Two Stroke versus Four Stroke

[roughrider]

I'd be equally happy with an 80cc boxer twin cylinder 2-stroke bicycle engine that could be attached to the SBP shift kit - It would be almost vibration free by design.

Yeah man! Boxers are just engineering marvels. Harleys may sound bad ass, but that BMW purr is every bit as cool.

Thanks for the tip on the exhaust extension. I'm already on that like white on rice. But when you say, "high temperature soft silicone hose," what IS that? Heater hose? Like we use in car engine cooling systems? I'd like to source that, but I'm not sure what to use.

 

[Fabian]

Try this link for the type of silicone hose you should be looking at.

http://www.firesleeveandtape.com/high-temperature-heat-resistant-silicone-rubber-tubing-round-star-natural-clear-oxide-red-group.html

 

[roughrider]

Try this link for the type of silicone hose you should be looking at.

http://www.firesleeveandtape.com/high-temperature-heat-resistant-silicone-rubber-tubing-round-star-natural-clear-oxide-red-group.html

Thanks for that. I see those guys only sell in large quantities, but that gave me the info I needed to identify the type of hose that can handle ~500° F. A bit of googling showed that there are hoses available in shorter lengths used in applications like coffee and beer makers. Also I see that you attached the hose at the tip of the muffler. I was planning on doing a splice just before the muffler with my fingers crossed that the temp of the metal would have gotten into acceptable margins by that point. So you're getting peak temps of maybe 350°F at that point. (Maybe?) I haven't found any detailed EGT analyses along the length of the exhaust systems for these engines, so I'm going by generic data--figuring a temp of about 700° F about an inch from the port and dropping off rapidly after that.

I've already designed a test using welder's crayons to mark strategic spots on the exhaust system, btw. I've heard of using paint with known burn temps too. (Bear in mind, I'm more concerned with the temp of the metal than the EGTs, though the two are related, of course.)

Last, that's one heck of a bike! I can see layers of years of trial and error tinkering in the design.

... OK. That was not the last thing. Here's the last thing. All my parts shipped yesterday. They should be trickling in over the next few days. I've been talking a lot, but I haven't shown anyone any pix of the bike I'm working on.

Cheers,
Rick

 

[Fabian]

My bike is fitted with a Koso EGT gauge and the exhaust temperature fluctuates between 650 and 850 degrees Fahrenheit, between cruise and the engine working it's guts out over long periods of wide open throttle at low speed and low airflow over the engine.

The silicone hose fitted to my bike is rated somewhere around 500 degrees Fahrenheit but in over 4 months of use with over spec temperatures, the silicone remains in good condition; maintaining it's soft and pliable characteristics.
I have no issues with replacing the hose every 6 months, or however long it takes for the silicone to degrade and require replacement.

 

[Fabian]

that's one heck of a bike! I can see layers of years of trial and error tinkering in the design.

Absolutely spot on. It's been three years of trial and error and tinkering in the design, and i'm still adding improvements and new and more efficient components to the bike.

By the time the project is complete it will be a 5 year assignment in maintaining my patience and sanity as well as the bike trashing a few relationships along the way, but lets face the cold hard reality of life: women come and go (usually with a huge tantrum) but the bike will always be there in the morning

 

[roughrider]

My bike is fitted with a Koso EGT gauge and the exhaust temperature fluctuates between 650 and 850 degrees Fahrenheit ....

The silicone hose fitted to my bike is rated somewhere around 500 degrees .... I have no issues with replacing the hose every 6 months, or however long it takes for the silicone to degrade and require replacement.

OK. So my guesstimates were right in the ballpark. I found several suppliers of high temp hose in various colors. Where is is the EGT sensor located? Fairly near the port? I can't see it in the pic. Also, what is the diameter of the pipe, and the tip, if different? (Haven't got my stuff yet, so can't measure.)

women come and go (usually with a huge tantrum) but the bike will always be there in the morning

Yeppers. One of sisters once told me that I needed to let a women know right at the beginning that I was intensely devoted to my art work, so if she ever got jealous and tried to fight that, she would lose. It may seem cold, but in fact, that policy has worked out. Any good woman can handle that. My break-ups have been over other things. Lately, I've been preferring to just have some really cool female friends with occasional benefits.

 

[Fabian]

Do a Google search for "Bike Build as of March 2012" and scroll down to No 38 and you will see photos detailing the Exhaust Gas Temperature gauge and how it is set up on the bike.

 

[Fabian]

You will need 1/2 inch internal diameter high temperature silicone hose with a length of 2 1/2 feet to replicate my setup.

Remove the end of the muffler and cut off the internal metal tube, leaving about 2 inches protruding. Take the tubing that's been cut off and cut out 2 sections of 2 inch (length) tube as you will need these to be inserted 1 inch inside each end of the silicone hose so you can zip tie the hose to the frame without deforming it and restricting exhaust flow.

Make sure you have generous radiuses as the hose exits the muffler tip and into the 2 inch metal tube sections that will be tied to the frame. You don't want the silicone tube to collapse in on itself as it enters the metal tubing.

 

[roughrider]

Found it. I see the gauge is mounted at the top of the muffler. I was not expecting temps so hot, that far from the port. Wow.

Now, I heard this from another mechanic. He said you want the gauge at the hottest point, so he'd paint this stripe of engine paint on the pipe, and put the gauge where the paint first burned through. I thought that was pretty clever.

Great page, btw. Nice to see the big list of all your mods.

But yikes! Overwhelming. So... one thing at a time, one thing at a time. And thanks for the data on attaching the hose.

 

[Fabian]

The literature that comes with the Koso Exhaust gas temperature gauge says to insert the probe 6 inches from the exhaust port. Because of the length of the probe, you cannot mount it on the small diameter of the exhaust pipe.
As things are, mounting the probe at the top of the muffler comes to about 9 inches, so that's good enough for me.. Also, when you place the probe in it's fixed position, the tip of the probe sits in the exact centre of the main exhaust flow from the small diameter of the exhaust pipe, and that's where you want it to be.