Kawasaki KLR Forum banner

1 - 20 of 31 Posts

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #1
Bike's been on the fritz last 4 work commutes backfiring and stumbling really hard n' bad around
5 g's rpms under acceleration.


I did the twist on the carb and took off both ends and did a cleaning, fine wire thru
the jets n' passages, etc. No improvement, even slightly worse. Pinched just a touch
of the diaphram which explained the "worse". I noticed this after pulling off the carb this time.
I have the paint can type carb solvent kit with the basket thingie ya drop in there for 10-15 minutes.
Did that with every piece removed. Nearly naked casting. All the brass
bits dunked in the basket and swished around. The diaphram was held up to the light and gently manipulated
for a full, thorough inspection. Perfect. With the choke cable clearance issues for reattaching the needle
and nut I had the tank off, and of course the sides and seat to get to the tank bolts.
Same problem as when it started.

"Bout this time the Cheapster's gettin' confused cuz it's a lean backfire (blue) and not an ignition issue.
Now the carb has been fully rebuilt. WHAT THE FLIP?????????????

While cruising to work two weeks ago the front T-mod line was swinging loose
in front of the tank behind the radiator. (I had noticed a lean surge at highway rpms a few
years ago and moved the line while riding and the problem stopped.) I stuck the line into a
gap but pinched off the line without knowing it. Today was warm and I'm farting around on the bike
recreating the stall under full throttle 5th gear, etc etc, and it was doing it repeatedly. Drop to 4th
and roll thru the bad spot, the thing catches and runs right up the tach the rest of the way to 6k which is my redline usually.
The lightbulb FINALLY flashes and I yank out the tube and run it down next to the top of the radiator
where originally installed and the problem disappears right then in mid-ride.
It hasn't returned.
I sucks the hours put into repairing a non existent problem due to whether that
line needs to be sucking or blowing, and I am very curious as to how the T-Mod can
affect whether which end of it is doing the emulsifying. I almost wanna
go back to the pink straw running up the inside of the tank after all of that.
All of that, combined with post-addict/alkie memory issues. LOL

There's something to learn here but I'm not sure what. Something about
the tube needing fresh air, but which direction does it flow? Two tubes split
from one makes it better (creating the t-mod)?

That's been my riding life last two hundred miles,
Cheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeap
 

·
Registered
Joined
·
5,566 Posts
Hard to diagnose, whether examining on-site or remotely from the description . . .

All the following may already be known; regrets if I'm telling something already obvious.

My understanding only; could be in error.

Basically, the carb vent line provides atmospheric pressure to the underside of the diaphragm, and, I think, to the surface of the fuel in the float bowl (so fuel can flow through the jets from venturi vacuum). Don't know if you have a Generation 1 or 2; Generation 1 carb vent line opening was about 10" above riding surface; left in stock configuration, subject to flame-out when water crossing level was deeper. Solution: Tee mod, providing alternate path to atmosphere when tube bottom was submerged.

Generation 2 carb vent opening is about 30" above riding surface; less likely to stop up from water crossings up to that depth. Tee mod not so vital for this model.

As to which way air flows in the carb vent tube, the answer is: BOTH ways. When venturi vacuum raises the slide, air flows IN; when venturi vacuum falls and the slide lowers, air flows OUT. Not a lot of flow, in either case; as mentioned, only enough to maintain atmospheric pressure on the underside of the diaphragm.

Given this scheme, an occluded (as in, submerged, stopped up, or pinched) carb vent hose will honk up your carb's ability to deliver mixture proportional to venturi vacuum.

Corrections and clarifications welcomed; regrets if I merely state the obvious and known.

-----------------------------

Alternate cause of symptoms described: Stopped-up fuel tank cap vent; impedes fuel flow into carb by restricting air flow to replace fuel used from tank.

Another thing to check: Petcock fuel flow. Since the problem occurs at higher rpm, the petcock may not be delivering at the desired flow rate.

Regardless: You now have a CLEAN CARB! :)
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #3 (Edited)


Gonna go with a single line up the top tube under the tank but a lil' longer than stock


Thank you for taking the time to reply, Damocles.

Fuel flow is vigorous. Full flow petcock, lines clean, float level good, and it screams
at higher rpms than the stall rpm speed. I think we're good now.........

It used to easily do an indicated 100 mph. It's falling asleep at 90 now leading me
to believe both T-lines are catching negative or positive airflow at speed and not a
two way flow then as much as is needed for a full slide of the piston.

I don't drive 100 but it lets me know it's close but not dead on yet as far as
mixing and airflow. Especially WOT airflow as it seems the slider isn't getting
fully out of the way. The wind blast as we know comes upwards in front of the tank.
I need to try sideways rather than up or down next on this now annoying lil' hose. LOL

The rain is present and steady today so a test'll have to wait till after works n' sleeps.
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #4
Been thinking on it a bit.

Rolled it into the garage/shoppe and capped off the rear tube.
That's all so far. It's very much turbulent between the tank and fairing
and I feel the line needs to end in "dead air". I'm thinking top tube under the tank
or going further forward behind the instrument cluster. Got tomorrow off to play
with myself, er, the bike.
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #5
Ran the batcycle hard today.

The back t-mod tube is plugged up and the front one along the frame rail protruding
in front of the tank about 8 inches flops in the wind blast or can be pinned a few places
and angles to the upwards blast. (if you so choose to run yours that far)

Running it down and left against the radiator cap: normal with a slight stumble at
a steady 60mph. Accelerated thru it easily. Topped at indicated 90 mph.

Straight down along the radiator: No stumble, 93 mph.

Straight up into the risers and cables: Ye-friggin' ha !!!!!
Pulled hard from idle to 6400 rpms showing 94 and still climbing when I let off.

This location of the tube-end seemed to be in a dead spot just missing the rush
of air. My opinion formed is that neither positive pressure nor vacuum at the
emulsion tube helps performance. The carb works best balancing the slide piston
height with the butterfly position without our interference. The T-mod isn't necessary
on gen 2's unless you cross water as deep as the tops of the tires.

This was on 15/42 sprockets, snorkel gone, cored exhaust, stacked needle, and 150
main. Wind was from the side a bit. Nice repaved Indiana 6 mile straightaway.
(yes there's crazy twisties too where I live near the big lake.)

Have an emusified day,
Cheeeeeeeeeeeeeeeeeeeeeeeeap
 

·
Premium Member
Joined
·
6,676 Posts
Damocles,
I beg to differ about the 'pink vent hose' supplying Any Air to either side of the throttle slide diaphragm. It only supplies atmospheric air pressure to the Float Chamber!

The 'eye-brow' shaped vent at the top of the carburetor intake bell throat supplies Filtered air to the underside of the throttle slide diaphragm. The small hole ahead of the mid-range jet needle, supplies filtered negative pressure (vacuum) to the top-side of the diaphragm.

CBT,
On the '08 and up KLR's, I always pull the pink hose out from along side the frame rail and route it 'up and over' the Large frame spine. Then Down alongside of the 1/4" Black rear fuel tank vent hose to near the top of the shock. Just don't let the blunt end rest on top of the shock adjuster, cut it at a 45 degree angle.

If I do the 'T-mod', the top hose is routed forward under and alongside the frame spine to the rear edge of the 'steering head gusset', and tucked Back into the L.H. Front corner of the tank puck mount.

These 2 different ways make a 'sink trap', to keep any water out and in calm air.
 

·
Registered
Joined
·
1,256 Posts
I like Damocles could be wrong, but I had my carburetor apart last week and am fairly certain that the area under the diaphragm is connected to the intake manifold side of the carburetor throat. The float bowl vent of course connects to a nipple on the left side of the carb and is ported across the the right side also and both sides have openings into the area above the float bowl to provide atmospheric pressure to the fuel in the bowl.

I wonder why your vent is run up under the tank instead of back over the fender next to the battery like on the stock gen2 KLRs.
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #8
This is getting weird.

The tube connects to a nipple above the fuel line. There doesn't seem to be a float
tank vent but one of the many interior passages could be doing that job. I moved the hose
a few times on the way home from work and got it to stumble again, and also found
the sweet spot again.

At this point I feel that the mentioned spot behind the steering head gusset sounds
like a great spot for permanent mounting. Interesting topic as it hasn't been talked
about nor tested much. We can learn from each other which is one reason I posted
the steps I was taking and each result.

Still, this only happens at speed. First 3 gears run perfectly all the way up the tach.
Once it gets windy things start to change if our hose is out flopping in the breeze. LOL
 

·
Registered
Joined
·
5,566 Posts
I like Damocles could be wrong, but I had my carburetor apart last week and am fairly certain that the area under the diaphragm is connected to the intake manifold side of the carburetor throat.
Maybe so; I thought manifold vacuum above the diaphragm, and atmospheric pressure on the underside of the diaphragm, raised the slide.

Thus I thought (perhaps incorrectly) manifold vacuum was routed to the mixing chamber area above the diaphragm, and the area under the diaphragm vented to atmospheric pressure.
 

·
Registered
Joined
·
1,256 Posts
This is getting weird.

The tube connects to a nipple above the fuel line. There doesn't seem to be a float
tank vent but one of the many interior passages could be doing that job......................
The nipple above the fuel line nipple is the float bowl vent connection. You say the line connected to that nipple runs forward under the tank. I am curious about that. On all other KLRs I have heard of (many) including my two, that carburetor vent line runs toward the rear. Did you change the routing of the carburetor vent line or did a previous owner?
 

·
Registered
Joined
·
1,256 Posts
Maybe so; I thought manifold vacuum above the diaphragm, and atmospheric pressure on the underside of the diaphragm, raised the slide.

Thus I thought (perhaps incorrectly) manifold vacuum was routed to the mixing chamber area above the diaphragm, and the area under the diaphragm vented to atmospheric pressure.
Well, we know the area above the diaphragm has Venturi vacuum from the little hole in the bottom of the slide. I think the pressure source for the underside is best left for a new thread. I will check closely and maybe get some photos when I remove my carb this evening to install a new easily adjustable knurled knob idle mixture adjustment screw that came in the mail yesterday along with the shorty choke/enricher cable you put me on to. Also, I need to find out why on my last fuel fill-up I clocked 223 miles and used 8.4 gallons of gas. That is 27 miles per gallon for all in town riding.
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #12
GoMotor,
The pink tube ran backwards from the showroom.
The T-mod tube retained that spot while the opposite direction of the "T"
naturally had a forward aim so I ran it with the wires up the left of the top tube
under the tank. The tube I know now was made too long and was just waiting to
give a headache.

Did another test on the commute today. Plugged off the front this time.
Ran pretty good but popped a few times at speed and throttle. It terminates
close to the top coil of the rear shock (not touching anything) It's in the tire
spin blast. I could see from the inner fender that the tube needs to run above
and possibly end under the seat on top of the battery? While riding I slowed
down and wiggled it out and left it hanging by my ankle coming out under the
ignition. Ran like crap once I sped up. Reached down and tucked it around
the frame tube and pushed the end in near the carb. Ran like Carl Lewis.
Again, weird.
More to follow as this is both interesting scientifically, and easy to alter to try different
points of the ventilation opening.
 

·
Registered
Joined
·
1,256 Posts
Most folks when they do a T-mod on a gen2 KLR cut the factory vent going back by the battery and connect the two pieces to the arms of a "T". Then they connect a new line to the leg of the "T" and drop it straight down behind the transmission. I haven't heard any complaints from people doing it that way.

I have not done the T-mod to either of my gen2 KLRs and never had a problem in about 120K miles with lots of dirt roads and stream crossings.
 

·
Premium Member
Joined
·
6,676 Posts
Even after 8 years of the Gen2 bike, I still don't like the thought/possibility of garden hose or car wash water having a downhill run at the carburetor.

With the pink hose laying alongside the frame and air box and the conditions just so, doesn't everybody see the possibility?
 

·
Registered
Joined
·
1,256 Posts
Yes. I see the possibility. Just never had it happen in many many miles on gen2 KLRs. I guess that is why some do the T-mod on the gen2 bikes.

I have had to go push a friend on a non-T-modded gen1 out of a creek when his vent tube went underwater.
 

·
Premium Member
Joined
·
6,676 Posts
Yes. I see the possibility. Just never had it happen in many many miles on gen2 KLRs. I guess that is why some do the T-mod on the gen2 bikes.

I have had to go push a friend on a non-T-modded gen1 out of a creek when his vent tube went underwater.
With the normal 'T' mod on a Gen2 bike, water could still flow down the pink hose and into the carb, imo only.

I have had to pull my bike backwards out of a river, with spring run off, by myself, because the Gen1 pink hose was under water. But, hind sight being 20-20, had I been able to continue forward with the 'T' mod, I Probably Would Have Been swept down-stream in that raging torrent!

'T' mod has been done on my '87, since then. But I'm never again going to attempt to cross that river in June, in the Rocky Mountains!!!

Who supplied that video just a while back? Normk, I think? Imagine twice as wide, maybe fuel petcock deep in the middle, at that time of year! By myself, I coulda' Died. Coulda' died, and taken a friend with me! Woooo!
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #17
Todays run came out factory perfect.

The front tube is under the tank ending behind but not against the steering head gusset.
The rear tube rides up and is under the seat. Both are in still enough air at all speeds,
and both have very good elevation from the ground.

Test over. Hopefully the discussion continues a bit.

Maybe a test on the first generation design is in order but probably not unless
someone is curious enuff to fart with it (like I was).

The only real test is to find an elevated still pocket.

Ride 'em if ya got 'em,

Cheeeeeeeeeeeeeeeeeeeeeeap
 

·
Premium Member
Joined
·
1,585 Posts
Discussion Starter #18
Reluctant update

Ran perfect for a commute or two and started up again.

First a pop here and there during full throttle accel, and after few miles
couldn't get it to do anything but steady cruise at 4,500 rpms and no higher.
This got embarassing real quick after two cleaning and rebuilds.

Early eliminated was the ignition as I could downshift into high rpms and
be past the bad spot and go all the way up the tach.

Done the carb a few times and didn't use the manual.
Two rebuilds later, (the first time with the book) showed me on a
good track but the grease hack on the diaphram to hold it in place
left a total mess atop the diaphram. I only used a dab n' fingertipped
a paper thin film around the circle so that told me there was a vac leak
at the top cap.

Wrong.

Those of us who have happened to have the carb all of the way apart
have had out the lil' steel cylindrical bit that goes between the main jet
emulsion tube and 1/4" into open air in the carb throat. The book showed
no orientation of the thing, but what I DID notice was a slight taper that
just so happened to match the needle taper. (Lightbulb moment.)
Guess I never noticed the orientation of it, got lucky on the reinstalls,
other than after the recent first rebuild.
Without doing much more than running a fine wire through the
emulsion tube and studying the steel tube thingie that slid out the
batcycle is it's old self again and running highly reliably as of this typing.
The carb cap has a micro coating and nothing more. The diaphram is
clean n' shiny, my teeth (not so shiny) are showing every ride again.

Have a better day than death row inmates,

Cheeeeeeeeeeeeeeeeeeeeeeeeeap
 

·
Registered
Joined
·
5,566 Posts
Those of us who have happened to have the carb all of the way apart
have had out the lil' steel cylindrical bit that goes between the main jet
emulsion tube and 1/4" into open air in the carb throat. The book showed
no orientation of the thing, but what I DID notice was a slight taper that
just so happened to match the needle taper. (Lightbulb moment.)
Guess I never noticed the orientation of it, got lucky on the reinstalls,
other than after the recent first rebuild.
Do you refer to part reference, 16017, "JET, NEEDLE?" 2007 Kawasaki KLR650 KL650A Parts, 2007 Kawasaki KLR650 KL650A OEM Parts - BikeBandit.com

I think some refer to it as a "collar;" word-on-the-street, sometimes this little part falls out of the carb and rolls away while the tuner remains unaware of its absence . . .

Glad you got your bike sorted out; way to go; NEVER give up! :)
 
1 - 20 of 31 Posts
Top