Overheating Airhead

Discussion in 'Airheads' started by Big John Sny, Apr 28, 2010.

  1. Big John Sny

    Big John Sny Been here awhile

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    I was riding the R100 to class last night and I noticed that there was a bit more valve clatter than usual after I got off the freeway. I started noticing that it smelled a little hot as I was pulling up in front of the college. I park the bike and I could not even touch the dip stick. i spit on the engine case and it sizzled. I wasn't idling very long, just a few red lights after the freeway. I rode about 20 minutes in high gear at about 4500 RPM before that. I was actually a little bit cool outside, so I am not sure what is going on. I went out and checked the oil level at a break in the class and found that the oil was a bit down but was still over the min oil line. I also saw that both of the brake/turnsignal assembly bolts were gone. I think the bike is just revolting against me. I had been only riding it up to the low 4000 RPM untill a few weeks ago because it had seemed like it has a little more vibration when I push it above that. Also for the last month it has leaked out the right hand carb if I park it with the petcocks on so I have been planning a carb rebuild. A week ago when I switched over to reserve on the left hand petcock it took a while to pick up fuel so yesterday before I rode it I had pulled off the fuel filters and noticed that the right one was easier to blow through than the left so I blew them both out with compressed air and switched the two (The left petcock is the easier to reach when I am rolling down the freeway), and I put new fuel filters on my shopping list with the carb rebuild kits. It was only a few weeks (600 miles) ago that I did the tune up on the bike so I don't imagine anything being that far out, but I guess it wasn't that long ago that I washed the bike and the tailight felt solid either. I grabbed a bolt out of my licence plate and took back roads at 40mph and 3000 RPM the whole way home. It didn't feel so hot. I still couldn't hold the dipstick, but no spit sizzle on the block.
    #1
  2. dazz

    dazz Been here awhile

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    If you have changed the oil lately, google $2000 Oring. It has to do with installing the oil filter correctly. It does not sound like you're lubricating properly. There is a pick up tube inside your oil pan that can come loose. Whatever, I suggest not riding anymore until you are sure you have corrected the problem. Was your oil light on?
    #2
  3. Big John Sny

    Big John Sny Been here awhile

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    I am at 1000 miles on this oil change and I put a new o-ring in last time. I figure if there was an oiling problem it would ahve come up some time in the last 1000 miles but, I will definitly change the oil now that it has gotten that hot and probably broken the oil down though so I can check then.
    #3
  4. bgoodsoil

    bgoodsoil Dare to be Stupid

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    I put in a Parts Unlimited oil filter last time I changed my oil. When I pulled it out the filter was crushed. My oil light kept coming on too. Did you use a BMW filter? Maybe these PU filters are junk?
    #4
  5. jwegman

    jwegman Been here awhile

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    I've only owned my '78 RS for a year (put 5k miles on it), however during that time the metal dipstick has always been hot after the bike gets up to operating temp (and I have the deep 3qt sump). However I must confess that I've never spit on the block to verify that it'd sizzle... :) I just presumed that it'd be hot.

    As I understand it, that's the reason why BMW switched over to a plastic dipstick handle in later model years.

    As to more valve noise, I'd speculate that with hot oil (thin), and perhaps a slacking timing chain, that you'd notice a different valve clatter then when cold.

    With regard to leaking gas when parked and taking that as a sign of needing to rebuild a carb... Not really as the petcocks really need to be turned OFF when parked.

    But you can see how well your float needle seats by removing the float bowl, push up on the float so that the needle seats, then turn on the petcock and see if fuel gets past the float needle. An easy why to attempt to clear any crud is to let the needle drop and let some gas flow through.

    You could then pull and inspect the needle face to see if there's a non-desired groove and inspect the seat for any crud. Both the needle and the seat can be replaced. (it's my understanding the seat is pressed into the carb body). The seat and needle seating issues will also lead to the carb leaking (overflowing) when the bike is running.
    #5
  6. lkchris

    lkchris Albuquerque

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    Verify your motor oil is not diluted by gasoline.
    #6
  7. Mandello

    Mandello Guzzista

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    I'd also check the plugs to make sure you're not running to lean, also doesn't hurt to check the valve clearances, especially the exhaust side. I ride Guzzis and they do make some a bit of valve sound :), some people try to tighten them up to reduce this sound but end up frying the motor.

    AlexM
    #7
  8. P B G

    P B G Long timer

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    Was the o-ring shimmed correctly?

    It could still be the culprit if you didn't set up the preload correctly.
    #8
  9. Middleweightboxer

    Middleweightboxer Middleweightboxer

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    I've had 2 or 3 instances of airheads overheating and it is always a combination of timing and fuel mixture. Most recently my R80 overheated on a sub-freezing ride to St. Jo.

    I run Mikuni carbs on my bikes that are more sensitive to air temperature. Generally I have to raise the needles in the winter and drop them in the summer. Except this year, I didn't need to drop the needles when the temperatures returned to normal, which leads me to believe they have screwed with our gasoline again.

    Check your plugs, if they are bone white you are running too lean. Assuming your carbs are in good shape, I'd retard the spark a little.

    Stock timing settings may well not be the correct prescription for the watered down crap they sell as gasoline in EPA targeted cities. Last year on the same day I got 300 miles to reserve on one tank full of gas and 260 on the next. That is a big difference in the quality of fuel.
    #9
  10. Yarddog

    Yarddog Been here awhile

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    I'd pay REAL good attention to this advice...if you're leaving your petcocks on, and you're leaking fuel because of it, it's not only leaking out the float bowl, but there's a real good chance it's getting into your cylinders...
    #10
  11. dazz

    dazz Been here awhile

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    About the fuel in the oil: he checked the oil level and it was not high. I think I may have read somewhere about the oring problem not neccesarily showing up right away? Anyhow I'd look into that.

    If he did not mess with carb adjustment in any way it should not change and therefore not present a mixture problem.

    As being so hot to sizzle when spit on, that's way way hot. Major problem.

    Timing? Again, did he mess with it??

    This problem did not occur overnight like catching a cold. What caused the problem.

    Big John......have you made any adjustments? Fixed something?
    #11
  12. Beemerboff

    Beemerboff Long timer

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    Have a good look at the plugs , any sandy type deposits on them indicates ignition which is too far advanced.

    The crap they sell in place of gas these days burns much faster than the leaded gas which was around when the bikes were made so 2-3-4 degress retard might be applicable - my twin plugged G/S performs best with around 26 degress advance on the crap we get in Oz.

    When you remove the O ring it should show signs of being compressed and be almost square -if it is still round like when it went in add a couple of shims, and/or remove the paper gasket if you have fitted it.
    #12
  13. Big John Sny

    Big John Sny Been here awhile

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    I haven't changed anything on the bike. The o-ring that was in there by itself before was compressed well so I installed the same sized oring in the same way, we will see what the o ring looks like when it comes out. The oil feels thick and doesn't smell like gas. The only thing I have changed is how I have been riding the bike. It has always felt kind of the like the vibration has gone up a bit at 4100 or so, so I have not pushed it beyond that. Last week or two I have been running late and probably running the bike closer to 85-90 mph (4500-5000rpm). It does feel like it has a less power up there and a bit more vibration. That may be both the explaination for the bolts vibrating out of the tail light and the overheating. I am wondering if the fuel filters or carbs are not up to the higher RPM and making it lean. I am in the middle of finals for my masters as well as end of the fiscal quarter at work, but I might get a few minutes to look at the bike this weekend. It is a lot easier to find a parking spot both at work and at the college that putting some time into getting the bike right may pay out overall. Thinking that carb rebuild, fuel filters, and re-run the tune up on it and see if anything is out/get fresh oil in it.
    #13
  14. dazz

    dazz Been here awhile

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    John if the bike sizzled when you spit on it something is really wrong. That temperature can cause permanant damage. I'm sorry I can't help you. Please find the problem before it's too late for that fine old bike.

    #14
  15. Wirespokes

    Wirespokes Beemerholics Anonymous

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    It's sounding to me like the filters are restricting the flow enough that the fuel level in the float bowls doesn't stay topped up at higher RPMs, causing it to run lean. Remove any extra filters and clean the screens on the petcocks.
    #15
  16. Reryder

    Reryder Onward through the fog...

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    Check the basics first:

    Drain the oil and see if it smells like gasoline. It could be polluted with gas from the leaking carbs and any excess level has been blown out the engine breather. Put new oil in anyhow. Cheap insurance.

    Check the $2000 o-ring and shim, and the filter while you are there.

    Fix your leaking carbs and park with petcocks shut. Ensure also that all fuel lines and filters are clean and clear. Check carb jets are not blocked.

    Check ignition timing with a strobe light.

    Ensure wheels and transmission turn freely with bike on the stand, so you know the engine is not overworking to overcome some partly seized wheel-bearing, brake or transmission bearing etc. The odd vibration you mention above 4,000rpm might indicate some thing wrong there.

    Also, drain the oil out of your gearbox, drive shaft and rear bevel and check for metal filings etc indicating something coming apart. Put in new oil.

    If that don't fix it, call for more help!
    #16
  17. Big John Sny

    Big John Sny Been here awhile

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    Dropped the carbs over the weekend. Two things stood out. 1) brown floats, so they have probably been sinking and causing the overfill of the carbs when it sits. The needles actually look replaced recently. It could possibly have caused the bowls to be overfull at lower RPM where I am setting mixture and lean out at higher RPM, but my problems are far more likely to be caused by 2) red silt in the bottom of the bowl. Yeah, saw that and knew I had rust in the tank before I even pulled the petcocks. When I pulled them out the screen was completely blocked up by rust for an inch up the screen and the fuel filters flowed less and less while I was draining the gas out (funny the liner doesn't look bad when I look in the top of the tank with a light). The fine rust making it through could also very well be holding the neadle and seat open causing the drippy carbs as well. I picked up the new floats, filters, oil change parts, and ordered the tank stripper/prep/liner to get working on the tank. When it gets here, I repair the tank, reassmble the now cleaned carbs, change the oil, run through tune up process and then carb adjustment and see where I am, but I guess I better get used to the car commute for a few weeks.
    #17
  18. Big John Sny

    Big John Sny Been here awhile

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    Ok, tank sealer gets here tonight. Anyone seal thier airhead tank? I have done one other tank (old Honda), but this one I will need to strip out the old liner. Any words of insight before I take this on? Prefered methods of stopping up the holes?
    #18
  19. Wirespokes

    Wirespokes Beemerholics Anonymous

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    What's the brand of sealer you got?

    That red stuff clogging the filters and in the bowls isn't rust, but bits of the old sealer.
    #19
  20. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Get a pound or two of roofing tacks/nails, add them to about 1/2 tank of soapy water and shakeroo. Drain, repeat til water is clear. Rinse, dry tank thoroughly. Follow the tank liner prep directions closely.

    Local hardware store (like ACE) may have a bin of variously-sized rubber stoppers; get two for the outlets, one for the filler. Be careful plugging the tank up, the solvent in the tank liner will evaporate, pressurize the tank and pop the corks out.
    #20