Snowmobile question?

[wbaj]

So I have a 2000 Skidoo MXZ in a 600 and have run it for quite a few years now with no problems what so ever. I was out sledding with a few new friends and discovered some of them run thier 2 stroke machines with pre-mixed gas even though they all have oil injectors! Just fouls the plugs a bit early they say, and it protects your engine if something should fail with the injector?
Does this make sense? Is this what most guys do? What's the best way to run your fuel?
I hate to change anything because this machine runs great now. In fact I think I can outrun most of them with similar engines?

Signed
Confused!

[dale7637]

Guys do the pre mix thing to cover themselves in the event of an injection pump failing.
I personally don't bother. Between 3 sleds I have put over 15k kms on and never had a pump fail.

[tullfan]

Think of it this way. We're going to simplify it ok. I'm also going to just use numbers for illustration purposes. That's all.
If your running 40:1 premix in your sled. You've got 40 parts gas to one part oil. Good! Now if you don't empty your tank or close to it and add more "premixed" 40:1 just to top up from say a quarter tank. Do you still have 40:1. No. Your actually richening your oil concentration and leaning out your fuel. You will actually get worse performance by doing the old if this much is good than more must be better.
Now injected units are designed to run a little leaner on the mixture at idle just because, well you just don't have the same demand on the engine. As your rpm's increase so does the amount of oil that is injected. The injector also in some cases lubricates main bearings that don't get oil through the combustion process.
So to answer your question. Injectors do fail, but rarely. Your more likely to cold seize or run to lean and hole a piston than have an injector go. They're basically a valve, the more you twist the more they dump. That's it.
You will have better performance and longer engine life by not pre mixing with your injector. Your friends are fouling plugs but also losing performance and in the end really that carbon building on the plug is also accumulating on the piston and the head between combustion chamber and head. This poses a multitude of issues I won't go into now, but heat and compression are the affected areas.

Hope that sort of helps.
Tullfan

[Sooner]

Guys do the pre mix thing to cover themselves in the event of an injection pump failing.
I personally don't bother. Between 3 sleds I have put over 15k kms on and never had a pump fail.


Same here, all sleds when sold had 10,000+ kms, one had a rebuild only because the lower seals went and we had to go into the engine anyways at 7000 kms. 96 Summit 583, 04 summit 800 and an old 79 340 yammy that's still going.

[Tfng]

I've seen a few engine failures of friends and family over the years. I've never had an injection system fail personally. It can happen due to worn cables or drives.

If you are going through the trouble of mixing you should just remove the injection system. It doesn't make sense to use twice the amount of oil required.

As a poster above stated it leans the fuel mixture out by exceeding reccomended ratios. I'm not sure I can agree with adding 40:1 mix to 40:1 mix in tank can change ratio but I get what he's saying. That's why mixed fuel should be mixed in a can not the tank.

It seems the systems on newer machines are very reliable. I do not premix my fuel. I like the convenience of just putting gas in it and topping up oil reservoir.

[pacs5]

Back east they used to have something kind of like an Idiarod race but for snowmibiles (snowmobile cross country endurance race each winter. The racers in teams of three would make many modifications to make their sleds more robust for the hard remote running. One thing that I noticed that seemed very smart was that they had actually identified the weak point in the oil injection system and it was actually the steel cable that is part of the throttle cable assy. that opens the oil pump as the throttle is constantly pushed and released. If and when that cable breaks you don't know but the sled will still run, only thing is that you are now without oil injecting.

What they did was to simply mount and wire in small red lamp on the dash and a small switch on a bracket activated by the arm on the injection pump when it is at idle so that the switch would be closed the lamp is on. When the throttle is pushed causing the oil injection pump to activate and the light goes out. But if the oil pump cable breaks when throttle is pushed the pump will go to idle position and the warning light will activate to warn that the cable and thus injection has failed before engine damage can occur.

They did lots of cool mods to their sleds to make them very reliable to take the beating they were dishing out. These guys and their sleds were very interesting to talk to and their sled moifications were a school of what a sleds weak points were and how to avoid failures.

No sure if they still run these endurance races but they were something to see. If I recall they were not allowed to run on any groomed trails, had to go like 600 miles a day for a week baiscally thru woods etc. to get from point a to b. think the prize money was like 100k for the winner.

[JohninAB]

First off, lean or rich technically has nothing to do with oil/fuel mixtures in a 2 stroke engine or any engine for that matter. Lean/rich technically refers to the air/fuel ratio going into the combustion chamber. Lean means too much air for the fuel mixture and causes the hole being burnt in the piston. Rich means too much gas for the amount of air. Leads to fouling of plugs plus loss of horsepower as need the proper fuel/air mixture to get maximum HP.

Secondly, if premixing your oil and fuel in a separate container then adding it to your fuel tank, it will not change the fuel/oil ratio of the fuel within the tank already if both are mixed at the same ratio.

One reason for running premixed fuel was to guard against oil pump failure and the subsequent damage to the engine. Had a snowmobile where the oil pump cable broke and subsequently cratered the engine from the crank up.

Another is weight savings. Back in the day, guys would remove the injection system to save weight on their sled. Believe removing the oil tank and pump saved around 10+lbs or so.

And removing a mechanical oil pump running off your crankshaft did save horsepower as well, as one less item the crankshaft had to turn. Doubt it saved much but was there.

Running a premixed fuel/oil mixture also removed the hassle of having to check your oil pump settings to ensure it was still set to factory specs. Do not have to do often but should but still it is a consideration.

Finally some removed the mechanical oil pump as it meant a lighter throttle pull as one less thing the throttle had to pull on (oil cable) which reduced fatigue in their throttle thumb for some. See this advertised in the new sleds today.

Oil injection systems technically should save you from fouling plugs as often as premixed systems (not an issue most times) plus should save you on 2 stroke oil costs as an injection system should reduce oil burnt as it meters it out based on throttle position. Reduced oil being injected into the fuelling system should mean less smoke and stuff spit out of the exhaust which is better for the environment especially when run in a fuel injection system on a 2 stroke engine. Optimax and Etec engines are examples of this.

My two cents on the theory of running premixed versus oil injection.

[garf]

All I can say, is to quote a 40 yr Polaris tech buddy of mine. "When I see scuff marks on the cylinders, the only cause is from low oil mixtures during idle."
For the cost of a few oz of oil added to the tank, just doo it!

[gmcmax05]

All I can say, is to quote a 40 yr Polaris tech buddy of mine. "When I see scuff marks on the cylinders, the only cause is from low oil mixtures during idle."
For the cost of a few oz of oil added to the tank, just doo it!

Than your "40 year tech" is an idiot. What do you think happens to a piston when you get into the throttle hard with a cold engine? The piston grows faster than the cylinder & you get scuffing, known as "cold seize". A lean condition will also scuff the exhaust side of the pistons as well, just before it puts a hole in the top of it.

[tullfan]

[QUOTE=JohninAB;2743163]First off, lean or rich technically has nothing to do with oil/fuel mixtures in a 2 stroke engine or any engine for that matter. Lean/rich technically refers to the air/fuel ratio going into the combustion chamber. Lean means too much air for the fuel mixture and causes the hole being burnt in the piston. Rich means too much gas for the amount of air. Leads to fouling of plugs plus loss of horsepower as need the proper fuel/air mixture to get maximum HP.

You are correct John in that the perfect fuel/air ratio is 14:1. If you add more air you run lean, more fuel you run rich. However that being said. If you richen up the oil mixture you are reducing the engines capacity for a complete efficient burn. Hence the loss of horse power. This is still a lean burning situation as far as the engines concerned. Not in an air fuel sense,it's still 14:1 (we'll assume),12:1 is better. But for sake of argument. Just to clarify. I was kinda simplifying it originally.
And technically if you have 40:1 in your tank and add more 40:1 to one to your tank it shouldn't change. However do that 3 times and the dyno says different. On a is KX250 anyway. The five gas analizer on the dyno also confirms the high hydrocarbons (raw fuel and oil) unburnt, and low C0 ( lack of complete burn, or the lean situation we were chatting about). Anyway, just an fyi. Just my two pennies.

Tullfan

[Huntnut]

The ones that I know that do it do not run at 40 to 1 premix in their tank along with injection. It's 100 to 1 at best. The reason they do it is the pumps are set at the minimum from factory to pass US emissions. Most Polaris guys either add oil to their tank or turn up their oil pumps to help combat Polaris's piston failures.

[Map Maker]

When the oil injector fails, it fails wide open.

[marxman]

Think of it this way. We're going to simplify it ok. I'm also going to just use numbers for illustration purposes. That's all.
If your running 40:1 premix in your sled. You've got 40 parts gas to one part oil. Good! Now if you don't empty your tank or close to it and add more "premixed" 40:1 just to top up from say a quarter tank. Do you still have 40:1. No.

Hope that sort of helps.
Tullfan

Yes your mix stays 40 to 1

[vinny]

Think of it this way. We're going to simplify it ok. I'm also going to just use numbers for illustration purposes. That's all.
If your running 40:1 premix in your sled. You've got 40 parts gas to one part oil. Good! Now if you don't empty your tank or close to it and add more "premixed" 40:1 just to top up from say a quarter tank. Do you still have 40:1. No. Your actually richening your oil concentration and leaning out your fuel.

Sorry but no. The mixture remains the same. You're adding pre-mix to pre-mix. Same ratio.

[jungleboy]

Think of it this way. We're going to simplify it ok. I'm also going to just use numbers for illustration purposes. That's all.
If your running 40:1 premix in your sled. You've got 40 parts gas to one part oil. Good! Now if you don't empty your tank or close to it and add more "premixed" 40:1 just to top up from say a quarter tank. Do you still have 40:1. No. Your actually richening your oil concentration and leaning out your fuel. You will actually get worse performance by doing the old if this much is good than more must be better.
Now injected units are designed to run a little leaner on the mixture at idle just because, well you just don't have the same demand on the engine. As your rpm's increase so does the amount of oil that is injected. The injector also in some cases lubricates main bearings that don't get oil through the combustion process.
So to answer your question. Injectors do fail, but rarely. Your more likely to cold seize or run to lean and hole a piston than have an injector go. They're basically a valve, the more you twist the more they dump. That's it.
You will have better performance and longer engine life by not pre mixing with your injector. Your friends are fouling plugs but also losing performance and in the end really that carbon building on the plug is also accumulating on the piston and the head between combustion chamber and head. This poses a multitude of issues I won't go into now, but heat and compression are the affected areas.

Hope that sort of helps.
Tullfan

That makes absolutely no sense. If you add 40:1 mix to 40:1 mix you still have 40:1 mix. Think about what you are saying. The only thing that would change the ratio is if you add un mixed fuel to the tank or a higher ratio mix.

[Headdamage]

I am currently running 100:1 premix in my 2008 Skandic with the 550F engine. I bought it in Dec and the premix is a precaution while I work the the bugs out of the sled. At this point the injection system seems to be working fine, if I don't have any plug fouling issues I might keep running premix as insurance.

[tullfan]

I know it doesn't't make sense. If you mix the two, 40:1 in tank40:1 in gas can it should not change. Everyone is stuck on the ratio. I said technically is should be the same. I'll clarify a bit as to why I said it changes. We ran 6 runs on a dyno. Kx 250. 3 runs from a mixed bottle (remote). Bike run, bottle emptied, fuel line emptied, carb emptied.then repeated fresh gasmixture Then we did the same three runs just adding mix from the same batch. The bike ran less hp with the mix just added to the bottle. It was a marginal change but still a change. I'm not going to get into the why's. It doesn't matter at this point. Fresh fuel mix for this guy each time. I'm also not going to get into the jetting issues when doubling up on the injector and premix. Anywho. Just remember this is just one fools $.02. Opinions vary,I get that.

Tullfan

[Battle Rat]

I know it doesn't't make sense. If you mix the two, 40:1 in tank40:1 in gas can it should not change. Everyone is stuck on the ratio. I said technically is should be the same. I'll clarify a bit as to why I said it changes. We ran 6 runs on a dyno. Kx 250. 3 runs from a mixed bottle (remote). Bike run, bottle emptied, fuel line emptied, carb emptied.then repeated fresh gasmixture Then we did the same three runs just adding mix from the same batch. The bike ran less hp with the mix just added to the bottle. It was a marginal change but still a change. I'm not going to get into the why's. It doesn't matter at this point. Fresh fuel mix for this guy each time. I'm also not going to get into the jetting issues when doubling up on the injector and premix. Anywho. Just remember this is just one fools $.02. Opinions vary,I get that.

Tullfan

By that logic you are saying that an increase in volume of the same ratio changes the ratio.
Therefore as the premixed fuel is used up in the tank the ratio must also change?

[vinny]

I know it doesn't't make sense. If you mix the two, 40:1 in tank40:1 in gas can it should not change. Everyone is stuck on the ratio. I said technically is should be the same. I'll clarify a bit as to why I said it changes. We ran 6 runs on a dyno. Kx 250. 3 runs from a mixed bottle (remote). Bike run, bottle emptied, fuel line emptied, carb emptied.then repeated fresh gasmixture Then we did the same three runs just adding mix from the same batch. The bike ran less hp with the mix just added to the bottle. It was a marginal change but still a change. I'm not going to get into the why's. It doesn't matter at this point. Fresh fuel mix for this guy each time. I'm also not going to get into the jetting issues when doubling up on the injector and premix. Anywho. Just remember this is just one fools $.02. Opinions vary,I get that.

Tullfan

So if I use a 50/50 antifreeze mix in my vehicle and I want to add more 50/50, I would have to drain the entire coolant system first, so the ratio doesn't get out of whack? And I have to burn a entire tank of premix fuel before adding more? What do you do with all those part used tanks of fuel. Cmon man, think this through. 😜 Not trying to bust your balls, but this is easy math. Dyno results don't prove the fuel is the issue.

[tullfan]

So if I use a 50/50 antifreeze mix in my vehicle and I want to add more 50/50, I would have to drain the entire coolant system first, so the ratio doesn't get out of whack? And I have to burn a entire tank of premix fuel before adding more? What do you do with all those part used tanks of fuel. Cmon man, think this through. 😜 Not trying to bust your balls, but this is easy math. Dyno results don't prove the fuel is the issue.

Actually, not drain the entire tank but you should measure the the glycol content of your antifreeze to determine what the content is. You could be changing its corrosion resistance,and freeze protection. That is why we measure before we add. But I get what your saying.
No the dyno results don't prove conclusively it's the fuel. The negative horsepower run rules out mechanical issues. The five gas analizer does show changes in the exhaust content though. Anyway, I get your point. It's taken and I will humbly agree to disagree.
Sorry to have the thread derailed.
Tullfan

[HyperMOA]

I can kinda see what Tullfan is thinking. I think I do anyways. Every jerry can of gas you mix is never exactly 40:1, it may be close but it never is perfect. Unless you had a lab and weighed out exactly 40 liters of gas and exactly 1 liter of oil you would never ever have 2 gas cans with the exact ratio. Plus the longer a can sits the gas could evaporate but the oil would not. Also depending on how long it has sat the fuel itself may lose its octane value. Fuel bought on different days or from different stations would be refined differently. There are many variables that would explain a change in ratios. It is never going to go from 40:1 to say 35:1. The change will be 40.03:1 to 39.99:1. The dyno would also be effected by consecutive runs with the bike. Different operating temps of the bike will effect the gas analyzer too as the engine will burn at different efficiencies dependent on engine temp, air intake temp, humidity, fuel temp . . . .

[polar_rmk]

I had bunch of different sleds and never did any premixing til I got a relatively new polaris on pro platform, these machines are kinda famous for engine troubles, factory setting on them 1:100 premix so a lot of guys burnt their engine, even though it is possible to adjust oil pump to get more oil into the engine most ppl prefer do premixing just to be sure
if you don't run Polaris pro you don't need any premixing

[jungleboy]

I had bunch of different sleds and never did any premixing til I got a relatively new polaris on pro platform, these machines are kinda famous for engine troubles, factory setting on them 1:100 premix so a lot of guys burnt their engine, even though it is possible to adjust oil pump to get more oil into the engine most ppl prefer do premixing just to be sure
if you don't run Polaris pro you don't need any premixing

You mean to say that Polaris is the only Manufacturer to have engine failure due to lack of lubrication ? I say baloney! Ski doo had their share as did AC. My Buddy had his 800 Doo melt down on him last year and his dads 800 Cat did as well both low mileage machines(less than 1000k) Myself I am running a 2010 RMK without issue for 1700 k and no premix, but it is a 600. Polaris had issues with the 800s but so has AC and BRP. All the brands whether sleds or ATV's have their quirks and issues

[polar_rmk]

Sorry forgot to mention 800cc motit's, 600Cc and 700Cc motors from Polaris are reliable.
As far as know the only Polaris owners do premixing I do personally never premix oil into my doo. Neither, I did premixing into Polaris machines before 2011.
polaris that sold in 2005 had 15000km never had any issue with motor, but compression went down.
some ppl suggest not to use modern synthetic oil, and back to previous mineral oil

[wbaj]

Well thanks everyone for your responses and opinions.
I believe I will continue to NOT pre-mix my fuel for this machine, so far it has taken me on many a mile with no issues. I suppose if my oil injector cable breaks I will regret the decision but I believe it's a small risk to take. I just don't believe the engine performance can be the same with double the recommended oil to fuel ratio!