Blown piston need diagnostic help - Page 2
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 2 of 4 FirstFirst 1234 LastLast
Results 11 to 20 of 34
  1. #11
    I dream skis E350's Avatar
    Join Date
    Jul 2015
    Location
    Sacramento Delta, CA
    Posts
    617

    Re: Blown piston need diagnostic help

    Quote Originally Posted by Jet Cowboy View Post
    You'll have to see if WFO or someone else can give you jet specs. What he is trying to tell you is that switching from oil injection to pemix will lean out the jetting. This combined with the already lean jet do to go mistake and recall results in disasater. It is leaner because the oil that was once injected now travels though the jets displacing a proportional amount of fuel.
    Great friggin' explanation! I have been running 40:1 Klotz Jetcraft. Will increasing the oil part of the ratio help the OP?

    (BTW an engine builder I know recommended 40:1)
    Learning Slowly...

  2. #12
    Resident Guru
    Join Date
    Oct 2013
    Location
    Ohio
    Posts
    885

    Re: Blown piston need diagnostic help

    While collecting parts to repair mine, I bought a 770 that had a burnt PTO piston. I learned from purchasing the engine that Suzuki used to pin designs to keep the bearings from spinning in the case. One type can be installed after the crank is installed, then they nest in little pockets in the top case half. The other type, the pin is inserted into a hole in the top case half before the crank is set in place, then as the crank is set into place, the bearings must be turned so the holes in the bearings align with the pins.

    The engine with the burnt piston had the pins that are in the hole in the upper crankcase half. When the crank was installed into this engine, the bearing holes were not aligned with the pics. This kept the case halves from pulling together properly and sealing the crankcase. This caused the lean condition that melted the piston.
    2, 1998 TS 770 L, restored and running great as of July 2019 (NO THANKS to the person at SBT, who put the WRONG crankshaft bearing into the rebuilt engine I got from them)

  3. #13
    PWCToday.com Is My Home Away From Home john zigler's Avatar
    Join Date
    Mar 2003
    Location
    wisconsin
    Age
    55
    Posts
    9,683

    Re: Blown piston need diagnostic help

    Hole in piston like that is typically from a lean condition.

    Lean condition can be from many things. Air leak, fuel delivery problem, dirty carb, etc.

    Sorry, I just don't believe the premix = lean scenario. yes, Oil IS thicker than fuel, but at 50parts fuel to 1 part oil, there is SO little oil IMO it should make no difference. I have run @ 25:1 for break in before.

    You need to assemble the engine and do a leak down test. I bet you find bad crank seals.

    Go through the fuel system completely. Clean/flush the tank, check tank pick ups, fuel select, replace ALL lines, fuel filter, and rebuild the carb and fuel pump. Be sure to use ONLY genuine OE carb kits, and parts. Replace needle and seat as well.
    RCJS also doing business as WATCON
    608-743-1305 9am to 5pm CST m-f
    email watcon@watcon.com

    Please visit our web site

    new parts / products / services www.watcon.com
    thank you

    Please check out and like WATCON on Facebook

  4. #14
    Resident Guru
    Join Date
    Oct 2013
    Location
    Ohio
    Posts
    885

    Re: Blown piston need diagnostic help

    Quote Originally Posted by john zigler View Post
    Hole in piston like that is typically from a lean condition.

    Lean condition can be from many things. Air leak, fuel delivery problem, dirty carb, etc.

    Sorry, I just don't believe the premix = lean scenario. yes, Oil IS thicker than fuel, but at 50parts fuel to 1 part oil, there is SO little oil IMO it should make no difference. I have run @ 25:1 for break in before.

    You need to assemble the engine and do a leak down test. I bet you find bad crank seals.

    Go through the fuel system completely. Clean/flush the tank, check tank pick ups, fuel select, replace ALL lines, fuel filter, and rebuild the carb and fuel pump. Be sure to use ONLY genuine OE carb kits, and parts. Replace needle and seat as well.
    Agreed, the premix would not cause the issue on its own. But, 50:1 = 2% oil, which means 2% less fuel. That is why sometimes, switching to premix sometimes make the engine run stronger, IF it was a little rich to begin with. It was on the edge of lean, then 2% less, or 2.5% if you use 40:1 can make a difference.

    For sure, everything needs to be checked. That is why I will never trust SBT. In my experience, they obviously do not check everything. They are careless in their work. If you have the skills, or are willing to LEARN the skills, you are better off doing it yourself.

    I have purchased an engine and two top end kits from them. I was burned on the engine and one of the top end kits. Never again.
    2, 1998 TS 770 L, restored and running great as of July 2019 (NO THANKS to the person at SBT, who put the WRONG crankshaft bearing into the rebuilt engine I got from them)

  5. #15
    I dream skis E350's Avatar
    Join Date
    Jul 2015
    Location
    Sacramento Delta, CA
    Posts
    617

    Re: Blown piston need diagnostic help

    Quote Originally Posted by john zigler View Post
    Hole in piston like that is typically from a lean condition.

    Lean condition can be from many things. Air leak, fuel delivery problem, dirty carb, etc.

    Sorry, I just don't believe the premix = lean scenario. yes, Oil IS thicker than fuel, but at 50parts fuel to 1 part oil, there is SO little oil IMO it should make no difference. I have run @ 25:1 for break in before.

    You need to assemble the engine and do a leak down test. I bet you find bad crank seals.

    Go through the fuel system completely. Clean/flush the tank, check tank pick ups, fuel select, replace ALL lines, fuel filter, and rebuild the carb and fuel pump. Be sure to use ONLY genuine OE carb kits, and parts. Replace needle and seat as well.
    Couple of things:

    First, reconsidering the "premix theory." It assumes that oil is not burned right? And lower gas to oil ratio increases air to gas ratio? Thereby causing a lean condition. But in fact, oil is burned and in fact it is my understanding (and a little bit of experience) that adding more oil has the same effect as adding more octane which reduces predetonation (pinging) which would cause the engine to run cooler, right?

    And assuming that there is no mechanical cause like hemmjo is talking about, isn't it an over heated piston top that gets a hole burned in it?

    Second, I have never seen a Tigershark or its engine. The thread implies that it has an oil injector but that the OP ran premix instead of using the oil injector.

    I was recently wrong in my consideration of running an engine without oil injection when the oil injector pump was still attached but without oil in the reservoir to inject.

    I have no experience with this (our X2 had the oil injector pump removed in 1988 when new).

    But would the oil injector pump inject excess air into the carburetor thereby increasing the air:fuel mixture ratio if the oil injector pump was left hooked up but not filled up with oil? Thereby causing the suspected lean condition?
    Last edited by E350; 10-23-2019 at 10:20 AM.
    Learning Slowly...

  6. #16
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
    Join Date
    Aug 2006
    Location
    Al-ugh-bam-ugh
    Posts
    28,204

    Re: Blown piston need diagnostic help

    Premix does not equal lean in most cases, I attribute the failures on the 770 top ends on the ski I worked on to being way too lean, the premix only came into play because after it was run out then they opened the ski on up running on too small main jets and it seized. If it already too lean running premix will only make it run leaner though, the higher the ratio of oil to gas the leaner it will be.

    On the ski I referenced the carbs were gone completely through as are any carbs on any engine I rebuild or install, I did not have any way of knowing that Artic Cat had installed the wrong jets at the time, on a properly tuned ski correctly jetted it's a non issue.

    I did have a business partner that would install a top end or engine , the carb would be laying in the footwell, instead of taking and extra 10 or 15 minutes to sort it he would slap it back on and run the ski, 9 time out of 10 he would come back and say I have to rebuild the carb. I could see no rational explanation for his reasoning as to why he didn't do the carbs while they were off the ski and it was costing us money.

    We parted company soon thereafter, the end.
    Last edited by WFO Speedracer; 10-23-2019 at 10:33 AM.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    WWSRD , What would Speed Racer do ?

  7. #17
    I dream skis E350's Avatar
    Join Date
    Jul 2015
    Location
    Sacramento Delta, CA
    Posts
    617

    Re: Blown piston need diagnostic help

    I am here to learn. And this statement is new knowledge to me:

    Quote Originally Posted by WFO Speedracer View Post
    [T]he higher the ratio of oil to gas the leaner it will be.
    Learning Slowly...

  8. #18
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
    Join Date
    Aug 2006
    Location
    Al-ugh-bam-ugh
    Posts
    28,204

    Re: Blown piston need diagnostic help

    Very simply put you can only force a certain amount of liquid (fuel in this case ) through an orifice (in this case a jet) given a certain amount of pressure (in this case atmospheric pressure) therefore adding more oil make the fuel thicker which means less of it will be able to be forced through the jet at the given pressure , in this case barring a change in altitude the pressure is set and cannot be changed.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    WWSRD , What would Speed Racer do ?

  9. #19
    I dream skis E350's Avatar
    Join Date
    Jul 2015
    Location
    Sacramento Delta, CA
    Posts
    617

    Re: Blown piston need diagnostic help

    Quote Originally Posted by WFO Speedracer View Post
    Very simply put you can only force a certain amount of liquid (fuel in this case ) through an orifice (in this case a jet) given a certain amount of pressure (in this case atmospheric pressure) therefore adding more oil make the fuel thicker which means less of it will be able to be forced through the jet at the given pressure , in this case barring a change in altitude the pressure is set and cannot be changed.
    Holy crap! You are talking about a mechanical constriction!

    Makes total sense without fuel injection and a pcm/ecu with a barometric or oxygen sensor to control fuel metering of the amount of fuel injected.

    Jet Cowboy was, if I am not mistaken, talking about a chemical effect, with more oil less gas to burn meaning more air to gas ratio.

    This stuff is so friggin' interesting. Thanks guys!
    Last edited by E350; 10-23-2019 at 11:03 AM.
    Learning Slowly...

  10. #20
    PWCToday Newbie
    Join Date
    Oct 2019
    Location
    Ontario
    Age
    28
    Posts
    7

    Re: Blown piston need diagnostic help

    Ok thanks, this is all very helpful information.

    My first question is why would only one piston have a hole and the other look completely normal. It would have to be from air getting in somewhere in only one cylinder right? Not do to leaning from pre mix? (Correct me if I’m wrong)


    Secondly yes the motor blew when I was going full throttle and had it up on plane .

    So by doing a pressure test this will rule out all seals or cracks correct? And if it passes the pressure test then I will know it has to be something with fuel delivery in carbs correct?

Page 2 of 4 FirstFirst 1234 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0