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Discussion Starter #21
Ok makes sense this is my 1st 2 stroke and all is new to me appreciate the info and help but i checked main jet again it a 250
 

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Lean mixture is less oil n the gas and rich is more oil n the gas ?? Is that right? And i dont see any other way to put oil n other then premix
 

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Its not a good idea to run any engine @ WOT for very long at a time if you care anything about it... and especially not a 2 smoke. Your automobile engine won't stand it for very long so why would you think an atv engine would?
 

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Discussion Starter #24
Well didn't recall saying it was long period of time because i didn't say it because it was not long period of time half mile maybe mile at top end
 

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Lean mixture is less oil n the gas and rich is more oil n the gas ?? Is that right? And i dont see any other way to put oil n other then premix
A lean mixture is too much air, not enough fuel to go with it. The air/fuel mixture is done inside the carb with the jetting. The oil/fuel ratio is done either at the injection pump or by adding oil to the fuel. In your case it appears that with the K&N filter which allows more air into the engine, the jetting needs to be changed so the carb lets more fuel into the engine. Main Jet and Pilot Jet sizes will probably need to be bigger along with the main jet needle style or size changed. I am not an expert when it comes to tuning carbs. I tend to stay with the stock stuff to avoid that. Latebird is an expert so he can get you started in the right direction.
 

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LOL... a mile @ WOT on a 2 stroke is a LOOONG time. Even more so if running somewhat lean anyway. After all, you DID melt a hole in the top of the piston?
A 2 stroke will run very strong when lean but they also run MUCH hotter so you have to be careful with jetting. I used to do a lot of radical hill climbing on a big bore 2 stroke dirt bike in my younger days. You always turned the fuel off when taking a break to prevent the possibility of fuel leaking while sitting around. If you forgot to turn the fuel back on and started up a long climb the bike would run like gangbusters as it leaned out just before the fuel in the carb bowl ran out and it quit right in the middle of the hill lol! Very strong but also very hot. The engine can't stand that for long.
 

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Lean mixture is less oil n the gas and rich is more oil n the gas ?? Is that right? And i dont see any other way to put oil n other then premix
No - lean is not enough fuel to air = high temperature burn - the oil is lubrication for the crankshaft, piston and rings - a lean oil mix actually enriches the fuel to air ratio as oil displaces gas and leans the fuel to air ratio. Does that make sense? One thing I learned about two strokes (I grew up with Kawasaki two stroke road bikes): the more oil you can run without fouling the spark plug, the more power the engine will produce and the longer it will last. Being stingy on the oil only promotes unnecessary wear and at high RPM the parts run exceedingly hot! Also, most oils will not mix with alcohol, so alcohol blended fuel in a two stroke mandates the use of special oil.

The Lucas oil you are using is approved for use in injector systems and any oil can be premixed. It is approved for use UP TO 50:1 ratios. 50:1 should only be used on engines with plated cylinders at relatively low (under 5000) RPM engines. The old 400 with a steel cylinder thrives on oil - more is better!

If this is your first two stroke, you really to take it to a knowledgeable mechanic who can check it for the oil injection system that it came with from the factory to see if it is there or has been removed or has been bypassed.

This akin to trying to teach yourself how to fly an airplane. It can be done, but can be costly. You have already encountered the first mistake and it is not catastrophic or too costly, but if you had an instructor you may have avoided the experience.

If the factory installed oil injection system has been completely removed and blocked off; that's one thing. If the system is there and running dry; that's another thing and it's not good. If the oil pump is there, disconnected and the oil tank removed; that another thing and it's not good. If the oil pump is there, connected, the oil tank removed and the system is not capped off; that's bad. If the pump is there, an oil line connected from the outlet to the inlet and filled with oil; that's a different thing and it's OK, but not what's best.

You should get a copy of the service manual and read it - it is not as good as the owners manual, but I don't know where you you could find an owners manual that old. I looked, but did not find one. I can email you a PDF service manual if you want to message me your email address.

On a two stroke 600 feet at WOT is a long time for a single cylinder engine. Do you know why Kawasaki and other manufacturers abandoned multi cylinder two stroke road bikes? Besides the environmentalist cry babies complaining about smoke; they were not fuel economical, they wore the rings out quickly and the seals on the crankshaft between cylinder crankcases would fail causing engine failure and high repair cost (cranks could not be rebuilt by most shops and required replacement that the crank be replaced or sent to a specialized shop for rebuilding - I used to rebuild cranks, but quit as parts became almost impossible to obtain). Also, running the old triple cylinder air cooled two strokes at full throttle for more than a mile almost always resulted in a seized center cylinder and on the liquid cooled Suzuki 750 triple, a hole in the center cylinder piston after about two miles. Of course the bikes were flat tracked and road raced and could be tuned to run a WOT, but they would not idle well, fouled spark plugs and didn't like to be run below 1/2 throttle.

Lastly; the guy you got it off of lied about the carb being jetted - if it has a 250 main jet, that is stock and it needed to be jetted for the K&N filter. Buyer beware!

When someone tells me a carb has been rejetted, my first question is "What size jets does it have in it?" If he can't tell me, then I know he is blowing smoke and make my decision's based on the fact that he is a liar, dishonest and is banking on me being stupid. Being experienced and a skeptic, I always ask for the owners manual and the tool kit. If the seller does not have the owners manual I cut the price by half and if they don't have the tool kit, I cut the price again. I walk away from most offers and get what I pay for on the purchases, but it's why I have driven a 97 Ford F150 that I bought for $3000 seven years ago and it is still my daily driver. 200,000 miles, started on -30 degree F mornings last winter, gets about 27 MPG and only burns a quart of oil between oil changes (every 3000 miles). It does have problems (rust, squeaks, rattles, hit a deer and the exhaust leaks), but it doesn't leak oil, the AC works, windows go up and down and the brakes will stop on a dime and give you 9 cents change.

There's been several posts since I started composing this lecture and some echo what I have put here before I got to hit the reply button.
 

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Latebird,
Appreciate your response on why WOT on a 2 cycle engine is bad. Makes perfect sense.

Also appreciate the detailed insight in the post above. Especially on what to look for when purchasing an ATV.

Stave and Polman,
You are also very helpful contributors as well. So grateful to have you all on this site.

Thank you
 

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Its not all that bad OP. As latebird said earlier, the cylinder probably isn't hurt. Get the carb jetted right, a stock air filter, the oil injector working or properly blocked off and a new piston and rings and you should be good to go. Even the 4 stroke manuals tell you not to run WOT for long periods. These are trail machines and not meant to run WOT on the road for miles at a time. WOT runs on the trail are fine and won't hurt a thing because you can't hold it there for long without letting up.
 

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Discussion Starter #32
LOL... a mile @ WOT on a 2 stroke is a LOOONG time. Even more so if running somewhat lean anyway. After all, you DID melt a hole in the top of the piston?
A 2 stroke will run very strong when lean but they also run MUCH hotter so you have to be careful with jetting. I used to do a lot of radical hill climbing on a big bore 2 stroke dirt bike in my younger days. You always turned the fuel off when taking a break to prevent the possibility of fuel leaking while sitting around. If you forgot to turn the fuel back on and started up a long climb the bike would run like gangbusters as it leaned out just before the fuel in the carb bowl ran out and it quit right in the middle of the hill lol! Very strong but also very hot. The engine can't stand that for long.
Yes it was really quick on take off and would have to turn fuel off or would run like shit for lil bit but the weird thing is that when it happened( burning the hole n piston) it wasn't that hot and i been watching u tube video's have better understanding between u tube and all the help from you guys
Its not all that bad OP. As latebird said earlier, the cylinder probably isn't hurt. Get the carb jetted right, a stock air filter, the oil injector working or properly blocked off and a new piston and rings and you should be good to go. Even the 4 stroke manuals tell you not to run WOT for long periods. These are trail machines and not meant to run WOT on the road for miles at a time. WOT runs on the trail are fine and won't hurt a thing because you can't hold it there for long without letting up.
I have been watching u tube videos all day and got better understanding of jetting rich and lean mixture all that good stuff and i ordered carb rebuild kit and piston and rings and found air box on eBay that stock n same year as mine so wish me luck lol and appericate the help i will let ya knw how things turn out
 

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Good luck - you will probable need a service manual - I can email you one in PDF - just message me your email address with a note of which manual you need (96 400L)
 
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