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Discussion Starter #21
I'm disappointed JP, I thought you would dive in and start experimenting. :)
I was Icarus and I flew too high with bike #1! I'm going to be a bit more careful/conservative with bike #2.

I emptied the tank riding to work today. Now it's time for some MMO and sober gas on the way home to see if it helps the hot start.
THEN we can talk about mods to fix it.
 

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Sober gas, teetotaler gas, lol.
 

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Discussion Starter #23
Well, I just found out my sober station just fell off the wagon! Fortunately there's a station not far away that has some. I'll have to buy some regular though just to get home.

Darn, it looks like I'm going to have to go out for ANOTHER ride to test this....it's s shame to have to ride more, but someone's gotta do the research... 😄
 

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Discussion Starter #24 (Edited)
I put in 1 gallon regular fuel plus 3 cap fulls of MMO. (4 oz per 10 gal or 0.4 is per 1 gal. I think I had 0.5 gal reserve and I estimate the cap is 0.5 of).

I rode 40 miles and stopped for gas, letting it idle until the fan kicked on. I filled up (2.6 gal) with ethanol free and added 5 capfulls of MMO. Took me 6min 30 seconds. Engine was hard to start. Taking 2-3 long cranks to fire.

Rode 4 miles and tried again, same temperature and 6.5 minutes off. This time, one long crank then it started immediately on 2nd attempt!

Technically, I'm still running about 2-3% Ethanol. One more tank will bring the Ethanol percentage even lower.

While typing this, I decided to measure how much a cap holds....it holds 1/12 of an OZ! So I drastically overestimate how much MMO to add. I put in 5/12 oz or enough for 1 gallon!

I'll add more and try again on this tank.

EDIT: I put in the correct amount of MMO, and rode another 6 miles. I let it idle until the fan kicked on shut it off for 6.5 minutes. when I tried to start, it immediately fired but didn't start. Second attempt took a couple cranks and then it started. It was about 5 degrees cooler outside and then when I tried earlier today. The real test will be tomorrow in the heat of the day.
 

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Discussion Starter #25
Well, ethanol free fuel seemed to improve it minimally, but not enough to conclude that that was the cause. I also got TERRIBLE gas milage on that tank of premium! It's also on the side of town where shootings occur, so I'm stopping my experiments with ethanol free fuel. So, I guess, who knows. Still unsolved.
 

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I run E-Free gas as much as possible (I love "sober gas" though, that's pretty funny!) I have pod filters, main jet jetted up to 138, 2 shims under the needles, and have done the pickup coil mod, so I have just about all the hard starting mods you can do, done.

Even with all that I have to hit the starter, then crack the throttle just about a 1/4 second later while still holding start to rev the engine to life after I fill it with gas or stop for just a few minutes. Anything longer than a half hour or so I put the choke on about halfway and do the same "hold start then crack the throttle" trick to get it running, then take the choke off. I don't plan to do anything about it, since I can start it easily myself, but I do acknowledge that my hot starts are different than cold starts (I consider it somewhat of an anti-theft device 😁). Cold starts I just choke it all the way and hit start until it runs, then back down the choke slowly until it wants to idle right.

I noticed I was having REALLY bad hot starts when I had a filter on my carb vent tube. I had a small filter element on the end of it after I did the earshave, but hot starts were impossible. I removed it and tucked the unfiltered, open-end carb vent tube into the upper frame rail that goes to the steering head, and having the tube free has caused no issues and solved that one. May not be your case, but figured I'd mention it anyhow.
 

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I should also mention that these bikes are probably best to run on the lowest octane fuel possible, I run 87 when I have to fill up with ethanol gas, and the E-Free I get is all 89. Higher octane = harder to detonate on lower-compression engines without advanced spark; our engines can't compensate for the different ignition timing required to get the most out of high-octane gas.
 

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So I have NOT done any mods geared towards “correcting” the hot start issue. I have been paying closer attention to what works. What I have found is half the time simply cracking the throttle and hitting the starter together does the trick. If that first attempt does not work, I’ll pull the choke and that usually gets me going. Because of this thread I even tried opening the gas cap for a few seconds and that hasn’t seemed to help or hurt anything. I’m a big proponent of “if it ain’t broke....” so I’m holding off changing anything until something definitive comes up.
 

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Yes Jason, the e-free around here is all a higher octane than 87, might explain the mpg. 89-91 octane depending on the station.

Hey I wonder what flex-fuel does to our bikes? I mean besides eat rubber.

Anti-theft... Be kinda funny for some poor baftard to hop on and get a huge backfire to announce his attempt at stealing my bike. Where ya goin' junior? Need a hand startin' that thing? :) Here let's work on your dismount, oops, try not to fall down so much....

I may install a primer bulb on mine for hot starts, if cutting the wire doesn't fix it.

On the race cars, if I had to restart it any time during or after a run, the only way was to pump the gas 5-10 times and hold it to the floor and crank until it fired. Anything else just made the battery tired.

One good thing about an old Harley carb, the accelerator pump.
 

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Discussion Starter #30
I noticed I was having REALLY bad hot starts when I had a filter on my carb vent tube. I had a small filter element on the end of it after I did the earshave, but hot starts were impossible. I removed it and tucked the unfiltered, open-end carb vent tube into the upper frame rail that goes to the steering head, and having the tube free has caused no issues and solved that one. May not be your case, but figured I'd mention it anyhow.
My old bike had an ear shave, and the vent was attached to the bottom of the gas tank. This one, it goes to the ear. I wonder if moving it to the tank nipple would help anything...

I should also mention that these bikes are probably best to run on the lowest octane fuel possible, I run 87 when I have to fill up with ethanol gas, and the E-Free I get is all 89. Higher octane = harder to detonate on lower-compression engines without advanced spark; our engines can't compensate for the different ignition timing required to get the most out of high-octane gas.
I still want to pick up the aftermarket ignition unit for custom timing curves.
I would add a MAP sensor to adjust timing based on throttle position. The vacuum port(s) are downstream of the throttle plate, so they would provide a decent signal.
Leaving the WOT timing stock but advancing it at light loads would boost the MPGs during cruise, and lower engine/exhaust temperatures.
Practically every car in the world advances timing in light load conditions.

The unit also has external switch inputs and ability to program in two timing tables, as well as a global timing retard.
I could set one switch to toggle between stock and modified timing.
The other switch, I could set to retard the timing. I could then advance both tables all throughout, for use with premium fuel.
I'd effectively have 4 timing tables to work with: Stock, Premium Stock, Modified and Premium Modified.
Of course, it would be my responsibility to know what fuel is used and set the timing appropriately.

I saw a test done on cars that are able to adapt to the fuel, they show a HP boost that coincides with the percentage increase in octane.
87 to 91 is 4.6% increase, and HP was up 3-5%. They didn't test MPG, but a lower exhaust temp indicates better efficiency.

Yes Jason, the e-free around here is all a higher octane than 87, might explain the mpg. 89-91 octane depending on the station.
The only E-Free gas I can buy in my area is 91 octane.

Anti-theft... Be kinda funny for some poor baftard to hop on and get a huge backfire to announce his attempt at stealing my bike. Where ya goin' junior? Need a hand startin' that thing? :) Here let's work on your dismount, oops, try not to fall down so much....
Hahahahahaha!!!

I may install a primer bulb on mine for hot starts, if cutting the wire doesn't fix it.
If you do, let us all know what you find!
Ultimately, what bothers me most about the hot start issue is the lack of a cause or cure.
I could live with it if I just knew conclusively what causes it!
 

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Discussion Starter #31
Ok, time to get scientific!
Using my lunch break and my work's FLIR camera, I took an infrared video of my bike during a 6:30 minute cool down.
It's in the low 80s today, and I didn't get it quite as hot as I did in my previous tests (the fan did not kick on).
The bike was on the side stand for this test. This was taken from the left side of the bike.
Spot 1 is the stator cover and Spot 2 is just behind the left ear. In retrospect, I should have put it on the carb bowl.

The exhaust pipe looks cold because chrome doesn't emit very much IR.
You can see the hottest part of the rear cylinder is the exhaust manifold above a black "cold" spot (which is the pipe).


Here are screenshots from the video, taken at 0 (shutdown),1,2,3,4,5,6,6.5 (just before restart), and 7 (after restart and running for a few seconds).
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I will try this again another day, but zoomed in on the carb. As well, I can set the temperature range narrower.
It looks like the carb stays well below 80C, and is mostly too cold to see.
 

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Interesting.

The video begins at shutdown, right?

Looks like it peaked around 192f. But the rear exhaust manifold started going white then cooling quick at the end.

Fluctuation of the numbers related to camera movement?
 

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Discussion Starter #34
Interesting.

The video begins at shutdown, right?

Looks like it peaked around 192f. But the rear exhaust manifold started going white then cooling quick at the end.

Fluctuation of the numbers related to camera movement?
Yes the video starts at shutdown.
I didn't have access to a tripod for this. I might be able to use a tripod for the next video, if I can find it.
 

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Doesn't appear to be too hot, but as you said, ambient temperature wasn't really high that day. A significant amount of heat soak is shown however.

Happens with all engines, this is why it's best to let a turbo idle for a bit before shutdown. Otherwise it gets "coking" of the oil and is eventually clogged with ash from burnt oil. Doesn't hurt air flow, but kills oil circulation and bearings.
 

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Thanks for the FLIR video, one of a kind!

Would win the 2020 photo contest, if we had one. :)
 

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Discussion Starter #37
I insulted the fuel and vacuum lines to see if that helps. I only did the vacuum lines for consistency. I didn't expect those to have any affect.

No change, but I'll leave it on because I like how it looks. :)

52233
 

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Discussion Starter #39
Best auto-correct ever! :LOL:
 
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