How does main jet size effect overall lubrication of a 2 stroke engine (700cc snowmobile) when pre-mixing gas and oil vs. just using the injection system. Regardless of jetting the oil pump is opened by throttle position when using the factory injection system. If I gut that system and go pre-mix then the oil must pass through the main jet with the fuel and the amount of available oil would be determined by the main jet size. Am I correct or full of BS. Need the 2 stroke gurus. Thanks
Snowmobile premix vs. injection.
- Thread starter snoboy
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you are corect.
on the other hand, if you premix you are guarinteed to not have an oil pump failure and wreck the engine. far too many 2cycles have been lost from oil injection failure, including one of mine.
so its a pick and chose system of up's and down's.
on the other hand, if you premix you are guarinteed to not have an oil pump failure and wreck the engine. far too many 2cycles have been lost from oil injection failure, including one of mine.
so its a pick and chose system of up's and down's.
i'd like to know if i need to change jets if i rip out the injection system on my 1990 polaris indy 500. i use the amsoil intercepter oil.
Depends on the type of injection system your have?
Some put the oil in the fuel before the fuel hits the carbs, no jetting would be needed as it's already running on oil/fuel mix. Others put the oil right in the case, here the need to rejet isn't as much as you'd think unless you jetted real close to the edge now. A stock 500 indy isn't anywhere near the edge so would probably be fine. Say your indy has a 300 mikuni main jet?, 300 x 98% = 294, this isn't even one jet size ! for a 50:1 (2%) fuel mix or 2% reduction in fuel at the main jet. Some injectors are set up to feed a hard to reach bearing, might wanna check if yours is like this before pulling it.
[ January 27, 2005, 02:37 AM: Message edited by: wileyE ]
Some put the oil in the fuel before the fuel hits the carbs, no jetting would be needed as it's already running on oil/fuel mix. Others put the oil right in the case, here the need to rejet isn't as much as you'd think unless you jetted real close to the edge now. A stock 500 indy isn't anywhere near the edge so would probably be fine. Say your indy has a 300 mikuni main jet?, 300 x 98% = 294, this isn't even one jet size ! for a 50:1 (2%) fuel mix or 2% reduction in fuel at the main jet. Some injectors are set up to feed a hard to reach bearing, might wanna check if yours is like this before pulling it.
[ January 27, 2005, 02:37 AM: Message edited by: wileyE ]
I think your right Wiley. I have an oil line that goes into a port right over the left side crank (PTO) bearing. Like you said it looks like premix would'nt get much lubrication to it. I think I'll leave well enough alone.
Is it a polaris per chance? If so dont go premix. The pump directs oil directly to the crank bearings and works reel well. If you decide to remove the injection system you will also have to tear the engine apart so you can drill a oil feed hole into the top crankcase half. I would just turn the pump up a little and keep it stock.
Just in case you are trying to prevent engine failure due to oil pump failure, you could also add a little synthetic oil to the gas for added peace of mind. I do this with my wifes scooter, as the oil injection does not provide the level of oil needed for the big bore kit I installed.
Chris
Chris
I've always had good luck with oil injection systems for over 30 years. If it is the type that has an oil line to the main bearings than you will find enhanced bearing life over premix in my experience.
The main killer of an oil injection system motor is lack of maintenance on the oil flow cable. And using to thick of oil for the pump gears to deal with.
If you are really worried about oil failure use a JASO FC type oil at 80:1 premix along with the oil injection system. This will save the motor as long as you see that your oil injection system is using or not using oil every ride. This is what many Yamaha dealers do on new bikes and ATVs for the 1st tank of gas to make sure the oil injection system is working.
The main killer of an oil injection system motor is lack of maintenance on the oil flow cable. And using to thick of oil for the pump gears to deal with.
If you are really worried about oil failure use a JASO FC type oil at 80:1 premix along with the oil injection system. This will save the motor as long as you see that your oil injection system is using or not using oil every ride. This is what many Yamaha dealers do on new bikes and ATVs for the 1st tank of gas to make sure the oil injection system is working.
Its a Polaris 700 thats ported, piped, heads and a high flow intake apx. 145-150hp. I think I'll keep the injection I seems to have worked well for 5 years now.
You have been given good advice about the small amount of synthetic oil to add into the fuel as a cushion if you feel it necessary for your peace of mind. I have always used Yamahas and have had great success with their Autolube injection system. No worries.
John.
John.
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