slow rpm fall and bike doesnt want to go.

[7oxSin]

my brother got his first bike the other week and we have been working on it. its an 02 ninja 250 with 3000 miles on it, and has sat for atleast a year. original owner, full muzzy, custom paint job, aftermarket sprocket, chrome wheels and grab bar all for 1000$. we get it home and change the oil, along with draining the gas tank (smelled like kerosene) put checked the tank for rust, and put a gallon of gas with a little seafoam. got it running that night, would idle but wanted to die when you would go to ride it. i play with it a bit and ride it around then bring it home and took the carbs off. did a standard carb clean getting into the channels ect. now that thats all done its still acting the same way. took it down to the gas station put some more gas in it just incase it was residual bad gas. but its still acting this way.

when you rev the bike in neutral the rpms fall slowly but the grip snaps back like new.

has problems going up hill

in gear has problems getting up to 11krpms

i have gotten it up to 50 mph max


any ideas guys? it has no air filter in it right this sec, going to pick up one today. any help will be awesome!

[jkv45]

Did you pull out the pilot jet and main jet/jet holder and run a copper wire through them? If not, they are most likely still partially plugged.

Did you remove the idle mixture caps and set the screws to 2 1/2 turns out for starters?

You may also have a vacuum leak. Check the manifolds with some carb cleaner to see if the RPMs change.

Not having an air filter won't help either.

[FvnnyL3tt3r1ng]

Sounds a lot like a bike that is running lean.

This could be that it needs to be re-jetted (muzzy exhaust calls for that doesn't it), the gas isn't getting into the carbs/engine effectively (rotten fuel filter, tap, float valves, floats...) or maybe the throttle cable could be too tight.

Did you check to see the size of the jets?

[Motofool]

I would check that plenty of fuel is reaching the bowls of the carbs.

Assuming that you have verified the height of the floats and the good seal of the boots, I would then verify the electrical part, just in case the engine is working on only one cylinder.

[7oxSin]

Originally Posted by Motofool

I would check that plenty of fuel is reaching the bowls of the carbs.

Assuming that you have verified the height of the floats and the good seal of the boots, I would then verify the electrical part, just in case the engine is working on only one cylinder.

how would i be able to tell if only once cylinder is firing?

[7oxSin]

UPDATE**

new plugs, no real change, when i cleaned the carbs i didnt run wire but ran carb cleaner through ever little hole untill it came out the other side, that included the removed jets. the needles where not shimmed or anything, if i have to rejet the carbs is there a way to do it reliably? if not whats around a good price to get it done?

[krolinked]

Put the air filter in before you try to fix problems that might not be there.

[7oxSin]

Originally Posted by krolinked

Put the air filter in before you try to fix problems that might not be there.

yeah on hold with the local stealership seeing if they have any in stock.

[FvnnyL3tt3r1ng]

Re-jetting is a process that is gonna take a bit of your time. I'd say at least 2 hours of total wrenching broken up into a few different sessions plus however long your test driving takes. Since you haven't done it before you have a lot of research ahead of you.

Really doubt the air filter is gonna make a drastic difference unfortunately.

If only one cylinder is firing you will have very slow revving, weak power output and a low top speed. I guess you could check by pulling one of your spark plug connections to see if the bike runs the same or not. Most people know just by feel.

[FvnnyL3tt3r1ng]

Check and see that the OEM fuel filter hasn't folded in half on you and is blocking fuel flow.

I'd also check the fuel level using clear tubing hooked up to the carbs' drains.

Rate of flow is also important and can be checked right after the fuel level check just by observing how fast the fuel goes into an empty carb (one at a time). Rule of thumb: If it just trickles/sputters you have a problem. If it's a steady stream you are fine....

[Lychee]

Put the air filter in. Running an engine without the air filter is really hard on the internals. Imagine all the dust in the air getting thrown into the cylinder, forced up against the cylinder walls and then blown up only to be scraped back and forth by the rings.

Since the muzzy is already there, it may already be jetted. Pull out the jet and look what size and brand is written on the jet. If it is stock, then pull off the exhaust from your 03 bike and slap it on to eliminate it as a possible problem. If it is stock, it should be running really lean due the increased flow from the exhaust and lack of air filter.

[Motofool]

Originally Posted by 7oxSin

how would i be able to tell if only once cylinder is firing?

One will be cooler than the other to the touch.
Yes, there is a little fuel filter at the end of the hose.

[7oxSin]

ok so put the new air filter on it and it is still acting the same getting a few backfires wide open, havnt changed the epa idle mixture screws yet. just updating incase someone can figure it out with the new info.

[The_big_dill]

The price and missing air filter make me wonder of its history. Although it may not be your issue, when you get a chance, check compression.

When i got my bike, it was in storage for a long time, so i changes the oil on the guys driveway, then when i got home, i changed the coolant.

[jkv45]

Originally Posted by 7oxSin

ok so put the new air filter on it and it is still acting the same getting a few backfires wide open, havnt changed the epa idle mixture screws yet. just updating incase someone can figure it out with the new info.

I still think the jets are not fully open. Just spraying carb cleaner through them isn't enough.

When you pull the carbs off again, check the size of the main jet. You probably want to go larger with the full exhaust system installed. Get some washers for the needles.

Check to see where the idle mixture screws are set now. Set them to at least 2 1/2 turns out. Remove them when the carbs are off, and make sure the rubber o-rings are in good shape.

As Motofool noted, check the temp of the exhaust pipes to confirm both cylinders are firing. Pull the plugs and look at their condition.

Did you check for vacuum leaks?

Check the fuel filters and notice if there is any sediment in the float bowls when you remove the fuel.

[The_big_dill]

Originally Posted by jkv45

Pull the plugs and look at their condition.

+1.

This will be the easiest way to know if you are running rich or lean.

[FvnnyL3tt3r1ng]

He's running lean no doubt.

'd either put the stock exhaust on or buy a jet kit from factory pro.

You're for sure going to have to pull the carbs again. If fuel flow is fine and unrestricted then you're probably running too small main jets and yeah you need to shim your needles as well if you don't wanna buy aftermarket needles.

This could be the reason the bike was sold, that is, the previous owner got a full exhaust and didn't like the performance of the bike anymore not realizing it needed to be tuned.

Check and see that the OEM fuel filter hasn't folded in half on you and is blocking fuel flow.

I'd also check the fuel level using clear tubing hooked up to the carbs' drains.

Rate of flow is also important and can be checked right after the fuel level check just by observing how fast the fuel goes into an empty carb (one at a time). Rule of thumb: If it just trickles/sputters you have a problem. If it's a steady stream you are fine....