KLX with pumper carb starts only with open throttle.
#1
08-06-2013, 08:18 AM
KLX with pumper carb starts only with open throttle.
Hi!
Short prelude: My 94' el. starter KLX was starting really well hot or cold for about an half a year after I bough it in well used condition. Than after some hard off-road use some starting problems appeared. I left my bike to mechanic who serviced it (New piston rings, new valves, cylinder polished). But, unfortunately, some starting problem remains.
Then I changed the original carb to Mikuni TM33 pumper one + fitted the original sport exhaust from the kxf. Now I still have a specific way to start my bike: I have to open a throttle on about 1/4 while the starter spins to get it running. Sometimes it takes a second to start it hot or cold, sometimes, when even it is hot, I have to spin it for about a minute or more.
And one more interesting issue - when it is cold, I'm using choke to start it, but I have to close the choke immediately right after it starts to remain it running.
Will be happy to hear any ideas! I already showed my bike to 2 mechanics (One of them was from the Kawasaki dealer's workshop) - but they have no ideas how to fix it, just saying that "KLX's always have such issues").
Short prelude: My 94' el. starter KLX was starting really well hot or cold for about an half a year after I bough it in well used condition. Than after some hard off-road use some starting problems appeared. I left my bike to mechanic who serviced it (New piston rings, new valves, cylinder polished). But, unfortunately, some starting problem remains.
Then I changed the original carb to Mikuni TM33 pumper one + fitted the original sport exhaust from the kxf. Now I still have a specific way to start my bike: I have to open a throttle on about 1/4 while the starter spins to get it running. Sometimes it takes a second to start it hot or cold, sometimes, when even it is hot, I have to spin it for about a minute or more.
And one more interesting issue - when it is cold, I'm using choke to start it, but I have to close the choke immediately right after it starts to remain it running.
Will be happy to hear any ideas! I already showed my bike to 2 mechanics (One of them was from the Kawasaki dealer's workshop) - but they have no ideas how to fix it, just saying that "KLX's always have such issues").
#2
08-06-2013, 08:53 AM
Sounds like your pilot circuit is WAY too rich. The open throttle while cranking the starter over trick is what you normally do when the bike is flooded as it allows the engine to suck in a lot more air to get the air/fuel mixture right to fire. The symptom you describe with needing to shut off the choke immediately when starting cold backs this up as you sound like you are litterally "choking" the engine with too much fuel if you leave the choke on.
When you start is there a strong smell of fuel in the air? I would guess there is.
Maybe take the carb off and give it a good clean so you are sure there is no gunk in there making any parts stick. Then check your fuel screw is between 1.5 and 2 turns open (turn clockwise till the screw is seated firmly - not too tight - then turn out counter clockwise 1.5 to 2 turns).
As a matter of interest, once the bike is started and warmed up, give the bike a quick rev to about 1/2 throttle then let it return to idle:
- If the engine drops below idle for 1/2 a second and then returns to idle, or maybe even dies in your case, it is too rich. Wind the fuel screw in/clockwise half a turn to lean it out.
- I think this is less likely in your case, but if the engine hovers just above idle for a second or two then settles the bike is too lean. Wind the fuel screw out/counter-clockwise a 1/4 of a turn at a time then repeat till it returns to idle properly.
If you have to have the fuel screw at less than 1.5 turns out then your pilot jet is too rich and you need to drop a jet size. If you have to have the fuel screw more than 2.5 turns out then your pilot jet is too lean and you need to go up a jet size.
I know it might sound strange that the carm and jetting worked before but doesn't anymore, but you may have had poor compression before and the richer fuel mixture compensated for it. Or it might be something else, I don't know, but my gut feel is that your pilot circuit is too rich.
When you start is there a strong smell of fuel in the air? I would guess there is.
Maybe take the carb off and give it a good clean so you are sure there is no gunk in there making any parts stick. Then check your fuel screw is between 1.5 and 2 turns open (turn clockwise till the screw is seated firmly - not too tight - then turn out counter clockwise 1.5 to 2 turns).
As a matter of interest, once the bike is started and warmed up, give the bike a quick rev to about 1/2 throttle then let it return to idle:
- If the engine drops below idle for 1/2 a second and then returns to idle, or maybe even dies in your case, it is too rich. Wind the fuel screw in/clockwise half a turn to lean it out.
- I think this is less likely in your case, but if the engine hovers just above idle for a second or two then settles the bike is too lean. Wind the fuel screw out/counter-clockwise a 1/4 of a turn at a time then repeat till it returns to idle properly.
If you have to have the fuel screw at less than 1.5 turns out then your pilot jet is too rich and you need to drop a jet size. If you have to have the fuel screw more than 2.5 turns out then your pilot jet is too lean and you need to go up a jet size.
I know it might sound strange that the carm and jetting worked before but doesn't anymore, but you may have had poor compression before and the richer fuel mixture compensated for it. Or it might be something else, I don't know, but my gut feel is that your pilot circuit is too rich.
#3
08-06-2013, 01:16 PM
Arctra - Thank You for a detailed answer! There definitely was a petrol smell on starting, I even inspected fuel pipes but didn't find a leak. I will take off current carb and will try with my original one (But the strange thing is that, as I remember, I was having problems with the original one as well).
By the way, what are right jet sizes for Mikuni TM33 jetting for KLX 250 engine?
By the way, what are right jet sizes for Mikuni TM33 jetting for KLX 250 engine?
#4
08-08-2013, 10:31 AM
Yesterday switched my pumper carb back to original CWK. Unfortunately, bike starts absolutely in the same way. Still have to pull throttle to start it. That made me thinking that problem is not in carb. Filter is freshly washed and lubed & brand new spark plug. Bike runs really good, but what to do with starting if it is not a carb's fault?
#8
08-11-2013, 09:13 PM
Sounds like both carbs have clogged idle circuit to me. The idle circuit is always the smallest ,of course. That's why they always clog first, and are the hardest to clear. I recommend an inline fuel filter on everything.
good luck
marc
good luck
marc
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