve, 0.78 gallons on Reserve and 0.22 gallons not accessible (2.7 + 0.78 + 0.22 = 3.7). At 35 - 40 mpg, range before hitting Reserve is 94.5 - 108 miles and range on Reserve is 27.3 - 31.2 miles. Thus, total range is 121.8 - 139.2 miles.

Notes on Valkna tank capacity

02/23/03. Measured gas after completion of modifications and painting. Installed tank and added 2.0 gallons. Turned petcock to "Run" and drained 0.5 gallons. Turned petcock to "Reserve" and drained 1.2 gallons. Therefore, amount in tank when necessary to switch to Reserve is 1.5 gallons, amount accessible at Reserve is 1.2 gallons and 0.3 gallons will not be accessible. Rode to gas station and added 4.15 gallons to bring fuel level to 1/4" up the inside lip with bike on side stand; assume I used 0.05 gallons to get to station (2 miles), 4.15 + 1.95 = 6.1 gallon capacity.

Range is 4.6 gallons from Full to Reserve, 1.2 gallons on Reserve and 0.3 gallons not accessible (4.6 + 1.2 + 0.3 = 6.1). At 35 - 40 mpg, range before hitting Reserve is 161 - 184 miles and range on Reserve is 42 - 48 miles. Thus, total range is 203 - 232 miles.

Total delta between stock and Valkna tanks, using 35 - 40 mpg as consumption rate is 81.2 - 92.8 miles

Magna tank capacity	Consumption (mpg)
Gallons	35	40	45
3.7 full tank
2.7 full to reserve	94.5	108.0	121.5
0.8 reserve	27.3	31.2	35.1
0.2 inaccessible
Total (miles)	121.8	139.2	156.6
Valkna tank capacity	Consumption (mpg)
Gallons	35	40	45
6.1 full tank
4.6 full to reserve	161	184	207
1.2 reserve	42	48	54
0.3 inaccessible
Total (miles)	203	232	261

This view shows relocated brake line, HD Deuce turn signals, polished fender spacers, polished rims, wheel spacers and forks. Pipes are Cobra turnouts, forward controls are by Highway Hawk with the recently released folding pegs.

I had to cut about 3/8” off the front of the seat to get clearance between the tank and the nose of the seat. I added the ¼” spacers under the risers to keep the HD harness clamps from possibly rubbing on the tank; the spacers would not be necessary with the stock Honda harness bands.