Keep me from buying a new carburetor

[f4ion1]

I have a late 90's 300ex. Rode it the past 2 seasons just fine. Went to crank it up the first time this season and it just wasn't running right. I tried everything I knew to do and couldn't get it right.

I ended up taking it to a local ATV shop and he found that the timing chain had jumped a few teeth(he checked the valves and everything was good there, wheeew) so I paid him to replace the timing chain and went ahead and changed the tensioner while I was at it. I went to pick it up and when he cranked it up. It ran a little better but bogs from half throttle all the way to open(as if the choke was on). I had cleaned the card twice before I took it to him and he said he cleaned it too.

His suggestion was to buy a new carburetor.

The weird thing is when we take the intake tube from the air filter off it runs great(just open air straight to carb). As soon as we put it back on it starts to bog again.

Somebody got anything else I could try before buying a new carb???

Thanks

[TRXRacer1]

Originally posted by f4ion1

His suggestion was to buy a new carburetor.


Thanks My suggestion is your mechanic must either be late on his bills or is an idiot.

If your problem from the mid to top end is remediable by allowing more air in then your main jet is too rich. Start moving down in size and see what happens. Your bike and wallet should like the results.

[f4ion1]

haha

Thanks for the quick response

I'm a backyard mechanic in training and thought that might be it but wasn't sure.

Just ordered a 110 & a 115(down from stock 120) main jet to see what happens.

[rooster300ex]

hmmm shouldn't have to go down from stock jetting. Sounds like a needle adjustment needs to be made. Make sure that is at the stock postion.

[f4ion1]

Have not checked that, don't know why it would have changed but will double check it to be sure when I get home tonight.

Thanks.

[sm00th026]

Originally posted by f4ion1
I have a late 90's 300ex. Rode it the past 2 seasons just fine. Went to crank it up the first time this season and it just wasn't running right. I tried everything I knew to do and couldn't get it right.

The weird thing is when we take the intake tube from the air filter off it runs great(just open air straight to carb). As soon as we put it back on it starts to bog again.

Somebody got anything else I could try before buying a new carb???

Thanks


Hi, You say it ran good the past 2 season right? Did you mod it in any why (Pipe,Filter,exc.)If not I wouldn't change a thing. And as of it running great with the intake tube off.Check your filter or your breather tube thru the frame to see if it is not stop up with a dirtdaubers nest or rats nest.

[f4ion1]

The only thing I changed was installed a new UNI air filter, which I would have thought would have given it more air over stock if anything.

The filter is brand new and clean and the passage is clean also....

[f4ion1]

Checked the needle last night and it is still in the stock position(3). Managed to strip the screws that held the needle down but I guess that's what I get with it being that old, grrrrr.

Back to the smaller main jet I guess. They're in the mail.

Thanks

PS. I know this sounds so much like a newbie it's not even funny but ya'll got any secrets to keep me from stripping all these phillips head bolts?? I've just been replacing them with alan head bolts when I can.

[rooster300ex]

I've noticed the right size screwdriver is less likely to strip.