Why not run an off road tank?

thearc
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thearc
Edited Date/Time 8/18/2022 7:04pm
I think in general manufactures want to keep weight as low as possible?
I'm an off road guy on a KTM and never understood why MX guys don't run the same tanks and don't fill them up. wouldn't that keep weight lower? What am I missing?


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Rickyisms
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Rickyisms 8/16/2022 12:41pm
8/16/2022 12:41pm
I can definitely feel a difference with a full SX tank vs a full off-road tank on my 125. The weights lower, but the bike isn’t made for it so it doesn’t work as good as you think. My big tank is a pain in the ass to get the plug out, I can get to it from either side. I like using the SX tank unless I have to switch, A lot easier to clean.
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Taylor415
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Taylor415 8/16/2022 2:23pm
8/16/2022 2:23pm
Us vet guys only do like five laps at a time, don’t need much gas!
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nskerb
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nskerb 8/16/2022 2:47pm
8/16/2022 2:47pm Edited Date/Time 8/16/2022 2:48pm
I guess if the weight HAS to be there (ie large fuel load for long distances covered) it’s better to be lower. But if it doesn’t have to be there at all then it’s better to just not have it.
LouisianaMotocross 8/16/2022 3:08pm
8/16/2022 3:08pm
I see no reason to run a larger tank typically, but at the Colorado national would it help? I know boiling is some of the issue and it possibly wouldn’t help in that case.

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slowgti
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slowgti 8/16/2022 3:28pm
8/16/2022 3:28pm
LouisianaMotocross wrote:
I see no reason to run a larger tank typically, but at the Colorado national would it help? I know boiling is some of the issue...
I see no reason to run a larger tank typically, but at the Colorado national would it help? I know boiling is some of the issue and it possibly wouldn’t help in that case.
The lower tank has more volume but it closer to the heat source. Sounds like testing time
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colintrax 8/16/2022 3:41pm
8/16/2022 3:41pm
Lower hanging gas is why these bikes have testicle tanks. You'll see it on rally bikes too. The idea works well, but I'd suspect we see regular MX tanks because they 1. Look better and 2. Moving 1 gallon lower won't make a huge difference.

MaxPower
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MaxPower 8/16/2022 3:55pm
8/16/2022 3:55pm
Taylor415 wrote:
Us vet guys only do like five laps at a time, don’t need much gas!
His point is to run the same amount of fuel just that it would be carried lower . I think it's a good idea.
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BobPA
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BobPA 8/16/2022 4:23pm
8/16/2022 4:23pm
Herlings ran an XC tank a few years ago at some of the sand tracks
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skeef2.0
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skeef2.0 8/16/2022 4:29pm
8/16/2022 4:29pm
I never went past half a tank on my xcf. It was more of a pain. Leaving gas in it, having the gas on half of the tank when I was at the track. Only time it came in handy was for long open desert rides. Besides that I wish I had the moto tank.
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hellion
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hellion 8/16/2022 4:32pm
8/16/2022 4:32pm
I’ve often wondered this too, although the XC tanks are a bit wider and taller so they do hinder movement slightly. But if you’re carrying one gallon of gas in either tank it would make sense to use the tank that carries it lower.

I can remember when we could but radiator relocation kits that would lower our radiators some insignificant amount too, think it was 10mm. And even full, a radiator is very light so I doubt this made any difference at all.
Forty
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Forty 8/16/2022 5:12pm
8/16/2022 5:12pm
Not a bad idea if all else is equal with the exception that the weight is lower on the bike. Worthy post
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Luxon MX 8/16/2022 5:55pm
8/16/2022 5:55pm
Fuel weight is variable - a full tank weighs a lot more than a nearly empty tank. One goal is to keep the feel of the bike consistent as that weight changes. You can imagine the huge change in feel over the course of a moto if the fuel tank were located on the end of the front fender. That's obviously an extreme example, but it holds true wherever the fuel tank is.

To minimize the change in feel due to the change in fuel level, the ideal tank placement doesn't necessarily lower the fuel on the bike, but rather puts it right at the center of gravity of the bike. That's not possible as there are parts in the way, but I imagine the OEMs put the fuel as close to it as they can.

Whether or not an off-road tank is better for fuel distribution than a standard tank depends on how close each tank keeps the fuel to the center of gravity of the bike. I suspect the standard tank does a better job of that, but I haven't had much of a reason to verify that suspicion either.
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KirkChandler
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KirkChandler 8/16/2022 6:11pm
8/16/2022 6:11pm
The only time I’ve ridden a motocross bike with an OffRoad tank it changed the ergonomics of the bike and it felt wider. It was also taller in the front and didn’t allow for sliding up as far forward with the stock tank. But it may be different on each model.
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BobPA
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BobPA 8/16/2022 6:50pm
8/16/2022 6:50pm
KirkChandler wrote:
The only time I’ve ridden a motocross bike with an OffRoad tank it changed the ergonomics of the bike and it felt wider. It was also...
The only time I’ve ridden a motocross bike with an OffRoad tank it changed the ergonomics of the bike and it felt wider. It was also taller in the front and didn’t allow for sliding up as far forward with the stock tank. But it may be different on each model.
The tanks on KTM's XC line are barely noticeable, if at all. They also do not carry a heck of a lot more fuel vs their SX counterparts.
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KiwiBermRailer 8/16/2022 6:58pm
8/16/2022 6:58pm
BobPA wrote:
Herlings ran an XC tank a few years ago at some of the sand tracks
Don’t mention the H word on Vital 😂😂
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FWYT
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FWYT 8/16/2022 7:01pm
8/16/2022 7:01pm
I run a big tank all the time just because I don't like switching back and forth between the occasional trail ride, GP race and then just spinning laps. Obviously I don't feel the thing up just for out doinging laps. And I'm not much of a bike squeezer so the size does not bother me. I don't even notice it.

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motomike137
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motomike137 8/16/2022 7:58pm
8/16/2022 7:58pm
It seems like half the commenters missed the point here. I'm assuming Herlings used it for the extra capacity, the OP is looking to lower the cg of the bike and only run 1 gallon in either tank. How much more does the off road tank weigh over the moto tank?
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Gravel
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Gravel 8/17/2022 6:02am
8/17/2022 6:02am
A big tank that’s half full makes for strange handling, 10 pounds of fuel wildly sloshing around isn’t good.

Maybe tank foam would help? I’ve been wanting to try that stuff for years, it’s common in car racing for handling and safety reasons.
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Nate_Ferderer 8/17/2022 6:24am
8/17/2022 6:24am
The Austrian OE off-road tanks are slim compared to some, like Honda’s, but it’s still wider than the SX tank. The lower CG is not worth the bulk. If range is not an issue (US national enduro’s, EnduroGP, ISDE) the factory guys use a translucent SX tank.
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Rider 5280
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Rider 5280 8/17/2022 8:22am
8/17/2022 8:22am Edited Date/Time 8/17/2022 9:00am
Gravel wrote:
A big tank that’s half full makes for strange handling, 10 pounds of fuel wildly sloshing around isn’t good. Maybe tank foam would help? I’ve been...
A big tank that’s half full makes for strange handling, 10 pounds of fuel wildly sloshing around isn’t good.

Maybe tank foam would help? I’ve been wanting to try that stuff for years, it’s common in car racing for handling and safety reasons.
I tried reticulated foam to reduce sloshing in a 3.2 gallon IMS tank I ran on my 2007 Honda CRF450R (stock volume was 1.9 gallons). This type of tech is used in helicopters, race cars, etc.

It did help with handling as far as better controlling the sloshing fuel (I'd rate it a 6/10), but it also did the following:
(1) Reduced range, which makes total sense given you've added something in the tank/reduced fuel volume. It just happens that this 80-mile loop a buddy and I would hit hard was the max range of the IMS tank. First time out with the tank foam and I came up about 1 mile short. Live and learn ...
(2) Fuel system contamination: the foam gives off little bits of debris initially, and in my case ended up clogging the in-tank fuel filter. It definitely affected performance, but once I cleaned things up, all was good. So basically, s good "rinsing" of the foam was required and accomplished on my 79 mile ride with vigorous sloshing of fuel. If I were to do it again, I'd wash/dry the foam several times in the kitchen sink before installing in the fuel tank.

Ultimately I ended up just getting rid of the foam. It wasn't that much of a game changer for the primary type of riding at the time (desert, not MX) relative to the hassle. That said, I was so used to no foam (and the impaired handling) that I was OK going back to my original setup AND running out of gas leaves an impression on you. In my case, in the middle of the desert, I wanted all the fuel I could get.
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Rider 5280
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Rider 5280 8/17/2022 8:25am
8/17/2022 8:25am
Dirt.Squirt wrote:
I swear to god my yz450 handles better with a full tank
I found this same thing on a 2007 CRF450R I ran a larger capacity tank on.

I assumed it was the extra weight on the front end that improved cornering.

The extra weight was also good for calming the chassis down in general for off-roading.

Was the bike as fun on an MX track in this configuration? Nope. But it wasn't bad.
Jeremy Macduff 8/17/2022 8:32am
8/17/2022 8:32am
If I'm remembering correctly, Ricky Dietrich used to run a desert tank when he raced some of the outdoor nationals. You'll never see a desert tank on the podium. Weight and CG is everything.
peelout
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peelout 8/17/2022 10:49am
8/17/2022 10:49am
i run an IMS 3gal at all times, and a kickstand. moto, offroad, fuck it
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rawjahdesigns
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rawjahdesigns 8/17/2022 8:44pm
8/17/2022 8:44pm
peelout wrote:
i run an IMS 3gal at all times, and a kickstand. moto, offroad, fuck it
Peely, Lets get flat brother. How do i get ahold you? Hong Kong in TJ?
GoggleFiend904 8/17/2022 9:05pm
8/17/2022 9:05pm
I recently put an IMS on my cr250, I can’t stand it. I did like the xc tank on my sx though, obviously the fit was great.

I really wish someone would make a slightly larger tank, no 3+ gallons. 2.5 would be perfect for me
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Gravel
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Gravel 8/17/2022 9:12pm
8/17/2022 9:12pm
Gravel wrote:
A big tank that’s half full makes for strange handling, 10 pounds of fuel wildly sloshing around isn’t good. Maybe tank foam would help? I’ve been...
A big tank that’s half full makes for strange handling, 10 pounds of fuel wildly sloshing around isn’t good.

Maybe tank foam would help? I’ve been wanting to try that stuff for years, it’s common in car racing for handling and safety reasons.
Rider 5280 wrote:
I tried reticulated foam to reduce sloshing in a 3.2 gallon IMS tank I ran on my 2007 Honda CRF450R (stock volume was 1.9 gallons). This...
I tried reticulated foam to reduce sloshing in a 3.2 gallon IMS tank I ran on my 2007 Honda CRF450R (stock volume was 1.9 gallons). This type of tech is used in helicopters, race cars, etc.

It did help with handling as far as better controlling the sloshing fuel (I'd rate it a 6/10), but it also did the following:
(1) Reduced range, which makes total sense given you've added something in the tank/reduced fuel volume. It just happens that this 80-mile loop a buddy and I would hit hard was the max range of the IMS tank. First time out with the tank foam and I came up about 1 mile short. Live and learn ...
(2) Fuel system contamination: the foam gives off little bits of debris initially, and in my case ended up clogging the in-tank fuel filter. It definitely affected performance, but once I cleaned things up, all was good. So basically, s good "rinsing" of the foam was required and accomplished on my 79 mile ride with vigorous sloshing of fuel. If I were to do it again, I'd wash/dry the foam several times in the kitchen sink before installing in the fuel tank.

Ultimately I ended up just getting rid of the foam. It wasn't that much of a game changer for the primary type of riding at the time (desert, not MX) relative to the hassle. That said, I was so used to no foam (and the impaired handling) that I was OK going back to my original setup AND running out of gas leaves an impression on you. In my case, in the middle of the desert, I wanted all the fuel I could get.
You just saved me $50 and a lot of hassle, thanks!
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Boomslang
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Boomslang 8/17/2022 9:19pm
8/17/2022 9:19pm Edited Date/Time 8/17/2022 11:05pm
Dirt.Squirt wrote:
I swear to god my yz450 handles better with a full tank
Interesting that you mentioned that. A kid over here said the same thing and his comment eventually steered him and his suspension guy in the right direction for a better base setting.

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