2-stroke mix ratio and kinds of oil

MotorEd · Post by **MotorEd** » Sat Nov 19, 2005 1:19 am

Great rad guards for side impact protection...however they dont protect the rads from a branch coming through the front of the rad. Of course you have to go off the trail and hit a tree to do such a thing

So I will stick with the ones from Flatland Racing.

WR_Dave · Post by **WR_Dave** » Sat Nov 19, 2005 6:43 am

I used the Devol rad guards and then I trimmed the bottom inside of both sets of fins and I used some very strong Zip ties to secure the four corners to the rad guard. This helps to keep mud from hitting the rad directly and plugging up the fins in the rad. They also help dirct the airflow better to the front of the rad. I experimanted with using foam to cap off the top and the bottom but I didn't seem to need it on my bike. I also use water wetter coolant additive to help cool the engine. I know I have a thumper now but I used Opti 2 for 15 years on my 2 Strokes and never had any trouble with the recommended mixture. WR Dave.

darren · Post by **darren** » Sat Nov 19, 2005 6:15 pm

I guess there's such a thing as back-mounting rad guards...Dave at A&E had them, so I'll check into that too. Today I overheated three or four times again...it's soooooo fun to bushwhack!

Post by **dirtyboy** » Sat Nov 19, 2005 9:27 pm

Those KTM rad guards are way thick. They'll stop any side impact issue for sure.

YouTube · Post by **Dobi** » Sun Nov 20, 2005 7:55 pm

dirtyboy wrote:Those KTM rad guards are way thick. They'll stop any side impact issue for sure.

I have them on my '03 and love them. I have put them to the test though and they will allow minor bending of the radiator tabs that hold the shroud on. A quick fix with the crescent wrench and you can hardly tell what happened

Post by **Rackman** » Sun Nov 20, 2005 8:40 pm

Rambling of a newbie :-)

This Oil topic interest me, as for what I have used, well I think that that would be like discussing tires or bike brands.

But here is some food for thought that every one may want to comment on.

When everyone talks about more oil IE 20:1 they say richer and 80:1 leaner?
Does the oil burn or lubricate? If it lubricates then 20:1 is in fact leaner than 80:1 because you are adding less fuel to air based on not changing your jetting. Air to fuel is my understanding of lean or rich which is taken care of by jetting. I've seen people dyno and make more horse power when the increase the oil ratio? Thus leaning it out?

I know that two much oil can foul plugs during idling and I have heard that too much oil does not dissipate the heat as well.

What I learned from karting was: (Not quite the same based on extreme RPM's)
Use good oil - Motul, Shell M, I am sure there are a lot of great others.
Lubrication is always good - 20:1 for high RPMS - 40:1
I am a fan of synthetic but I am old school and I mix as I use, especially in the cold.

Just my ramblings,
Jamie

Novo · Post by **Novo** » Mon Nov 21, 2005 1:52 pm

From my old days of building and racing 2 strokes engines, including Karts. (135cc International)

Maintaining a strong reliable motor requires the right Oil mix with a hi quality oil designed specifically for hi performance 2 stroke applications.

The fuel/oil ratio affects many characteristics of engine performance. This includes the oil ring seal performance which can significantly effect compression and
thus torque (HP) produced throughout the RPM curve. i.e. To hi a mix ratio and the oil seal is degraded amongst other factors.

Brent · Post by **Brent** » Mon Nov 21, 2005 7:13 pm

I always thought that rich-lean jetting in the carburetor was a completely different thing than rich-lean conditions of your fuel.
The carb mixes air to fuel(fuel that has already been mixed lean or rich with oil), more air makes the mix lean and more fuel which is a larger jet is rich. This is directly effected from the rich or lean fuel to gas mixture in your tank. A 20:1 mix in the tank would cause a slight leaning out in the carb because the thicker fuel now doesn't flow through the tiny jets as well. Where as a lean mix in the tank 80:1 would cause the carb to richen because of the thinner fuel.
The mix of your fuel does not effect the jetting settings on your carb that much, unless of coarse you ride red with there ever so finnicky mikuni carbs.
If you talk to enough people you will find a hater for every type of oil?!

Post by **Rackman** » Mon Nov 21, 2005 10:19 pm

Hey Nova and Red dog,

Both interesting replies that I had not thought of:

Nova, Are you saying that too much oil reduces the seal of the rings? (Was the 135 direct drive and aprox 18000 rpm. just curious)

Red dog, the viscosity of the fuel and the jet size is new to me, if that is true then I am sure that the type of oil used would also affect this?

And to think I was considering going back to a two stroke! I think I might just stay with my thumper. :-)

Jamie

Post by **cladoo** » Tue Nov 22, 2005 6:40 am

The higher the ratio the richer your jetting will be. Because there is more fuel than oil with higher ratios. Viscosity in high quality two stroke oils are about the same and would go through the jetting the same. In my experiences, synthetic oils are the best for modern day engines. I never run higher than 50:1 in my engines, I hate rebuilding engines prematurely. There are some excellent threads on http://www.ktmtalk.com/ you just have to search for them. There are some very knowledgable people on that website.
Claude

Novo · Post by **Novo** » Thu Nov 24, 2005 12:26 am

Rackman wrote:Hey Nova and Red dog,

Both interesting replies that I had not thought of:

Nova, Are you saying that too much oil reduces the seal of the rings? (Was the 135 direct drive and aprox 18000 rpm. just curious)

Red dog, the viscosity of the fuel and the jet size is new to me, if that is true then I am sure that the type of oil used would also affect this?

And to think I was considering going back to a two stroke! I think I might just stay with my thumper. :-)

Jamie

Rackman, its the other way around, to little oil reduces the ability of the oil ring to maintain a proper seal.
One runs the risk of a less reliable motor that produces less power due to compression loss, increased friction and premature wear.

It was a Zip Kart, direct drive - Parilla with lots of mods - the 250cc shifters could not keep up!!
Closest comparision to an F1 ride and the best racing bang for the buck in my experience.

Having said that, I sure am enjoying getting back into riding cross country

Post by **Rackman** » Fri Nov 25, 2005 1:05 pm

Hey Nova,

Actually what you replied was exactly what I was thinking.

The karting seen has grown in Calgary with the new track at the south end of race city. The Rotax max class looks like it is worth checking our (Water cooled 125cc with clutch and electric start) Not as quick as a shifter but more finesse to drive and a lot of fun.

I ran shifters for 5 years.
125cc yam lots of mods CRG chassis
125cc Pavasi rotary PCR Chassis.

Actually I think all of the adrenalin junkies here should check out that seen!!!

Jamie

Post by **dirtyboy** » Thu Jan 19, 2006 4:17 pm

[quote=Shibby!]I need to find a better premix oil. I used one liter of Yamalub last time and that stuff smokes and burns thick. I rely on a richer mix just for ease of mind (40:1), but it still didn't burn well and its recomended 32.. yea right.

But this should be in the other topic, so I hope not to stear it off into the premix talk.[/quote]

Shibby,

I used to use Yamalube 2 at 32:1 and 40:1 and later Yamalube R(2) with no spooge or smoke. I think that your jetting is the culprit.

Pick an oil ratio that you are comfortable with and then jet accordling. 40:1 to 60:1 is reasonable. I've heard stories of some guys with MX 250 bikes having to go 10 MJ sizes leaner and needles and pilots.

Shibby! · Post by **Shibby!** » Thu Jan 19, 2006 8:11 pm

dirtyboy wrote:
Shibby! wrote:I need to find a better premix oil. I used one liter of Yamalub last time and that stuff smokes and burns thick. I rely on a richer mix just for ease of mind (40:1), but it still didn't burn well and its recomended 32.. yea right.

But this should be in the other topic, so I hope not to stear it off into the premix talk.

Shibby,

I used to use Yamalube 2 at 32:1 and 40:1 and later Yamalube R(2) with no spooge or smoke. I think that your jetting is the culprit.

Pick an oil ratio that you are comfortable with and then jet accordling. 40:1 to 60:1 is reasonable. I've heard stories of some guys with MX 250 bikes having to go 10 MJ sizes leaner and needles and pilots.

This could very well have been.

I brought this bike from Sasktchewan (with a lot less elevation), and rode it here without messing around with it. It rode fine, but I knew it wasn't perfect, or it could have been improved.

I am selling the bike this spring and will definitly inform the buyer to toy tune the carb to get the most out of it. I knew it had problems as the plug would build carbon/oil quick if you let it idle for too long or weren't riding it hard enough.

The RM has already been jetted for this elevation so it should be better. I'll still keep an eye on it. The PO said he used 40:1, so I'll stick with the same.

I don't like messing around with carbs and transmissions. Two things I like to stay away from, but on a more simple carb I guess its the best place to learn!

Just curious whats the general consenses on a good quality premix oil for a decent cost? Its like guys putting Motul "motorcycle" mix in their streetbikes (or any road bike) and paying a lot more then me when I am putting Mobil 1 full synth. Sometimes that extra money does nothing at all.

If this has already been covered, ignore it. I will read the post from the begining as I have already skimmed through some of it!

cedric · Post by **cedric** » Thu Jan 19, 2006 8:36 pm

Shibby! wrote:Its like guys putting Motul "motorcycle" mix in their streetbikes (or any road bike) and paying a lot more then me when I am putting Mobil 1 full synth. Sometimes that extra money does nothing at all.

Using a proper motorcycle oil is probably better than the best car oil, as it is designed to work with a gearbox and clutch, while the car oil is not. The exception would the Honda CRFs, which have separate oil for the crank and transmission.