Gas /oil ratio vs power?

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Chris142

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I've got 2 Weedeaters. Little green ones. I think 25cc. One runs pretty good and the other has low power. It won't rev up as high as the other one.

I've cleaned the carb, changed the plug and even cut grooves in the fuel mixture screws to adjust the mixture but nothing has helped.

Thing is about useless.

They call for 40:1 and I'm currantly running the weedeater brand oil that came with them @ 40:1. Last year I ran some Echo oil in them @ 50:1 and this one was gutless then.

I'm considering different fuel/oil ratios.

Would more or less oil provide more power? I'm guessing less oil = more power.

It's pretty much useless as it is so I don't care if it blows up.
 
I would inspect the piston and cylinder and check compression. These cheap string trimmers have the carb set to run lean in order to pass EPA cert. and therefore wear out rather quickly. You will get 50 hrs out of them if you're lucky.
 
Ive purchased cheapo weed wackers before that had bad engines from the get go. I went through 2 in a row before I checked online and it seems that China had an issue and still shipped them, then Home Despot decided to still carry them.

Not much to do besides go get a better quality machine. I took the 2nd one bought and spent an extra $100 on an Echo. It has been awesome. Lightweight, powerful, and easy to start for 3 seasons now.
 
Mine specs 1:50, I've found 1:30 much better.

I like to have a damp exhaust, as it shows that oil is getting all through.

When I get home, I'll dig up a book (by AG Bell) on two stroke tuning, which showed richer was better to a point
 
If running O.K. but low power, as was posted above, the spark arrestor screen is a candidate as the cause. They WILL cause a problem if not cleaned at some time,(or removed).
 
Originally Posted By: Shannow
When I get home, I'll dig up a book (by AG Bell) on two stroke tuning, which showed richer was better to a point


He was really anti the lean mix trend,and his dyno chart was very convincing.Always using Castrol R of course.

Thanks for the link - every few years I get his 2 and 4 stroke books out of the library and review them,I learn something new everytime.Now I have my own copy...

Interesting he was foreseeing the use of ethanol in fuels as the way forward way back then.
 
People often confuse the term "rich" when talking oil:fuel ratio and fuel:air ratio.


For those who have not read Bell's book, less oil will not generate more power. More oil will increase lubrication and power to a degree but may also cause a lean fuel/air mixture because oil will be displacing gasoline. However, the amount of oil would have to be substantial.

For OPE, I prefer a mix between 32:1 and 40:1. I run nothing but a good quality conventional oil and have had no problems with it. I probably own somewhere around 30 to 35 two cycle machines and one of them is a 1997 Craftsman single stage snow thrower with a Tecumseh two cycle engine it. I am purposely flogging it by over-riding the governor and running it under load between 5000 and 6000 rpms. I worked it hard all winter and really whipped it a couple days ago. We had approx. 10 inches of slush fall and I ran a full tank of fuel through the Craftsman at above mentioned rpms. All the time, the machine worked spectacularly (better than my new Toro 221 in the same snow) and it never skipped a beat until it ran out of fuel. That Tecumseh engine has been getting the same hard treatment all winter with 35ish to 1 fuel ratio. It doesn't seem to mind it. It's rated at 5 h.p. at 3800 rpm. I suspect I'm squeezing close to double the horse power out of it. It will be interesting to see how long it holds up. I've got another much newer machine (2008) with a replacement engine on stand-by if it [censored] out.
 
Less oil would probably equal higher RPMs, while giving up much needed oil. Most all my stuff is 50:1 and I mix it just that.
 
My 2-stroke L-B calls for 32:1, and that's what I run in the Echo and Bolens string trimmers also. Just like BITOGers and stretching OCIs, there are a lot of 2-stroke guys who like 100:1 and 150:1 in their 2-stroke stuff using exotic oils like Saber. It might work fine, but especially with the 2-stroke stuff, I'm old school, and I'll err a little on the thick side for mixture.
 
You can try a 16 to 1 mix and see if that helps. The oil rich mixtures tend to help ring sealing. Plus the more oil, the more power, jetted properly, of course.
 
Have you tried switching carbs from machine to machine?

If not, give it a shot.

If it doesn't do anything to improve performance, then I'd say there's a good chance that the lame machine is just that. Lame.

One other possibility it that the timing might be off. Is there a way to check for timing marks compare the position of the flywheels on each machine?
 
Just about all the obvious solutions have been covered above. Maybe check the less obvious ones....I once had a throttle cable stretch and the carb. wasn't opening up all the way.
 
Throttle is opening up all the way. Air filter clean. I cant disassemble the muffler to get to the spark arester.

I'm thinking of removing the muffler and soaking it in Chem-Dip to clean it out. I dont want to start swapping parts and end up with 2 broken machines.

I'm going to try 32:1 which is what I ran in my dirt bikes for years.
 
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