Any help? Racer won't run.

[XFactor45]

I've got a 85 LT250R quadracer hasn't been ridden in years. I've rebuilt carb, tuned up, changed oil, cleaned air filter and fresh gas. Had it running better than when it was new. Running about 60 sounded like it ran out of gas but has plenty. Now will only start and run for about a second then die. Changed spark plug twice getting plenty of spark, checked carb, and rotor key. Everything seems fine but will still only start and run for about a second or two. I'm stumped and missing something it was just running to good. Please Help ready to go ride I miss it. Thanks for any help.

[axellmusic19]

Have you taken off the head of the engine to see anything that might be going on in there? Is it hard to kick over? Have the electronics been kept dry and clean? Something tells me it could be a clutch issue too but that wouldn't explain the shutting off at 60.

[XFactor45]

The shutting off and not running is the problem. Clutch wasn't slipping at all. It has good compression and still kicks over the same. It will start on the 2nd or third kick and run for a second or so the die.

[headache]

check the reeds. One of them could be broke. Alot of times it will let it start for a second or two then die. Could also be flywheel key...

[XFactor45]

Checked the flywheel key all ready. I keep thinking reeds just not wanting to pull cylinder. Checking spark again and it seemed a little weak. Leaning towards coil first. And it is a little out of spec.

[Rebel lt250r]

Sounds more like the reeds or a air leak of some type. Had something similar happen to my 86. All of a sudden it wouldn't run, had a small air leak before the carb. took it all apart, put back together and it fired up and ran great.

Also could be a jet issue, have you taken the carb apart? sometimes older bikes get gummed up, wouldn't hurt to take the carb apart and put in all new mikuni jetts, factory specs. it isn't very spendy and will rule out a fuel delivery problem.

[jerkin]

Not sure how replacing jets rules out a fuel delivery problem. Any one of a number of passages in the carburetor could be blocked, float could be set wrong and not allowing enough fuel into the bowl, pickup tubes in the tank could be plugged, etc.

Even a new coil can be a little out of spec, mine was supposed to be between 3k-5k and was 2.85k brand new. If it's an original coil it should probably be replaced anyways. Get the OEM one, not one of those "40% more spark" kind.

I'd run a compression check first and see where you're at. If that's good and the new coil doesn't help I'd pull the jug and check the reeds. You can do it in the frame, not that big of a deal.

Have you already checked the pickup and source coils on the stator?

[Rebel lt250r]

taking a close look at the carb CAN rule out fuel delivery, bud. If it has spark, and doesn't kick over any different i would still start there if you are positive you have spark.

(take it from someone that owns a couple of them)

When it come to simple machines keep it simple. Most of the time it is something simple, that you overlooked.

1. check you fuel petcock, make sure your getting fuel.

2. When you get the carb apart check your jets, then measure your float level. Yes you cant check for debris visually, however with some sort of air tool you can find out pretty quickly if you are plugged.

If it hasn't been apart as long as you have owned it, you owe it to yourself to look there.

Attached is a picture of your stock jet setting. in order

1. carb
2. size (mm)
3. Float level
4.air screw beginning position
5.needle clip position (dead center)
6. jet needle
7. Main jet #
8. Main air jet
9 needle jet (or emulsion tube)
10 pilot jet
11 starter jet

One other spot i would check is the flywheel. if there is any moisture or oil down there from that seal, that is your culprit.

It wouldn't hurt to check compression.

[jerkin]

Sorry to tell you bud, but like I said before replacing your jets does NOT rule out a fuel delivery problem, nor does just cleaning or inspecting the carburetor.

(Take if from a guy that owned his first lt in 1990 and is now on his 4th.)

Amongst the other things I mentioned I've seen related to fuel delivery were mud dobbers built a nest in the gas tank vent line causing a vacuum in the tank that wouldn't let enough fuel to the bowl at high speeds. Another one was an air filter that was so plugged that there wasn't enough air coming through the carb to pull the fuel out of the bowl. All fuel delivery problems are not related to the carburetor at all let alone the jets.

Other than that I agree with what rebel said in his second post, actually what I said in my first that he repeated. Check the petcock, check the float level and make sure none of the passages are blocked. There's no reason to replace jets unless you need a different size, they can be cleaned very easily with a can of carb or brake cleaner and a set of torch tip cleaners.

You really need to do a compression check, just because it feels ok doesn't mean that it is. If you don't have one you can purchase a cheap one at harbor freight for $10. If you're below 140 psi then you need to pull the top end anyways.

Another thing you can try is to pull the plug and dump a little fuel in the cylinder then put the plug back in and see if it fires. If it starts and runs for a while then you know it's a fuel problem, not an ignition or compression problem.

[XFactor45]

OK guys I'm not a complete novice. haha I've been riding sense the late 70's and have 5 different kinds of 4 wheelers till I tried the 85 LT250R and I like it so stay with it. I do all my own work including complete overhauls. I'm just missing something small. I will find it sooner or later. But I do thank you for all your help. Flywheel key good, compression 207psi, pulled jug reeds good, seems to be good spark, pulled carb and gone completely through it 3 times soaking it in a carb dip vat once overnight. I'm putting all back together and starting from scratch.

[Rebel lt250r]

i'm sure you'll find it, its probably something simple, looks like good compression.

[fearlessfred]

i have seen a cdi on a cr 500 do what your descibing.it seems that u have ruled out almost every thing. fuel delivery would have been my first guess . a gummed up needle and seat could cause it but it sounds like u have already cked that. this is gonna sound dumb but try shutting the fuel off remove the screws that hold the bowl and dump the fuel out off the bowl hold the bowl to the carb with your hand ,level and turn the fuel on for 30 seconds, remove the bowl, it should be half full. if it is u can rule out fuel delivery.

[XFactor45]

Already did it. Plenty of fuel. I think I've tried everything but the CDI unit. Can you still buy them? I haven't checked yet. Ready to bite the bullet if I can still get one. CDI unit haha not the bullet yet. :)