18:1

[Rockey5000]

I'm confused, I did some research and have found that 2-Strokes make their best power and longevity at 18:1. Why don't more people use this ratio? All the money that people spend on powerups for their bike and they run it at 50:1? It just doesn't make sense to me. Can someone tell me the disadvantages of this ratio? I want to switch and need to figure out how much richer to jet the bike to make it run right. What do you guys think?

 

[125 rider]

Because most poeple probably dont know how to properly jet a bike so switching to a radically richer oil mixture (or leaner air/fuel mixture) will leave them with a poorly running bike. I run 32:1 in my bike because 1. thats what its jetted for, 2. it's an adequate amount of protection for my riding style and conditions, and 3. because 2 stroke oil is not cheap and with the amount of riding I do i'd be going through buckets of oil a week at 18:1.

 

[rc331]

A two stroke will make more power with a higher ratio of oil to fuel up until the point of fouling the plug. I think the disadvantages would be like 125 rider mentioned cost of pre-mix oil would be out of this world, jetting would be a nightmare, spooge would be a problem, carbon deposits on the head would be a problem, powervalves are already icky enough to clean, there would probably be no mosquitos (a good thing ) as they would all be dead due to smoke but the greenies would have a real reason to complain. Throttle response may suffer?. Silencer packing life may be shortened. ;)

 

[Jaybird]

You can jet your bike for what ever ratio you choose to run. However other factors enter in like, humidity, elevation, and riding style.

I'm a bit confused, rc331...are you saying these events will happen when going to the 18:1 ratio or the 50:1?

 

[rc331]

I was thinking this stuff could happen at 18:1 maybe I'm way off base?
also doesn't the addition of oil to gasoline lower the octane rating of the gas? I suppose you could re-jet and avoid the problems I mentioned in my earlier post but would you be able to run 18:1 on pump gas without detonation?

 

[Jaybird]

You are indeed off base, rc331. That's why I asked.
If you are jetted up for 50:1 and you got to 18:1, I realise that conventional wisdom would say you would have fouled plugs, spooge, and the like, but it is actually quite the opposite.

Too much to go into, do a search and be enlightened. :)

 

[rc331]

Jaybird

o.k I did a search but enlightened I'm not....more confused...maybe! :confused:

Originally posted by Rich Rohrich
Using a high volume of oil and pump gas in a high output two-stroke engine is a REALLY BAD idea.

 

[Jaybird]

Well, for one thing, if you are after optimum performance, pump gas will not help you to succeed. It is very inconsistent, to say the least.
When you are running a high volume of oil and jetted up correctly, you should be close to the edge of being lean. Detonation is bad and pump gas can contribute to detonation.
Keep in mind that many times Rich will be describing high performance tuning with the maximum output as his goal.

Take look at this thread:
http://www.dirtrider.net/forums3/showthread.php?s=&threadid=49832

 

[David Trustrum]

Ooh ooh! Can we get onto what brand oil is best to use next? My personal favourite is:
Honest Dave’s slippery eel oil. Made from recycled sump oil it comes to you pre-tested, no other oil can claim that.

It is best run at 50 parts oil to one part petrol so you buy more.

Send your cheque to. . .

 

[rc331]

Jaybird
o.k I read everything I could find on the subject and my thinking was wrong! so I guess I am enlightened. ;)

 

[Rockey5000]

Originally posted by rc331
A two stroke will make more power with a higher ratio of oil to fuel up until the point of fouling the plug. I think the disadvantages would be like 125 rider mentioned cost of pre-mix oil would be out of this world, jetting would be a nightmare, spooge would be a problem, carbon deposits on the head would be a problem, powervalves are already icky enough to clean, there would probably be no mosquitos (a good thing ) as they would all be dead due to smoke but the greenies would have a real reason to complain. Throttle response may suffer?. Silencer packing life may be shortened. ;)

If you jet correctly at 18:1 the plug will not foul any more frequently than ay 50:1. Premix cost is a disadvantage, but an engine costs more. Jetting wouldn't be any harder than at 50:1 or 32:1 etc. If the bike is jetted correctly spooge would not be a problem neither would carbon deposits on the head or excessive smoke. Throttle response would be increased on a correctly jetted bike as the extra oil increases compression and extra compression increases throttle response. Silencer packing life wouldn't be shortened with out spooge in it.

 

[Jaybird]

rc331...very cool!
Don't feel lonely though, I talk to guys who think they are ace tuners (racer dads, bike shop mechanics, A riders, etc...) who still think that if your bike is spooging, the simple solution is to lessen the amount of oil in the ratio.
They are clueless, but if you try to have a decent discussion with them, they will let you know right away that THEY are the pro tuners and know what they are doing. Mere mortals can't compete with genius' such as those. :)

 

[rc331]

Originally posted by rc331
Jaybird
o.k I read everything I could find on the subject and my thinking was wrong! so I guess I am enlightened. ;)

ROCKEY5000 see above....I got the point ;)

 

[Rockey5000]

rc331 I was in no way flaming you! I understand where you were coming from and was trying to address what many people believe about using more oil. Im sorry if it came off as a flame, I didn't mean it that way.

 

[125 rider]

Originally posted by Rockey5000

If you jet correctly at 18:1 the plug will not foul any more frequently than ay 50:1. Premix cost is a disadvantage, but an engine costs more. Jetting wouldn't be any harder than at 50:1 or 32:1 etc. If the bike is jetted correctly spooge would not be a problem neither would carbon deposits on the head or excessive smoke. Throttle response would be increased on a correctly jetted bike as the extra oil increases compression and extra compression increases throttle response. Silencer packing life wouldn't be shortened with out spooge in it.

So what was the real question here? I think you've answered them all yourself :confused:

 

[Rockey5000]

The question is why do people who spend $1000's in performance mods and top ends overlook this simple and effective way to increase performance and longevity.

 

[marcusgunby]

It doesnt sound as cool as 'i have a pc pipe'

 

[dell30rb]

Marcus is right@!!

 

[2001yz250]

So why not just run a 1:1 ratio or just put all oil in it and no gas? This is not a flame by no means, I'm just intellectually challenged! :ugg: There has to be a limit somewhere, is it at 18:1?

 

[JTT]

Originally posted by marcusgunby
It doesnt sound as cool as 'i have a pc pipe'

ROTFL! You da man!

 

[marcusgunby]

As others have said eventually you will dilute the gas and cause detonation.For max power on good fuel 18:1 is a good ratio.I run at 32:1 on mine just because oil is expensive.

 

[Rockey5000]

If you want the best mixture, run race gas with 18:1. I run Cam-12 110 Octane race gas with an 18:1 mixture of MX2T. The added performance is very noticible.

 

[2001yz250]

So if my bike is jetted correctly now, to run at 18:1 would I need to richen all the carb circuits?

 

[Rockey5000]

Yes, one main jet size, one pilot jet size, and one or two clip sizes up will compensate for the change. Are you running race gas or pump?

 

[2001yz250]

Normally I run pump but I bought a couple of gal of race gas and I can't tell any difference, maybe even less performance. I have a gallon left unmixed and was thinking of trying a different ratio.