Project Loose Fillings AKA The Goblin

[Gabriel]

It says NON-SPILLABLE SEALED.
It’s not exactly sideways. Maybe 40-45 degrees. Guess I’ll find won’t I? Ha!!

[ps2fixer]

Yea, I'm not 100% sure if that's good or not lol. I think inside it's still liquid acid like a flooded acid battery, it's just sealed so when charging it doesn't vent. That also means it can't be over charged to balance the cells like a flooded acid battery (shorter usable life I'd guess). A quick google search suggests mounting it an an angle is fine, but upside down is a no go so based on that sounds like it should be fine. The battery type I was thinking was needed for the angle was a AGM battery since the acid is absorbed into a glass mat.

One perk of low mounted batteries is lower center of gravity, should make handling on cement a tiny bit better (probably near unmeasureable though lol).

Also read up a bit on how 2 stroke exhausts work since you're fabbing your own exhaust system. I'm not sure if there's an online calculator or anything, but pipe size and length are pretty critical to have a good running engine. Since it's likely to be putting around, going OEM sized or even smaller would be ideal for low end torque I'd think. Large around pipes are for more HP, or high rpm power generally. Going too big isn't good either. Think about it, a small car engine can run with a 1.25in exhaust making 75hp+, how big of a pipe does a ~13hp engine need. Also don't run an exhaust tip that flares out, it acts like a megaphone. I'm not sure how much pipe size effects noise. For the muffler, from memory, the tractor pipes are straight though with packing around the pipe and small holes. In the car world I'm pretty sure they are called a resonator. They don't quite it down a lot, just a little but has very little effect on flow. Most standard mufflers force the gases though a screen and/or little maze to make it quieter. I'd say go to an ATV junk yard and buy 2 mufflers from atvs that are straight/simple to modify, like the 250es/sx style mufflers and stack them. It will be just a whisper of air. I've seen that kind of setup for hunting machines and the guy I talked to claimed he rode up on a deer and it saw him before it heard him. That setup was on a TRX350D 4x4 (stock pipe + a 2nd pipe clamped to the outlet pipe).

FYI, with the longer pipe and more muffler, you'll probably loose a little power and the carb jetting might end up being too rich. Don't forget to retune once you get the system setup.

[Gabriel]

Yeah but an over sized pipe is pretty easy to deal with should it be a noticeable issue.
A simple restrictor baffle anywhere in the system would increase back pressure.
Unlike two stroke, I don’t think internal volume of the exhaust is much of an issue for this four stroke engine. I could be wrong. We’re gonna find out.
One thing about me and my hobbies....I have no shame when I F’ something up. I’m happy to tell off and maybe someone will learn from it.

[ps2fixer]

All engines have some effect, just 2 strokes whole design on how they run is based on it so it's super critical to get it right. I'm sure the 4 stroke OEM made exhaust pipe has this as part of it's design. For a quick example, I had a parts Jeep Grand Cherokee with the 5.0L V8. The exhaust sounded really good and balanced/happy at the stock length. I went over a hill and pulled about a 2.5ft section off (wasn't clamped down), and the thing sounded like a pile of crap, had a slight backfire sound to it and very unbalanced sounding. The section of pipe was just pipe, nothing special, but it made a huge difference in the sound, and I'm pretty sure it effected how the engine ran, but I didn't' bother trying to get dyno numbers lol.

In either case, the engine will run, but over sized pipe makes you loose out on bottom end torque, but it's high rpm should benefit. If the pipe is sized too much, you loose the speed of exhaust gases to help scavenge the cylinder (just like how a 2 stroke works). This has nothing to do with actual back pressure, it's just a horrible term to explain the scavenge theory to a non-technical person. A by product of having a smaller exhaust pipe, is it builds up more pressure, but it's like a garden hose, more pressure, more volume (speed). It's kind of like the water effect when you run water and slam the valve shut, the volume of the water moving is what causes it.

I never dug into the physics of the exhaust systems too far, but what I've learned seems to make sense. Like a drag race engine with short header pipes that just dump directly into the air is designed as a target length, all the same length (to balance it), and it's purely for WOT max power. I don't have the math handy to run theatrical numbers to give ideal pipe size etc, but the old school way of tuning a 2 stroke before they started using expansion chambers was to put on a straight pipe that's too long, and start cutting off 1/2in at a time till they get the right tuning they are looking for. Either case it's a neat read. I know this isn't a high $ OEM build or anything, just trying to apply what I know as a way to keep the engine performing atleast similar to OEM.

Here's a quick result I found on google, looks like it talks about what I'm thinking in depth. I didn't mention the intake since you're not modifying that, but it has similar effects like the exhaust.

http://www.challengers101.com/IntakeTuning.html

[Gabriel]

The only reason I am considering 1-1/2 pipe is availability
For $15 I can get a mandrel bent 180 degree pipe from eBay. From that moving the metal around wouldn’t be too bad. Then there’s the mass of options.
1-1/2 had LOTS of aftermarket and generic parts support.
Our little one inch pipes....we get squat. There ain’t a muffler shop around (I know cause I’ve called) that can work with 1 inch pipe. No expanders or decent clamps. It sucks.

Move up to 1-1/2 pipe and the whole world is at your feet for options. Ebay has short lengths in a variety of bends. Especially if you look for custom made header pipe parts. People making their headers for automotive use get more than we will ever get. There’s nice quality clamps and ready flared mufflers.
I digress.

I’m going to try it. It will work well or it won’t. I will learn and pass it on.

[ps2fixer]

What about 1.25in? a lot of small 4 cyl Japanese cars run around that size I think. 1.5in is like a 3.0L sized engine worth of piping lol. I think a geo metro used 1in pipe for it's 1.0L lol.

[Gabriel]

You know, you may be more right than you know on this.

I thought the stock exhaust was around an inch. NOT. I took a rotted out stock header (cause I never throw stuff away) and cut it in half.
Looks like it’s actually two pipes, one inside another. The ID is a little over 3/4”.
1.5” would be double and no doubt that would NOT be good.

GD’it! Back to the drawing board.
I can get a 1 inch bender from harbor freight but an expander is just unobtanium.
I didn’t want to do it as my laziness overtook me BUT I’ll just have to lathe turn sleeves to step up to the size I need and weld them in place.

Always learning from failure. Lol!

I suppose a Thank You is in order for making me reevaluate things.
Thanks Cory.

[fabiodriven]

Gabriel, I've made head pipes before from pre-bent pipe shipped to me in multiple pieces. Think about a custom header kit. They ship you bends, you cut them up and use them however you see fit. The diameter we need is difficult to find, yes, but it can be done. You can weld together anything you need from that. Also, you can buy a used head pipe from any number of other applications and cut and weld that into anything you need. You can also find whatever flared pieces you need that way as well.

[Gabriel]

Yeah and something else I’m doing wrong....I’m sitting here trying to build a cart but I ain’t got a horse to put in front of it.

(Focus dumbazz!)


Back to the engine. When I have it complete and installed and wired, I’ll do the exhaust.
Should have the last pieces of the engine case detailed by days end and I’ll post up a picture. See what y’all think about what I’ve done with it.

[ironchop]

Gabriel...it's a busy place inside your head, isn't it?

I'm not far from you, I think. Holler if you ever need something. I might have it

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[Gabriel]

Gabriel...it's a busy place inside your head, isn't it?

I would do what all those voices are telling me to but they’re not speaking English. I can’t understand a word they say.

[ps2fixer]

Not a problem, I'd hate to see someone have issues when it's preventable. I was assuming the stock pipes were about 1in as well lol. FYI if you wasn't aware already, going from 3/4in to 1.5in is more than double the surface area. It's been a while but I was researching exhaust tuning a bit when I was going crazy on MPG stuff. The Idea I had was if I needed to replace my exhaust, I'd go down a size. I'd loose overall HP, but gain in torque/bottom end and the engine should be more efficient MPG wise.

Found a quick online calc for exhaust pipe size. 1.5in = 92hp, 1.25in = 64hp, 1in = 41hp, and 3/4in = 23hp. The calc doesn't say exactly what he HP numbers are exactly. I'm guessing they are ideal hp for the given size. I threw in 13hp and it says the pipe size should be 0.56in lol.

Note: all of the HP ratings are in BHP, if I recall correctly, the two numbers are so close it's not worth converting to "American HP".

https://www.mk5cortinaestate.co.uk/calculator5.php

You're not the first person to make this kind of mistake. My cousin had the silly idea of putting larger exhaust on his 2000 Tundra. He wanted straight pipe dual exhaust for the 4.7L v8 Jap engine so he could hear it roar or whatever. It sounded pretty good but you could tell the engine wasn't too happy. His MPG dropped, he said it felt slower than his 3.4L Tacoma and he got rid of it after like 6 months. His dad got the same truck, didn't touch a thing on it, and he's had it for 2+ years and still loves it. I think he went from around 2in single pipe to 2in or 2.5in dual pipes, no mods on the engine or anything.

I've also seen people put STOVE PIPE (like 10in!) for exhausts. Looks so stupid, and I'm sure their truck runs like crap. Who knows what size of lead pipe they use from the engine though. I wish the general population didn't view loud exhaust as a performance thing, it's a byproduct, not the cause.

[Gabriel]

Won't let me send you a PM. Where abouts is 'Gone'? LOL!
Actually, I got a thing or two I am trying to track down.

Gabriel...it's a busy place inside your head, isn't it?

I'm not far from you, I think. Holler if you ever need something. I might have it

Sent from my Z958 using Tapatalk

[ironchop]

Won't let me send you a PM. Where abouts is 'Gone'? LOL!
Actually, I got a thing or two I am trying to track down.

Yeah I think I turned off my PMs and locked my build thread so that I wasn't bombarded with notifications while I was off the grid.

Tapatalk is awful about that stuff.

I live about 20 miles south of Bowling Green Kentucky, roughly an hour to downtown Nashville from my house.

I'll send you my cell number, text is quickest way to catch me.

Sent from my Z958 using Tapatalk

[Gabriel]

Got most everything ready to start rebuilding. Still need to paint the head and sand the cooling fins. Can't do that until I get a new set of valves and lap them in. Spent all my play money for now, so it'll have to wait.
BUT, here's the Goblin engine so far. Gotta get with Dirtcrasher about the seals and bearings. He's got a good line on that stuff.

Trying to come up with a cool idea for the face of the pull rope housing. Too much empty grey. Needs......something
I'm gonna color in the Honda lettering on the clutch side cover the next time I have the green paint out. Probably when i do the tank and repaint the frame.

I'm getting there, slowly.



The cylinder is a 65.5mm bore 200X. I'm gonna tell you, cleaning the side of those cooling fins wasn't as easy as I imagined. The VHT black wrinkle paint is gummy as heck even after three days hanging over the wood stove, and it took several sanding drums on my dremel