250cc watercooled atv, doesn't get up to speed!
 

Hey!

I have an XF250F atv a pretty large one for a 250cc. It's currently having some issues getting up to speed and all in all, just using the drive gear.

The last time I used it It ran fine for like 5 minutes, then after an acceleration it started popping and backfiring. And couldn't get up to speed again.

Yesterday I tried lifting the rear tires off the ground (it's rear wheel driven). Then giving it gas, and for the first few seconds, the wheels rotate fine, but after a few seconds it starts to drift between which wheel drives and which is not rotating. It's for the most part the right rotating the most.

I have just switched out the carburettor and the airfilter along with the sparkplug, to make sure it wasn't a fuel related issue.

It revs fine in neutral all the way up, and it drives like it should in reverse, drives even faster than the forward gear atm.

I have tried adjusting the gearselector, but with no luck. Atm it doesn't really go into forward unless you do it with your hand on the gearbox.

I hope someone can help, it has been pretty frustrating.

Thank you in advance
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Apart from elderly Kawasaki 300s all ATVs I know of have "fixed" rear diffs, many just have a solid axle. If yours has a car style diff, then which wheel drives will vary. Starting to pop and miss after a few mins of riding can be the tank vent blocked causing fuel starvation, or an electronic component breaking down as it gets hot. Exciter and trigger coils are the usual suspects as they heat up with the engine but CDIs and ignition coils can do this too. Having to hold it in gear indicates a gearbox fault or adjustment needed on the linkage, so it could be thinking it is in neutral and adjusting the rev limiter to suit.

It doesn't matter how long I drive it, it always does it. If I start it and accelerate it will pop and backfire, and not get up to speed.

There's one green cable from the carb not plugged into anything, from the auto choke.

And the original air filter is also missing so it might be due to it running too lean (Not enough fuel for the amount of air).

Most auto chokes are on choke all the time except when the engine has been running for a while. So if yours is disconnected it will probably be on choke all the time. Easy to check, take the plug out after a decently long run, if the plug is black and sooty it will indicate that the choke is still on. This may be why someone removed the air filter, to try to lean it out a bit.

Where would I put that wire, there's nothing that fits in it. All wires on the atv are already plugged in something.

Could it be a ground since it's green?

Hey, so I found the issue.

The carburettor was not getting enough fuel from the tank, due to the fuel lines not being properly placed.

Thank you for your help, Merryman.