problem with my 86 atc 250r

[Beastmasterb]

My 86 atc 250r fouls plugs more than usual, i stepped the main down to a 145, and the fuel mixture is at 20:1 as stated on the machine. The machine upgrades include, v-force delta 2 reed valves, paul turner racing pipe and to my knowledge bored .010". What can i do or try to prevent this? i would like to take it to the dunes or trail riding but isnt dependable enough for me to do so!!

[pantera1975]

Welcome to the club. I got he same mods as you pretty much and Running 40-1 with stock jetting and have 1/3-1/4 and idle issues. Went down to a 40 on the slow jet for 80 plus deg weather. But in your case try a good 2 stroke oil and 32-1 or 40-1 with the jetting you have oil today is alot better than 25 yrs ago. I use Klots technaplate R50.

[cattle-dog]

first make sure your air cleaner is clean. i also found that once i modded my 250r i needed to allow more air into the air box.

[harryredtrike]

when did the fouling start?after the mods?i run mine at 24-1 and dont have issues with a paul turner pipe

[Beastmasterb]

actually i do use the R50 2 stroke oil, i have a friend who also told me to try 32-1 or even 40-1 to see if that helps but i don't wanna have to rebuild it cause it burned up.

It does have a k&n air filter that i cleaned when i got it out, it had mouse nest and crap in the box so that is all clean now too.

Well to be honest i bought it this way 2 yrs ago, didn't have a problem the first year, then last year it kept dying, replaced a head gasket once, and then it died before the summer was up. just got it out about 3 weeks ago found out it quit because my reed valves were busted up. replaced those and thought i wouldn't have any problems but i still do.

[gleep]

i have a fmf pipe on mine and im running 32:1 and it runs and idles perfect..

[ceaserthethird]

Try cleaning out the Carb, removing and cleaning it well .

32.1 to 40.1 mix will be what you want to run. ( I run 40.1 Synthetic )

Also check your compression - between 170 -199 PSI anything below 170 will need a rebuild.

[pantera1975]

I got 2 comp gauges one reads 148 and the other reads 170. Mac and Matco brand. I dont know which to beleve. Will low compression make it idle bad and seam like you have the jetting off?

[Beastmasterb]

An update on my situation, I just cleaned the carb thoroughly and checked the reed valves. It looks great. Tried 40:1 fuel mixture and still problems. New plug again but no different. I can't even run it long enough to shade the plug. Next question, could it be an ignition problem? Maybe the stator isn't putting enough out to run it? Hit me with feedback cause the dilemma I'm in ruined my trip to silver lake this weekend.:(

[David komatina]

--------------------------------------------------------

Terms and Definitions

Jetting: The term comes from the two main circuits that control fuel flow in a carburetor. The pilot jet and the main jet.

Main Jet: This is the main fuel circuit in a carburetor. It's a common misconception that this circuit only effects engine performance at wide open throttle. The main jet actually has a trickle down effect on other adjustments and should be adjusted first.

Needle: The needle is attached to the carb slide and is raised and lowered when you push and release the throttle. When you let off your throttle, the needle lowers into the main jet circuit, cutting off fuel flow as it goes down.

Needle Clip: This is the small circular clip that is used to adjust the needle position.

Pilot Jet: This is second jet in your carb. Much smaller than the Main Jet and typically has no effect beyond approximately 1/4 throttle. It's used to adjust your mixture at idle and low throttle.

Air/Pilot Screw: The air screw works in combination with the pilot jet. You can consider it a fine tuner for the pilot circuit. It's most obvious effect is noticed by throttle response.

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level.

Rich: A "rich" condition is what occurs when you have too much fuel in your fuel/air mixture. Symptoms of a rich condition can be a rough running engine (sputtering), a black spark plug, a wet plug or excessive plug fouling.

Lean: A "lean" condition is what occurs when you have insufficient fuel in your mixture creating an over abundance of oxygen. Symptoms can be a rough running engine (bogging), a white or light gray spark plug and sometimes can result in overheating or even severe engine damage.

Sputtering: This isn't exactly a technical term but is commonly used to describe how an engine runs when jetted too rich. For example, using too large of a main jet will cause more fuel to enter the combustion chamber than it can efficiently burn. This will result in a "sputter" at full throttle. It could best be described as a rapid misfire. Note: a rich condition is not the only possible source of this type of problem.

Bogging: Again, not a technical term but commonly used. Bogging can be a result of a lean setting where not enough fuel is entering the combustion chamber for the motor to run properly. In some instances this can cause the machine to "bog" as if it were actually running out of gas. Note: a lean condition is not the only possible source of this type of problem.

WOT: This an acronym that stands for Wide Open Throttle.

Plug Chop: Plug chops are the most accurate and easiest way to check your jetting. A proper plug chop should be done with a clean spark plug. Example; to check your main jet, put in a clean spark plug and run the trike at Wide Open Throttle (WOT) for several seconds, then in one motion, pull in the clutch (if applicable), kill the engine and let off the throttle. Remove the spark plug and check the color (refer to chart in this thread).

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level. If worn it can cause the float bowl to overflow.

---------------------------------------------------------------

Nobody can tell you exactly what jets to use!

This is especially true with these 20 year old trikes. No two are exactly alike. Different mods, various states of mechanical well being and different locations (altitude, humidity etc) all play a part. Something as simple as removing your airbox lid can have an effect on your jetting. This is why it's critical that you understand how jetting works so you can get it dialed in perfectly for YOUR machine and riding conditions.


---------------------------------------------------------------

Proper Jetting Procedure

The first step is to get your Main Jet dialed in. This circuit should be done first because it has a trickle down effect.

The Main Jet effects your performance most noticably at WOT. You do not fix a low throttle problem by changing your main jet. When the main is correct, there should be no sputtering or bogging at WOT.

Other than performance, the way to test your main jet is by doing WOT Plug Chops. The color of the plug will tell you if you need to do any fine tuning. DO NOT assume it is correct just because the engine appears to be running good. Remember, white and light gray is LEAN which means you need a larger main jet. Black and wet is rich which requires a smaller main jet. The target is a nice tan color. For a much more in depth explanation of plug reading and pictures, click here!

--------------------

After your main jet is dialed in, it's time to move on to the needle.

The Needle effects performance from approximately 1/4 throttle to 2/3 throttle. If you're experiencing performance issues in this throttle range but your main jet is correct, this is where you fix it.

To adjust the needle richer(more fuel), you need to raise it up out of the main jet. You accomplish this by lowering your needle clip. This allows more fuel to flow from the main jet by raising it out of that circuit earlier in the throttle's range of motion. It will make sense once you take a good look at it.

To adjust the needle leaner (less fuel), you need to raise your needle clip. This leaves the needle in the main jet circuit longer, allowing less fuel to flow past.

------------------------

Now it's time to adjust the pilot jet and air screw.

This is how I adjust my pilot jet. If anyone has a better technique, chime in.

If the engine does not quickly return to idle after a good rev, it's too lean and needs a bigger pilot jet. If there's bogging when taking off or reving from idle, it's too rich. These problems can often be tuned out with the air screw.

There's a couple techniques for the pilot/air screw. One that I've heard is to set the idle somewhat high, tighten the air screw until the motor starts to die, then loosen it until it starts to die again, then set the screw right in the middle between these two points, then adjust the idle. I haven't tried that technique, personally.

The way I do it is basically by checking off idle throttle response. Adjust it both ways until you get a clean response when you stab the throttle.

When adjusting the air screw, tightening the screw is richer and loosening it is leaner. This is because tightening the screw allows less air to pass (resulting in more fuel in the mixture which = richer), loosening it lets more air through. Edit: depending on the carb, it's possible that this adjustment might be the opposite. Some experimentation will show you which way does what. The type above is the most common with 3 wheelers.


---------------------------

[David komatina]

I hope this might help u out it realy helped me alot!
--------------------------------------------------------

Terms and Definitions

Jetting: The term comes from the two main circuits that control fuel flow in a carburetor. The pilot jet and the main jet.

Main Jet: This is the main fuel circuit in a carburetor. It's a common misconception that this circuit only effects engine performance at wide open throttle. The main jet actually has a trickle down effect on other adjustments and should be adjusted first.

Needle: The needle is attached to the carb slide and is raised and lowered when you push and release the throttle. When you let off your throttle, the needle lowers into the main jet circuit, cutting off fuel flow as it goes down.

Needle Clip: This is the small circular clip that is used to adjust the needle position.

Pilot Jet: This is second jet in your carb. Much smaller than the Main Jet and typically has no effect beyond approximately 1/4 throttle. It's used to adjust your mixture at idle and low throttle.

Air/Pilot Screw: The air screw works in combination with the pilot jet. You can consider it a fine tuner for the pilot circuit. It's most obvious effect is noticed by throttle response.

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level.

Rich: A "rich" condition is what occurs when you have too much fuel in your fuel/air mixture. Symptoms of a rich condition can be a rough running engine (sputtering), a black spark plug, a wet plug or excessive plug fouling.

Lean: A "lean" condition is what occurs when you have insufficient fuel in your mixture creating an over abundance of oxygen. Symptoms can be a rough running engine (bogging), a white or light gray spark plug and sometimes can result in overheating or even severe engine damage.

Sputtering: This isn't exactly a technical term but is commonly used to describe how an engine runs when jetted too rich. For example, using too large of a main jet will cause more fuel to enter the combustion chamber than it can efficiently burn. This will result in a "sputter" at full throttle. It could best be described as a rapid misfire. Note: a rich condition is not the only possible source of this type of problem.

Bogging: Again, not a technical term but commonly used. Bogging can be a result of a lean setting where not enough fuel is entering the combustion chamber for the motor to run properly. In some instances this can cause the machine to "bog" as if it were actually running out of gas. Note: a lean condition is not the only possible source of this type of problem.

WOT: This an acronym that stands for Wide Open Throttle.

Plug Chop: Plug chops are the most accurate and easiest way to check your jetting. A proper plug chop should be done with a clean spark plug. Example; to check your main jet, put in a clean spark plug and run the trike at Wide Open Throttle (WOT) for several seconds, then in one motion, pull in the clutch (if applicable), kill the engine and let off the throttle. Remove the spark plug and check the color (refer to chart in this thread).

Float: The float controls fuel level in the float bowl at the bottom of the carburetor. It has no effect on jetting but can cause some symptoms that can be easily confused with a jetting problem. If the fuel level is too low for example, it can cause a bog similar to a lean condition.

Float Seat/Valve: Basically the valve that stops fuel from flowing into the float bowl when the float reaches a specified level. If worn it can cause the float bowl to overflow.

---------------------------------------------------------------

Nobody can tell you exactly what jets to use!

This is especially true with these 20 year old trikes. No two are exactly alike. Different mods, various states of mechanical well being and different locations (altitude, humidity etc) all play a part. Something as simple as removing your airbox lid can have an effect on your jetting. This is why it's critical that you understand how jetting works so you can get it dialed in perfectly for YOUR machine and riding conditions.


---------------------------------------------------------------

Proper Jetting Procedure

The first step is to get your Main Jet dialed in. This circuit should be done first because it has a trickle down effect.

The Main Jet effects your performance most noticably at WOT. You do not fix a low throttle problem by changing your main jet. When the main is correct, there should be no sputtering or bogging at WOT.

Other than performance, the way to test your main jet is by doing WOT Plug Chops. The color of the plug will tell you if you need to do any fine tuning. DO NOT assume it is correct just because the engine appears to be running good. Remember, white and light gray is LEAN which means you need a larger main jet. Black and wet is rich which requires a smaller main jet. The target is a nice tan color. For a much more in depth explanation of plug reading and pictures, click here!

--------------------

After your main jet is dialed in, it's time to move on to the needle.

The Needle effects performance from approximately 1/4 throttle to 2/3 throttle. If you're experiencing performance issues in this throttle range but your main jet is correct, this is where you fix it.

To adjust the needle richer(more fuel), you need to raise it up out of the main jet. You accomplish this by lowering your needle clip. This allows more fuel to flow from the main jet by raising it out of that circuit earlier in the throttle's range of motion. It will make sense once you take a good look at it.

To adjust the needle leaner (less fuel), you need to raise your needle clip. This leaves the needle in the main jet circuit longer, allowing less fuel to flow past.

------------------------

Now it's time to adjust the pilot jet and air screw.

This is how I adjust my pilot jet. If anyone has a better technique, chime in.

If the engine does not quickly return to idle after a good rev, it's too lean and needs a bigger pilot jet. If there's bogging when taking off or reving from idle, it's too rich. These problems can often be tuned out with the air screw.

There's a couple techniques for the pilot/air screw. One that I've heard is to set the idle somewhat high, tighten the air screw until the motor starts to die, then loosen it until it starts to die again, then set the screw right in the middle between these two points, then adjust the idle. I haven't tried that technique, personally.

The way I do it is basically by checking off idle throttle response. Adjust it both ways until you get a clean response when you stab the throttle.

When adjusting the air screw, tightening the screw is richer and loosening it is leaner. This is because tightening the screw allows less air to pass (resulting in more fuel in the mixture which = richer), loosening it lets more air through. Edit: depending on the carb, it's possible that this adjustment might be the opposite. Some experimentation will show you which way does what. The type above is the most common with 3 wheelers.


---------------------------

[Rocketblt]

I was having the same problem on my second motor for the last two seasons. I would burn through plugs within a days riding. Nothing would cure it. Jetting tweaks, new reeds, new air filer. thinner oil ratios, thicker oil ratios 20:1 32:1 40:1, you name it, fouled a plug after every trail ride. I even replaced the stator the ignition coil and the cdi, then it started hesitating on start up in the 1/4- 1/2 range with a fresh plug. So i checked the compression... ehh.. 175 psi...nothing to gawk at. I tear down the top end, look on the under side under the piston head, and there it is ... brown oil...not blue.... So I'm figuring crankcase seals need replacing... If you can do a compression check on the top and a leak down test on the bottom. Try checking your crank seals. Put a dye in your tranny oil, and or specifically measure the amount of oil put in your tranny, and drain it after every trail ride. If your tranny oil is getting sucked up into your combusion chamber, you ll foul plugs, and youll know it with a dye, or with the amount you use up in a certain period of time.

[Beastmasterb]

i thought of doing that cause it will fire once in a while (just like it would with bad reed valves that it had), but will not run to perform other test. How much psi can i put in the crankcase, maybe 10psi of air and check things over with soapy water to see if it sealed around the gaskets? Will that work on the crankshaft seals?

[Beastmasterb]

I just did a compression test and couldn't get it over 140psi, now that seems lower than anyone's i know so any help with that would be appreciated!! I'm going to try another compression tester before i jump to conclusions first!!

[ceaserthethird]

Yes time for a new piston and rings, 140 PSI means rebuild time !

When u do a compression test hold the throttle all the way and kick it over till the needle stops moving about 10 kicks.

Service limit psi 170 !

[Beastmasterb]

Yea, I held the throttle wide open. Couldn't I just get away with rings, the last time I looked at the cylinder bore it still had the cross-hatches left from the previous rebuild. And could this be the answer to all these problems I've been having?