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Rejetted- wont start with choke on

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Hi All,

 

I recently rejetted my 03 Dr-z 400. When I got the bike it seemed to start better without the choke and smelled like it was running rich. I figured that the rich condition would be fixed with a rejet which I did today, with a JD jet kit, blue needle, third clip and a 160 main jet. I also added an FMF powerbomb header and a Powercore 4 pipe and did the 3X3 mod. The bike runs fine but it pops and stumbles if I try to start with the choke on. If the choke is off it fires up right away. Is this something that needs to be fixed? Is it running rich and if so, what do I need to change?(needle, main jet, fuel screw etc...) I live in FL where it is typically in the 90's w/ high humidity (during the winter it can get into the 50's).

 

Thanks,

Ace.

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When summer began, I one day went to leave work, where my bike had been sitting in the sun all day, and it would not start. It had been running fine, I knew I had gas, so I started to panic. Then, I thought to try starting it with the choke off. Sure enough, it fired right up. I took it home and adjusted the fuel mixture screw to lean it out. Now, it starts with the choke on, as it should, again. 3X3 mod and re-jetting is only part of it. It sounds like you are indeed running rich. You need to be able to tune the fuel mixture screw, and possibly even move needle clip positions, depending on temperature and humidity.

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Hi All,

 

I recently rejetted my 03 Dr-z 400. When I got the bike it seemed to start better without the choke and smelled like it was running rich. I figured that the rich condition would be fixed with a rejet which I did today, with a JD jet kit, blue needle, third clip and a 160 main jet. I also added an FMF powerbomb header and a Powercore 4 pipe and did the 3X3 mod. The bike runs fine but it pops and stumbles if I try to start with the choke on. If the choke is off it fires up right away. Is this something that needs to be fixed? Is it running rich and if so, what do I need to change?(needle, main jet, fuel screw etc...) I live in FL where it is typically in the 90's w/ high humidity (during the winter it can get into the 50's).

 

Thanks,

Ace.

 

Adjust your fuel screw using this procedure.....http://www.thumperta...ad.php?t=327405

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OK, so I went out and started the bike this morning, it started right away, again with no choke. I took it to a back road and got on it to warm it up and rode home. I shut it off for about 30 seconds to take my gear off and started it again, it hesitated to start, but when it did it ran fine. I immediately started adjusting the fuel screw per Eddie's instructions above, however the fuel screw was fully seated before the idle started to drop, it starts a lot easier hot now, but I suppose I still need a new pilot jet. The JD kit I have only came with a #25 jet, what size(s) should I order? Also, am I OK to ride it like this til the parts come in?

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Are you using an extended fuel mixture screw or the stock one? The bike should shut off with the screw fully seated.

 

Extended = 22.5 PJ

Stock = 25 PJ

Edited by blakestree

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I just went out and double checked, its definitely seated and the bike does start/ run fine. Does this indicate I missed a part on the install? Also, it now runs like it should with the choke on (rpms increase, no more stumble/ popping).

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Did you change the pilot jet to the one included with the JD kit? If so, you need to put the stock PJ back in. Most extended screws have a richer taper.

Edited by blakestree
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Yes I did change the pilot jet, I'll put the old one back in. I had to use a little rtv on the float bowl gasket because it was not in the greatest shape when I took the carb apart. Am I OK to ride the bike til I get the gasket in so I can replace it along with the pilot jet?

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Yes I did change the pilot jet, I'll put the old one back in. I had to use a little rtv on the float bowl gasket because it was not in the greatest shape when I took the carb apart. Am I OK to ride the bike til I get the gasket in so I can replace it along with the pilot jet?

 

Gas eat's most RTV, which can result in small pieces of RTV floating around clogging up passages in your carb. It's generally never recommended to use sealant on a carb, it's asking for problems.

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Right, I put a very small amount on the outer most edge of the bowl, pushed it down, then removed the bowl to make sure none had made its way into the bowl. It's only a temporary fix til I get the new gasket in, I'm just wondering if it's OK to ride like this til I get the gasket.

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Ok thanks, its not leaking after the RTV. I know its not a proper fix, but I figured it would work if I was careful and did used a small amount. So far, so good.

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Ok thanks, its not leaking after the RTV. I know its not a proper fix, but I figured it would work if I was careful and did used a small amount. So far, so good.

 

Hopefully you were precise on the placement with the RTV ....excess won't make your fuel jets happy..... :(

Edited by Craig-o

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I was but even if some get into the jets I have to pull it again to swap the pilot jet so I'll spray the jets with carb cleaner before putting it back on.

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I just went out and double checked, its definitely seated and the bike does start/ run fine. Does this indicate I missed a part on the install? Also, it now runs like it should with the choke on (rpms increase, no more stumble/ popping).

When I first did my rejet w/ extended fuel screw i forgot to take the washer off the old fuel screw and add it to the extended one. Bike just would not run right.Maybe look at that?

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...I'll spray the jets with carb cleaner...

 

Try brake cleaner, instead, followed up with compressed air.

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