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Thread: Stumped (Oil leak, level, gas contamination)

  1. #1
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    Question Stumped (Oil leak, level, gas contamination)

    Sorry in advance for the slightly longwinded post, at this point I'm so confused that I don't know for sure which details are relevant so I'm trying to summarize everything:

    I bought a 2001 Blast this spring, it was low miles (650) so I hoped I wasn't buying "a project" as my experience level is pretty low with all things that take spark plugs (I can usually do brake pads and oil, that's about it). Unfortunately it wasn't long until the problems started.

    Within a couple weeks I began to notice what I now know to be an oil leak, but at the time based on the spray pattern and the fact that the previous owner mentioned a slightly dodgy fork, I mistook it for fork fluid and brought it to a local shop to have the forks rebuilt. While it was there I had them change the crank and primary oil since I didn't know the bike's maintenance history and also the crank oil smelled of gasoline (I used Mobil1 V-Twin per a recommendation I found in the mega thread). The first time I rode it after the oil change I thought maybe they just did sloppy work, but by the 2nd ride it was undeniable that the leak was not fixed. At this point I checked the oil level and found that it was high and also smelled of gasoline again. I bled off the excess and tried my best to clean off the spilt oil, another ride confirmed that it was still leaking (looks to be coming from somewhere on the head) and yet the oil level was climbing. The leak had me thinking head gasket, but that wouldn't explain the gas in the oil (I don't think).

    At this point I parked the bike for a good week, due to weather and a stomach bug. After asking around with friends, I had hope that maybe it was simply a carburetor issue and the leak was maybe just excess oil finding its way out through the breather system. I made a post on the parts board and subsequently bought a "compatible" carburetor rebuild kit off of ebay. When I finally got the carb off and torn down it was immediately apparent that the kit I got was wrong; float too big for the bowl, (sorry for ad-hoc terminology) the part that slides up and down and houses the needle was the wrong shape and too small, the float valve was too small for the bore it goes in, etc... So seeing nothing but more of the same available on ebay, I cleaned it up as best I could and put it back together with original parts. Along the way I noticed 2 issues that I really hoped were my problem: 1) A previous owner had attempted to shim the needle, but their washer stack came to a total of 0.065" -- I just removed one of them since it was said that under 0.050" was to be preferred vs. going over, if I'm following along correctly this would tend to allow too much gas to be dispensed. 2) The float adjustment was slightly out of spec according to the maintenance manual procedure (on the side of filling the bowl too much), so I adjusted it until it was reading right in the middle of the specified range.

    This brings us to yesterday, I cleaned spilt oil again and had planned to bleed off excess oil so I could warm the motor up to change it. What I found when I opened the dipstick baffled me, it looked bone dry. I decided to drain it cold, and what I recovered was around 0.75qt, and the gasoline smell had dissipated considerably, it's barely detectable. My immediate thought was the other half had leaked off somewhere while it sat but after looking around for a good 20 minutes I couldn't find evidence of this (I now believe the other half was gasoline that manged to evaporate through the open breather line / possibly less-than-tight dipstick while the bike was disassembled for a couple days). I filled up with fresh oil and it took the full 1.5qt to get me to the bottom fill line. I proceeded with reinstalling the carb and other essentials so I could attempt to start the bike (wanted to know it would run before I put everything back), it started back up without issue, idle was a bit lower than before but it seemed to be running fine. After it had run for about 2 minutes I shut it back off and measured the oil level again, it was very high (half again vs. max) and somewhat bubbly. I gave it a couple minutes to rest and found the level was still high, so I drained off the excess until the level read right in the middle of the range. I finished reassembly and took it for a short ride to fill up the tank, before I even got to the gas station (2.5mi/6min away) I noticed the leak was not gone. Upon returning home I checked the oil again and it was high once again (same roughly half again the maximum while hot).

    This morning after letting the bike cool overnight I checked the oil level once again and I found it was just slightly above the minimum line, and I detected a slight gasoline smell.

    One other potentially-relevant detail is I've consistently gotten 40-42mpg with this bike, I'm a bigger guy (6'1", 250), but I think this is significantly lower than expected for this bike?

    Any input on the following would be greatly appreciated:
    1. A quick web search suggests I was probably wrong to be checking the oil level hot, but is it normal for the oil level to climb significantly when the engine is hot, or is that indicative of a problem?
    2. Is it plausible for oil to leak around the rocker cover breather without filling the breather line with oil? (What drained out was just a few drops of yellowish frothy liquid that didn't want to mix with the oil in my drain pan) Or am I looking at a blown gasket?
    3. There is a brass screw on the bottom of the carb which I believe relates to the idle, the maintenance manual procedure didn't have me touch it but a youtube video I watched showed noting the number of turns to the fully down position and removing it. Was that potentially my mistake on the carb side or is there another cause more likely for the gas entering the oil? The bike seems to run fine but admittedly I have no basis of comparison for what this bike "should run like".

    Thanks!!

  2. #2
    Senior Member Barrett's Avatar
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    Sir: Readily identifiable what's going on here and actually quite normal in the world of carbureted motorcycles.
    You have a serious carb problem and/or a failing petcock. Your Blast has a high-mounted substantial fuel tank...a fuel control valve(petcock)...and a fuel inlet control portion of the carb known as the float/needle/seat combination. One or more of these components have failed, flooding the crankcase with raw gasoline that enters the combustion chamber from the carb via the manifold and intake valve and eventually filling the crankcase. Horrible situation that can quickly lead to terminal engine damage.

    IMO you're in over your head. Drain all fuel from the tank...drain the oil and dump the filter...do NOT operate engine again...and contact someone locally who can competently rebuild your stock Keihin CV carb and either rebuild or replace the petcock. Those components are the source of your problem. Can't make it simpler than that.

  3. #3
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    Thanks for the quick reply! The petcock refers to the fuel shutoff valve which is mounted to the bottom of the tank? If so I believe that is working properly... I just had the tank off the bike for a couple days (I put a couple boards across a large drain pan to keep the weight off of the valve), there was no leakage. And when I was first learning the bike's range I ran out of gas a couple times and was able to confirm the reserve position is also working as expected... Is there something else that can go wrong with that part?

    Also, am I understanding correctly that a professional rebuild on the carb, and fresh oil and filter should address the oil leaking from the head/rocker area? Or is it still likely that there's been subsequent damage there that's causing that to happen?

    Thanks!

  4. #4
    Senior Member Barrett's Avatar
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    My pleasure Sir. The petcock is the tank mounted fuel control valve mounted to lowest portion of your tank. It is simple mechanical device and has ON/OFF/RESERVE positions. Simple test is to fill tank at least half-full...disconnect fuel line from carb and place line end into jar...place petcock in OFF position....let sit overnight and see if any fuel dribbles into the jar. If an ounce or more does, the petcock is NOT fully shutting off and needs rebuilt or replaced. In all likelihood your problem lies within the carb itself as I explained above. Have the carb examined and properly rebuilt including new float/needle/seat/seat gasket, by a competent person familiar with Keihin CV carbs. Some of these Keihins, as they age, become non-rebuildable due to a multitude of reasons. A competent carb tech will be able to determine if it is rebuildable or not.
    And yes on fresh oil and filter. These P3 engines are rugged lumps so hopefully no internal damage has been done.

  5. #5
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    Thank you so much! I will arrange the test you described when I pull the carb later to take it to the shop

  6. #6
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    Check your rocker box gaskets an grommets for your oil leak and the petcock only works if you use it. Are you turning it off every time you get off the bike for more than a half hour? A poor float needle seal like Barret pointed out would explain the high gas contaminated oil level
    If you want to get back on quicker and not hurt the bike change the oil/filter install a clear fuel filter in a spot you can see. Then ride , at the end of your ride turn off the petcock and let the bike use the fuel in the bowl. If the clear filter is empty and the bowl dry you won’t be contaminating the oil while it sits.
    Your mpg if not jetted WAY too rich should be high 40’s to mid 50’s I have had several Blasts about 50 mpg on all of them

  7. #7
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    I'm pretty rigorous about the petcock, and per Barrett I did arrange a test for that (grabbed an old painter's cup with lid and cut a small X in lid and stuffed hose through), as of yesterday there's still no gas in the cup and that's been sitting since Wednesday.



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