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Won't start unless chokes out and revved.

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This is not new but thought I would ask. Bike will not start even if its 90 deg out without out the choke and throttle assistance.Any ideas?

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This is not new but thought I would ask. Bike will not start even if its 90 deg out without out the choke and throttle assistance.Any ideas?

specify current carb settings and mods please.

does it continue to run after it's started or it won't idle at all?

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Hey all,

I am once again visiting this site after being held hostage for nearly 7 years since my last visit. I will be following along on this thread in attempt to diagnose the same problem as the OP.

I just picked up an '03 400S from my Bro-n-Law, I had sold it to him a few years ago when I was purchasing a new home, now I'm going to try to get it back into running condition. When I sold it to him, it ran beautifully, full power, great idle, mid was strong, fired up every time without any cranking needed.

Now it will start only under throttle and choke pulled out, once you press in the choke it stalls and will not start without the choke. If I can keep it running it will pull hard and clean through the gears just off 1/4 throttle and pull clean to the top. Once the throttle is released it dies and cannot be started until the choke is pulled again.

History on the bike:

I purchased the bike new in 2003.

Installed the HotCams intake cam,

Kientech air mixture screw,

rejected the carb I believe I used the Dyno Jet kit.

Still currently running a stock exhaust.

3x3 air intake mod.

Aftermarket air filter, lightly oiled.

Again the bike ran solid when I sold it to him, now it stalls without the choke and will not idle.

I will need to get back into the carb to see what jets I had installed but that should not matter as nothing has changed since I sold it to him, he is not a tinkering kind of guy. He simply allowed the bike to set for a year at a time with old fuel in it before riding it on his elk hunt scouting trips. This bike is in mint condition and exactly the way it was when I sold it to him with perhaps 100 extra miles logged on.

I start the process today and will update all of my findings.

Thanks in advance for any help.

👍:smashpc:

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Yea I guess that would help. Fcr, open hmf slip on, 3x3

Jetting:

142 main

200 main air

Emp needle

Clip 3

45 pilot jet

100 pilot air

6000-9000 ft

Just checked the pilot circuit and with fuel screw all the way in it just barely stays running

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I second what Erik said, and would like to add needing choke on a cold bike is normal, and if you don't need choke to start a cold bike your pilot jet is probably too large.

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Okay.....UPDATE on mine.

I'm still running the stock CV carb with a few jet changes. I did learn too that a mechanic from Hinshaws Motorcycle Store has been into the carb a year or so ago, could be why the jets appeared to be messed up from crappy screw driver mis-use.

I tore the carb apart and found the pilot jet was completely plugged.

Cleaned it out and now all back together, runs perfect from idle thru top end, well, I shut it down at 75 mph and it was still pulling hard. But it runs clean through the entire rpm range. HOWEVER.....Now when I slow down to make a turn it dies as it is coming into idle.

I am suspecting the pilot jet is the culprit. I am running a #25 Pilot Jet and when I screw in the FUEL MIXTURE SCREW until it stops or bottoms out, it continues to idle smoothly.

Once it cools I'll pull the carb out and swap the pilot jet to a 22.5, that should take care of the problem I hope. I also need to put a fuel filter inline as I think the gas that was put into it long ago is dirty.

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Just thought I'd mention has the idle screw been fiddled with?

I had this problem and it turnt out the idle screw wasn't set properly so nothing was going from the carb to the engine

Jake

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Just thought I'd mention has the idle screw been fiddled with?

I had this problem and it turnt out the idle screw wasn't set properly so nothing was going from the carb to the engine

Jake

Yes, I set the idle a little high and then after bottoming the fuel mixture screw I pulled the idle screw down and it idled smoothly.

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Yes, I set the idle a little high and then after bottoming the fuel mixture screw I pulled the idle screw down and it idled smoothly.

I think the proper way to test the fuel mixture screw is to set the idle lower (still running but not as high as normal) and then turn the fuel screw to check for changes. Turn the screw in until the idle stumbles and then back it out until it idles smoothly. At that point turn the idle speed back to normal.

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I think the proper way to test the fuel mixture screw is to set the idle lower (still running but not as high as normal) and then turn the fuel screw to check for changes. Turn the screw in until the idle stumbles and then back it out until it idles smoothly. At that point turn the idle speed back to normal.

I did that and had no change. So I set the idle up to keep it from stalling then turned the fuel mixture screw all the way in. After it was in I backed down on the idle screw to see if it would stall, it didn't. That tells me the pilot was too large.

Now I just swapped the 25 pilot to a 22.5 pilot, it's running but still stalls when the idle is set too low with the fuel screw all the way in. I am going to ride it some to get rid of the old fuel then see what happens with fresh fuel. I noticed some oily substance in the fuel bowl. My Brother n law told me he put fuel stabilizer in the fuel tank and it's 6 months old or more.

It runs awesome just off idle and thru the rpm range, so it could be crap settling in the bowl at idle.

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Update

Okay, I let the bike cool down for a couple of hours and tried it again. It started right up without the choke and ran pretty good around the ranch at 6 - 10 mph. Blip the throttle and it pulled hard. Cruised at 25-35 mph, blip the throttle and it pulls hard no hesitation at all.

As it warmed up it began dying again at idle, played with the fuel mixture screw and brought the idle screw up some and it would still stall and die. Does that sound like jetting or possibly something else? It usually fires right up with a little throttle and pulls hard.

So my off idle, mid and top end are dialed in, it's just getting it to continue to idle once it is warmed up is my only issue now.

Current jetting:

Main Jet = 130

Pilot Jet = 22.5

Needle = #2 groove from the top.

Hotcams Intake cam only

Stock exhaust system

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3x3 air intake mod.
Current jetting:

Main Jet = 130

Pilot Jet = 22.5

Needle = #2 groove from the top.

Hotcams Intake cam only

Stock exhaust system

assuming youhave the 3109 dj kit-

needs to be 150 main jet,clip 4,25 pilot jet,2.75 turns fuel screw.

you have mixed up the setting for 2 different dyno jet kits and 3x3 vs no 3x3.

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Eddie, Thank you!! Yes, I am using the 3109 kit.

And a big thanks guys for all the help. I will order up some new jets and try it again.

I'm thinking for the time being, I'll try the 155 Main Jet I have. Since the owner never runs the bike at WOT it may work very well for him with that setup.

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Have you checked the oil for fuel contamination?

Thats good advice.

If fuel leaked past the petcock and float needle valve while sitting, and is now in the oil, then as the bike warms up and the fuel evaporates it exits at the oil separator and the fumes go into the airboot between the air cleaner and carb, making it way too rich. If it is at higher revs it might keep going but at idle it will stall out. See if the oil smells like gas. If it does there could be more than the desired 2 liters of oil, and it won't lubricate very well. No it will not be ok, until after oil is changed.

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Thats good advice.

If fuel leaked past the petcock and float needle valve while sitting, and is now in the oil, then as the bike warms up and the fuel evaporates it exits at the oil separator and the fumes go into the airboot between the air cleaner and carb, making it way too rich. If it is at higher revs it might keep going but at idle it will stall out. See if the oil smells like gas. If it does there could be more than the desired 2 liters of oil, and it won't lubricate very well. No it will not be ok, until after oil is changed.

Yes I have checked the oil, it's clean and does not have a fuel odor.

Current settings:

Pilot Jet = 25

Main Jet = 155

Needle clip on the 4th groove.

I now am experiencing a serious mid range bog

Now, when I set the idle and attempt to make a fuel mixture screw adjustment at below normal idle there is no difference in idle. When I blip the throttle with the fuel mixture screw in snug it will cause the bike to die when it comes back to idle.

If I screw out the fuel mixture screw about 1 turn or so it will idle and with a blip of the throttle it will come back to my low set idle without stalling.

I can reset the idle at near 1500rpm and it will continue to run after a blip of the throttle. It will run smooth with a slight hunt when ridden at 5 - 10 mph in 2nd gear.

When I roll the throttle on tight from a 10 - 15 mph speed in 2nd gear, it will bog real bad and not recover until I back off for a couple of seconds then roll it back on, then it pulls smooth.

Question??? Is there suppose to be an O-Ring under the black plastic cap next to one of the screws on top of the carb? There is a small indentation and if I recall a small hole in the black cap. If so, it is missing which could be creating a vacuum leak.

I don't have a manual for the bike and it's difficult to find a diagram for the stock carb.

The other thing, on the needle, under the clip now set on the 4th groove, is a nylon washer and a small thin metal washer that fit between the clip in the groove and the bottom of the slide, are these suppose to be there?

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Yes to washers under clip. Yes to oring which in conjunction with the carb body acts as a blank off plate for the passage in the black plastic. It is tempting to just epoxy the hole.

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Yes to washers under clip. Yes to oring which in conjunction with the carb body acts as a blank off plate for the passage in the black plastic. It is tempting to just epoxy the hole.

Okay, well the O-Ring is missing and I didn't loose it. Maybe that explains the reason I can't get the idle to change with the fuel mixture screw. Vacuum leak!!

Thanks a bunch :smashpc:

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