[Casey_m]

Are the old TRX350D’s (mine is an ‘88) known for being gas hogs? We went up to the mountains last week and rode all over, and I had to switch to reserve while my dad (riding my ‘88 TRX300 2WD) had barely used 1/4-1/3 of a tank. Is this normal?

 

[PatrickB]

Well they are heavier and full time 4wd compared to the 300 which is lighter and 2wd.....so I think that would have something to do with it. Plus the 350 gas tank is actually quite small, probably smaller than the 300 gas tank.

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[Casey_m]

Well they are heavier and full time 4wd compared to the 300 which is lighter and 2wd.....so I think that would have something to do with it. Plus the 350 gas tank is actually quite small, probably smaller than the 300 gas tank.

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You’re right. 2.8gal to the 300’s 3.3gal, and #150 more weight, plus I weight #40 more than my dad. I was just surprised that I was sputtering and his fuel level was dang near full! Thinking ahead to hunting season, I might have to carry an extra fuel bottle, just in case.

Aside from that, this was a great shakedown run after bringing the bikes back from the dead. Still need a few more parts (rear tires on the 350, new front fender on the 300, couple other little things)

 

[PatrickB]

Yeah I actually took my 350 on a 20 mile trail ride before and barely made it without running out of gas haha.

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[Casey_m]

Yeah I actually took my 350 on a 20 mile trail ride before and barely made it without running out of gas haha.

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Sounds familiar. A few short jaunts up and down the roads around camp, a lot of idling, then 12 miles up the mountain (4000’ to 7200’), and I had to switch to reserve a couple miles into our return trip. That’s where I learned that the petcock doesn’t want to let fuel past in reserve, and actually had to pull the tank from the 300 and drain some gas into the 350 tank.

 

[Goober]

I get about 17 mpg on trails

 

[Casey_m]

I get about 17 mpg on trails

I’m used to my old XL350. I can ride that thing around the mountains for 2-3 full days before switching to reserve!

 

[Goober]

Yeah I actually took my 350 on a 20 mile trail ride before and barely made it without running out of gas haha.

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Sounds familiar. A few short jaunts up and down the roads around camp, a lot of idling, then 12 miles up the mountain (4000’ to 7200’), and I had to switch to reserve a couple miles into our return trip. That’s where I learned that the petcock doesn’t want to let fuel past in reserve, and actually had to pull the tank from the 300 and drain some gas into the 350 tank.

Have you checked for blockage in the petcock or the reserve line. Get a beer line brush or s stout pipe cleaner and ream the line

 

[shadetree]

they are gas hogs.

 

[Casey_m]

Yeah I actually took my 350 on a 20 mile trail ride before and barely made it without running out of gas haha.

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Sounds familiar. A few short jaunts up and down the roads around camp, a lot of idling, then 12 miles up the mountain (4000’ to 7200’), and I had to switch to reserve a couple miles into our return trip. That’s where I learned that the petcock doesn’t want to let fuel past in reserve, and actually had to pull the tank from the 300 and drain some gas into the 350 tank.

Have you checked for blockage in the petcock or the reserve line. Get a beer line brush or s stout pipe cleaner and ream the line

Pulled the petcock and blew ~5psi compressed air into each tank line. Probably not an OSHA approved test, but I got bubbles from both lines. I think petcock is worn. Blowing air into it, no blockages in either position, but I still get some flow in “off” position and can feel air coming through the “on” when it’s in “reserve” position.

On the trail, I switched to reserve and the fuel pump started racing, but engine kept sputtering. I added fuel, switched back to main, and it was fine again.

I’m thinking the petcock rubber is shot, causing it to pull air when in reserve.

 

[shadetree]

ya know, what gets me, is when folks are told to turn their fuel off on gravity fed tanks ?, and then they think they need to do the same with these models ?, well, seeing how they are pump fed ?, there is no reason to turn the petcock off or whatever. just fill it up, ride it. but..when you run out of fuel, you have no choice to turn it to reserve, sooo..there goes that..lol. I keep mine full, and always keep close to my truck..lol.

 

[Goober]

ya know, what gets me, is when folks are told to turn their fuel off on gravity fed tanks ?, and then they think they need to do the same with these models ?, well, seeing how they are pump fed ?, there is no reason to turn the petcock off or whatever. just fill it up, ride it. but..when you run out of fuel, you have no choice to turn it to reserve, sooo..there goes that..lol. I keep mine full, and always keep close to my truck..lol.

I never considered that lols

 

[Goober]

Sounds familiar. A few short jaunts up and down the roads around camp, a lot of idling, then 12 miles up the mountain (4000’ to 7200’), and I had to switch to reserve a couple miles into our return trip. That’s where I learned that the petcock doesn’t want to let fuel past in reserve, and actually had to pull the tank from the 300 and drain some gas into the 350 tank.

Have you checked for blockage in the petcock or the reserve line. Get a beer line brush or s stout pipe cleaner and ream the line

Pulled the petcock and blew ~5psi compressed air into each tank line. Probably not an OSHA approved test, but I got bubbles from both lines. I think petcock is worn. Blowing air into it, no blockages in either position, but I still get some flow in “off” position and can feel air coming through the “on” when it’s in “reserve” position.

On the trail, I switched to reserve and the fuel pump started racing, but engine kept sputtering. I added fuel, switched back to main, and it was fine again.

I’m thinking the petcock rubber is shot, causing it to pull air when in reserve.

Look in the back you might see the packing partially dislodged. You can buy a rebuild kit from openspc on fleabay we put up a thread on it.

 

[retro]

Ya, your rubber spool seal is shot under the petcock spool. You can take those apart and fix them. Just drill the heads off from the two rivets. Then use a smaller drill bit to make holes down through the center of those rivet bodies suitable for a #4 or #6 threading tap. Cut new threads with a tap leaving the shells of those two rivets in place so they can be used as alignment dowels to center up the cover and spool when you reassemble. I think you can buy those 4-hole Viton rubber seals on eBay, but they might not be an exact fit. They'll still work though. Lube the new 4-holer and use two new screws to put the petcock back together. Your other option is take your chances on another used one.

 

[retro]

Ooops! Goober types much faster than I. Didn't mean to step on ya Goob!

 

[Goober]

Hey Retro no problem we know how to fix these @Okie too!
@Casey_m I have rebuilt at least 8 of these. Is your stem damaged in any way? Does the plastic lever still screw on yours? Then it can be rebuilt. I will look for that thread—you only want to shave off the top of that rivet but first you want to drill a perfectly centered and straight pilot hole for your tap.

 

[Goober]

Another thing that happens to affect fuel consumption are leaks at the petcock, fuel pump and lines. You’ll smell that leak fosho

 

[Casey_m]

Thanks guys - good info. I’ll have to get a #4 tap for that rebuild. @Goober yes the red plastic handle is still attached. No leaks - new o-rings on the tank-side of petcock, all new lines, filter, and pump. I’ll look for that thread, and the rebuild kit as well

 

[Goober]

Bumped it for ya, so you can see if you wanna do it.
I use a mini drill press and a homemade jig

 

[Casey_m]

Bumped it for ya, so you can see if you wanna do it.
I use a mini drill press and a homemade jig

That jig looks handy. I’ll make one. Thanks!