Still having heat problems :(

Discussion in 'Motorized Bicycle General Discussion' started by Dougan, Jun 3, 2010.

  1. Dougan

    Dougan New Member

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    I was having heat problems earlier this week, and asked you guys for some help, and got a ton of feedback. I checked my plug, fine. I tried 16:1, 24:1, and 32:1 with similar/same results. Checked for air leaks and cleaned the air filter. I decided I would put a few more miles on it so I could be sure it was broken in, before I continued annoying you guys.

    Anyway, I've run a decent amount more gas through it, and it's still a problem. It seems that people here are a little divided over whether or not it'd OK for water to boil off of the head, but for the short length of time it takes to get to that point, there's no doubt in my mind that it's not doing what it's supposed to.

    Also, something that I didn't mention before, when I open the throttle too quickly (much more prominent on a cold engine) the engine bogs down-- I am pretty sure it is four stroking. With such a cheap engine, I would be surprised if four stroking *didn't* happen, but, it happens a lot... do you think I might have a fuel-air ratio problem? or any other ideas?

    Thanks guys, sorry to be so pesky about this.

    Grubee skyhawk 66cc slant head.
     
    #1 Dougan, Jun 3, 2010
    Last edited: Jun 3, 2010
  2. Cabinfever1977

    Cabinfever1977 New Member

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    My engine ran so hot that if it rained while riding my bike, my engine was always dry.
    You could probally cook food on top of these engines.
    Road side barbeques.
     
  3. dag_29307

    dag_29307 New Member

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    As far as the bogging out when you throttle up, that sounds like a jet problem. There is a thread here that explains how to fix that. As far as your heat problems I am curious as to what type of oil are you using? I know there are many different types but many say synthetic is the best. I have heard many guys say they use Opti-2 synthetic. I don't know where they get it from or where to purchase it besides the internet, So I use what is available. I get mine from Dollar General $0.80 a bottle Coastal 2 stroke 50:1. I put one bottle to a gallon of fuel and that's how she has been running since day one. The only major problems I have had are basic weak parts supplied with the kit originally, cable, chain, and now the muffler. But nothing major. You have an odd case. Is there a restriction of air flow getting to the engine? I mean are you running a wide fender or something? Can you post some pics? I will be monitoring this thread to see how this goes. We will figure this out and get you rolling again. Have no fear we are on the case.
     
  4. corgi1

    corgi1 New Member

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    have u,,,Checked w/sprayed WD-40 around carb.sides,,"top"(where the slide is) and where manifold bolts to motor and carb?,to look for rpm changes(leaks),,,,could the float be set a little low in the fuel bowl?,,,,there is a thread here with pic's of the color of the spark plug when the fuel mix is ,,rich,,right ,,,lean,,that will give clues what too look for might look around the top and bottom of the cyl. for oil traces,w/a clean paper tissue,,,any where a shaft goes through or there is a seam where the motor goes togeather is a possibility,,,,
     
  5. Dougan

    Dougan New Member

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    I will try and post pictures tonight or tomorrow. I don't think there is anything unique about my build, though, so I wouldn't expect any great discoveries. :) The intake has plenty of room.

    I have sprayed WD40 all around the intake areas and had no changes in RPM. The only leak I've identified is right where the muffler mounts to the motor, there is a slight bit of oil. I replaced the gasket here and it seems to have fixed the problem. Tonight I'll wipe it down so once it stops raining and I can ride it I'll see if there's more oil stains.

    The spark plug has a good healthy brown to it. I have not yet taken apart the carburetor, but I am a little green when it comes to that. I'll have to do my research. I saw a video of someone taking apart the carburetor on a china girl and it looked very simple.

    Thanks so far guys, I'll keep you updated with pictures and my experiments.
     
  6. Dougan

    Dougan New Member

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    A little concerned that it "ran" and doesn't "run".

    :)

    Definitely could cook on what I'm working with though. It's not that it's boiling water, it's how quickly it gets to that point that worries me. And how much hotter I saw it get that day *after* the point where it would boil water. That combined with people here saying that their motors can go wide open without getting water to sizzle and pop on it, and I go half throttle and take pedal breaks to cool down and I still am that hot... all of that combined makes me pretty confident that there is a problem.
     
    #6 Dougan, Jun 4, 2010
    Last edited: Jun 7, 2010
  7. corgi1

    corgi1 New Member

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    On another thread yesterday I saw muffler blocked,,,what is your speed up to,,how does it accelerate (Taking your 's and the bike weight into concideration)if ""hot at all oil mixes"",then it does sound to be a psyical or mechanical failing (timing key?but then how strong or weak is it pulling/starting?) Take the muffler to your friendly auto repair garage and try checking aie flow through it,or looking in the ends w/a lite,or a small vaccum w/a hose and listen to air restriction build-up or not comming out the other end.
    .......I don't see the cool at WOT entry above(and then was it a winter ride)
    .......I got to lean toward muffler after "the same at all oil mix's thing",and "no air leaks"
     
  8. Dougan

    Dougan New Member

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    http://motorbicycling.com/f3/how-hot-19319.html <-- I posted here a week ago, to reference the WOT stuff.

    I haven't yet topped it out, but I can get it up to 26 mph and I feel like I could probably get a few mph on top of that.

    It accelerates about how I would expect for something with only one gear-- low end is a little slow to accelerate, but after a bit it accelerates pretty well. Again, though, if I open up the throttle too far while accelerating (especially when cold) the engine will bog down. It will stay bogged down until I let off of the throttle a bit. When It's bogged down like that, as I let off the throttle, the "bogginess" stays at the same level until it gets to the throttle level it wants, and then the bogginess just shuts off-- not a gradual thing. Aside from that bogging down, the engine does not seem to have power problems-- as long as I give it the correct throttle, it shows the power I would expect. The bogging down is not a problem, as the solution is simply to not go overboard with the throttle-- but I mention it in detail in this thread in case it might be related to my overheating. If it's not causing the heat, then I don't care.

    I will look more into the muffler. For what it's worth, I tried putting it to my mouth and blowing through it and I felt like I was blowing through an empty pipe.
     
  9. corgi1

    corgi1 New Member

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    empty pipe is good, Help Norm ,I'm out of ideas
     
  10. Dougan

    Dougan New Member

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    Took a quick look after work today. Didn't have a chance to take apart the carb, but blew through the exhaust again to see and it was clear. Did the WD 40 test again a little more vigorously and got nothing.

    Drove around my parking lot at half throtttle, maybe 500 or 600 yards of total running and it was boiling water when done.
     
  11. GearNut

    GearNut Active Member

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    The only other culprit that I can think of is that the timing is too advanced. That could only be caused by the wrong placement of the keyway in the crank shaft or the keyway in the magnetic rotor during manufacturing; unless...... the key has somehow sheared or is missing and the rotor has shifted clockwise as viewed with the mag cover off. That would also make for hard starting, horrible lower rpm performance, but really good high RPM performance.
     
  12. nolan_speed

    nolan_speed New Member

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    Sounds like it could be running lean, how's the plug look? The easiest way to richen the mixture (air/fuel not gas/oil) is to unscrew the part where the cable goes into the carb and remove the slide. Take the cable off the slide and remove the needle, there will be 5 or so groves in the top of the needle and a clip will be in one (probably the center one) carefully remove the clip and move it to a lower grove, you could just go one grove or go all the way to the bottom to see if it makes a difference.

    Put the carb back together, take it for a ride and se if it's any cooler.

    As far as the bogging when opening the throttle too fast, I think some of that is normal as these are super simple carbs.
     
  13. Dougan

    Dougan New Member

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    Checked the plug and it looked perfect.

    Kind of what I expected to hear. As long as the bogging isn't causing my overheating, I'll have no problems w/ it.
     
  14. nolan_speed

    nolan_speed New Member

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    Even if the plug looks good, it may be worth trying to richen it up a little, the extra fuel helps cool the engine. I'd try raising the needle one notch and see if it helps. What's the worst that can happen? Your MPG might go from 150 down to 140 and there's a chance you could foul the plug. I'd say it's worth a shot if you don't have any other ideas, I can touch my engine for a second before i need to pull my hand away so your sounds really hot.
     
  15. wildemere

    wildemere New Member

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    A nicely tuned HT will run at ~180C when WOT up a hill.

    The pipe 1" from the head is about 10C hotter.

    When lean expect 10C more & 10C less when rich.

    When lean the pipe gets 25C or more hotter, the opposite when rich.

    Idle temps are 30 to 50C less.

    I use a non-contact thermometer for initial tuning as it saves pulling the plug over and over, saving the threads.

    The head & pipe needs to be painted black where measuring and the readings are taken next to the plug. My numbers are at sea level and 20 to 25C ambient.
     
  16. moronic_kaos

    moronic_kaos New Member

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    Basically that cylinder will be hot enough to melt/burn whatever comes in contact with it besides decent gasket paper (but there's a reason the head gasket is made of metal). There's a post somewhere that mentions the tip of the exhaust reaches about 1100 degrees (though I'm not sold on that being true), but yea touching the block for even a split second after it's been running a couple minutes should burn you quite severely. I tried to use a candy thermometer to measure it once, but it resulted in 8888 and kept turning itself on and off as if it was shorting itself out every time I touched the motor. I think it was something to do with the motor being grounded at certain intervals, as it did it even when cold. Maxed out a 280 degree meat thermometer after 1/4 mile trip.

    Moral: Protect your wiring, and don't wear shorts.

    Edit:
    That's ~350 Fahrenheit right? Yea, that seems about right.
     
    #16 moronic_kaos, Jun 5, 2010
    Last edited: Jun 5, 2010
  17. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    EGT should be around 1100F max, but can go as high as 1200 for short periods before the piston melts.
     
  18. Dougan

    Dougan New Member

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    Unfortunately, I learned the one about shorts the hard way. I got quite the burn. We should probably start a thread dedicated to calf burns.

    My wires are "upwind" of the motor and I haven't had any problems yet.
     
  19. corgi1

    corgi1 New Member

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    Keep the baby cows away from the motor bike
     
  20. Creative Engineering

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    After a good run:

    If you can tap your finger against the cylinder head for 1/2 second without getting a dry skin scorch that leads to a blister...the engine temp is fine.

    Jim
     

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