What kind of plastic are fuel tanks made of?

[plynn41]

1. What kind of plastic are newer Honda tanks made of?
2. Where can I find some of it?

My attempt at modding my Gen4 tank with a heat gun didn't go so well. I tore a hole in the plastic next to the fuel spigot. I don't think I was going to like the results even if I hadn't had problems, because it looks like it would still be very difficult too change a plug.

Sooooo, on to plan "B", which I think will be a better solution. I cut the bottom 1.5" off of the tank with a table saw. This will be an MX only bike, so I won't miss the loss in tank volume. Now I need to find a piece of compatible plastic that I can fabricate and weld to the tank.

Thanks!

[Tharrell]

Probably the same stuff on all plastic tanks.
Find someone with a graveyard and go to town.

[plynn41]

That's a good idea and I think I know where I can score an old tank.

But I still need to know what kind of plastic they are for the welding process. Anyone?

I think it may be High Density Polyethylene (HDPE), but need confirmation.

[UknowDamright]

well when you do figure it out, you should post some pictures of the process because it would be interesting to see!!

[bearorso]

Couple of things to consider:

A few years ago, CA's CARB legislation (or all over EPA rules?) meant that many tanks had to be changed to meet evaporation / permiability rules.

Honda may have already had no problems with this.

Or they may have just increased thickness in just bikes that came under the legislation.

They may have changed the materials used in tanks that had to pass the legislation. Or all of their plastic tanks.

I know that some companies just added a interior liner to tanks, a cheaper alternative.

Maybe some of the above, are part of the problems people experience with tank mods?

[plynn41]

I've verified that the tank is HDPE. It's 1/4" thick. I purchased a 12x12x1/4" piece of black HDPE from Grainger for $10 that will give me enough to put a new bottom on the tank, and also fabricate the airbox-boot piece. I'm practising my plastic welding right now on scrap, but also asking around for a pro to do the work due to the nature of being a fuel container.

I plan to put the new tank bottom in the oven to preform a slight recess in the middle so fuel will naturally flow toward the spigot. If it goes to plan, it should look slick and give plenty of room to change plugs. I'll lose maybe a quart of fuel capacity, but don't care since I only ride on mx tracks. I'll post up pictures when I do this work.

[Mik329]

How did this go??

[plynn41]

Sorry about the delay. I'm not done yet. We're racing this weekend so it'll be the first of the week before I can put some pics up. I've welded the new bottom of the tank on and it is structurally sound. I have yet to fabricate a "catch-pool" resevoir for the spigot so that the bike will not starve for fuel before it actually runs out. The welds aren't pretty, but they do work. It's actually not that difficult to do the welding, but it is easy to overheat the plastic with a torch and lose everything (plastic melts and shrinks).
The tank is on the bike right now, and with the new bottom, I will have plenty of room to change plugs, and I can also run the stock coolant lines out of the head. I'm estimating the tank will hold about a gallon of fuel. Obviously not a good solution for offroad guys, but won't be a problem for mx.