Finishing the $800 Kawasaki KFX700 quad
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- čas přidán 24. 07. 2021
- I’m back working on the Kawasaki Kfx700 quad again. It’s still giving me problems. As you know from the last part i’ve check the timing chain on the kf700 engine. I’ve cleaned the carburetor, the engine has spark. I’m starting to think the problem might be a stuck valve or bad timing chain. I’ve heard that the kawasaki kfx700 can have valve issues over time. I at least got the quad running god enough for now and it’s time to put the kfx700 for a bit. Let me know what you guys think the issue could be?
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Gotta step on the brake pedal to go from reverse to fwd. there’s a lockout, that’s part of the reason it’s so difficult to shift.
Just wanted to say that
Think he'd rather be welding than messing with fuel/air mixtures.
😂🤣
Idle is set to low,adjust it when it's up to temperature. Also,with those aftermarket pipes,it sounds like it's lean and needs jetted properly.the popping back through the exhaust indicates a lean condition.
I was thinking the same thing. it need jetted badly for his altitude and pipes.. Its def lean popping
Totally agree. Lean pop is evident.
Looks like it had a filter on it too. Hey Chris, take some plastic and cover half the filter. Run it and see if the popping goes away. Try 3/4 covering the filter also. If it gets better, the carbs are lean like others have said. Easy way to check is find out the stock jet sizes and see if they are still in there. Pipe and exhaust will need a large change in everything, including 2 sizes larger pilots. (Or more)
My thoughts exactly
That's a really common problem with a lot of Harley's, on deceleration the exhaust pulls in fresh air and causes the backfire due to pressure. People change the exhaust and don't get the carb re-jetted or the Injection system Tuned for the new exhaust. Could also be caused by a leak somewhere in the exhaust system causing the backfire.
I would put a stock exhaust back on it. It was probably not jetted for it anyways
I 100% agree the amount of air out doesn't equal to the amount in with fuel its popping and farting stock cans or do cams and valves to match them sweet hmf s
Even an adjustment on the air fuel screw would help
That’s a great find for $800! My money would be on a sticky valve. Might improve with some run time.
You idiot its either the stator or the voltage regulator when one of these components fail it causes pre-detination resulting in a backfire . do your research dude before you give up on a project #buildsnotprojects
Jets, jets, jets!!! Find a stock exhaust and rejet back to factory. Also, let some air out of those back tires. Great videos!
No more likely it wasn't jet with new exhaust
@@SHSPVR Could be. Either way, as I said, I believe the jetting is the problem. I said to get a new exhaust because I personally don't like loud exhaust anymore. When I was younger I did. Now it's just annoying and let's game wardens know where you're at.
@@denniscooper6328 that true
Yes I was going to say same thing or see what size jets you would need for that hmf exhaust
@@justinluce7773 It actually the pilot jet that cause this not the main jet just so you know
Backfiring like that could be the sign of running lean, which could possibly be caused by the aftermarket exhaust.
Its running lean and needs to be re-jetted. That is why its back firing. It also looks like the headers got pretty hot near the engine another indication of running lean.
The HMF exhaust requires carburetor re-jetting. I guess he doesn’t realize that.
That was my thought as well watching the vid. Running lean. Justin W is correct. After-market exhausts require exact jetting
It's the Venturi effect. it's also used in carburetors to suck the gas into the air intake. You were kind of close with the name.
Came here to say the same
Me too 😂
Smarter everday' just did a video on it recently.
You realize the venturi effect is based on Bernoulli's principle?
@@gt1man931 That I didn't know. Also that makes him right then?
I would mess with the jetting. Seems lean. But, there's no shame in taking things to a professional when necessary. I'm a fairly good hobby mechanic but i occasionally run into stuff that i can't figure out and a professional is the best option.
That's what I was going to say lol
For real, I would check the jetting on the carbs. If you can't see the jetting number on the them, just find the stock jetting size and swap them out. Plus you can get a whole jetting kit with different size for like 5 or 10 bucks.
@@Music46and2 it's probably got stock jetting running aftermarket exhaust. My buddy had the same bike with stock jetting and aftermarket exhaust it ran the same way
I am a long time viewer...love this channel and I am thrilled at the success you are having. You deserve it. I love your skills and abilities and your humility. Keep on keeping on!!!
The carbs need to be jetted because it has that performance exhaust system on it
Used to have one of these Kfx’s, they have lots of power and are lots of fun but also gave me lots of issues. When going and switching from reverse make sure your leg is pressing hard on the rear brake to allow smooth switching between reverse. Great vid
I used to race one of these in GNCC"s many years ago and I had the same issue with mine. It came from the cheap idle adjustment cable on these things. It's the cable sticking out the right side (if you're sitting on it correctly), with the little black twisty knob on the end of it. Water gets in there and it corrodes it to where it just stops working. I wished there was an aftermarket option for this piece because it surely needed one. Btw, u have to have the rear brake pressed to shift the gears easily. These bikes were notorious for wearing out their rear brakes often to where the censor wouldn't pick up the brake being pressed to let the bike change gears. I know this is probably a year or so late but wanted to drop a line. Great vid
V-twins are pretty good at cooking long spark plug caps. I’ve had a similar thing in the past. The bad cylinder would get too much fuel due to no Spark then randomly ignite and back fire. The caps can look real good but they have micro cracks in them that arc off into the cylinder head wall. If it does have long spark plug caps I’d whip them out and test them for arcing. :)
Awesome buy Chris.
Found a list for jet sizes relative to running altitude for The KFX700. These are indications only and any mods will affect final sizes. Note the larger jet size in the rear carburetor. Minor adjustment to needle height can be done with shims under the the needle clip as far as I know. Read the plugs after a good run at normal operating temperature.
0- 1,600ft - 135f-140r
1,600- 4,900ft - 132f-138r
4,900- 8,200ft - 130f-135r
8,200-11,500ft - 128f-130r
11,500-14,800ft - 120f-125r
After market exhausts usually need next size larger jets as a minimum.
Those exhaust backfires are usually caused by exhaust leaks that let in outside air/oxygen that explode the un-burned fuel in the pipe.
Good luck mate.
It's called the venturi principle just how your carburetors work as air passes over the hole it creates a vacuum that sucks up fuel or any liquid for that matter great video by the way.
You have a nice four wheeler I hope you get it figured out and have a lot of fun with it
I agree with the running lean aspect. One other thing I have run into is spark plugs. A partially fouled or cracked ceramic plug can give you fits.
Great vid. keep up the good work Chris.
They are a beast of a quad my brother owned one for some time and they have so much torque
Oh my gosh! That is so wild that I did the very same thing yesterday with making a suction with a airhose into the side of a tube pointed the direction you want flow. And now I see you doing the same in a video. Its a very handy thing when you need it. I was sucking squirrel corn stash from breather tubes on a mustang that has been setting for a bit.
Thanks for making me spend 2 hours reading about Bernoulli’s principle and fluid dynamics lol! Seriously though, interesting read.. I’ve heard it in reference to carburetors before so I looked it up
The 700s are insane my friend use to have one an it was freaking sick it pulled really hard. They did have a decent amount of electrical issues tho.
The kfx700 has always been a decent quad when taken care of Rather Be welding will get it figured out Hopefully we can get together and Rip sometime I have a Yamaha Raptor 660r Yamaha Vmax 600 twin hybrid a Honda 300ex big bore stage 2 hot cam T4 Pro Circuit Exhaust a Yamaha Moto 4 350 a Polaris Trail Boss 325 with a Polaris Indy 400 twin a Suzuki Quadrunner 250 my son's 50cc ATV 2 buggys a utv side by side a offroad go kart and 6 Off-road mowers check out our channel
@@phoenixarizona8441 dam bro. Im coming to hang out with you. Lol
Do those carburetors even have idle adjuster screws? Cuz the idle definitely sounds a little low
you can put shims on for low speed fuel and then richen the primary jets for quite a few steps when you havde the duals and k and n, both need more fuel to run right and you should not be driving it lean you will blow the piston if you keep reving it lean and drive it on the trails
Chris had you would've cleaned those carbs and tank in last video we wouldn't have got this great video, awesome work!
1. You have a habit rev..rev..rev..and chopping the throttle. That loads up the fuel in the intake and can create a small backfire. 2 Since it is running well enough to drive, just riding it around may clear up some of the issues. 3. I suggest adding some Chemtool carb cleaner in the fuel and ride it around. Great video as always. Love your channel.
Been waiting for this 👍
Finally... Nice work buddy 😉
Back on your grind!
👋🙃👍
Yeah back to the projects!
Yes 💪 been waiting for this one
Backfiring in the carb: Lean/false air, if the manifolds has O rings, coat them in a bit of oil, and when its running, spray some brake cleaner to all of the mating surfaces, if the idle goes up, then its an air leak. Also check the sparkplugs to see what color they are, i had this same problem with my atv, it was an air leak, and i hear that is an air leak because the rpms arent going down that fast as they should.
Check the rubber diaphragms in the top of the carbs for stiffness, rusted springs or corroded needle seats. The diaphragms may have pin holes in them and cause the low idle and backfiring.
lean condition, re jet it or you will hurt it,love your projects but spend some time learning about tuning and how to check the spark plugs
"Timing is everything":Valve Lash,Valve Lash.2 Cyls.,and they aren't even.With the way you drive,(easy 90%)it's harder to diagnose,but I watch enough to hear the wrong.Great buy !
100% needs re jetted. Either put a stock exhaust on it, or jet it correctly for that exhaust.
Call hmf and get the right jets . Maybe check the air screw settings too.
After jets… check the header nuts where it bolts to the head and make sure they are good and tight. Sometimes that can sound like lean pop if they are loose and exhaust is leaking out around the exhaust flange.
The air method you used is the exact way old school centerpoint injection works. Kinda cool if you ask me
Check your valve lash and coolant temperature sensor would be my first look, In coolant temp center helps regulate the fuel intake on an engine
I agree with Lucas below, lean conditions will cause backfire, plus the exhaust sounds either gutted or the baffles are removed. Either way, this causes a lean fuel condition, re-jetting or restricting the exhaust could help the backfire.
Good job on the seat cover.
check torque on heads, or could need head gaskets. check spark plug gap and it gots the correct spark plugs in it, Premium gas will also make a change for the better. ignition coils could be funky, check them also i just noticed you did'nt mention any of these things. it could be any one of these because this seems to be an older model. Best of luck to you Chris, I have been a sub for a long time really enjoy your work and skills, thanks.
Sticky valves bud ad some valve ease in the feul and let it run for a bit
You can’t call it finished until you clear up that lean condition. Checking plugs, jetting sizes, carb settings and even checking silencer baffling are all logical steps. Gotta get it right to call it finished. Best of luck.
It’s green so it’s nature, great vids!!
Chris, you can tune that bog/backfire out of it. Adjust the a/f mixture screws.
Usually if you are running on choke you have a disconnected vacuum line or a vacuum leak. The carb and timing could also effect it. The gas typically just makes it sputter a lot. The backfiring makes me think timing, like the timing chain is off a tooth or two on the timing gear. Yes the airbox will effect it as the carb is tuned with that resistance. Usually on an older bike I would replace all the vacuum lines and gas lines as they are cheap. Then properly fix any janky wire reparse and mods people have done over the year. Clean all the plug connections and switches. Lube everything you can, including the cables and chain. I also replace the oil and filter, intake filters, and spark plugs. First though I typically pressure wash them. I typically run some carb cleaner through on a 1/4 tank of gas before I change the oil. It also sounds like they took the baffles out of the exhaust... which sometimes makes it run worse.
Id say the low speed idle mixture ports may be clogged up. I just went ham on my carbs and got the low speeds pristine with vinegar and a wire brush. The thing will idle at a seemingly 300rpm no more pops. Also changed out all the orings to with new viton seals. I did a jet kit and clean years ago it ran well but no where near what its like now.
If it smells fully at the pipes when running may be choke sticking a bit.. ground wire for coil pack/ maybe plug wire . Not shure but my problem is cured know. But I cleaned th he carbs also too. Hope it helps mine sounded like it was choking up like a hiccup sounded like vedic on starter sound almost low idle cutting out anyways best of luck. Sometimes a break is needed . An a cold one as well! looks amazing.
Leak down test of possible. Sounds like valves might now seat right and needs clutches cleaned and new belt would be a plus
I had the same problem with my yamaha raptor 350. I had to replace the pickup coil and after that it was running perfectly.
I would check the mixture screws with it blowing that little bit of smoke on acceleration looks like it's running a bit rich
Had a couple of em with after market exhaust
HMF usually has the recommended jet sizes and carb adjustments to use with there pipes on the website.
Pour some 500ml of brake fluid at both carburetors intake while holding acceleration at half maximum rpm. This old school recipe helps a lot on valve sealing by removing any unwanted material there. It makes a lot of white smoke but it works. Bad valve sealing may be the cause of back firing
Put some seafoam in your gas tank and a bit in the oil, also it has aftermarket exhaust, try rejetting it.
I worked on a Kawasaki prairie a few year's back and after messing with that thing i found that there was a toggle switch inside the belt cover that had went bad causing it to have similar problems that your having
You have to do a cylinder leakage test suspect intake valve leak
I'd check the factory recommended cam lobe tolerance and see if the one in the motor is worn. With everything else done, I'd think there could be cam lobe wear. Easily this can cause the symptoms your motor is experiencing. Its easy to do too.
That thing sounds like it’s running much better man! It’ll be so good to see it ripping on some tracks! Would you ever put the engine in something else?
and when you sell it, say "i inherited it and didn't do anything to it"
Check for vacuum ports on the carbs that may be open, and block them off.
By the 1990s computer controlled ignition systems were becoming common and the need for more energetic spark generation with newer higher compression and forced induced engines was becoming apparent. This was accomplished by moving ignition coils into assemblies that sat directly above the spark plug. Known as coil-on-plug ignition, the one coil per cylinder configuration coupled with the shorter direct path of current flow allows for extremely high voltages to be used, often well past 100,000 volts.
On modern fuel injected cars, higher compression ratios as well as tighter control of combustion timing is used to extract as much energy as possible, increasing power and efficiency. As an engine’s rotating speed increases, triggering an ignition event slightly before the point of maximum compression within a cylinder, or advancing timing is done to give the combustion process more time to occur.
Under certain conditions uncontrolled combustion can be triggered as smalls pockets of air-fuel mixture explode outside the envelope of the normal spark triggered combustion front. This is known as detonation and it can occur when timing is advanced too aggressively or the air-fuel trim is mismatched for the conditions within the cylinder.
Engine knock sensors were developed for this task and they functioned as highly tuned microphones, listening for the tones of sound produced on an engine block as it experiences detonation. The ability to accurately manage detonation also kept combustion chamber designs relatively conservative. During the late 1990's several manufacturers were researching better methods to detect detonation. The advent of ionic detonation detection used spark plugs to sense chamber ionization.
Good . Th
it is ok
one possibility? thats an aftermarket muffler, possibly whole aftermarket exhaust, it may need jetted for that exhaust; May need slightly bigger main and pilot jet
My thoughts too. It may just be a tune issue.
This would be my guess also. High flow air filter and aftermarket exhaust requires jetting.
Jetting like much others have said. But I've owned a few of these make sure those carbs are synced and valves lashed correctly
nice use of a Venturi to get the last bit of fuel out of the tank, i think some of the commenters here are on the right track, it sounds lean, either find a stock exhaust, or richen up the mix with slightly bigger jets
I think when you make them louder then the stock quiet , you have to go bigger on the main and Idle jets
It sounds to be idling low. Also with the aftermarket pipes the jetting has to be spot on. When the motor is decelerating it will pop like yours is.
thats the set up you need to run in one of your buggies, it all ready has revs
The seat cover would have looked better if you removed the original one first. Other than that, just run it and see if it will clear up. You get that sometimes with an engine that has been sitting for a while.
If it’s backfiring into the intake, there’s an extremely good chance the valves are gunked up and not seating right. I’d check that first
dude great vid! i think its lean too as other people are saying also im in nc we should get together sometime and have a offroading day lol
Finally, the” okkkkaayyyy “ is back
Hi. It’s sounds like a jetting problem to me. The trx 450 does that when it’s not well calibrated. Good luck and keep bringing this good videos.
As many folks have said, you’re probably running lean. Plus, there’s a chance your carbs aren’t in sync. Which surprises me that you don’t have a sync gauge with as many motorcycle engines you use. Fix your jetting, readjust the idle, and check your carbs are in sync.
About the only things I can think of that you haven't checked would be plug wires, coils and ignition control module. Coils can be ohm tested. Plug wires can be misted with water to see if insulation is breaking down. If all else fails you can try an ignition control module/cdi to see if it helps. The cdi module is not able to be tested so replacement is the only way to know. Coils can be intermittently bad even if they ohm out ok. Check for any bad connections or wiring between ignition components too. (Including at ignition switch) Fuel pump pressure ok? Good luck man, I am pulling for you.
Alot of the people are correct in the comments... I was a motorcycle mechanic for 11 years... re-jet it for "stage 2" or 3 since it has the K&N and the exhaust... the are called afterfires not backfires... the gear shifting problem is either a bad adjustment (if cable) or electronic issue (if electric). Also for carb adjustment do not go off manual for air/fuel mixture screw ...start at 3 turns out from lightly seated and move 1/4 turn out until it makes no difference then back it off 1/2 turn
maybe get yourself a gunson colortune as it makes the setting and jetting easier for a beginner and it may be worth working through the electrics as you service it in the future as a friend had similar issues with missfiring that ended up being a wire fractured inside the insulation!
best wishes to all
Been waiting on a video 😂
That thing sounds mean with that exhaust. 🙂
Play with fuel/air mixture or put stock exhaust back on. You may have to re-jet the carbs with that after market exhaust. Nice 4 wheeler.
Because there is spark it doesn’t mean plugs are good. Breaks of conductive material inside of plugs will alter timing because more gaps to jump.Happened on a lawnmower with me. Changing a what looked to be a good plug with a new one fixed it.
I had same problem flywheel key !!
Idle needs to be turned up. There’s a black knob on the front fender foot well to turn it up
if you haven't done it I would suggest syncing the carbs or checking the fuel pressure
If it backfiring into the intake, it can only be one thing sticky valves. if you run it a while they will probably free up.
I'd read plugs and see if it's lean or rich then re-jet. Then sync carbs.
With that exhaust you likely need to re jet. Like a 46 pilot and I don't remember the main jet sizing, but one step over factory if it's stock otherwise. I have the same motor in a twin peaks, with cross over manifold, cdi, and a can... jetting changed A LOT... 1/8" drilled mains.
Great video,i like
Backfiring into intake can be a sign of a slightly bent intake valve, this engine timing set went out, so a good chance that the intake valve ‘Just’ kissed the piston.
The reverse to neutral issue, is that the belt is too tight (probably) You can usually shim the rear clutch pulley to adjust this. On the newer ones, they may actually have an adjustment using screws 🤷♂️. The drag of the belt causes pressure on the gears that are engaged and so they do not want to slide out / into the next gear.
IF you sort out the clutch issue and make the belt looser, then you can raise the idle a little and it will help somewhat with the backfiring. My bet is that the slide needles and emulsion tubes are slightly wore as this is fairly common with these, and that causes them to run poorly. I just really hate CV carbs.
Sometimes you can cheat this by coming to a complete stop, letting the engine to go to idle and then releasing the brake as you try to shift. This doesn't always work, but if the machine is allowed to roll just a little, it can release the pressure on the gears and allow it to shift.
I would put quieter mufflers on it an see if it changes the lean running or up the main jets sizes might be a cheaper option.
Backfiring in the intake is only one thing that causes that intake valve is hanging open or bent or burnt Valves
The cdi or ignition. It's whatever makes the spark plugs fire
With the airbox lid off it will let more air in which will make it run lean unless you put bigger main jets in
Dyno time to get it set up sweet.
Have you synced the carburetors? Try that, if it doesn’t work, adjust the pms screw or try some bigger jets.
Make sure the carbs are balanced in. Both pulling same amount of vacuum