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gwoods27

DR350se carb question

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Ok..I have a 96 dr350s.  Everything appears to be stock.  Except the petcock that was changed to a manual non vacuum type.(on off reserve) I purchased a carb rebuild kit and completely disassembled the carb cleaned all passages with gumout and compressed air.  Replacing the air mixture screw I noted the prev owner had it set to 4 turns out.  When i put it back together I set it to 2 turns out since the spark plug looked pretty black from running too rich.  The bike starts right up with the choke on...and as it warms up idle will go up to 4K rpm..turning the choke off the rpm goes down to under 2k.  And if given any throttle the engine sputters and stops.  The air box is open and the filter off.  If I cover the air intake in the air box with my hand.  The throttle sputter goes away and the throttle response is perfect.  When doing this I can feel the air being sucked in past my hand.  The air filter I have is the foam( UNI ) type theair box has the side door and rubber snorkel on top.  So I put the air filter back in the box, screwed the door on and put the snorkel in.  Back to the sputtering issue.  If I put my hand over the snorkel...the throttle response is great...no sputtering.  Any ideas would be most appreciated.  Thanks

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When you mention 2 turns out, do you mean two whole turns? Because that's a bit lean for an open airbox and clean filter for fall, let alone the coming winter.

 

What's your needle position?

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Typical of being very lean on the needle - have you left out the white plastic spacer that sits under the needle clip?  Also did you check the pilot airways were all clear, just blowing air through them won't necessarily clear them.  Pilot air jet on the airbox manifold side,  - see arrow on pic, its a different carb but same principle. and the middle hole is the main air jet.  Blow in the pilot air jet and it needs to come out the pilot jet (in the bowl), the fuel screw (take it out first) and the exit into the carb bore.

1126918085_FCRCarbAirJets.jpg.3ebe605e92815ef272b13e3c8bcf46a6.jpg

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On standard jetting these bikes will run bad if you leave off the airbox side, or chop a hole in the top, so leave all that standard/fitted for now until you have it running properly.

Is the diaphragm fitted correctly and not split? What size main jet and pilot?

Edited by thedktor

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On 11/5/2018 at 7:55 AM, Foil said:

When you mention 2 turns out, do you mean two whole turns? Because that's a bit lean for an open airbox and clean filter for fall, let alone the coming winter.

 

What's your needle position?

It’s 2 full turns out.  The needle I have has only 1 notch and a white spacer that goes underneath. Ive gotten a thumb screw adjustable fuel mixture screw I’ll be installing so I can make adjustments while the carb is on the motor.

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17 hours ago, thedktor said:

Typical of being very lean on the needle - have you left out the white plastic spacer that sits under the needle clip?  Also did you check the pilot airways were all clear, just blowing air through them won't necessarily clear them.  Pilot air jet on the airbox manifold side,  - see arrow on pic, its a different carb but same principle. and the middle hole is the main air jet.  Blow in the pilot air jet and it needs to come out the pilot jet (in the bowl), the fuel screw (take it out first) and the exit into the carb bore.

1126918085_FCRCarbAirJets.jpg.3ebe605e92815ef272b13e3c8bcf46a6.jpg

The white spacer is in there.  I cleaned all the passage ways with gumout and compressed air.  Also got a rebuild kit that  replaced all the jets including the 2 on the intake of the carb.  

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17 hours ago, thedktor said:

On standard jetting these bikes will run bad if you leave off the airbox side, or chop a hole in the top, so leave all that standard/fitted for now until you have it running properly.

Is the diaphragm fitted correctly and not split? What size main jet and pilot?

The air filter is back on and side door screwed back on and rubber snorkel back in place.  The diaphragm on the carb was in good shape.  Not sure what the main and idle jet sizes are, I’m guessing stock.  I’ll have to take it off to check.  So the last thing I did was put three pieces of electrical tape across the top of the rubber snorkel on the top of the air box and the throttle response is perfect.  Thoughts? I’m going to install that thumb adjustable fuel mixture screw.  When I do that I’ll check the idle and main jet sizes.  Would the type of air cleaner be affecting the air flow (too much)?  

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If it runs well with that small an opening, then I'd say it's running much too lean, but then again, with a stock bike it really shouldn't be that bad.

 

Have you checked for air leaks around the carb?

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10 hours ago, Foil said:

If it runs well with that small an opening, then I'd say it's running much too lean, but then again, with a stock bike it really shouldn't be that bad.

 

Have you checked for air leaks around the carb?

Checking for air leaks around the carb...is that where you spray starting fluid around the rubber intake on the cylinder, etc to see if the rpms go up? 

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OK so its not a question of adjusting the fuel screw so leave that alone for now and make sure all the passages are clear.  And I would check the main jet size first as if its too small you will get the same issue.

Back to the air jets as per my pic above, the pilot air jet is about 1mm and the main air jet is smaller about 0.7mm, check they are not the wrong way round!  They are the opposite size to what you would think logically...

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22 hours ago, thedktor said:

OK so its not a question of adjusting the fuel screw so leave that alone for now and make sure all the passages are clear.  And I would check the main jet size first as if its too small you will get the same issue.

Back to the air jets as per my pic above, the pilot air jet is about 1mm and the main air jet is smaller about 0.7mm, check they are not the wrong way round!  They are the opposite size to what you would think logically...

Ok...took the carb off to add the thumb adjustable fuel air mixture screw.  Here’s a pic of the air jets:

Looks like I have the larger jet in the center hole and the smaller one to the right.

A852E5FB-947F-478A-9C52-F563CAE27D34.jpegAlso took a look at the fuel jets I put in from the rebuild kit: 37.5 idle and 127.5 main 

Edited by gwoods27

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Ah you are making us work hard with this one!   

From your pic it looks like the air jets are correct, the middle one should have a hole about 0.7mm, the right (pilot) should be about a 1mm hole.

 

So, you say you have the white spacer that fits under the needle clip, what about the white spring locator that goes on the other side of the needle clip, on top?

We are running out of ideas, next thing is to put a bigger main in, start with a 130. , or raise the needle with a small 1mm thick washer. I have done this with one of mine to fix a similar problem.

 

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On 11/10/2018 at 4:35 AM, thedktor said:

Ah you are making us work hard with this one!   

From your pic it looks like the air jets are correct, the middle one should have a hole about 0.7mm, the right (pilot) should be about a 1mm hole.

 

So, you say you have the white spacer that fits under the needle clip, what about the white spring locator that goes on the other side of the needle clip, on top?

We are running out of ideas, next thing is to put a bigger main in, start with a 130. , or raise the needle with a small 1mm thick washer. I have done this with one of mine to fix a similar problem.

 

Verified the jets .7mm in the center hole and 1mm in the hole to the right.  

Heres a pic of the needle setup

 

CC51796B-FE48-416C-86ED-A70C46141C07.jpeg

78B61B3C-6DFC-445E-A020-17673376BFEB.jpegThe spring sits on the top white spacer.  Next thing is to order the jet kit...got any recommendations?

Edited by gwoods27

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Ok that is all good.  I can see the needle is quite a lean one ie fat.  You could try a very cheap experiment and raise the needle 1-2mm with washers under the clip -  I am pretty sure that will help.  A needle with grooves has each groove 1mm apart to compare.  If you can't find small washers you could make some from some plastic sheet, eg an old oil can.

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