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So, I recently did a carb rebuild an my 300. I did it because the thing didn't rev up all the way, and the vent leaked. So, I rebuilt the carb, and it fixed nothing. I bought some bigger jets, and I'm still playing around with it. But as for the vent line, I can't get it to stop leaking. Any ideas?

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When you say leaking vent do you mean its leaking out the drain tube out bottom of carb? Vents would be out the top of the carb. If its leaking out the bowl drain its either a leaking float valve or the drain screw isnt all the way tight. Alot of times carb rebuilds come with a new needle but the seat is still the original one. Crud can build up on the seat and cause it to leak.

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I think I got the problem fixed. The brass tube in the bowl leaked at the base, causing gasoline to flow down it, I have an extra bowl that didn't produce air bubbles when I blew up the drain with the brass tube plugged. I'll see if it fixes it.

 

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Yep no doubt that would cause a leak out the overflow. Glad you got it sorted!

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Still having trouble with jetting tho. I can't seem to get it to rev up all the way, and when I hold the throttle at a position that isn't wide open, it spudders a bit, and won't stay at one single rpm. Any ideas?

 

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Not all 300 carbs have the same jets , and even though they all look the same there are differences over the years in the bodies  , especially on the 1st gens  -----  check the code  number on the base of your carb against the year of your 300 , then check the size / number of the jets  , I would try to get it back to  stock 

 

what year is your 300 ? --- has anyone ever changed the cam or the head as an assembly before ? did you know the 1st one had two more horsepower  bigger cam, bigger jets and a more tuned  exhaust 

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26 minutes ago, Andy bauska said:

mine is a 1993, and the cam is stock. It had a 125 size in it when I started missing with it.

 

So your the original owner  ?  never know what the P.O.'s  did along the way 

 

 

The 93 OEM carb code  is VE90EA and only used on a 93 , there were two choices of main jets from the factory in 1993 , 120 or 125  , slow jet was 40 and the starter jet  was 85 

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10 hours ago, Andy bauska said:

Still having trouble with jetting tho. I can't seem to get it to rev up all the way, and when I hold the throttle at a position that isn't wide open, it spudders a bit, and won't stay at one single rpm. Any ideas?

 


Did you put the fuel mixture screw back where it was when you started?

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Posted (edited)

Here’s my 93 carb VE90E; it’s looking pretty dirty but i laid out all the parts just like they should be installed.
 

BTW the starter jet passage plug is missing here.
 

if your quad idles well but stumbles at higher rpm, then your Air Fuel mixture is off or your carb is dirty. Restore the VE90E carb to its original configuration. If your spark plug is dark then you need to lean out the mixture. Change the plug. Very possibly your carb vacuum piston is not opening, choke valve is bad, hole in vacuum piston, incorrect carb synchronization  
 

This ignores the possibility you might also have a worn cam chain or valve/compression problems.

345F12D7-351D-45FD-B884-8B7DACDE38A7.jpeg

Edited by Goober
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I don't know what the choke valve is, so is it expensive, and hard to replace? And my diaphragm has no holes. Is it possible I need a 120-jet size? I was only able to find a jet kit with sizes 125-150, so where would I obtain one?

 

 

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Posted (edited)

Btw, would a slow jet interfere with it running being wide open?

Edited by Andy bauska

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2 hours ago, Andy bauska said:

I don't know what the choke valve is, so is it expensive, and hard to replace? And my diaphragm has no holes. Is it possible I need a 120-jet size? I was only able to find a jet kit with sizes 125-150, so where would I obtain one?

 

 

Partzilla still has 4 left , other sites are a bit cheaper , like Rocky Mountain ATV 

 

JET, MAIN (#120)

99101-393-1200

by Honda

$7.54 2% OFF

$7.36
 
 In Stock · Only 4 left in stock

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Ok. I was doing some thinking, and since I've done a full rebuild, a lot of stuff has changed, more compression, valves fit tighter, ect. So it is burning less oil and more gas, so I think a smaller that stock (it wasn't running right before) would hinder my performance. What do you think?

 

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2 hours ago, Andy bauska said:

Which would be? A 125 size jet?

 

Not sure what your asking ?

same part number 99101-393-1200 =120 jet  just change the ending  to 99101-393-1250 =125 jet 

 

works just about all jets , 

99101-393-1220 = 122 

99101-393-1280 =128

99101-393-1300 =130

 

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3 hours ago, Andy bauska said:

Which would be? A 125 size jet?

 

I think so. Just to be sure, you remember where to find this info in the service manual?

 

if you go to the Honda shop they probably have some single jets in a cigar box in the lead tech’s race bin

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Well, I had a 125 size, and it was clearly running out of fuel, so I don't think a 120, or 125 will fix my problem. I think I have a 140 size in it now, and it's almost there, but not quite. I had surgery yesterday and haven't gotten the chance to mess with it.

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