How To Mount The RS EHO 33CC Engine On A Flat Surface?

Discussion in '4-Stroke Engines' started by Mike St, Jun 25, 2011.

  1. Mike St

    Mike St Member

    I'm am going to try a rack mount of a Robin Subaru EHO 35 engine and would like to know if there are any bolt holes on the bottom of the engine that can be used to mount the engine to a flat plate. This is very difficult information to get, no pics on the net. Can anyone who owns one of these engines tell me? MIke

  2. sparky

    sparky Active Member

    Take flat piece of metal (steel?) and bend the left & right sides up so that you can use the 2 engine bolt holes and 2 gearbox bolt holes....

    Then you'll have a flat plate underneath the engine/gearbox!

  3. Mike St

    Mike St Member

    Where are these two bolt holes on the engine? Are they under the engine? I thought there were three bolt holes under the engine. PLease explain. Thanks. MIke
  4. ocscully

    ocscully Member

    Here is a photo of the bottom of the EOH35 compliments of Staton Inc. I believe that the only mounting points on the bottom are the two threaded holes on the far left in the photo. I've seen the motor mounted using a large L-Bracket before. (see bracket in second Photo)


    Attached Files:

  5. sparky

    sparky Active Member

    Here's some pics of my bike. Didn't design it, but it's a sweet design alright. It was actually intended for a Chinese 33cc scooter engine, but a little bird told me that the Subaru would "bolt right up". That's not entirely true, however!! The gearbox bolts right up, because it's the same one that came with the bike.... the engine has nothing supporting it, reall. The engine rests just right on the vertical part of the plate, so I just wedged part of an old belt (fake leather, at that) in between the mount plate and the clutch housing.

    Anyway, here's the pics. Hopefully you can see the two separate vertical plates on the gearbox side. That's all I'm using right now. I should drill some holes that line up with the engine bolt holes... and get a half-inch long spacer... but I don't think that's absolutely necessary with the belt wedge mount. Lucked out there.

    Oh yea... the pics...

    CIMG0012-00.jpg CIMG0014-00.jpg CIMG0015-00.jpg CIMG0016-00.jpg CIMG0017-00.jpg CIMG0018-00.jpg CIMG0019-00.jpg CIMG0020-00.jpg CIMG0021-00.jpg CIMG0023-00.jpg

    You can see the bolt holes I was referring to in the 5th picture and on. It's got a half-inch gap between the vertical plate and the engine itself. Just bend your plate half-inch sooner and/or use long enough spacers.

    You can see the vertical gearbox plates in the last 2 pics. Each pic shows one vertical mount plate. There's a broken piece of metal in front of them that used to be a handle, which made picking the bike up (especially up a couple flights of stairs) particularly easy because of weight distribution. Unfortunately, the thickness of the metal around the handle where it broke was not very good at handling all that weight. Still have the handle, but I doubt I'll ever weld it back on. :(

    And ignore the tie wire. That's just a failsafe catch. Hah... :dunce:
    Last edited: Jun 25, 2011
  6. Happy Valley

    Happy Valley Active Member

    If you remove the factory gas tank, you will notice threaded holes in the bottom of the flywheel shroud and the insert nuts in the lower plastic extension of the pull start. They are not designed for mounting the engine at all but made for a lightweight fuel tank guard when the engine is used on hand held power tools.

    I mention this because I have seen attempts at mounting the engine using these points.

    This was from a prototype, apparently unsuccessful, from Spooky in Az. It never went further anyway, and mounting an engine from these points may have contributed because IMO it would be extremely flimsy.

    As mentioned above, an L bracket or similar fabrication that utilizes the factory designed engines mounting holes is a much more secure way to go.
    Of course, it's entirely possible to first mount the engine to a transmission or cvt for example, then use the mounts on the trans/cvt to secure the drive train to the bike.
    Last edited: Jun 25, 2011
  7. Mike St

    Mike St Member

    Well thank you so much. This is the first time I have seen what is under the engine, and also under the fuel tank. I have enough confidence to purchase the motor and contunie building. I'm planning to bolt up the EHO 35 to an X2 cvt which I have already ordered. Very exciting stuff. Will have pics when finished. Mike
  8. Mike St

    Mike St Member

    I think I'll use the two left mounting bolt holes plus two bolt holes on the cvt and that should do it.
  9. Happy Valley

    Happy Valley Active Member

    Heh, yes it works quite nicely.

    SAM_0026.jpg SAM_0024.jpg

    Not sure what you mean by 2 left mounting holes. The CVT mounts with the standard 4 bolt pattern onto the clutch. Then, I've used the 2 CVT rubber mounts to a fabbed bracket on the frame.
    Last edited: Jun 25, 2011
  10. Mike St

    Mike St Member

    I meant the two threaded engine holes on the bottom plus the cvt holes.
  11. sparky

    sparky Active Member

    There's two allen screws where I was alluding to in the pics. Just get the same thing, but longer (as long as you need), and two nuts that screw on you'll be able to attach it to something then. At least I don't see why not.

    I actually had to cut the bottom of the engine for it to even fit in the mount. Had I realized what I was doing, I would have taken my time in cutting it off to use that as a type of mount point for my already made plate. Just slide a piece of rubber/leather..

    I really should just get the longer screws and spacer and be done with it... but my rims haven't crapped out yet, so why not let it ride? :whistling:
  12. Happy Valley

    Happy Valley Active Member

    Good luck with the build then, I wouldn't plan on the 2 holes on the bottom of the shroud holding much though. They are kinda flimsy tabs not meant for it, I think you'll see what I mean when you see them.
  13. Mike St

    Mike St Member

    No, not the shroud holes but the threaded holes in the engine under the engine. These are the ones I will use.
  14. Happy Valley

    Happy Valley Active Member

    Righto and just to be be clear, I was referring to the flywheel shroud and the threaded holes shown here in red.

    RS bottom.jpg

    You'll have yours in hand soon enough to judge all that for yourself, I'm sure.
    Good luck and good riding.
    Last edited: Jun 26, 2011
  15. Mike St

    Mike St Member

    If I use the threaded holes, I also use the cvt mounting holes. Like you say, I will make a judgement after receiving the engine. At least I now have aome idea of the possibilities. Thanks.
  16. HeadSmess

    HeadSmess Well-Known Member

    im dubious of the two(the 25 has 3!!!) holes on the underside.

    why? cus i have a lil subu 25 that i cant use now cus they broke!

    i sorta knew they would anyway. call it experience with this stuff.

    theres the two on the shroud. these are fine in themselves still, but the shroud itself then cracked. and the third hole was on the sump cover. that broke.

    vibration+ alloy = breakages.

    the four holes on the shroud, that are parallel to the shaft, where a brushcutter would normally bolt up, are best. though the shrouds only attached to the engine by three screws theres the weak point. shrouds DO BREAK! holding the engine to the frame with m16 hi tensile bolts is pointless if the engine isnt held together just as well!

    just remember that these engines ARENT held rigidly when used in the intended manner - as a hand held lawn implement.
    so any vibration is irrelevant except to the hands of the user. as soon as theyre strapped down tight, there was the previously mentioned vibration, along with torque reactions, twisting forces, and any misalignment issues...

    on the same topic... if someone nice sent me a sample sump from the 35 i would cast one up with mounts :) im already making the mold for the rocker cover so it can have a mount too (off a 25 though) :) (head steady, like all good engines have)

    as it is, im not spending 400 dollars on buying one just to make a new sump pan... hondas are even more here... :'(

    hence the requirement of "someone nice" :)

    the BEST (and easiest) method would be to remove the sump pan. tap out the 4 bolt holes for the next thread size up. find longer bolts...20/30mm more. get some steel tube and cut four spacers. replace sump pan with the longer bolts, and spacers as "washers".
    now its a fairly easy task to drill four holes in a piece of plate in the right spots. have the holes big enough to go over the spacers. weld spacers to plate. the plate is now solid and the chances of breaking anything are minimal.

    i havent done it this way myself cus the shroud broke... and until my neeew tig arrives... no fixy!
    Last edited: Jun 30, 2011
  17. Stoney

    Stoney Member

    Happy is a nice guy he'll send you the sump:jester:
  18. Mike St

    Mike St Member

    Headmess, you bring up a good point, vibration. I'll take what you say into consideration, but I am planning to use the mounting holes on the cvt also which are very substantial and are rubber insulated. I'll also look at the clutch face mounting holes where the cvt will bolt up to.
  19. HeadSmess

    HeadSmess Well-Known Member

    my tig arrived :)

    vibration is the killer of many a fine engine :(

    anyway. i never actually welded alloy before, it seems fairly easy though so far, so ill post a pic or two of my abortions in a few days :)

    Last edited: Jul 7, 2011
  20. Mike St

    Mike St Member

    I have the motor now and after studying my options, I have decided to use six mounting points, all with rubber cushions, 4 on the motor, and two on the cvt. On the motor, I will use an "L" bracket, mating to two horizontal holes on the clutch shroud, and two threaded studs into the oil case, and then two "L" brackets connected to bolt holes on the CVT. There are no really strong bolting points on the bottom of the motor, so I have to use as many fastening points as possible, all shock mounted. I also sit the motor down on rubber cushions.