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Discussion Starter #1
Hey you, yes you, I really need your help. You have little knowledge, you have a lot of knowledge, I don't care, what I do care about is finding out what in the world is wrong with my bike, and I know regardless of the amount of knowledge you posess about quads, you still can contribute to the fix.
Now this might seem a little long but please, please bare with me, and the topic title does not do my problem justice.

I have a 2004 KFX400, Sparks pipe, K&N pro flow kit (no lid), 175 Mikuni main, stock pilot, Dynojet needle w/ clip on 3rd notch, fuel/air screw either 2 1/2 or 3 turns out. Now I have had so many people on here say that I'm probably going to be running rich, but prior to this problem, my bike has been running flawlessly, neither lean nor rich, I felt the gain throughout the entire range.

Then today comes! I go for a warm-up ride, seemed a little funny with the delivery of the power, but I usually ride it a little longer and everything falls into place perfectly with no problems. Anyway, I came in, waited a few minutes, then decided to go out for a hard ride. And that is when all my problems began.

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Problems(plural)
First, it takes a while until it kicks over (unacceptable), however, switched the petcock to primer, and now it takes half as long (faster, but still unacceptable). So I get it started, sometimes it idles fine, as if there isn't any problems what-so-ever, but sometimes it will just bog down and turn off, I need to rev it in order to keep it running, then eventually it will idle fine on it's own. However, the idle sounds a little sporadic at times, this never happened before. So I take it out and it starts off well, then when I start to really ride, it acts up. If I apply constant throttle, it will keep running, as soon as I let off the throttle a bit and start to hit low RPMs, and try to let it idle, the bike immediately shuts off if I don't rev it up again. It seems as if it's starving for fuel when it tries to idle on it's own.
*(Scenario: I'm pounding it in 3rd, I'm approaching a berm(sp?), so I start to down-shift, as I make my way into the berm I'm in 2nd, rolling into the berm with the momentum that I already have, now when I'm down-shifting I let off the throttle a little, and then I rev it up again and wait to pop the clutch so that I can do a major berm hit/spray, and then exit the turn in 3rd once again. At that exact moment when I let off the throttle, my engine will cut out when it is in fact suppose to idle until I start to rev it up again.)*
Running the bike in primer mode, helps really little. It might give me a second or a 1/2 of a second, before it will shut off.
Another problem occurs when I am actually trying to pound it, 3rd and up. the bike will start to bog and the power delivery becomes very sporadic. It feels like a miss hit with the power, and then right after that little bog it will give sort of a half-a$$ power deliver, neither smooth nore constant.

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Attempts to Fix:
The first thing that came to mind was a dirty carb. Opened it up and sure enough there was some dirt in there. Blasted the entire carb with a ton of carb cleaner, every nook and cranny you can think of. So I figure, problem fixed, but I was wrong. So I cleaned it again, to really make sure I got everything, and it still wasn't a fix. And yes I even did it a third time. I also cleaned the fuel hose that connects the petcock to the carb, figure maybe something got into the fuel tank, and some how lodged itself somewhere, obstructing the flow of fuel, and still no fix. I changed my spark plug, no fix. Before this started happening, I didn't touch anything in the motor, or in the carb, the only thing I touched was my suspension.

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An Idea:
Could something have gotten into the petcock? Before today, I had not started my bike for almost three weeks, maybe something got settle in the tank and then was sucked into the petcock not allowing fuel to be freely sucked in without throttling. Another factor that's making me think it has something to do with the petcock is, when ever I'd take the carb out, the fuel-line would leak fuel, not a lot, but a small steady stream. The flow of fuel performed with a vaccum effect, right? So it shouldn't leak anything, it did not leak like that before. What do you think?


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If you read the whole thing, I thank you, even if you don't have a clue as to what's wrong, I still thank you for atleast hearing my problem out, I really appreciate it.
Again, if you have even the slightest idea as to what's wrong, or an opinion, please let me know.

thank you
 

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From what I read, the motor is stock. Your check of the fuel delivery system was great but did you actually check the petcock out?

If you have stock carb, check out the choke system. Several things involved with it could create these conditions.

1)choke lever partially in choke position. Cable could be stuck.
2) Choke mechinism in carb froze up. Cable would probably still move.

Let me know what you find
z400racing
 

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Discussion Starter #3
Thanks man, I really appreciate the help.

I was planning on thoroughly inspecting the petcock on Friday. I'm also going to take out my jets to make sure that there isn't any dirt or a really small rock that somehow made it's way into the jet and clogging it.

thanks again, and I'll let you know what I find.
 

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Something that comes to mind for me is maybe water in your gas. I have had this happen to me and it did the same thing as your quad. empty the gas tank, empty the "bowl" on the carb and put new gas in. if you arent using 93 octane try it. I hope my information has helped.


Doug
 

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Im with crazy, check your gas. That would be a quick and easy fix if it is the problem. did you add any additives to the gas?
Good Luck Man!!
 

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Discussion Starter #7
QUOTE
Something that comes to mind for me is maybe water in your gas. I have had this happen to me and it did the same thing as your quad. empty the gas tank, empty the "bowl" on the carb and put new gas in. if you arent using 93 octane try it. I hope my information has helped.[/b]
I'm gonna empty my gas on Friday when I inspect my petcock assembly. I always run 92 octane, the funny thing is I run better gas in my quad than I do in my car. Before Sunday, when the problems started, the bike was running fine, and I hadn't opened the tank, so I was still using the gas that was left over from the last time I rode. But I'm going to try everything.
Thanx Crazy

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QUOTE
Bump your pilot to a 27.5 and turn your a/f mix out to about 2.5 turns.[/b]
I was thinking about messing around with my jet settings, however, prior to this past Sunday, everything was running perfectly. I haven't done any power modifications what-so-ever. How is it that my settings will all of a sudden stop working? That's where I get confused, but I'll start messing with my jetting after I try everything.
Thanx bvstone

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QUOTE
Im with crazy, check your gas. That would be a quick and easy fix if it is the problem. did you add any additives to the gas?
Good Luck Man!![/b]
I never add any additives to my gas. But thanks anyway safetyman.
 

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Slurpee ... i think same thing happened to me ... My main was lean , The quad run great and last weekend suddenly bog ... I think it cause wheater coming very cold (5 C) , i also shim my pipe and taht maked a little leak ... Ill mess with it this week end ...
 

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Yes, I still believe you are way too rich(refer to my mods, which are dead on). Leave your pilot alone, you don't need that until you get cams. I say jack up your idle screw (The big black knob on the left of the carb) it's very possible that you accidentally bumped it when you kept messing with the carb. I also think the choke cable is stuck. try the easy before the complicated because it seems like a simple fix.
 

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Discussion Starter #10
Originally posted by DVX Rider@Oct 20 2004, 07:34 PM
Yes, I still believe you are way too rich(refer to my mods, which are dead on). Leave your pilot alone, you don't need that until you get cams. I say jack up your idle screw (The big black knob on the left of the carb) it's very possible that you accidentally bumped it when you kept messing with the carb. I also think the choke cable is stuck. try the easy before the complicated because it seems like a simple fix.
I've been getting that from a few people. They all tell me that I'm probaly running rich, however, everything is perfect, well, everything was perfect until this problem started. From it's low end grunt, to the hard hard hitting mid, and all the way up to the screaming top end, my bike seemed flawless. The power delivery was, for lack of a better word, "buttah." Believe me I had messed with the idle screw throughout the day. And yes I have had experiences where I had accidentally hit it. Now, when you say the choke cable might be stuck, what exactly do you mean? How does it get stuck? I inspected the cable and saw no problems externaly, and the choke seemed to work fine.

My cousin was the first to ride the bike that day that it started to act up. He said that the problem might have started when he almost flipped with my quad. I'm thinking, well I'm hoping, that when the bike jerked and almost flipped over, some how a piece of dirt or a small rock made its way into one of my jets and lodged itself somewhere where a simple blast of some carb cleaner couldn't dislodge it.
 

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Make sure your carb intake boot is tight and/or not cracked.(boot between the cylinder and carb.)Shouldn't be broke as the quad is a 2004 but you never know.

When you pull the carb off Friday, look at how the choke mechanism works. I haven't had a stock carb in a long time to be able to explain it to you.The choke is a fuel enrichment system, not a butterfly to close off air flow to the venturi.

Keep me informed. z400racing
 

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Discussion Starter #12
I'll make sure to check that out.

thanks z400racing
 

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Discussion Starter #13
Well it's Friday, and I made my attempts at fixing my problem.

Attempt - The first thing I did was give my carb another good cleaning, mind you this is the 4th cleaning, however, this time I unscrewed all of my jets and blasted the hell out of the carb with carb cleaner, not leaving anything uncleaned. I also cleaned all the hoses, making sure nothing was obstructing the flow of fuel. Then I decided to empty and filter out my gas tank and clean it. After examining the filter screen of the funnel I noticed alot of crap(sediment). Some small grains of rock, dirt, and some things that appeared to be small metal or paint chippings, weird :wtf . Unscrewed the petcock assembly and started to shoot out the tank with some carb cleaner, letting whatever was left to drain out throught the petcock holes. Then I proceeded to give the petcock a thorough cleaning. After giving the tank, the petcock, and all the hoses a good cleaning, it was time for a test.

Test - To my surprise it started good. I let it idle for a minute, sometimes it would sound like it wanted to die, but it didn't, I didn't even have to rev it or anything :) . Proceeded with a ride in the lane. I got it up to third, clutched it, and then started to down shift, keep in mind this is where the problem would occur. As I'm down shifting from third I let the engine try to come down and idle by itself, at first it sounded a little weak, but it idled steady, and didn't cut out. I thought it was just a fluke, so I tried the same thing again, and then I tried a little clutch work and played around in the low RPMs close to idle, seeing if it would starve for fuel. Well, I'm happy to report that the bike seems to be running like clockwork, but I'm not signing any checks just yet, and I hope that I haven't already jinxed myself. I have to wait until Sunday to give it a thorough test, Sunday will be the moment of truth. I just hope that was the fix, because I don't want to spend another Sunday fixing my bike rather than riding it.
 

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Discussion Starter #15
Originally posted by Mudslinger@Oct 31 2004, 09:01 AM
I was running a 175 main with my mods in my sig, ran great, pulled hard, wasn't too rich, (mikuni jet).
Hey, finally someone who knows where I'm coming from. :thumbsup:
 

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Hey there hoping you guys are still willing to give a hand .. an also did that fix the problem with your bike ? .. my bike has been doing pretty near the exact same thing sense maybe few months after I bought it .. when I first bought second hand the guy Dident have the choke cable said one was orderd on way but insisted I still take for quick test ride . Remind you this is my first quad let alone learning the shifting ,so hard for me to say what is normal sounding or acting or not .. anyways I really wanted to try bike when I got home but sounded like was sucking to much air so I put a piece of paper towel in hole to test again up dirt road then put away till choke came in .. I never installed choke before but watched a video an as far a I know I installed right , it deffintly acts like the choke is working when cold starting .. anyways after that started thinking I could hear some sort of slapping nose every time I let off throttle ,anyway eventully my friend said he could try to change timing chain .. while he did that I’m prettt sure a bolt stripped hole on cam cover so he had to heil coil it an honestly I’m not sure if he knew what he was doing but I got bike back seemed to work alright I’m pretty sure anyways .. then I did notice once when I flipped backwards an broke wheelie bar it really acted up an stopped starting with electric an only way to Start was to jump start it everytime ... but noticed like you said everytime you would go to down shift or let off gas it would stall out an would jump start on the fly again , only time it would idel on it’s own an start with electric was when it was already running for awhile an motor really hot ... also noticed it kinda bogged some .. once again sent to a friend of a friend an once again he said he knew what was doing an that who ever opened head before made mess and hoping it stays .. he said he set values , an timing chain was good (I thought I could hear slapping sound again ) . Got bike home worked alright but backfired everytime I let off gas , sounds like going to cut out everytime it’s ideling or I try to press throttle lightly , but it was starting on its own so to me that was the main thing ... then once again I start getting use to bike an driving it I started trying to stay up doing wheelies again an once again went over broke wheelie bar (third gear on a rock road ) .. soon as I got back on bike in really bad pain it started the whole only starting with a bump start Not electric, an was still back firing bad and was at the point that I just wanted the bike I bought to work right an tired of bringing it to people for cheap an it still acting up right after .. anyways sent to a dealership that charged 95 $ a hour to finially just get it done right .. anyways 1200 $ later witch the guy said ( I may have them mixed up but said ) my exhaust value was way to tight , an intake was way to loose , (I don’t know much about them an was year ago so might of got witch one tight an loose wrong An also said he thought it could of been bent an if so wouldent be good but would let me know , an I’m pretty sure the only other part he called an said I needed a new carb kit that that’s why the gas always dripped outta overflow when had parked .. anyways I said ok fix that to I just want my bike working 100 % an not to have any problems for the summer like the last two .. when I go to get bike dealership packed with people , so couldent even talk to guy who worked on bike but the guy at desk said everything went good took him little longer but done now an 1200 $ pretty much 900$ Labour .... the guy gave me key an said my bike was out back an that I could use ramp to load .. first thing I go to start it ( mind you it’s pouring rain outside an I gotta load myself everyone busy inside).. start the bike an electric start works so was happy bout that but noticed every tome I hit gas it back fires still an it was like bogging when I was in In first to third , soon as I left to go back to work I kept trying to call the guy who worked on it to tell him that the only thing different is that my bike now starts everytime but the backfiring an bogging like not getting all the power or something , an acourse have to leave him a message 3 different times an he never got back to me again .. so once again I gave up on my bike an hope of getting it fixed an so mad I paid 2700 for it an been nothing but money sense so said that’s it for spending on it.. also I noticed my throttle cable was sticking sometimes so said frig it I’m not paying no on an I bearily know any thing about them but I’m doing it myself .. I changed cable an noticed where my slip on meets the header pipe the seal looked all bent an the pipe looks pulled out some where I can see a part of the slits that are suppose to be on the inside pipe , then noticed my slip on the tip was all bent up must be from all the times I went over doing wheelies on payment an feild ,, now I’m really starting to think that is the whole problem with the backfiring when letting off gas an the not feeling like it has all the power it should .. I say that to some people but they still think could be valves or carb , but I’m really determined it’s how the slip on isent sealed right to header and that’s why it never backfired when I first got the bike ( witch I would tell people that it would of backfired when I first got the bike if it had to do with being jetted right , an the two last people one being dealership both said they settled the valves so shouldent be that .. I just bought an installed heat wrap that’s suppose to go like steel yesterday am hoping today it will be hard an I will be able to tell if that was the problem all along or not, cause I’m not spending no more big amounts unless I know for sure it’s the pipe then I would almost want to just buy a full exhaust instead to make sure it’s good.. really hoping someone will take the time to read this really long story an sorry for being so long but this has been driving me nuts for the last 3 years I just want to have it good for this summer .. ( also when I was reading your story about what happend to your bike the whole time I wanted to message you to see if maybe you have ever flipped your bike doing wheelies but read threw it all hoping for a answer , I kept thinking in my head if he never flipped doing wheelie wounder if he’s got any buddy’s like mine who would try an run er hard end end up crashing an sure enough you said at the end your friend drove it an almost flipped it lol so probably more then likely did an maybe we could have same problem .. hoping you have a answer 16 years later lol
 

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That has to be a record for the world’s longest sentence! I’m also quite sure this guy is long gone after 17 years.

With that said, I have very little info to go off of like carb jets and settings, air box lid on or off, etc. I agree your problems sound more like improper jetting in the carb. Depending on how bad the exhaust is smashed, it can also effect how it runs. Think airflow and back pressure. Other possibilities are a dirty air filter, dirty carb, valves closed up again, etc. Too many variables.

I wouldn’t give a dealership $1,200 to rebuild the engine, let alone play with the carb and adjust valves. That’s why they call them stealerships. You got robbed.

Personally, you need to find a mechanic with a good reputation that knows these quads. I don’t know what year yours is, but it’s at least 12 years old and sounds like it may have had a hard life. The older the machine, the more maintenance it needs. If you don’t feel comfortable doing it yourself, it’ll break you in repair and upkeep costs. Not trying to sound harsh, but that’s just the reality of it.
 
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