Really getting tired of my FL250

[whammo77]

I've got an '81 fl250..... was running great up until October of '09. Then it started running rough, and was very hard to start. Finally it just got to where it pretty much didn't want to start at all.

 I took it to a local mechanic and it pretty much puzzled them. It has perfect compression.... as per the book. It has good spark. So naturally, they thought carburator (so would I). So they completely rebuilt the carburator.... still wouldn't stay running. Replaced the fuel pump... still nothing. Replaced the coil despite having good spark. Nothing. Changed out the CDI despite having good spark. Nothing. Nothing Nothing Nothing.

They finally gave up after over a month of having it.... so I brought it home and messed with it some more. Changes all the fuel lines, went back through everything they had done. Still no luck. So, frustrated, I took it to another mechanic. He went through all the same things, checked all the connections, and by all rights, says it SHOULD run. But again, it wouldn't.....

 So after another 2 months of being at this mechanic's shop, I brought it back home, put a gravity fed tank on it, took the carburator off once again, totally disassembled it, soaked it in new parts cleaner for over a week, blew it out with my air compressor, then put yet another brand new carburator kit in it.

 Well, as of this moment, it's the same problem as always.... it starts (using starter fluid), runs for about 30 seconds, and then promptly dies. I have tweeked, tweeked, and re-tweeked the carburator air and throttle settings. Nothing changes.

 So before I push this thing off in to a lake, I thought I'd come on here and see if anyone has any other clue as to what might be the problem with this thing?

 I would appreciate the help. I am severely frustrated with this thing (and have spent a lot of money for nothing trying to get it running!!!)

[Adnoh]

In order to keep it out of the lake. I'll try to help.

Read the entire post before doing any of these steps. If you do not understand any of this ask before doing work.

Sounds like you have compression( unknown level) would be good to know the number. It has spark and timing ( since it ran with starter fluid, do not recommend using starter fluid). The carb has been cleaned and set. I would bet the shops have not done a leak down test since there was no mention of it. Since you have a gravity feed tank  getting fuel to the carb,One can rule fuel pump out.

Is this a factory cylinder or a CR conversion with reeds?

First make sure the filter is clean and flowing air or removed for test only.
The filter being removed will effect the pilot jetting and air screw adjustment.

Next get a compression number. If too low it will be hard to start and will not pull fuel up from the bowl into the carb throat and then pulled in to the case and then up the cylinder transfer port and compressed with the air and combusting.

If your compression number is 100 psi or above ( gap the throttle all the way and pull four to five times). If your number is under 100 psi poor in a cap full of two stroke oil and re test.  Then compare the two numbers and let me know what they are.  Then check vac port ( fuel pump port) to be sure it caped off since you know have gravity feed.

Lets try this first. Instead of spraying fluid in the carb,
#1 Buy a new spark plug
#2 Set the gap per manual.
#3 Untwist the plug cap and cut off 1/4 inch of the wire and reinstall cap
#4 Fresh fuel mixed at what ever ratio you use
#5 Make sure your air screw is set at factory
#6 Take a cap full of  the new gas/oil mix and pour it into the cylinder and then install the new plug.
#7 Now pull and see what happens.

If it fires but does not continue to run.
 #1 check the bowl to be sure it has fuel ( by cracking the nut on bottom of bowl)
If No then check the vent cap and make sure your petcock is on.
If yes than check your pilot jet and choke to be sure there is no obstruction.
If no obstructions than make sure the air screw has not been smashed but being tightened in to hard and damaging the needle and tip. Then reset.

Please let me know your results to see what step is next.

I mention leak down test because if you have an air leak the fuel mixture will be too lean ( to much air) or will not pull fuel ( loss of vacume) loss of vacume will also cause the fuel pum not to work. As teh piston move up toward top dead center and building compression teh piston moving up past teh ports create a vacume which pulls the fuel out of the carb. A seal leaking will hinders this and low compression does the same thing. The air will enter the crank case through the seal instead of pulling it through the carb. The air must enter through the carb so the fuel can be pulled out of the bottom of the carb bowl through the main jet and idol circuit ( piot jet and air screw). If your compression is low than the air and fuel in the cylinder is getting past the rings as it compresses ( piston moving toward top dead center) and the pressure is equalizing in the case and loss of vacume accures and then no fuel can be pulled to make the engine run.

Since the fuel pump and tank is know gone and it appers it does not pull fuel than I would bet you either have low compression or an air leak.

If you have a fuel pump guage ( low pressure/vacume) you can hook it up to the vacume port and then have some one pull it and see if the guage pulses. Since the fuel pump has been removed the port was caped correct ? An open vac port will cause your condition ( air leak).

[cupcake]

Check the flywheel key. It is very common for this to shear and change the timing. Yes it will still have good spark but not  at the right time. Easy to see if you pull the flywheel off.

[whammo77]

Slow about giving any updates.... have been very busy. I ended up taking the motor out. I did a crankcase pressure test and found that the seal on the drive side was leaking badly. Replaced it, and replaced the other side and both bearings for good luck, and now she's back up and runnin good as ever!   I certainly appreciate y'all chippin in!