CarboTech VTR1000 Fuel Tank

A message I posted to the SuperHawk mailing list on 5/13/98.

Quick Summary:

It didn't fit, the replacement tank didn't fit either, I modified things to *make* it fit, & (for me) the increased fuel capacity *was* worth the trouble.

Gory Details:

I ordered a CarboTech 5.9 gallon tank for my VTR several months ago from Knut Wagner of MaxMOTO, Oakland, Ca., 510-595-8017. MaxMOTO is the U.S. importer & distributor of CarboTech, Remus, & several other European motorcycle-related companies. The tank, as ordered with Ca. sales tax, was about $1285.

I requested a couple of design changes in the VTR tank; (1) move the top-mounted vent line connection back to the bottom of the tank to allow room for a larger tankbag, & (2) install an aluminum-alloy, locking fuel cap & outer trim ring assembly, instead of the flush mounted scheme used on their VTR tank. The purpose of the second item was to get the outer trim ring that should help prevent damage to the eventual painted tank while re-fueling with our wonderful California pump nozzles. These things have huge, spring-loaded, rubber foreskins (uncircumcised) that must be fully retracted before it will work properly. Since I plan to leave the tank unpainted til next year, I also ordered the "carbon-view" option for the entire top of the tank. CarboTech uses a carbon & kevlar woven fabric that looks kinda like a black & yellow checkerboard pattern. Its kinda ugly. The "carbon-view" option places one more fabric layer on top (where specified) that is pure carbon fiber.

The 1st tank arrived about 6 weeks later, but there were a couple of problems. The rear of the tank has 2 vertical cf pieces that the "pivot tube" is epoxied into. This pivot tube is where the bolt goes through for the rear mount & allows the tank to pivot up if the front bolts are removed. With the front bolts in place, the pivot tube was too far towards the rear of the bike (10-12 mm) to align with the rear tank mount bracket on the frame. The inside diameter (i.d.) of the pivot tube was also too small to allow the oem bolt & rubber bushings to be inserted. The bolt would fit, if the bushings were not used. The tank did have the aluminum outer ring for the fuel cap, but it was not the *locking* cap I had specified. Since the rear tank bracket alignment was so far off, I decided to call Knut & discuss the problems.

Knut arrived at my home (Concord, Ca.) a couple of nights later with a "loaner" CarboTech tank. I showed him the fit problems & we tried the loaner tank on my VTR. It did fit, but with the top-mounted vent line, I couldn't use my tankbag. I thanked Knut for bringing the loaner tank, but told him I didn't need the tank immediately & would prefer to have *MY* tank back ASAP as I did have a 5-day 1800 mile trip planned in early May that I MUST have my new tank for.

About 4 weeks later, my tank arrived again. CarboTech had actually made me a new tank, instead of repairing the original. Immediately, I noticed that the aluminum outer ring & locking fuel cap were not as specified. They were both carbon-fiber & non-locking. Knut told me that it arrived from CarboTech that way & that he would get them on the phone that evening to get the correct pieces shipped. That evening I removed the oem tank and checked the fit of the CarboTech. DAMN! The s.o.b. was *closer* to fitting correctly that the 1st tank, but the rear bracket was still too far back! It was one week from the beginning of my long May trip & I was *seriously* PISSED!

Looking closer at the oem Honda bracket that the rear of the tank & front of the seat interface to, I noticed that this bracket *could* be moved farther back, if I were to slot its bolt holes that are used to attach it to the frame. I called Knut & told him about the fit problem and he offered to take the tank & give me my money back. I thanked him for the offer, but I didn't want my money back, I wanted a tank that fit & that I was going to try to make this one work.

I removed the Honda bracket and slotted the two bolt-holes to slide it back. With this done I was able to bolt the tank in place & the seat still fit OK also. So next, I removed the petcock & reserve fuel sending unit from the oem tank and installed them on the CarboTech tank. With the tank fitted back to the bike, I filled the tank with enough gas to bring the level about 1 inch above the petcock opening. I noticed during this filling process that about 0.5 gallons of fuel was needed to bring the fuel level above the petcock opening. Hmmm... Letting the gasoline sit over night to verify that I didn't have any leaks, I noticed that the tank could be tilted side-to-side because of the missing rubber bushings in the rear mount that didn't fit. In this tilting process, I noticed that the tank appeared to be resting against something *hard* underneath in its normal position. Upon closer inspection, I noticed that the front of the slightly repositioned petcock was hitting the top of the valve cover on the rear cylinder.

Off to the hardware store, I pick up a piece of 1/8" (inch) thick aluminum bar stock & some large rubber "sink stoppers". I cut the aluminum bar stock to size, drilled it, & used it to shim the "slotted" Honda bracket higher up to help the petcock clear the valve cover. I then cut the rubber stoppers down in length so I could use them on top of the frame rails on each side for the tank to rest on. This would raise the rear of the tank a little higher & get rid of the side-to-side tilting problem I had noticed earlier. With the shim, stoppers, & tank in place; I now had ~3/16" clearance between the front of the petcock & the rear valve cover. Yes, the seat still fit OK.

It was at this point I noticed the strong smell of gasoline near the petcock & fluid on one of the petcock mounting bolts. The petcock-to-tank seal was NOT leak tight. The sealing mechanism is a flat flange on the tank, o-ring flange on the petcock, & the o-ring around the fuel filter tube that passes thru all of these. Apparently, the flatness of the CarboTech tank flange area was not flat enough. I smoothed & leveled the surface as best I could, called Loctite technical support & discussed this metal/carbon-fiber flange & o-ring seal problem, & got a recommendation of their Permatex #2 non-hardening Form-a-Gasket product to use across the flat flange area as a backup to the o-ring seal. It worked!

With everything back together & 0.7 gallons added at home, I rode it to the gas station a couple of blocks away & added 5.3 gallons with some room to spare.

Conclusions:
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I just returned from that 5-day, 1800-mile trip on the VTR. The tank is about 2 inches taller than the oem, so it sets my tankbag a little higher & I can't get quite as far out of the wind when tucked in. This is the only difference I noticed about its physical size.

The increase in the fuel range of my VTR with this tank is amazing. During this trip, we had numerous gas stops where I took 4.1 to 5.1 gallons. Each and everyone of these trip legs would have left me stranded on the side of the road with my OEM tank & its 3.9 gallon *actual* capacity.

I generally like the design of the CarboTech tank. The problem as I see it is that CarboTech has a mis-aligned VTR jig that they need to fix. The correct placement & ID of the pivot tube would have eliminated ALL of my mounting & alignment problems. I'm going to consider finding a shop locally that can make up a correct size pivot tube & re-mount it in the correct location to fit my VTR. Then I could replace all of my *modified* Honda parts & have the oem tank fit also without changes.

Would I recommend this tank to other VTR owners? Yes, BUT ONLY if you are patient, have good moto-mechanic skills, and *really* need more fuel range from your VTR.

Catfish ...
_________________________________
Mike Chaplin <catfish at endorphin-express dot com>
Concord, Ca.
http://silcon.com/~catfish/