Jump to content

rmz250 fuel in the frame mod

Recommended Posts

Back in 02-04, the crf450 you could tie into the frame spars and get almost a half gallon of extra fuel. Last night I was looking at my rmz250 and started to investigate if this was doable. Long story short a it is! So here is the basic plan. I won't be able to get into until later this week,but this is the basics. The bolt that holds the tank-tap that to a larger size with hole through center and attach breather (like the small ones for gas cap). The frame spars have about 3 holes on each side (6 total). The top 2 on each side will need to be sealed. Simply tapping and small bolt with washer will seal them. Jb weld could be used. Where the cast spars meet the tubing section there is the 3rd hole. This gets tapped and a barb will go in.Then a T fitting to attach left and right side. Lastly,from the tee-tubing gets ran to the breather on the gas cap. As fuel is burned in the tank, it will siphon out of the frame rails. Rough math,should get .3-.4 gallons of extra fuel for a total of around 2 gallons of fuel. The downtube could also be tied in for fuel and would add quite a bit more. With the crf's that section was used for coolant recovery. Hope this may help others and I will try to get more info available as I get into it.

  • Like 2

Share this post


Link to post
Share on other sites

OK guys. No BS. This works! Just measured the fuel capacity. 46 fluid ounces which is about .3 gallons. This puts the 2010-15 rmz250 fuel capacity just over 2 gallons! Just thread the center tank bolt to an M8. Drill hole through middle. Plug 2 holes on each frame spar. I used plastic push in plugs and jb weld to seal. Advance auto and Napa have 1/4" threaded barbs-thread them into lower 3rd hole,put t in the middle and barb fuel line into gas cap vent line. As the bike burns fuel,it will create a vacuum and pull the fuel into the tank. Frame spar fuel will get used first. If a barb breaks or line disconnects a fuel will hopefully be used up,drain or just stay in frame. Pretty simple mod for good increase in fuel. Most will be able to do 2+ he's of riding this way without worry.

  • Like 1

Share this post


Link to post
Share on other sites

Sorry. Was finishing it up. You can see where I jb welded over the holes and where I threaded in the 1/8 pipe three 90 for the fuel hose adapters. The holes do not need to be drilled. Just run the 1/8 pipe tap through and install fitting. You can remove this stuff and bike would look like it was never installed. I ran 1/4" fuel line from each frame spar fuel tap beside the frame rail and tee'd them together at the gas cap breather hose. To fill-just get a funnel,pull hose off gas cap tee. Make up a funnel with a piece of hose. Dump fuel in and it will go down both lines and fill until fuel comes out frame breather (drilled bolt). Like I said earlier a it comes out to around 46-55 ounces or .3 gallons.

NCM_0029.JPG

NCM_0027.JPG

NCM_0025.JPG

NCM_0029.JPG

Share this post


Link to post
Share on other sites

I will post up the final pics tomorrow. Today I was busy testing shocks. Another cool thing I noticed today- looking into the intake through the throttle body...you can look through and align the injector. The throttle body boot on the head has 2 little keepers/alignment parts moulded I to the rubber. Cut these off. It is not precise. We aren't talking a huge improvement,but with the tabs cut and the injector better aligned to the divider in the head-i definitely noticed better throttle response and ran smoother. I'd try to get pics of that but its pretty hard. I will try though

Share this post


Link to post
Share on other sites

Good shit ac. I got it to work. I want to note. My frame had rust. (04 steel) i put a drain plug in the bottom, sprayed a canof carb cleaner in it. This is dope! I wanna do this with oil...like the XRs. Much expanding on this idea but now i don't have to ride with two Gatorade bottles full of gas in my back pack

Share this post


Link to post
Share on other sites

Eric- the downtube in front of the motor can be used for oil or coolant. With the steel frame I think the bottom of the tube has to be plugged. Simple to plug and jb weld and you got an oil reservoir or a coolant catch tank. Buell uses a fuel in the frame design and as mentioned, xr and other bikes have used the frame for fluids. Simple idea really. Could kick myself in the ass for not thinking of it sooner lol. Want to mention also a the tubes coming from frame to tank or the frame breather- a larger tube like 3/4 to 1" radiator hose can be ran inline for additional fuel. You can also use the tube as a simple catch can for rad overflow. I will get more pics up this week.

Share this post


Link to post
Share on other sites

Thread from the grave, sorry I have researched this topic quite extensively and I've been unable to find any concrete guides or much information on here or youtube.

I've been looking into this, more looking to do a coolant catch but possibly both if I can.

I am curious what model you did this on and if anyone has tried on a 2014.

Your pictures are very difficult for me to make sense of. Where are the holes you filled located?

Thanks all for any info!

Share this post


Link to post
Share on other sites

Thread from the grave, sorry I have researched this topic quite extensively and I've been unable to find any concrete guides or much information on here or youtube.

I've been looking into this, more looking to do a coolant catch but possibly both if I can.

I am curious what model you did this on and if anyone has tried on a 2014.

Your pictures are very difficult for me to make sense of. Where are the holes you filled located?

Thanks all for any info!

My bike was a 2013 rmz250. Where do you want the coolant to go? If you want the frame down tube-the one in front of motor. You will need to drill and tap a hole at the bottom of the tube and run he over low tube to it. You will also need to drill a small hole at the top of the square down tube for an air bleed. Just like a 1mm hole. The overflow tube hole only has to be like 1/8" and use a vacuum line fitting. The frame fuel mod-the bolt where the fuel tank-that is where fuel goes in. On each frame spar-there are 2 holes already in the frame at the bottom back of the spars. That's where the fuel comes out. Then hoses are run up from the spars,tee together and then a small piece of hose goes to the fuel cap. As the tank fuel drops-it sucks the gas out of the frame and drops into the fuel tank from the fuel cap. Very simple.

Share this post


Link to post
Share on other sites

Ok if I'm understanding correct, I should fill the upper hole (red) and use the lower hole (blue) as the feed line pictured below.

20161023_184451.jpg

Then I use the upper bolt hole (orange) as a fill up/vent hole? If this is so, how does this work as a vent with the bolt in?

Run my line to a T and the up to the tank vent hose (yellow)

And again fill the holes in blue

20161023_184615.jpg

As far as the coolant in the front frame bar, are there other holes that would need filled in?

There is one hole at the top (blue) are there others? Can I use this hole (blue) as a fill hole and overflow tube, then tap a hole in the bottom for a fitting?

20161023_185650.jpg

Thanks so much!

Share this post


Link to post
Share on other sites

Yes on everything you mentioned . The upper hole-put a plastic auto plug in itlike they use for fender plastic and jb weld I to seal. Tap the bottom hole and thread fitting in. The top bolt hole where tank goes- needs to be tapped to a larger bolt or-keep it same size. Either way, you have to drill the center of a bolt out so it's hollow. Basically making a long hollow stud. You can still put a nut on it to hold tank down. Then slip rubber fuel line over it with a fuel filter attached. I had another fuel tank, which was a coolant catch tank from a wr450 or wr426 under the left side panel. So-my hose from the frame ran back to that and then I had a check valve on fuel line into the airbox. I would hook a funnel to the fuel line with check valve and put fuel into the side panel tank. When that was full it would then fill the frame spars evenly . The t from the bottom of the frame spars connects to the breather on the gas cap. When gas level drops in main tank-fuel is pulled from side panel tank into frame spars. Then frame spars drain into main tank and lastly the main tank drains. Hope this helps. From what I see you are on the right track. Just make sure no leaks.

Share this post


Link to post
Share on other sites

I have been running this for a while now.. Works great on my 11 rmz250.. With 2 gallons I can now make 70+ miles.. I also added another short hose and petcock to the right side bottom hole as a drain.. I've now used it 3 times on the trail to give other people gas and comes in real handy to drain the tank into a gas can for whatever reason I have to pull the tank off..

Oh and I added a fuel filter between the T between the frame spars and the bulkhead going in the tank.. I pulled an injector once already and don't want to deal with that again..

Share this post


Link to post
Share on other sites

Thanks for he replies, I haven't had the chance to get this going yet. I changed sprokets and chain this past week. I'm thinking of getting this going when I check valves this winter.

Thanks for the help and suggestions!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×