Where's the 4-stroke DIYs?

a_dam

a_dam

New Member
While browsing through the big-box stores, I'm seeing 4-cycle yard tools getting more common. Even Wmart had a few things. The leaf blower (31cc?) seemed no heavier than the 2-stroke model - about 2x the cost, though.
My dad bought a 4cyc wacker last year and it does run smooth.

Anybody got a small-cc 4-stroke creation to show off?
 
I had a 31cc 4stroke FD, ran great, but was a little weak for the hills in my area. Would seem that the current Ryobi variants would be no harder to convert that a similar 2 stroke. Fuel mileage would be phenomenal!
 
Ive got a 4 stroke weed whacker and it has less power and eats more gas then my 2 stroke they are both 33 cc
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I tend to think of 4-strokes having better torque, but that's probably not necessarily true. Does your 4cyc wacker run smoother? Not having to mix fuel would be nice. Amsoil at 80:1 only costs me about $8 a year and the exhaust leaves no oily deposits and hardly any soot. Cant beat a 2-strokes power/weight.
 
Mine was very smooth and fairly quiet. They will turn 7k rpm so some decent speed is possible and they do produce more torque. I conveted a Honda GX31 for a large R/C photo plane. It would turn a larger prop with more pitch than a comparable 2 stroke at less rpm. Was very quiet and smooth. Would just about double the time on a tank of fuel vs a 2 stroke. A 4 stroke makes a neat FD, I would still have mine if I lived in the flats (sold it to a rider in Fla, and it is serving him well). Takes some major HP in my area.
 
I worked on a year old honda trimmer for a friend.
It was very powerful, but was very heavy compared to the redmax or husky I prefer to use.
Gotta use the sling!

As you had said, initial cost of the motor will hamper their use until a bunch of 'em are available, used.

really hard to beat the simplicity of a 2 stroke, though.
rc
 
Thursday I bought a ryobi trimmer from a craigs ad. They wanted $70 but I pointed outthat they had premix in the fuel tank and that the oil was in the crankcase. Thankfully there was oil in there and I got it to start in the cold w/ premix so I offered them $50 after the cloud of smoke cleared. There was no permanent damage. I dumped the oiled gas, cleaned the plug and ran it on straight Seafoam for about 10 minutes. I dumped the Seafoam except what was in the primer and lines, then filled the tank with 91 octane (best available from normal stations 10%methanol) I pumped the primer several times to clear the seafoam and mix it back to the tank. As I run it more the smoke is completely gone! :D Its only 26.6cc and weighs about 13 pounds in working string trimmer trim. I hope the motor and clutch could be 7-8 lbs. It turns the head smooth and strong to ~6400 rpm according to a multimeter. I think it sparks on the exhaust stroke and the bang, don't know yet. Should be a fun toy. I'd like to build a front wheel drive 26" streetfighter type of hybrid. I'm tired of fighting my happytime chain tension problems. I might buy a GEBE front kit or buy a welder, teach myself some welding and build my own jackshaft drive. GEBEs cost about the same as a good 110v welder and jackshaft parts. Hmmm.

Check the used equipment ads. I got what was a $225 machine for $50. Its a sweet little motor. According to the manual it should turn 8k and make 1bhp. That's optimistic but this should be fun. The manuals are free PDFs. The sparkplug contains unobtainium and costs $5.
 
You mean like this:
422218_3263344864232_1285534369_3377828_1254749888_n.jpg

Turns out I'll have to turn the engine around but you get the idea.
 
Here's what my project looks like so far.

DSC01464-M.jpg


Here's the mystical $5 spark plug that has to be ordered special (ryobi RDZ19H) and the tools needed to adjust the valves. They were tight cold. Who knows how long the DPO ran it on premix.

DSC01467-M.jpg


There's some good reading about these ryobi OHVs on RC plane forums. In my daydreams I see syncronius pulleys 10:40 belt driven single jackshaft turning a 10:66 chain final drive with the whole thing mounted equally from the bars and forks. I'll keep the pull starter, throttle trigger, kill switch and air cleaner stock at first. I have a homegrown LED turnsignal,brake/tail rig using auto and chinascoot parts and a 9v batt.

I'm taking apart the disappointing 48cc grubee happytime Orange Crusher and going in a different direction...

5-4-2011-M.jpg
 
Wow, that thing's really wedged in there! Pedal only when necessary.

What's the details on that motor?
 
corim123 said:
You mean like this:
422218_3263344864232_1285534369_3377828_1254749888_n.jpg

Turns out I'll have to turn the engine around but you get the idea.
Click to expand...

You can reverse the power and leave the motor that way. Just use a idler sprocket rather distant from the engine, and run the jackshaft sprocket against the OUTSIDE of the motor chain. It's that simple.
 
Thats probably the only option Wayne, doesnt look like it would fit the other way. Could be wrong, usually am!
 
WayneC said:
UNOBTAINIUM? Please explain...

...anything like "Upsidaisium" Cap'n Peachfuzz?

Whatsamatta U
Click to expand...

Unobtanium is a rare earth, similar to the Obscurium that coats so many car windscreens; also related, is Krappite, a sort of cheese textured alloy for structural parts of engines. Polycrackathene is widely used for indicators and lighting covers.
 
Of course it was my experience with unobtanium that drew me back to this thread...
Years as a builder led me to explain a number of times how a clients desires could only be accomplished by the use of it, and the cost was prohibitive for the application.

I'd like to know if anyone has documented a build with the jackshaft run from a center, outside running sprocket of a three ring primary chain drive setup, to achieve reverse rotation? 180 degrees of chain engagement is of course best, yet many ratios probably get down to 120 degrees when running a very small 10T against 40T+ in a short run.
Running the backside would most likely be even less than that???

I guess the obvious solution is to run gears for the primary reduction.

Best
rc
 
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