Ryobi weedwacker engine

Discussion in '2-Stroke Engines' started by MikeL, Jul 30, 2011.

  1. MikeL

    MikeL New Member

    The head broke off of it so my friend brought a replacement echo gt-200r.. anyways I'm going to guess the engine is 25cc.. It needs some work like the recoil is messed up but I'm curious on how many people use a ryobi WW engine.

    I haven't got my bike at but what I'm looking at is one I'm not sure what tire size would be best? mind you I'm 5'9" and 125Lb So I'm not too sure how a 25cc engine would do.

    I'm also new to this so I'm still reading around here and figuring out

    I should also note that the Ryobi has been sitting for at least 3 years I guess so I'm sure it's going to have to be cleaned up.
    Last edited: Jul 30, 2011

  2. HeadSmess

    HeadSmess Well-Known Member

    see the rubbish bin over there? please place your junk in there :) thankyou.

    ryobi is :poop:

    plain and simple. dont bother.

    and once somethings gone wrong with it? :jester:
  3. MikeL

    MikeL New Member

    Really? hmm seems like I was reading here that they are pretty good :eek:

    Nevertheless do you think 25cc is a little undersized for my weight? 125 lb (56.7 KG)
  4. motorpsycho

    motorpsycho Active Member

    25 c.c. is undersized for ANYTHING that's going to do more than spin a string to wack weeds.
  5. MikeL

    MikeL New Member

    Hmm I might be wrong around the engine size it might be 31cc I'd have to get the model number on Monday to be 100% sure.
  6. HeadSmess

    HeadSmess Well-Known Member

    but its still a ryobi :jester:

    cheap nasty junk that is next to impossible to mount to a bike, will do a better job at driving you mad than driving your bicycle, and seriously belongs on the shelf at kmart or costco or whatever shop was selling such a lousy inferior piece of equipment.


    only trying to save you from yourself here...

    mount it in the bench vise, learn how it works, then learn how to beat it up with a hammer before it kills you in your sleep or now im just getting carried away :eek:
  7. HeadSmess

    HeadSmess Well-Known Member

    please explain " the head broke off"

    as far as im aware, ryobi has a combined cylinder head thats held to the crankcase by a whole 2!!! highly impressive...screws? not bolts mind you, with real threads, but these dodgy things that resemble wood screws... self tappers prob. anyways.

    dodgy dodgy dodgy! kill it!

    you are being given it for a reason... look in the horses mouth this time!
  8. srdavo

    srdavo Active Member

    Isn't the bottom end of a weed whacker called a head, too? trimmer head?
  9. BentTooner

    BentTooner Member

    Hi, MikeL
    My first MB was a home built friction drive with a Ryobi weed wacker engine. I think they are usually 31cc and it's plenty of engine for your size. I got about 22 MPH out of it and I weigh 170 lbs.

    The main problem with that engine is I could not figure out a good way to use a clutch with it because the clutch they use is pretty light weight and probably won't last long.

    So, I made a frame to hold the engine and mounted the engine to the frame and found a BMX foot peg that had the right bore and threads (mine was 3/8" x 24 TPI) and threaded it directly to the end of the crank shaft. Then, I pivoted the frame up and down with a long handle so the foot peg, acting as a drive spindle, either contacted the tire or not. I used bungee cords to help hold it down on the tire. I think it's called a 'suicide clutch.'

    I copied a design I saw posted here by one of the regulars who took some good pictures of his setup. Sadly, I can't recall his screen name at the moment. Maybe Mountain Man or Happy Valley... I'm getting old... I just can't remember right now.

    Anyway, it worked great and I rode it that way for a year. I accidentally burned up the engine by letting it run against the tire on a long downhill section after I ran out of fuel. Without fuel, the engine had no lubrication and a ring broke.

    I got another one off ebay for $20 and that engine is still going strong. I also got a couple of Ryobi 25cc 4 stroke engines and used them. They were great, too.

    Eventually, I moved on to a BMP FD kit with a Robin EH035 35cc 4 stroke engine to get the convenience of the clutch and the ease of the 4 stroke engine. It's been a great way to go. Right now, I'm building a trike and I plan to use that same engine.

    If you need any more info, please let me know. I thought it was a great way to start out in MB for no money at all since I had the engine laying around and I built the frame out of junk wood and aluminum I had in the shop.

    I think some guys here have made MB with the engine and the clutch and they might have some good ideas for how to make the clutch last.

    Good Luck!!!
  10. MikeL

    MikeL New Member

    Whoo a lot happens here when your sleep ;)

    I just pulled the motor off the shaft.. It's a Ryobi 766R and it is 31 cc

    I don't have a bike yet lol so I'm in no rush.. I would rather stick with 2 stroke if I can.. I know the Subaru engine is everyone's pick but I'm trying to go lightweight..

    I MIGHT do a slight teardown of the motor today or tomorrow.. Interesting it's a 32:1 mix seems a bit much for the engine.. all my other stuff is 50:1

    I'm not looking to go crazy with a build like some others here

    The bike I'm just going to buy a road bike if walmart has one I already own a welder so that's good.

    I know I will have some more questions.. Like when you had a spare engine around did you do a full teardown of it? This one has been sitting for a few years because I guess the recoil spring broke (I want to keep it if possible) Also the primer bulb has cracked but I'm sure those are easy to come by?
  11. BentTooner

    BentTooner Member

    Hi, again

    Yes, I completely tore down the Ryobi engine and that's how I know the ring was broken. The parts to repair it were more than a used one in good condition off ebay.

    That little primer bulb is easy to find but costs about $10 to replace. They always crack after they've been sitting, dry for a couple of years. A piston and rod assembly will run about $35. The flywheel is over $30. And so on. In the end, it's just cheaper to get one used.

    That little Ryobi puts out about 1.6HP which is about the same as the 35cc Robin engine so it works great for a MB project. My Ryobi 2 strokes all got about 225+ MPG which is better than the Robin 4 stroke where I get 180 MPG. I never understood that...

    The Robin has more low end torque since it's a 4 stroke. That's nice for hills.

    I didn't bother with the starter because I just lowered the drive spindle onto the rear wheel after I was moving at a good speed and relied on a compression start. Works great and no need for the starter mechanism.
  12. MikeL

    MikeL New Member

    Doh! I must of overlooked the part about the rings haha that would need a tear down :) I can't have high hopes since it's been sitting for so long.. this thing says 32:1 but what happens if I do 50:1? I still almost got 1 gal of pre-mixed 50:1

    So with a 2 stroke I'm limited to a friction drive? I've been reading here and trying to figure this out.

    Last edited: Jul 31, 2011
  13. BentTooner

    BentTooner Member


    If you have 1 gallon (128 ounces) of 50:1 premixed fuel, you have about 125 ounces of gas mixed with about 2.5 ounces of oil.

    To get it down to 32:1 ratio, you would add about 1.4 ounces to get it up to about 4 ounces of oil in the 1 gallon (plus the added 1.4 ounces of oil) of gas.

    It's not necessary to be that precise but it's better to be too rich rather than too lean so I'd a little oil.

    The pictures are great! That engine has a lot of wear and, FWIW, I wouldn't put any serious money in it - just some time, if you want. You could clean it up with carb cleaner but the primer bulb will have to be replaced and that's $10 unless you can get a used one somewhere cheaper.

    You won't need the recoil starter mechanism if you're going with a direct friction drive.

    No, you're not limited to a friction drive with a 2 stroke. I didn't mean to imply that. You can use any kind of drive you want (chain, belt, etc.) but the friction drive is the easiest way to get started.

    If you haven't already, you might look in the gas tank to be sure it's in good shape and the filter is there, in one piece and tight to the bottom of the tank. Also, if you haven't already, you might want to check the fuel lines for cracks. I've found that the lines can leak, especially at the joints and the gasket at the bottom of the tank can leak, too.

    In the end, you can easily spend $30 just getting little parts for an engine that is pretty worn. So, before you do that, you might check on ebay for a similar engine in good shape and see what it would cost you.

    I've got at least one used Ryobi 31cc in my shop that I was using on a bike when I bought the Robin engine. I've also got a couple of the Ryobi 4 stroke engines that work well that I'm no longer using. And, I've got a NEW 31cc 2 stroke that I bought and never used except to start it to see that it worked. If you're interested in any of them, please let me know. I don't know where you live so I don't know if it would be worth it due to shipping costs.

    You might be able to find one on a weed wacker at a yard sale in your area for dirt cheap, too. That would be best to save shipping costs.

    Good luck! I hope this helps.
  14. MikeL

    MikeL New Member

    Thanks for the help on the mix, so I've taken this motor apart and this is my first time taking a 2 stroke apart.. the piston top cleaned up good and as well as the cylinder head.. rings look a bit worn.. I might be able to get a little more life out of it, if not for a bike something else..

    As for the fuel tank the filter is in it but all the fuel lines just pretty much broke upon touching them.

    I just put the head back on so that was easy.. now for the carb the yellow and red adjustments are for the H and L carb adjustments right? The carb is pretty cheap so not much to do with that.
  15. MikeL

    MikeL New Member

    updated shots before bed.. lubed with oil.. only one thing is I guess RTV gasket maker is not going to work for the cylinder head because it's not thick enough so the flywheel hits the coil.

    having said that where is the clutch on this thing?? In the cutting head? it seems direct drive to me..


    lol and how the poor shape this was in


    Surprising the piston seals pretty good. I poured a decent amount of 2 cycle oil in the plug hole and let it sit for awhile and 10 min later it was still at the top.
  16. MikeL

    MikeL New Member

    hmm this ryobi has no clutch which is odd they list a clutch cover in the parts manual.. seems to be from the 1997 era.