Need help from carb experts. 2t 250 | GTAMotorcycle.com

Need help from carb experts. 2t 250

S

SVeezy

Well-known member
New to me 2000 yz250, it was running fine a few months ago but wasn’t getting spark recently. I cleaned the plug cap and now getting a spark but the carb is pissing fuel out the drain tube. I suspect there is a float stuck but really don’t have any knowledge of carbs.


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SVeezy said:
New to me 2000 yz250, it was running fine a few months ago but wasn’t getting spark recently. I cleaned the plug cap and now getting a spark but the carb is pissing fuel out the drain tube. I suspect there is a float stuck but really don’t have any knowledge of carbs.


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Try tapping the carb body/bowl with a rubber mallet or the handle of a screwdriver. If it’s a stuck float, this will usually do the trick.


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I actually did give it some taps with a wrench, it seemed to help but not solve the issue


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Next would be drain the carb and remove the carb bowl and check the float movement. Also, check the float’s condition for cracks. Hopefully you can do this without removing the carb from the bike.


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^ whats said above and then..

lay bike on left side, then lay down on right side - and then look / see again if fuel stopped coming out the overflow. or not.

pretty easy to remove the carb on a 2 stroke single. look/see - sometimes the float valve and seat are old and not sealing - replace seat and float valve as a set.

best luck. watch vids; find a friend w some carb experience. get assistance first time into a carb.
 
Thanks gents. This is exactly the advice I was looking for. I’ll dig in and report back.

Cheers


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Just a quick update. I managed to blow some air through the lines and that stopped the overflow leak. I’ll likely have to clean the carb up soon.

There is spark but it doesn’t look as strong as I’d expect. I’m going to have to dig up some testing details on the coil and work from there.

This is taking way longer than it should but it’s a back burner project at the moment


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SVeezy said:
Just a quick update. I managed to blow some air through the lines and that stopped the overflow leak. I’ll likely have to clean the carb up soon.

There is spark but it doesn’t look as strong as I’d expect. I’m going to have to dig up some testing details on the coil and work from there.

This is taking way longer than it should but it’s a back burner project at the moment


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Maybe check resistance in the plug cap and also that the cap and wire have a strong clean connection.

Also, check the spark plug gap is within spec for your bike.


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Cleaned the cap and have a new one on order just in case, I figure it’s cheap insurance. Cleaned up the connection to the wire as well.

I bought a new plug at the start of the issues so that’s covered. Gapped it too.


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I should check the resistance on the cap, I think 15ohms is common but will have to look it up


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Well I haven’t done much of anything on the bike. Unfortunately I’ve been dealing with health issues and not riding much, definitely not wrenching much.

Pretty sure spark is not the issue. I managed to stop the massive fuel leak and just trying to get back into this job.

In an ideal world I’d just pull the carb and try to rebuild it (would be a first time)

I looked at buying a second so I can work on one while the other is on the bike.

At this point I really think it’s the carb, bike was running fine initially and spark/air don’t seem to have any issue

I’ll dig further when I get a chance


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Often it’s recommended to disassemble, clean and re-use the original brass. If there is obvious damage or wear, then it’s best to replace with oem.

Not sure if it applies to your bike, but some aftermarket carb kits end up making the bike run worse because the components are not quite to spec.


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If it was running fine before and suddenly not you could have clogged a jet (crap in gas makes it way through).
Stuck float will pee gas, happens once in a while, a few taps and it should right itself. If it becomes regular then yes pull and clean and reset the height. If you want to avoid a rebuild pull the cap at the bottom of the carb and remove the main and pilot, read the sizes on the outside and order replacements, cheap (assuming there is a cap and you don't have to pull the float bowl off). You won't be able to tell if they are clogged a little and new jets will return normal running if that was the issue.
 
Just an update for anyone interested…

I had rebuilt the carb but issues persisted. The valve seat is pressed in and after several scrubs with fine steel wool (I didn’t want to go at it too aggressively) the fuel overflow issue was resolved.

I was still having issues with it starting though. Sometimes it it would fire right up and others I’d have no luck. I traced it back to a faulty coil and she is now running great


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with ignition coils; when cold, a coil may work fine, but fails as it heats up during normal use. go away a couple hours and bike fires up normally. hmm
tricky find sometimes..lol good work
 
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