robin subaru engine trouble

Discussion in '4-Stroke Engines' started by rcfighterpilot, May 2, 2009.

  1. rcfighterpilot

    rcfighterpilot New Member

    hi, i removed this robin eh035 from my gas scooter and decided i want to buy a friction drive engine kit. well the problem is that it does not run very well. it doesn't start on the first pull like it used to, and when i do get it started, it doesn't run smoothly, it has a consistent pop pop pop at idle, the idle adjustment screw is all the way forward. it wont go full throttle either, when i push it to full throttle, it just wants to die, like at the end of the video.

    already tried cleaning the carb, maybe the valves need adjustment? problem is i don't know which one i should adjust.

    any thought? thanks guys!
    Last edited: May 3, 2009

  2. bamabikeguy

    bamabikeguy Active Member

    I did 3 cleanings at one time, the gas filter, both air filters (the foam and that fiber material) and the spark plug, that got things back up to normal.
  3. rcfighterpilot

    rcfighterpilot New Member

    spark plug is brand new, air flilter is clean, just took the white paper one out and left it out so it just has the foam one, and the fuel filter is new and gas is fresh 91 octane.
  4. bamabikeguy

    bamabikeguy Active Member

    91 octane could cause problems.

    You can wash out the cardboard one, let it dry completely, and try some 89 octane. 87 is the recommended, but since the big ethanol switch, I stick with 89.
  5. rcfighterpilot

    rcfighterpilot New Member

    it said in the Manuel a while back to use 89 or above otherwise it voids the warranty. dont know much about gas these days, please inform me!:sweatdrop:
    the guy at the local lawn mower shop said the gas in California has alot of stuff in it to reduce smog or something like that.
  6. bamabikeguy

    bamabikeguy Active Member

    Gas consistency is better at the major - national brands, so avoid those discount type stations. I mainly use my local Standard or Amoco.

    High octane gas takes longer to burn than low. 91/93 are intended for a more high performance engine, while we need the quickest explosion we can get.

    On my breaking in of the R/S, I use the Mobil 1 synthetic oil ($6.50 a quart), and change it really quick, and tell the customer to do the same thing in the first 10-20 tankfulls, the compression gets better as it gets more miles.
  7. Nuttsy

    Nuttsy Member

    I would definitely look at the valves. Mine had the WRONG lash setting from the factory (actually no lash at all) and would bog and knock under load until I adjusted them. Easy 10 min. job. Worth looking at, at least.
    Did the performance go south all at once or gradually over time?
  8. rcfighterpilot

    rcfighterpilot New Member

    i think it was gradual, when i stored it for about a half a year, and then brought it back out, it wasn't the same.

    i know how to get to the valves but i don't really know how i should adjust them?

    i tinkered with them last night, and i got it to go to full power under no load without dieing sometimes, but it still doesn't have that nice purr when it idles like it used to.
  9. Happy Valley

    Happy Valley Active Member

    These are great little engines, I've had more than a half dozen. They are precision little machines and a bit more complicated than the average 2 stroke, however they are simple to work on if you know what you are doing.

    Nowhere in the factory manuals does it mention octane. It says "Automotive unleaded gasoline". I've spoken with a couple of Robin America engine techs and they recommend 87 octane. I don't think it's the cause of your problem but these engines have a tendency to carbonize in the upper cylinder and piston crown. A higher octane gas will only exacerbate that problem.

    Sounds like you already have elements of your answer in your own question.

    How did you store the engine? In an outdoor environment in the winter? Did you service the engine for storage before you put it away?

    How did the plug read that you replaced? You can also shine a bright light into the plug hole and read the wash on the piston at TDC.

    I wouldn't do anything. Not until I felt comfortable with what I was doing.
    You said you didn't know how to adjust the valves then you tinkered with them. Not good. Valve adjustment is part of regular maintenance and not very difficult but not something to tinker with.

    My early guess would be, and it's just a guess not knowing more about the particulars, is your problem is simpler than you think, fuel gone bad or the fuel system contaminated or compromised in some fashion.

    Here is a pdf of the service manual. It contains the valve adjustment procedure and tolerance. You simply have to prep yourself to get it right and the prep is harder than the actual adjustment if you've never done it.
    Do you know how to find TDC?
  10. rcfighterpilot

    rcfighterpilot New Member

    what is tdc? the plug inside was an ngk cmr6a i replaced it with a ngk cmr7a. how do you have your engines serviced? nobody around me deals with robin engines and they cant even get parts. it was stored outdoors under shelter, it was not used very much before that so it was not serviced. i recently changed the oil, it was on the low side. i put the valves back to their original position. it runs, just not very well. the piston looks very dirty, but i haven't really looked at many pistons so im not too sure.
  11. Happy Valley

    Happy Valley Active Member

    Top dead center, it's when the piston is at the top of it's stroke and the position the crankshaft must be in to check valve clearance. There is a mark on the flywheel that lines up with a corresponding mark on the engine case that aids in determining that position.
    (this has to be done when the engine is dead cold btw)

    I'm a bit reluctant to offer any advice at this point. I gave you a link to the service manual, I suggest you read it completely. You have changed the heat range on the spark plug by going to a 7a. The recommended plug is the 6a.

    If you are at all interested, a primer on spark plugs and how to read them can be found here:

    Often with small engines, particularly those that were running well, a bit of a problem might develop and it's rather simple, something we did or didn't do. Bad fuel or storage or it got knocked about, etc. It usually doesn't mean you
    have to overhaul the engine or try to fix problems that don't exist. It also doesn't mean you should avoid routine maintenance like checking valve long as you know what you're doing otherwise you create more problems looking for a complicated answer when the problem is much more simple.

    I maintain my own engines but I've been doing that for many years.
    When I need service I go to an authorized dealer which can be found here:

    If your engine is under warranty you could get it serviced at one of the listed dealers. If it isn't you could try calling one of the repair guys and asking for help.
    Last edited: May 3, 2009
  12. rcfighterpilot

    rcfighterpilot New Member

    ok, i know that it had to be in that position so the valves would be at the lowest point, just not familiar with the term used.

    it was the only plug they had, so i just bought it while there is an identical one on order. just wanted to see if it would start. the heat range shouldn't be that different.
  13. seanhan

    seanhan Member

    Hey did you try running some good fuel treatment in the gas to clean the carb out !!!!
  14. fetor56

    fetor56 Guest

    For example,cos i'm looking for something like this myself?
  15. seanhan

    seanhan Member

  16. fetor56

    fetor56 Guest

  17. rcfighterpilot

    rcfighterpilot New Member

    the fuel is new, what kind of treatment do you mean? ive cleaned the carb out several times with clean r carb and have blasted the jets with an air compressor.

    maybe i need a whole new carb:confused:

    can timing get off tracked on these? it kinda idles like the spark plug is firing at the wrong time.
  18. seanhan

    seanhan Member

    Can You

    Run your engine in the dark to see if the spark wire is shorting anywhere?
  19. rcfighterpilot

    rcfighterpilot New Member

    ill try, dont think its that though, seems like its got a bad mixture or something.
  20. seanhan

    seanhan Member