GEBE R/S 35: Am I running too rich?

Discussion in 'Rack Mounted Engines' started by Cowled_Wolfe, Nov 18, 2007.

  1. Cowled_Wolfe

    Cowled_Wolfe Guest

    Hey ya'll. Right now, I think my engine might be running too rich, or perhaps my carb is dirty (I'm the mount kit's second owner, but the engine's third owner!).

    Here's a list of symptoms:

    • My top speed is only 20-22MPH on the flat, with no winds (I'm 190lbs, and I haul maybe 20lbs of gear). That's with a 12-tooth gear.
    • I never need choke for a cold start.
    • The engine idles very nicely when cold, but once it warms up I have to give it a little throttle to keep it from dying (enough that I can hear the clutch lightly rubbing).
    • To re-start the warm engine, I need to apply a bit of throttle while pulling the starter cord.

    I'm going to be running some carb cleaner in my next bit of fuel to see if that helps, but I think for a full fix I need to adjust my richness. Does anyone know how to do that on an R/S 35?

    Alternately, what else could be the culprit?


  2. OldPete

    OldPete Guest

    Have these symptoms been present since you first started using this R/S 35??

    If so...someone has drilled the main jet or the airfilter is increadably dirty.
  3. Cowled_Wolfe

    Cowled_Wolfe Guest

    Yeah, they've been present from the day I got the engine. I just looked at the air filter and found it incredibly wet with an oily compound -- I've just blown it out, but haven't test-run the engine yet. Right now I'm cleaning the spark plug (I think it's been neglected).

    Also, there's a bit of carb cleaner now in my tank.

    When I'm back from work tonight, I'll post any improvements.

    By the way, what sort of speeds are "average" for the R/S 35? I'd like to judge my speed against others', as a rough performance metric.

  4. OldPete

    OldPete Guest

    28~30mph with #12.

    Neglected? Might want to check the valve clearence.

    Is the crankcase breather tube blowing oil onto the a/f. If so that would mean piston ring blow-by or the crankcase was over-filled with oil. When these motors are used on hard-tail bicycles the oil level should be kept near the low level mark NOTthe high level mark(as per Julia of GEBE).
  5. sabrewalt

    sabrewalt Guest

    Max Speeds RS/35

    My new kit got top speed on a flat is 26-28 mph. I don't like that speed but the reserve is good for hills. I am 250 lbs and I have knobby mtn tires. So a tire change and 50 lbs of weight removal would easily yield book values.
  6. Pablo

    Pablo Motored Bikes Sponsor

    What does your spark plug look like?
  7. Cowled_Wolfe

    Cowled_Wolfe Guest

    The plug looked pretty good. Today I actually think performance went up a bit. The idle was rough, but better... And I had to use choke to start it! That's a first for me.

    If I had to guess, it's because I'm running the carb cleaner and because I lowered the oil level.

    Either way, I'll post if thins change (or if they don't).

  8. OldPete

    OldPete Guest

    "Lowered the oil level." Your welcome. ;)
  9. Cowled_Wolfe

    Cowled_Wolfe Guest

    Lol, thanks there Pete. ;)
  10. Yeah Cowled Wolfe, believe it or not, I weigh in at around 345, and running fairly fast tread street tires, (26X2.125), w/mr tuffy liners. I used to get 31 mph on flats w/o wind, and since installing the tuffys, (with standard gear), I get 29 or 30mph....depending on her R/S 35 with about 750 miles on 'er. And definitely keep the oil level on, or just very slightly above the lower level mark. Any more than that means an oily engine, and air cleaner. Oh by the can download an owner's manual, and service manual for that Robin online. I can't find the link right now, but just put "Robin/Suburu EHO35 manual" into your favorite internet explorer, and you'll find the downloads without much dificulty. The manuals are in PDF format, and are read with Adobe acrobat reader. The service manual is real nice;)
    Last edited by a moderator: Jan 7, 2008
  11. OldPete

    OldPete Guest

    This thread is 6 weeks old and he already got the solution. Bwahahaha!
  12. JemmaUK

    JemmaUK Guest

    "depending on her mood" is about right - if mine with the 32cc is in a good mood with a following wind I can get 34.9 (GPS) - if shes got a bad case of you know what its more like 26mph...

    Another odd thing is the vibration at top end - I've the idea that its the back side of the belt twanging at speed which I have never seen before...

    To check on the tune & mixture I look at the plug - if its a nice chocolate brown im ok... I have noticed with the Tanaka 32cc that at first the engine runs rich - and slowly as the engine runs in becomes closer to the right tune...

    Strangely this mirrors some of the cars my father had - after maybe the first two service periods we'd regularly get 2-5mpg more than when the engine was tight...

    Jemma xx
  13. I may have been a little too rough on mine during break-in as well. My dad always maintained "break 'em in like yer gonna drive 'em" I'm still well pleased with the speeds I'm getting considering that I'm not far removed from a If wear this one out, I'm going for the 40cc Tanaka......zoooooooooooom!!! hehehe.
  14. Cowled_Wolfe

    Cowled_Wolfe Guest

    Four months later:

    Alright, so I figured I'd post an update after the 4 month mark... First of all, I've found that the solution for my engine dying is to add an entire bottle of carb cleaner to each gallon of gas (this does nothing for my top-end speed problems though). I've been using 'Super Tech' brand 'Fuel Injector and Carburetor Cleaner' from Walmart, which comes in 8oz bottles marketed as treating "up to 20 gallons"...

    Second, my engine has been mounted (from the onset) at a pretty far backwards angle, which definitely helps blow oil into the filter -- I wouldn't be surprised if the carb is full of the stuff too.

    So my current thoughts are to get a new engine this spring, and build a new mount with a bit more forwardsy orientation pretty soon too (possibly out of stainless)...

  15. kerf

    kerf Guest

    Just for the heck of it, have you checked the spark arrestor, sometimes they get clogged?
  16. Cowled_Wolfe

    Cowled_Wolfe Guest

    So I finally found the solution, back in May. It turns out, my intake and exhaust valves both had clearances well in excess of the .13-.17mm recommended by the service manual.

    My biggest feeler guage was 2mm (that's 2.0, not 0.2!) and still had room to wiggle freely...

    In hindsight, it's amazing my engine even ran! Let alone carried me hundreds of miles in such a sorry state... It's a testament to Robin/Subaru's design!

    On the bright side, I learned a lot more about my engine while working on it. I even made/discovered a performance tweak (moved a nut on the throttle cable, allowing the throttle to open a bit further) in a vain effort to prevent the engine from dying.
  17. astring

    astring Member

    CW could you walk me through that intake/outtake valve clearance thing how to measure and adjust it. I have a little stalling thing also.
  18. Cowled_Wolfe

    Cowled_Wolfe Guest

    Astring, I'll try to get some instructions up soon. I'll try to get some detailed instructions up within a week. For now, you need to collect a couple of tools.

    - A phillips head screwdriver
    - A flathead? (Forget if I needed this or not.)
    - A tiny* metric allen wrench.
    - A small* wrench, box prefered.
    - An automotive feeler gauge. You might need to borrow this if you don't have one. Or maybe I'll find a household object flose to factory specs? ;)

    The actual job takes somewhere around half an hour to an hour, depending on how mechanically inclined you are... And the best part is that it's really easy on the R/S 35.


    * = Not sure what size, but I'll find out when I post later.
  19. Torques

    Torques Guest

    I would be interested too on what the fix is. I have a friend who has a eho35, is it possible that recently during some maintenance when the motor was lying on it's side, some oil may have bypassed the breather tube and got into the carb. This also might be due to the fact the crankcase was overfilled (he filled it last and not saying he overfilled it but in case he did). His engine runs rough now. It idles rough and runs rough especially between 15 and 20 mph. Specifically, what is the fix if oil has entered into the fuel system. Will lots of Seafoam clean out the oil or does the engine have to be disassembled and cleaned?
  20. WU7X

    WU7X New Member

    I'm glad that I found this thread. I have been having similar problems, and I only have ~250 miles on my R/S 35. I noticed the oil smells a bit of gasoline awhile back. I have the engine mounted slightly leaning backwards because of the location of the rear brake mount on the mountainbike frame it is on. So I am going to throurghly clean the spark plug, the air cleaner, rechange the oil to a lower level and then see what happens. It is very hilly where I live so I went with the lower gearing. It dropped my top speed a very slight amount but certainly makes up for it when climbing the hills. Top speed now ~28 mph. I'm satisfied with that.

    Dale WU7X