18:1

[Rich Rohrich]

Originally posted by Rockey5000
Yes, one main jet size, one pilot jet size, and one or two clip sizes up will compensate for the change.

Jeez the BS is getting deep in here. :silly:
You have NO IDEA what effect adding additional oil volume wil have on the combustion process without having an intimate knowledge of the combustion characteristics of the oil being used and an understanding of the fuel being used. Jet it richer across the board is not necessarily the answer. One last thing, Cam 2 110 octane isn't a particularly good choice of fuel for your 125. The end point distillation temps are to high for normal MX use. The bike will likely make more power at high rpm by switching to one of Sunoco's Unleaded race fuels like GT100.

2001yz250 - Pick an oil you like, mix your fuel at 32:1, buy the best fuel you can consistently afford and go ride your bike. 18:1 ratios are of little value for applications that don't spend lots of time at WOT, and MX bikes aren't going to be magically transformed by dumping a ton of oil in the gas. High oil volumes have their place, but MX is rarely one of them. It's not a magic bullet.

 

[Rockey5000]

Rich, I was just telling him from a personal experience. When I switched over from Sonoco 94 pump to Cam-12 110 Race gas at 18:1 I noticed a power increase. I jetted MY bike ricer across the board because that is how it ran BEST. Suprisingly enough, even at 15 I do know how to jet my bike correctly. It runs perfect, never fouls plugs and has never siezed a piston. I TRIED an 18:1 mixture based on info about how 2-Strokes make more power at 18:1 due to increased compression. I like how the bike runs at 18:1, and im sorry if its ** to you, but if you read the question I asked upon creating this post, it was why don't more people use this ratio. Its one thing that just annoys me, you take me to be an idiot, and I think its because of age. After reading your insulting first paragraph, I see your reason for not using an 18:1 ratio (Its of little value for applications that don't spend much time at WOT). Thats all you needed to write.

 

[Rich Rohrich]

I can assure you my distaste for your posts is purely content related. Your capacity for giving bad advice seems to grow by the day.

Fortunately it's a simple problem to fix. :D

 

[jmics19067]

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.

well I am new to the wonders of racing fuel but I can tell you that "race fuel" is not the wonderful cure all most people have the misconception of.
VP Racing has about 25 different blends of fuel available in there pamphlet for all sorts of different applications . And if you are really smart in knowing what you want and have the money they will custom blend something for your application. Going down to the boating dock or to the airport and buying a high octane fuel is far from actually getting a decent fuel for a motox application. Those fuels are more than likely designated for constant throttle constant load situations .
Once you find a particular blend that is designed for your application just mixing it up an dumping it in is not going to guarantee you any big results.It might run better, it might run worse and it might actually blow your bike up <if you happen to be buying a heavily oxegenated fuel>. What it does guarantee is that it will be consistent and fresh ,a sealed 5gallon pail of VP C12 is a sealed 5gallon pail of VP C12. No winter blends, no sitting in the tank for a month before the next shipment comes in, no lower emission blends in certain areas, no uncertainty of water or other contamination etc etc.. .With that consistency it will make it a lot easier to safely tune to a strong clean running engine.

2001yz250, I am sure that if you give Rich the manufacturers name of the fuel available in your area ,if he is familiar with it , he would be more than willing to give you a recomendation on a particular blend that should work good for you. And probably give you a slight idea on which way to go for jetting compared to pump gas in your area.

 

[David Trustrum]

Much as I lament the immanent passing of the 2 stroke as the perfect performance motorcycle engine. . . perhaps the real reason behind US legislation is that someone up there is getting real sick of dumb arguments about oil ratios.

Next up for ‘environmental reasons ' fuel injection will be compulsory & there will go a bunch of jetting questions.

Only to be replaced by map programming debates.

 

[2001yz250]

Since the pump gas is MUCHO cheaper, I'm stickin' with it and my normal 44:1. I'll probably try Rich's suggestion of 32:1 to see if there's any difference, though. I was just shocked to read that 18:1 is going to give me any more power.

 

[Jaybird]

Why shocked?
The more power relates to a better seal that the increased amount of oil provides. Better seal, more compression, which equates to more HP.

Let me also add that this increase of HP is not noticible by me during a ride test. I very much doubt that Rockeys "very noticible" has anything to do with the better seal. I t may have been the atmospheric conditions at the time that Rockey made that evaluation more than anything. (just my humble opinion)
I see a better seal from a static test of compression. 50:1 vs 16:1 I see about a 2-3 psi increase of compression on the dial.
Many,many, many more factors are to be considered.

 

[Rockey5000]

Jaybird, I agree. When I started trying race fuel, it was premixed at 18:1 with MX2T. My normal gas and oil was Sonoco 94 and Golden Spectro 32:1. When my bike started pinging after the gas was 2 weeks old, I decided to try race fuel to make my gas last longer. I did not expect a performance increase at the time, but when I drained my tank and filled it up with race fuel, the bike had noticibly more power. It may have been because it was jetted to run race fuel when I bought it, it may have been atmospheric conditions.

 

[jmics19067]

. perhaps the real reason behind US legislation is that someone up there is getting real sick of dumb arguments about oil ratios.

well the EPA and DEP implemented these stringent codes to cut down on noise pollution :confused: :confused:

I am not sure if having a lot of oil in your mix can and will produce more power but I will not discount it. Extra oil is like having extra octane in my book more than you need is a waste . But I can definately see a particular scenerio that the extra safety margin is welcomed. picture this;
Sunday morning hot and muggy practice bike is running a bit sluggish, lean out the jetting to crisp things up a bit . Bike is running nice and crisp , up at the gate waiting for your moto the temp. drops the skys open up and downpour right before your moto. The track is now a quagmire of well groomed slop the speeds of the track are slower so your radiators get less air, your radiators are going to clogged up with mud, and the load on your engine is going to be a lot more. That extra safety margin of the higher octane and extra oil will just make you smile while the guy who had the "perfect" octane/ratio could very well be pushing his bike back to the pits halfway thru the moto.

 

[Stew312]

Now I have a question... I was running 50:1 in my bike, and switched to 20:1 because a) its supposed to be running that way, b) It fouls plugs faster than anything I've ever seen... Now with the 20:1 it still fouls plugs.. Not only does it foul plugs, but it kills them completely, they don't spark anymore even after being dried, burnt out, cleaned, etc.. Should my jetting be leaner or richer than stock for a 20:1 in a 1988 RM 250?

 

[Stew312]

My current jetting is 370 for the main (stock) and a 15 for the pilot (stock is 20).

 

[JTT]

As Rich mentioned in an earlier post on this thread, it can vary, but it does sound like you are too rich and probably were before as well. My suggestion is that you simply take the time to try different combinations...teach a man to fish and all that :)

 

[Stew312]

BUT: As I forgot to add earlier, you have to put the bike on its left side in order to start it.. This floods the engine.. You can kick it until you are blue in the face but it won't start until you lean it on its left side when its cold..

 

[Rockey5000]

Would richening the pilot cure this?

 

[Rockey5000]

Originally posted by Rich Rohrich

One last thing, Cam 2 110 octane isn't a particularly good choice of fuel for your 125. The end point distillation temps are to high for normal MX use. The bike will likely make more power at high rpm by switching to one of Sunoco's Unleaded race fuels like GT100.

Thanks for the reccomendation, this may sound like a dumb question but would I find this fuel at a Sonoco gas station?

 

[jmics19067]

check your reeds. worn damaged reeds can make a bike hard to start and then also make the bike seem like it is running too rich. You know that your intake system and carb is in good shape and in the ball park for idle circuit jetting if it starts easy when cold with the choke on and starts easy when warm with the choke off.

 

[Stew312]

Maybe richen the pilot and lean the main?

 

[Stew312]

Reeds are perfect, I just had the bike torn down, replaced parts of the exhaust valve system, piston/ring, gaskets, cleaned carb, checked reeds, etc..

 

[MikeT]

Originally posted by JTT
it does sound like you are too rich and probably were before as well.

Probably so.

 

[Stew312]

Tonight I am going to check the compression, and replace the main jet (370) with a 340, and replace the pilot jet (15) with a 22.5.. We'll see how that runs..

 

[Rockey5000]

http://dirtrider.net/forums3/showthread.php?s=&threadid=12926&highlight=Mobil
Look at this link, this is where I got some good info.

 

[DEA]

Heres a kicker :think:
I remember the Bell-Ray oil claims(that's what the bottle said) of 100:1 with little or no jetting changes :ugg: Back in the 70's. when 20:1 was the standard O.E.M. mix