Why did factory teams use aluminum tanks back in the day?

Mike P.
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Mike P.
Edited Date/Time 7/23/2015 1:56pm
I just don't understand why they were used? I get why they use them today as the 4 strokes run so much hotter, but this was not even on anyone's radar as far as i know back in the 70s, 80s & early 90s? Would love to here the reasoning since plastic is lighter…but alloy does have the coolnest factor, but was the added weight worth it?
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Murph
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Murph 2/24/2015 10:14am
2/24/2015 10:14am
I would say the main reason was to save weight. The works tanks were hand made from very thin sheet aluminium and therefore would have been significantly lighter than the production tanks, especially in the 70s when fibreglass was more common.

Then of course, the other reason is simply the exclusivity factor.
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Brad460 2/24/2015 10:20am
2/24/2015 10:20am Edited Date/Time 2/24/2015 2:46pm
In my experience (having worked for one of the current manufacturers, but in a different product line) aluminum tanks were made by our fab shop when the stock tank dimension did not work or fit the design/function. Mostly when there would be a small number of tanks built.

Most all early model prototype units came with aluminum fuel tanks and they were not made from plastic until later into the prototype testing stages when the design was finalized.

From a racing prespective they built aluminum tanks because the tank sizes were either decreased or increased (more fuel of less fuel) or the shape was slightly changed..design change..etc..

In one race application a very small aluminum tank was built and put inside the plastic tank..

Too expensive to make a plastic mold for a handful of one off tanks.

Murph
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Murph 2/24/2015 10:28am
2/24/2015 10:28am
Good point, and the factory bikes before the production rule was brought in bore very little resemblance to the production bikes so the standard tank probably wouldn't fit anyway.
Mike P.
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Mike P. 2/24/2015 11:08am
2/24/2015 11:08am
all great points and well taken, but how does this explain the use of aluminum tanks in the early 90s when even the factories were often using OEM frames? Take a look at the below photo of Davy Stribos' 1989 RA125 with an aluminum tank, however the bike is clearly based on the stocker save the works swing arm and few other prized bits…



The Shop

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Banana_oil
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Banana_oil 2/24/2015 12:31pm
2/24/2015 12:31pm Edited Date/Time 2/24/2015 12:31pm
All alu tanks I have seen are larger than stock and I'm pretty sure that's the main reason. Sometimes much larger but mostly just a little. The RM125 tank goes further down than the stock tank on the left side.



vanillaice782 2/24/2015 2:10pm
2/24/2015 2:10pm Edited Date/Time 2/24/2015 2:11pm
Banana_oil wrote:
All alu tanks I have seen are larger than stock and I'm pretty sure that's the main reason. Sometimes much larger but mostly just a little...
All alu tanks I have seen are larger than stock and I'm pretty sure that's the main reason. Sometimes much larger but mostly just a little. The RM125 tank goes further down than the stock tank on the left side.



Holy shit! How much gas does that thing hold? I second the holds more gas theory. I remember seeing some ex-factory parts for sale at random times and it seemed like it was for extra capacity.
Mike P.
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Mike P. 2/24/2015 2:44pm
2/24/2015 2:44pm
Thanks guys, i'll have to weigh the stocker against the aluminum tank to see how much more the aluminum tank weighs and then fill them both up with water and weigh them again (stand by the for results)…my gut feeling is that the extra gas at least on a 125 may not necessary be worth the added weight as weight is everything when it comes to 125 (unless you are talking cross country desert or woods riding). More to come!
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jtracing6 2/24/2015 7:27pm
2/24/2015 7:27pm
On the works bikes of the eighties it would have been easier to fabricate an aluminium tank than a plastic one. The plastic tank would have been moulded, thus making it necessary to manufacture a mould. The aluminium tanks used on modern four strokes are due to the vacuum pressure from the fuel pumps and most plastic tanks would collapse though I'm sure Honda use a plastic tank on CRF's.
MaxPower
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MaxPower 2/25/2015 5:15am
2/25/2015 5:15am
Mike, isn't the tank on your 77 RM super light? Im probably wrong but i thought it weighs less than a plastic tank.
I remember wear marks from knees rubbing a 77 RM metal tank were something riders tried to prevent with tape and covers. Now i think its cool looking
Mike P.
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Mike P. 2/25/2015 12:15pm
2/25/2015 12:15pm
Kevin,

The 77 RM tank is very light, but I don't think they ever made a plastic replacement for it so I have no idea of the weight differences (plastic vs aluminum). I do know that Clarke makes a plastic replacement for the 76-78 RM250/370 but not for the 125. I purchased an aluminum tank for my 1990 RM125, which is why I am asking all the questions because the tank of this bike is much bigger than the 77 tank. I should have some pics up on it shortly. Mike
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GIwasB4 2/25/2015 1:56pm
2/25/2015 1:56pm
The aluminum tanks are made for capacity and form testing prior to producing the form to mass produce the plastic. The plastic tank is usually lighter. The forms for plastic are expensive and can only make so many units before needing to be redone. Hence the reason the Strictly Hodaka guy has not made the Preston Petty Tony D repop, his current form is worn out and I think he said $30,000 for a new one.

My 1980 YZ125 plastic tank weighs #3.2, the aluminum tank tops the scale at #4.6. The alloy tank also has just over 3 pints more capacity.






Mike P.
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Mike P. 2/25/2015 2:16pm
2/25/2015 2:16pm
Okay this explains a lot. So my 1990 RM125 tank is likely going to be heavier. I'll have to check the capacity as this can be the only reason Suzuki used them. It's kind of funny, I know Honda had went to the stock tanks after the production rule went into affect in 86 (they were always the hold out on this rule), yet Suzuki the one company that did their own self-imposed production rule before anyone else did was still making these alloy tanks as recent as around 1996.
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GIwasB4 2/25/2015 2:32pm
2/25/2015 2:32pm
Also the reason you can't buy certain models of body work from the manufacture. The forms are toast and to retool new ones is not worth it to sell to such a limited buyer base.
Sure would be nice if Honda just popped out new 1979 or 1984 (etc.) CR fenders, shrouds and tanks.
MaxPower
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MaxPower 2/25/2015 6:21pm
2/25/2015 6:21pm
DC or whoever makes plastic for DC replicates body work for some pretty uncommon bikes. Is there a cheaper way they are making them? I dont see too many 80/81 KXs or 76 Pentons around and cant see them breaking even with those models.


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Cancerman 2/26/2015 7:50pm
2/26/2015 7:50pm
Mike P. wrote:
Kevin, The 77 RM tank is very light, but I don't think they ever made a plastic replacement for it so I have no idea of...
Kevin,

The 77 RM tank is very light, but I don't think they ever made a plastic replacement for it so I have no idea of the weight differences (plastic vs aluminum). I do know that Clarke makes a plastic replacement for the 76-78 RM250/370 but not for the 125. I purchased an aluminum tank for my 1990 RM125, which is why I am asking all the questions because the tank of this bike is much bigger than the 77 tank. I should have some pics up on it shortly. Mike
Back in the early days, they raced 40-45 min. motos, and the pros would run out of gas. They tested, and would add just enough oversize to make it. They do this now for the outdoors. And of course with the heat of the modern 4 stroke, you can start boiling your fuel, as well. Running out of gas with 2 laps to go is a bitch. A modern 125 2 smoke can run 2-5 lap motos and practice, one one tank of gas!
Mike P.
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Mike P. 2/26/2015 11:16pm
2/26/2015 11:16pm
I get it in terms of running out of gas, but I also like the argument about the cost of plastic molds and it being easier to make an aluminum tank. However, none of this really makes sense regarding the 89-94 RM125s, because i do not recall hearing of any of the privateers on the GP circuit running out of fuel and they were using the standard plastic tank. I think (and this is just me), the Factory team used the aluminum tank on this bike because it gave them options such as adding additional space to the tank (should they need it), but other than that the plastic tank, which they had the mold for is by far the weight saver of the two…I'll enjoy my aluminum tank and use titanium bolts to hopefully save a little weight. But If all else fails, it is certainly something to look at and sit around and talk about in the pits. Thanks everyone, Mike.
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NetMXer 2/27/2015 2:08am
2/27/2015 2:08am
It's a lot easier to build a custom sized tank out of aluminum than it is from plastic. Unless you need to make a large number of tanks the same size, just making the molds for plastic tanks would be as much effort as making the aluminum tank itself.
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GIwasB4 2/27/2015 4:37am
2/27/2015 4:37am
Mike P. wrote:
I get it in terms of running out of gas, but I also like the argument about the cost of plastic molds and it being easier...
I get it in terms of running out of gas, but I also like the argument about the cost of plastic molds and it being easier to make an aluminum tank. However, none of this really makes sense regarding the 89-94 RM125s, because i do not recall hearing of any of the privateers on the GP circuit running out of fuel and they were using the standard plastic tank. I think (and this is just me), the Factory team used the aluminum tank on this bike because it gave them options such as adding additional space to the tank (should they need it), but other than that the plastic tank, which they had the mold for is by far the weight saver of the two…I'll enjoy my aluminum tank and use titanium bolts to hopefully save a little weight. But If all else fails, it is certainly something to look at and sit around and talk about in the pits. Thanks everyone, Mike.
Maybe Hubbard can pose the question to Cooper as to why they ran aluminum?

Maxpower: "DC or whoever makes plastic for DC replicates body work for some pretty uncommon bikes. Is there a cheaper way they are making them? I dont see too many 80/81 KXs or 76 Pentons around and cant see them breaking even with those models. "

Yes, they use a different process which is why the result is a matte or dull finish, and not as smooth or shiny as the OEM injection molded plastic.

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YAMATHUMP
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YAMATHUMP 2/27/2015 3:32pm
2/27/2015 3:32pm
Brad460 wrote:
In my experience (having worked for one of the current manufacturers, but in a different product line) aluminum tanks were made by our fab shop when...
In my experience (having worked for one of the current manufacturers, but in a different product line) aluminum tanks were made by our fab shop when the stock tank dimension did not work or fit the design/function. Mostly when there would be a small number of tanks built.

Most all early model prototype units came with aluminum fuel tanks and they were not made from plastic until later into the prototype testing stages when the design was finalized.

From a racing prespective they built aluminum tanks because the tank sizes were either decreased or increased (more fuel of less fuel) or the shape was slightly changed..design change..etc..

In one race application a very small aluminum tank was built and put inside the plastic tank..

Too expensive to make a plastic mold for a handful of one off tanks.

Now why would they need a tank inside a tank? Could have been a little illegal activity?

Things that make you go hmmm.
philG
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philG 2/28/2015 6:52am
2/28/2015 6:52am
Its all down to cost, a good fab guy can make a tank on a bench by hand, and it will be exactley what you need, a plastic tank will need thousands of dollars of tooling to produce , and once you have decided what shape it is , you are stuck with it.

The factory bikes that run aluminium when the stockers are plastic, might be different underneath , coils in different places and stuff done just to make it easy to work on , not built down to a $$ price.

Once you got to production , plastic is the way to go , cheap clean and really easy to automate.
Mike P.
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Mike P. 2/28/2015 1:18pm
2/28/2015 1:18pm
The alloy tank arrived today and I probably should have just waited until I had it in my hands before opening this topic as a lot was revealed when I put the two tanks side by side. First, the weight difference is not at all as different as I thought it would be, in fact the alloy tank is only slightly heavier (check the photos of both tanks on the scale). I think the reason the weight is not all that different between the tanks is because the mounting hardware is drilled into the alloy tank where as the hardware for the plastic tank has been added (I'm talking about the bolts used to mount the petcock, seat & radiator shrouds). Next, the works tank sits slower in the frame or rather the top of the tank (at the gas cap) is lower which will give the bike a flatter feel (much like a modern bike). I took some measurements and the dimensions are slightly different between the two. Lastly, I don't plan on painting the tank but I am going to add yellow decals (like the ones on my plastic tank in the photo). This way I cover up enough of the aluminum to give the tank a yellow appearance while exposing enough of the aluminum that it can be seen. Thanks again everyone, Mike
















Mike P.
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Mike P. 2/28/2015 1:22pm
2/28/2015 1:22pm
I spoke too soon, take a look at the last set of photos I sent and pay attention to the appearance of the two tanks in the photo side by side...see the differences at the bottom of the tanks? Looks like I am going to have to powdercoat this tank as the decal will not run along the lines of the tank...that sucks oh well...
Banana_oil
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Banana_oil 2/28/2015 2:01pm
2/28/2015 2:01pm
Very nice tank! You can always buy yellow vinyl and cut it to fit your tank. You won't need the perforation on the alu tank anyway.
Mike P.
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Mike P. 2/28/2015 2:17pm
2/28/2015 2:17pm
Banana_oil,

Where can I find yellow vinyl in large enough sheets?
Banana_oil
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Banana_oil 2/28/2015 2:26pm
2/28/2015 2:26pm Edited Date/Time 2/28/2015 2:28pm
Thick background sheets is an option but may not be large enough. Otherwise you should be able to get it from Evo-mx. I'm pretty sure they also can make a customized tank piece for you at a reasonable price.

http://www.ebay.com/itm/N-Style-Cut-To-Fit-Background-Yellow-12in-x-14i…
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wolfy0067 3/1/2015 4:49pm
3/1/2015 4:49pm
Look at the 84/85 factory RM250's the trick back then was to run a 125 tank this allowed you to lower the radiators, then we had works pipes to clear the lowered radiators. Just recently sold mine can post pictures, had a preproduction engine, boost ports drilled in the top of the intake modified head with a trench cut on the backside to match th boost port
Mike P.
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Mike P. 3/1/2015 5:40pm
3/1/2015 5:40pm
Wolfy0067,

Would love to see the photos. The sort of good and bad thing about Suzuki was there budget (or lack there of). Suzuki seemed to have budget issues and yes, back in the early to mid 80s they had bonafide works bikes, but by the late 80s they were production bikes with a lot works parts. That was the bad, the good is that it's easier to build a true works replica because they were based on production motorcycles.
Sidecar
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Sidecar 3/3/2015 10:30am
3/3/2015 10:30am
Please don't put viynl or paint or powder on it...... They look soooooo good polished!!
Iv got 5 bikes with polished alloy tanks on
Inc a 1997 TM, a 1990 Husaberg, a 1998 YZF400, a 2003 Vertemati 500 mx and my 1989 EML KX500 sidecarcross outfit in my avatar pic.
newmann
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newmann 3/3/2015 11:44am
3/3/2015 11:44am
Definitely don't powder coat an alloy tank. That stuff is nearly impossible to get off and most people blast the surface to get the powder to stick if I am not mistaken. You can do an acid wash, epoxy prime and paint and be able to strip it in the future if you ever wanted to and the aluminum would still look new, no sanding scratches or anything.
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FreshTopEnd 3/3/2015 2:28pm
3/3/2015 2:28pm
The used them because they are trick as beans, and they can afford to replace them every moto when they get knee-crushed.

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