Need help motor problems 250es

[Jobin545]

Hey guys , I am working on my 1985 act 250es and it's missing/cutting out. Last season I rebuilt the top end and still has 165 psi compression. It's runs ok at idle or low rpm but as soon as the rpm pick up its cutting out periodically. It's not a steady miss, any thoughts on where to start ?

[Russman1986]

I would start by cleaning the carb and making shure all the Jets and pick ups are spotless

Sent from my SAMSUNG-SM-N900A using Tapatalk

[arlaunch]

Then replace the plug and set it to the correct gap if you have not done so.

[Jobin545]

Then replace the plug and set it to the correct gap if you have not done so.

Yup I have cleaned the carb , changed plug and gaped correctly three times, I have also checked the valve clearance and it's perfect



Sent from my iPhone using Tapatalk

[newby200x]

I'd go ahead and order a rebuild kit for your carb, you would be amazed at the difference it could make. I use Shindy for all my rebuild kits.

[RubberSalt]

I'm assuming after the rebuild, it ran fine until recently?

Check the fuel filter. Could be fuel starvation.

Have you checked for air leaks between the carb and the head? If a gasket has failed or the boot has dry rotted, it could cause these symptoms.

I'm leaning more towards the carb though.

[Jobin545]

I'm assuming after the rebuild, it ran fine until recently?

Check the fuel filter. Could be fuel starvation.

Have you checked for air leaks between the carb and the head? If a gasket has failed or the boot has dry rotted, it could cause these symptoms.

I'm leaning more towards the carb though.

Yes it ran great for a whole season , I went to fire it up this year and the miss was there. I've cleaned the screen in the tank and the petcock. I've also torn down the carb and soaked in carb cleaner for two days. Do you think replacing the jets could do it ? They looked clean I could see through all the port holes with no obstructions


Sent from my iPhone using Tapatalk

[UncleJerm76]

Sub'd!
I'm having the exact same issue on my '86 250es! Replaced petcock, added inline filter, cleaned carb twice.

Curious what you find, please post updates if you can as I'm stumped.


...Tools ...Toys (same thing)

[UncleJerm76]

Took carb apart again. Noticed the rubber plug on the second jet (added in '86 to block off the jet) was nearly disintegrated. Drilled and tapped the hole, and put a 5x.8 machine screw in there this time. I have to wait for a new bowl seal since it tore to see if it helped anything. I don't think it would since I believe that's the starter jet.

Have you gotten anywhere?


...Tools ...Toys (same thing)

[Jobin545]

I'm curious to see if that will work for you, I haven't had a chance to work on it again yet going Into it deeper tomorrow. Im going to check for any possible air leaks after the carb and maybe a loose fuel line letting in air.

Do you think a lack of air getting to the carb could cause such a miss ?


Sent from my iPhone using Tapatalk

[UncleJerm76]

...Im going to check for any possible air leaks after the carb and maybe a loose fuel line letting in air.

Sent from my iPhone using Tapatalk

I could wrong here, but since the fuel flows into the bowl and is then picked up I wouldn't think it would matter. But it would be strange to me that you would be sucking in air from a loose fuel line but not leaking any fuel when the motor isn't running.

I've heard that if the big rubber tube connecting the carb to the head is cracked and sucking air that it can cause misses on the high end like we are having, but I've never experienced it and my tube is fine.



...Tools ...Toys (same thing)

[Jobin545]

That's a good point ! , I do always shut off the fuel when I'm not running it , im looking at all options this one has me stumped.

Yeah I have also herd of air leaks after the carb being an issue but mine seems to be in good shape too. I'm going to take the plastic flange that bolts to the head from the carb off and inspect everything with a fine tooth comb






Sent from my iPhone using Tapatalk

[RubberSalt]

Any air leak after the carb can cause problems. Gasoline isn't sucked out, it's boiled out of the carb under the vacuum produced by the engine. This is why any air leak can cause problems. The vacuum produced wont be as strong.

If the top of the carb is missing the seal, that can cause an air leak.

A quick check for this is carb cleaner. Get the machine running, and spray carb cleaner around the intake boot where it bolts to the engine and the carb. Also make sure your spark plug is tight. The last thing is to check the cylinder head where it meets the jug. The gasket could be blown or the head bolts came loose.

As for a cracked fuel line. It's unlikely that this would be the cause. The gravity fed fuel should move slower than the air bubbles can rise. I'd check and replace if it was a concern, but wouldn't worry to much about this.

[Jobin545]

Any air leak after the carb can cause problems. Gasoline isn't sucked out, it's boiled out of the carb under the vacuum produced by the engine. This is why any air leak can cause problems. The vacuum produced wont be as strong.

If the top of the carb is missing the seal, that can cause an air leak.

A quick check for this is carb cleaner. Get the machine running, and spray carb cleaner around the intake boot where it bolts to the engine and the carb. Also make sure your spark plug is tight. The last thing is to check the cylinder head where it meets the jug. The gasket could be blown or the head bolts came loose.

As for a cracked fuel line. It's unlikely that this would be the cause. The gravity fed fuel should move slower than the air bubbles can rise. I'd check and replace if it was a concern, but wouldn't worry to much about this.

Ok I will try the carb cleaner test tonight , if the head gasket was blown wouldn't it affect my compression ? And it's also very weird this problem popped up the first time I fired it up in the spring. The bike ran amazing all last season, but not this season.


Sent from my iPhone using Tapatalk

[RubberSalt]

I'd think it would affect the compression, just tossing the idea out there.

I could see thing dry rotting while sitting. You've already gone through the carb, so I'll rule out bad gasoline.

You replaced the gas, right?