Fuel Tank Failure & Briggs 61102 Upgrades

[Minimichael]

It had been a long time since I'd checked the 2 screws holding the tank on. Then, while out enjoying a pleasant Sunday afternoon ride, I hear what sounds like a big shuffle board puck skidding along the street under me. Time for some upgrades...

 

[Minimichael]

Roughing a manifold for the slide carb. This configuration may change depending on how tuning goes. I'm steering the mani away from the exhaust outlet because I haven't yet decided on a header/muffler design.

 

[Minimichael]

The tank will be this plastic Tecumseh, recently whitened with Rust-Oleum lawn furniture paint. The bracket is eBay, after adjusting the holes slightly to fit the Briggs head.

 

[Minimichael]

Needing a pulse for the fuel pump, I put a two-way vent in the valve cover. I don't expect much oil mist getting through the vent, as it's placed upper left on the exhaust valve spring side of the box. But I also put a small filter inline to catch whatever.

 

[Mariah]

Needing a pulse for the fuel pump, I put a two-way vent in the valve cover. I don't expect much oil mist getting through the vent, as it's placed upper left on the exhaust valve spring side of the box. But I also put a small filter inline to catch whatever.

I give you 10 atta boys for that breather idea...that should work real nice!

 

[Good Vibrations]

Michael,
You are The Man. My bike is on its way to you. You must have watched a lot of MacGyver as a young man.

 

[Studeman68]

Very Nice! I just learned somenthing useful today!

 

[Minimichael]

Thanks. Yeah that breather box pulse is tried and true in my book. And it's just a random plastic barb from farm & fleet's power washer aisle.

To keep the fuel line semi-primed between pump and carb -- even after the motor is turned off -- I'll install a couple one-way check valves along the main stretch of fuel line. Anybody ever notice the resistance level to blow through those check valves can vary from valve to valve?

My biggest creature-comfort upgrade will be splicing a small primer into the fuel system. The primer is a sturdy little bulb, and I'll install it dashboard-style in one of the bike's old crossbar tabs. It'll go right next to the old kill switch (the one with the upgraded wiring).

Also, one badly needed safety upgrade will be a well-fitting flywheel screen. I've blown that off for long enough...

 

[Minimichael]

With this bucket list of must-haves like a fuel pump, check valve, filter to the carb, filter to the primer, and On/Off, ...I might need Photoshop to clean up some of these pics.

 

[Minimichael]

I want the exhaust to be lightweight, fit the bike, and sound cool.

The engine's block is aluminum, so a small collection of expensive aluminum 1/2" npt fittings will form my experimental header mount. The pipe nipples are standard wall, and the elbow is rated for low pressure. I'm not real clear on their heat rating, but want to say they are 6000-level aluminum.

Some cheap flexible steel hose will stand in for the typical heavy iron pipe. It's called rigid wall, and rated for high heat.

And for sound, I'm going with the way more growly 3/4" npt sausage muffler. I wanna say I got that on clearance at Menards for five bucks...

 

[Minimichael]

My plan here is to insulate the block and exhaust port from the stresses of expansion, and contraction, and just all the weight and rattling you get with steel screwed into aluminum...

With this solution, I'm screwing aluminum into aluminum, which should reduce these stresses. I suspect the thing won't last long, but you live and learn. Right? Oh, and I'll put a locknut at the nipple, to prevent bottoming out in the block.

And while I ain't superstitious... I'm going with a healthy dab of dialectric grease on that nipple, too. That, and crossing my fingers...

 

[f4radar]

Nice upgrade but for some reason that 45 on the exhaust looks unnecessary.

 

[Minimichael]

Nice upgrade but for some reason that 45 on the exhaust looks unnecessary.

Indeed. It was straight in my original sketch, but the flex radius of the hose is limited, and it wouldn't clear the bike's fender and frame.



Overnight, that elbow and additional nipple almost doubled the cost of my diy header. $25 turned into $45 right quick.

 

[Minimichael]

I got an aluminum locknut for my diy exhaust manifold but it came too snug. I made a tap with an iron pipe and hack saw, and I thought I'd send pictures.

See the smearing of aluminum slag that built up on the iron threads in that one pic (pipe pointing left)? I learned to go slow after that.

I made my final turns on an intact iron pipe.

 

[jeep2003]

Cool project you are a handy guy! I would be weary of that air filter iv had problems with filters like that being too restrictive for the engine to run right. It might be fine just beware and try it with and without when its on the bike.

 

[Minimichael]

Cool project you are a handy guy! I would be weary of that air filter iv had problems with filters like that being too restrictive for the engine to run right. It might be fine just beware and try it with and without when its on the bike.

Thanks for the tip. I'll watch for that and post more about the carb as I get it tuned.

 

[Minimichael]

I reorganized the fuel lines. I'm counting here on the tank above, gravity, as well as the pressure from that main filter to help the one-way valve operate smoothly. I've found this type of pump doesn't like a lot of push back, especially during idle rpms.

The primer filter is tucked out of the way now, but also more accessible.

I'm getting sort of filter-happy these days with each new carb I learn about. Tuning carburetors well means getting to know their variables. But working with dirty fuel is like letting ghosts into the machine.

 

[Minimichael]

One more thing about the Tecumseh fuel tank bracket..

Aside from fitting the headbolt holes, I also had to grind down a bit of the leading edge where it meets the shroud. See pic..

 

[Minimichael]

While I wait for an eBay throttle to come so I can test ride and finish tuning the carb... These pics are just my getting things refitted.

About that carburetor: It's a Nibbi PE24. It came with two pilot jets (35 & 40) and four main jets (108, 110, 112 & 115).

Some bench tuning has so far helped me settle on the #40 pilot, with the air screw opened less than three turns. (I could barely start the engine with the #35 pilot, and did only after tweaking the air and idle screws to stupid positions.) Unless the test riding results dictate otherwise, I'm going with the #40 slow jet at 2-1/2 turns out.

Some more on current settings: Main jet is the #112 for now; Spark plug is reading tan; Needle in position 3.

The 2-way breather vent and rest of the fuel system appears to be working perfectly. And yeah, it starts right up, idles smoothly, and sounds awesome already.

I'll post again as I complete the tuning.

 

[jeep2003]

One of my bikes i cut the bracket and raised it up an inch or so and it eliminated the need for a pump. But i used a tecumseh carb with the inlet low on the side.