Joined Nov 2012
2K Posts | 821+
Iceland
I don't know how generalizable this is, but when tuning the fuel screw on the stock DR-Z400S's Mikuni carb, the pilot jet is wrong if the fuel screw cannot stall the bike if all the way in. In other words, turning the fuel screw in should stall the bike (or at least make it idle roughly).
ya u got to be carefull with the dellorto carb the parts wearout fast and need to rebuilt often.i had a 94501 fe and was doing same thing I had to replace needle jet and seat,floats,and the float valve. rebuild kit is about $115
Joined Nov 2012
170 Posts | 0+
Transilvania
The bike is a 2003 FX 650. About the jetting I can't really say anything. I never had the carb apart, all I know is I was fiddling with the mixture screw about a month ago and when I screwed it all the way in, the bike stalled. And this time it didn't. The main thing that led me to check this out was the fact that I was riding this weekend and in 5th and 6th gear when I agressively accelerated, the bike choked for a second and only then it started pulling. And also the e-start stopped working and when the bike is hot and you kickstart it, it start to build up revs slowly. Meaning that it barely starts on the first kick and then if you don't use the throttle it chokes. It also started backfiring. Upon decelarating whit engine break it starts popping.
Cheers, Tom
Cheers, Tom
Joined Mar 2009
1K Posts | 251+
Portugal
Hi Tom
If the bike was ok and then not ok, and you didn't opened the carb, it's not the jetting.
From what you are saying you have too much gas in the pilot area, so something has happened to make this.
I'm assuming it's a Dellorto. You must take the carb and open it, clean it and check it. Check the air passages that comes from the back of the carb (one is closed) take out the air filter adapter and also check that little piston that you open when you pull the choke.
And basically check everything.
:cheers:
ZAGA
If the bike was ok and then not ok, and you didn't opened the carb, it's not the jetting.
From what you are saying you have too much gas in the pilot area, so something has happened to make this.
I'm assuming it's a Dellorto. You must take the carb and open it, clean it and check it. Check the air passages that comes from the back of the carb (one is closed) take out the air filter adapter and also check that little piston that you open when you pull the choke.
And basically check everything.
:cheers:
ZAGA
Joined Nov 2012
170 Posts | 0+
Transilvania
Finally got around to clean the carburetor! It was a little dirty and floaters weren't quite parallel but I fixed the floaters and put them as they should be,cleaned it out and put it carb back in place. Fired up on the first kick. Went around the courtyard a couple of times in 2nd gear and no stalling yet. Tomorrow will be the real test. Will post tomorrow as well.
Thank you again, Zaga
Thank you again, Zaga
Joined Nov 2012
170 Posts | 0+
Transilvania
Final report .
The bike starts well without choke, idles great,cold and hot, doesn't stall if you pull the throttle aggresively but stops if you pull the choke. What could be wrong now? I did check the routes on the choke and all seems fine, the mechanism seems to close well. Oh and the bike still runs if you screw the mixture all the way in, but it does get a pretty ruff idle, in other words it barely stays running.
Cheers, Tom
. The bike starts well without choke, idles great,cold and hot, doesn't stall if you pull the throttle aggresively but stops if you pull the choke. What could be wrong now? I did check the routes on the choke and all seems fine, the mechanism seems to close well. Oh and the bike still runs if you screw the mixture all the way in, but it does get a pretty ruff idle, in other words it barely stays running.
Cheers, Tom
Joined Mar 2009
1K Posts | 251+
Portugal
Hi Tom
Good to ear it's all running well.
All the things that you are saying suggests that your pilot jet is a bit too big, so when you pull the choke and your bike should idle very ruff the bike stops and when you close the pilot screw and your bike should stop it idles very ruff.
When you set the pilot screw to the best idle speed, how many turns out do you get ?
Did you take notes about your jetting when opened the carb ?
If you don't have a problem running with that setup it's ok to leave it like that, too much gas wont kill your engine, if it was the opposite then it could ruin the engine.
:cheers:
ZAGA
Good to ear it's all running well.
All the things that you are saying suggests that your pilot jet is a bit too big, so when you pull the choke and your bike should idle very ruff the bike stops and when you close the pilot screw and your bike should stop it idles very ruff.
When you set the pilot screw to the best idle speed, how many turns out do you get ?
Did you take notes about your jetting when opened the carb ?
If you don't have a problem running with that setup it's ok to leave it like that, too much gas wont kill your engine, if it was the opposite then it could ruin the engine.
:cheers:
ZAGA
Joined Nov 2012
170 Posts | 0+
Transilvania
I turned one and a half turns on the mixture screw. As I noticed after started screwing outwards from all the way in and the bike was still running that the bike reached maximum idling after 1 turns the rest didnt make any difference no matter how many turns. I am just a bit worried how it will start in the cold... it seems that using the choke isnt on option and it may not start whitout it !?
Cheers, Tom
Cheers, Tom
Joined Mar 2009
1K Posts | 251+
Portugal
One turn out it's inside the correct range for the pilot screw, and if you go further it doesn't make any difference it's normal. You should do this with the bike hot.
Did you checked the o-ring in the pilot screw ?
I still think you are rich in the pilot area. Jetting ?
The bike should need choke when cold.
:cheers:
ZAGA
Did you checked the o-ring in the pilot screw ?
I still think you are rich in the pilot area. Jetting ?
The bike should need choke when cold.
:cheers:
ZAGA
Joined Nov 2012
170 Posts | 0+
Transilvania
I did check to O ring and it is good, it looks new to me, it has no wear marks. About the jetting, Im not quite sure what I should be looking for in that area , so that beats me . All I know is that since I cleaned the carburetor warm starts are much better and even cold it starts on the first or second kick. About the e-start, I believe it is the auto decomp mechanism to blame, since if I start playing with the manual decomp lever it fires up after a while, plus it sometimes slips from that clutch mechanism where the starter is situated.
Cheers, Tom
, so that beats me . All I know is that since I cleaned the carburetor warm starts are much better and even cold it starts on the first or second kick. About the e-start, I believe it is the auto decomp mechanism to blame, since if I start playing with the manual decomp lever it fires up after a while, plus it sometimes slips from that clutch mechanism where the starter is situated.Cheers, Tom
Joined Mar 2009
1K Posts | 251+
Portugal
Hi
The pilot jet is were I've pointed and it has number written on it, it's that number that I would like to know.
About the e-start, you are right, it's probably the autodecomp and it's spring to blame. It can be changed. Also the starter has one clutch inside the motor and some times also can be blamed. Don't what to scare you mate Probably you can solve all that with the autodecomp.
Please do me a favour, check your bikes engine number and post them on the engine numbers that I've started.
Thanks
:cheers:
ZAGA
The pilot jet is were I've pointed and it has number written on it, it's that number that I would like to know.
About the e-start, you are right, it's probably the autodecomp and it's spring to blame. It can be changed. Also the starter has one clutch inside the motor and some times also can be blamed.
Don't what to scare you mate Probably you can solve all that with the autodecomp.Please do me a favour, check your bikes engine number and post them on the engine numbers that I've started.
Thanks
:cheers:
ZAGA
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