mbe301

Hey All

I've seen alot of post of people saying the gas moters are the same type as ones used in weedwackers, but can you convert one easily? I have a 31cc that's in great condition from mime (ran over the rest of it)

John d

Hi
I think they may look the same but the engine output is different lower rpms
[>:][sm=devious.gif]

cobaltltblue

it would work. you just have to overcome 2 main problems. #1 mounting, the weedwacker will not have the mounting places on it like a R/C motor does. #2 clutch, finding a clutch to fit the motor and output shaft and have the correct gears to mate up to your trans. it would be a monster for size and power with a 31cc motor. i know a lot of people do it with boats. changine the power band is simple with a diffrent tuned pipe/carb. it's a good idea i'd like to see it when your done!

bigmodman

you do have mounting holes on it already,cuz i have done it but i took it out cuz it was so small.the mounting holes for the head is what i used.and i just made mounting brackets with some stainless steel plating.and you can get a clutch from the dealer and clutch adapter then you can modify the clutch bell and make it work with your application.and to get a little more torque and power out of it i would port and polish the intake and exhaust about a 1/16 bigger than the orig...hole and then modify the insulator block by increasing the size of it to match the hole,then you would prolly need to rejet your carb to a new setting and record your data to make sure you have it right,so if you have to redo it,you know what you need to get.then i would make a pipe or go buy a highend race pipe for it and you're ready to rumble.if you where to make a set of cool pipes like i did,you would need to get an old expansion chamer or 2 and then modify it to make it match,see what i did is i cut off what i didnt need like the flange and stuff like that,then you would need to make your new flange and tail pipe section to match. the expansion chamber could be used from an old 2 stroke 50cc dirtbike.

Earth Surfer

Weed wacker engines are "utility engines". They are made to make power in lower RPM, usually do not rev very high and made to last a long time. The Zen RC engines are more race ready as they are ported for more performance, and almost double the RPM of a utility engine. A utility engine can be modified to make raceable power, but if a Zen RC engine is available in the size you want, you might as well start there because you need quite a bit of work in a simular size utility engine to match the stock performance of the RC engine.

Bratch96

I knew Earth Surfer would speak up on this subject.[sm=wink_smile.gif]

T I G

I was thinking the same thing Bratch

ttoks

port a gas two stroke is nothing like porting a nitr, it is much easier, so it wouldn't be to hard to get the porting right as long as he did some research to find out what had to be done, run a tuned pipe (just something homemade, you can make your own tuned pipe out of sheet metal, just to some calculations to how long the tuned length has to be), there a guy on here making a quarter scale drag car with a chainsaw engine, he claims to have gotten it up to 16k rpm after adding a pipe and doing some modding.

bigmodman

ttoks is right

PAPE

I have convered a couple of chain saw engines for planes and they work really good you should take a look at the engine conversion forum you will fines tons of information about this and the 31cc Ryobi too

R.Robinson

Yes and NO.[] Only commercial quality trimmers are a good source for using these type engines. RED MAX or Green machine. They are Zenoah power plants. All other engines fall short. Older Homelites and Echos are good for boats . Everything else is low quality and isn't worth using. YOU need good HP to make the grade to use. Chainsaws work OK but weight is a issue.

Earth Surfer

What makes you think working on gas engines is easier than a rotary valve nitro engine? They are both two strokes, and you even have more options for intake porting on the rotary valve (hollow crank shaft for intake). There are a few more dimensions that greatly effect the pipes performance than just tuned length (but that is a big factor), and most people don't know how to correctly measure tuned length--including some engine builders. Every dimension on the pipe effects power--every diameter, every tapper, and every length of each part of the pipe. I have been playing with two strokes for decades, and I have been a machinist with two engineering degrees for a long time. Engine work to me is one of the most involved types of work I have ever done----so I have to disagree. The cutting is the easy part---and good porting with a pipe that does not match the target RPM the ports are set at will not run as well as a pipe made for the porting.---that part is pretty involved also, and I have done enough homework to know it is not easy if you want a well built engine/pipe combo. But, it is not to hard to improve the stock power. 16 year old kids can do that--they can't do the math, but they can cut the material---so for them--yes, it is easy

I don't believe anybody in the world can possibly know every aspect of two stroke performance--even the god father of the two stroke Gordon Blair. I don't think he would agree with you either on how easy it is.