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Discussion Starter #1
Just got a new 2012 KLR 650 a month ago. Not my first KLR. After riding in extreme temperatures, turning off bike and coming back to it inside of 20 min., it will eventually start after cranking for 30 seconds. Never had problem like this with previous KLR's. Dealership, told me to use 91 octane fuel instead of 87. I don't know about that, my owners manual says 87 octane is called for. Seems like some kind of a vapor/pressure lock due to extreme ambient temperatures. Next time I will open gas cap and relieve pressure and then start. Anyone with similar issues that may have a remedy.
 

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What's your starting procedure; e.g., use "choke" (starting enricher)?

Vapor lock unlikely, IMHO; also . . . doubt the octane of any consequence.

I'd look into the starting circuit of the carb; starter jet and/or pilot jet may want cleaning.

(Assume vacuum-actuated petcock operational.)

You should be entitled to warranty service on this issue; IMHO. 30-second starting interval on a warm bike ain't normal, given proper starting procedure.
 

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Just got a new 2012 KLR 650 a month ago. Not my first KLR. After riding in extreme temperatures, turning off bike and coming back to it inside of 20 min., it will eventually start after cranking for 30 seconds. Never had problem like this with previous KLR's. Dealership, told me to use 91 octane fuel instead of 87. I don't know about that, my owners manual says 87 octane is called for. Seems like some kind of a vapor/pressure lock due to extreme ambient temperatures. Next time I will open gas cap and relieve pressure and then start. Anyone with similar issues that may have a remedy.
Welcome to the forum!

I live about 60 miles from Death Valley, extreme temps? My 08 starts fine when it's hot.

My .02 on starting:

Don't ever give the bike any gas when you start it. When's it cold give it choke but don't twist the throttle especially when it's hot.

Has the bike been on it's side? The charcoal canister under the battery (left side) can get filled with gas and make the bike hard to start.

How's the aircleaner? A dirty filter will effect how the bike runs.

Good idea with the gas cap. If that clears it up check the vent tubes. They can get pinched under the tank seat junction.

Octane doesn't have any effect on starting or how a KLR runs. It's a low compression motor. Higher octane ratings prevent pre-detonation (pinging) in higher compression engines. It would make me suspicious if a dealer told me that.
 

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Discussion Starter #4
LoneRider & Spec

Thanks guys for responding.
I don't apply any choke at all cause of extreme warm weather. Yeh, I think I am gonna take her down to the dealership.
That is good to know. My bike should start in hot weather. It has never been laid over. It is brand new, thus all components are new as well. Yeh, I figured octane rating had nothing to do with problem. Again, thank you for responding. I will let you know what remedies the issue.
 

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My suggestion; use the "CHOKE," JJNyborg!

First, it ain't REALLY a "choke," it's a STARTING ENRICHER.

When the engine is "cold," regardless of the ambient temperature, the starting enricher, when applied, provides a fuel-rich mixture to the engine for the purpose of . . . well, STARTING!

When you engage the choke lever, you withdraw a plunger from a hole in the carburetor and also open an air passage; fuel flows from the hole and mixes with the incoming air, not unlike the starting arrangement is a "mini-carburetor," only the misture is especially fuel-rich, for the purpose of starting the engine.

Try this, next time you start your bike: Ignition switch on, kill switch in RUN position; petcock ON; transmission in neutral or clutch lever pulled; activate choke lever (choke ON). Hit starter button, 'til engine starts. Gradually move choke lever to OFF position, as engine is able to sustain operation without enrichment.

Your automobile likely has a mechanism richening your starting mixture also, but transparent to you as driver. The KLR650 requires human intervention (activating choke lever) to start easily, most usually.

Good luck!
 

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From, "Care and Feeding of the CVK40:"
STARTER ENRICHER - KLR Morning Coffee


This system is referred to as the
choke. But that's a misnomer. When
you apply the choke lever, what
you're doing is retracting a plunger
that opens a tube connected to the
starter jet, allowing additional fuel
to enter the venturi just below the
vacuum hose nipple. It supplements
the pilot system at start up.
If you want to know more about your carburetor, click here: http://www.gadgetjq.com/keihin_carb.htm

If you do not click on the link, no offense taken--some motorcycle forum members prefer not to use posted links.

Regardless, I think using the "choke" will facilitate starting your bike.
 

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My suggestion; use the "CHOKE," JJNyborg!

First, it ain't REALLY a "choke," it's a STARTING ENRICHER.

When the engine is "cold," regardless of the ambient temperature, the starting enricher, when applied, provides a fuel-rich mixture to the engine for the purpose of . . . well, STARTING!

When you engage the choke lever, you withdraw a plunger from a hole in the carburetor and also open an air passage; fuel flows from the hole and mixes with the incoming air, not unlike the starting arrangement is a "mini-carburetor," only the misture is especially fuel-rich, for the purpose of starting the engine.

Try this, next time you start your bike: Ignition switch on, kill switch in RUN position; petcock ON; transmission in neutral or clutch lever pulled; activate choke lever (choke ON). Hit starter button, 'til engine starts. Gradually move choke lever to OFF position, as engine is able to sustain operation without enrichment.

Your automobile likely has a mechanism richening your starting mixture also, but transparent to you as driver. The KLR650 requires human intervention (activating choke lever) to start easily, most usually.

Good luck!

The ambient temp is the temp in a "cold" engine.

A choke is designed to be used for cold weather starting. Small drops of gas don't evaporate well when cold. You are enriching the mixture with the choke (in the KLR application) by adding fuel not air. The higher the ambient temps the less the enriching is needed. If you choke in warm/hot weather you are providing an excessevly rich mixture and will make the bike harder to start.

When the valves are in spec the motor should start with 2-3 turns of the starter, no choke in warm (>70 deg.) weather.
 

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You are enriching the mixture with the choke (in the KLR application) by adding fuel not air.
While the mixture enhancement from the application of the "choke" (starting enricher) is fuel-rich, withdrawing the plunger opens both a fuel orifice, and an air passage, allowing air to mix with the auxiliary fuel flow.

The tip of the plunger, withdrawn from the carburetor, allows fuel to flow; the reduced-diameter cross-section near the end of the plunger, when withdrawn, allows air to enter and mix with this auxiliary fuel.

Thus, the starting enricher system comprises a sort of, "mini-carburetor."

My KLR650, perhaps, is "cold-natured," use of the choke facilitates starting, even on moderate-to-hot days.
 

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This image illustrates the entry of BOTH air and fuel into the carburetor when the choke is engaged:



The vertical flow, represented by the arrows shown moving from the top towards the bottom, shows AIR entering the carburetor, possible at this juncture only when the choke is ON, or "fully open" as depicted.

The horizontal flow, shown coming in from left to right in the image, is FUEL, as the plunger point is withdrawn from its orifice in the carburetor.

The air and fuel are mixed, resulting in the fuel-rich starting mixture, and this fuel-rich mixture then procedes downward from the center-line of the enricher plunger, ultimately into the venturi and the engine.

When the choke is OFF, or "fully closed" as shown, the plunger seals the fuel hole, while the larger-diameter cross-section area of the plunger seals off the air passage.

This drawing shows how the starting enricher ("choke") system functons as a "mini-carburetor," mixing air and fuel to create a fuel-rich starting mixture.
 

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Another tip, JJNyborg, KLR650's typically come adjusted fuel-lean at the factory; if you remove the tamper-resistant plug, bottom forward portion of your carburetor, and then bottom (gently!) your fuel screw, then back it out about 1.75 turns, you may realize an idle air/fuel mixture much more agreeable to your engine, enhancing starting and operation from idle to 1/4 throttle.

If you want to continue along this line, shim your needle with one # 4 washer, to fuel-enrich the mid-range air/fuel mixture, and then . . .why not go ahead and enlarge the vacuum port in your slide to 7/64" diameter, for enhanced slide response (I've outlined the "22-cent mod")?
 

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Discussion Starter #11 (Edited)
Another tip, JJNyborg, KLR650's typically come adjusted fuel-lean at the factory; if you remove the tamper-resistant plug, bottom forward portion of your carburetor, and then bottom (gently!) your fuel screw, then back it out about 1.75 turns, you may realize an idle air/fuel mixture much more agreeable to your engine, enhancing starting and operation from idle to 1/4 throttle.

If you want to continue along this line, shim your needle with one # 4 washer, to fuel-enrich the mid-range air/fuel mixture, and then . . .why not go ahead and enlarge the vacuum port in your slide to 7/64" diameter, for enhanced slide response (I've outlined the "22-cent mod")?
Thank You Again for your input. The next time I am out riding in the heat and my issue occurs.
First: I am going to open tank and relieve pressure.
If that doesn't work.
Second: I will try choking it.
I feel that extreme heat is building pressure in tank causing excessive fuel to be pushed into carb. If this is the case. I will take the bike to dealership and have them figure out what is going with evap system. I failed to mention that when cranking engine in extreme heat, I smelled gasoline, as if it were flooded. Cracking the throttle a little seemed to help it start. Allowed some air in there to mix with all that fuel. However, this is a bike with less than 300 miles on it. I shouldn't have to crack the throttle. It should start up, no problems.
 

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Discussion Starter #13
The ambient temp is the temp in a "cold" engine.

A choke is designed to be used for cold weather starting. Small drops of gas don't evaporate well when cold. You are enriching the mixture with the choke (in the KLR application) by adding fuel not air. The higher the ambient temps the less the enriching is needed. If you choke in warm/hot weather you are providing an excessevly rich mixture and will make the bike harder to start.

When the valves are in spec the motor should start with 2-3 turns of the starter, no choke in warm (>70 deg.) weather.
I agree.
Especially when this new.
 

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I respectfully disagree (as noted previously); at least in part!

Certainly, the starting enricher system includes BOTH air and fuel, not fuel alone; and . . . to my mind, the choke's not exclusivelly for cold weather--rather, to fuel-enrich the starting mixture as necessary.

YMMV!
 

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Have to disagree also with using the choke (enricher) for hot starts. For example many MX 4 strokes, and I’m sure other bikes, have a hot start lever, what this does is simply open an air only venturi on the side of the carbi that allows fresh air to enter the intake and lean the mixture. To my understanding the only time you need a very rich mixture to start is when the fuel will not atomise well eg when cold.


In regards to the OP, at high ambient temperatures and with a very hot motor, sitting for 20 mins could possibly be enough time for the float bowl to evaporate most or even all fuel from it and vent out the carbi breathers.

When you then go to start and seeing as the KLR has a vacuum operated fuel tap no fresh fuel can flow to replenish the bowl until you start cranking. Therefore you have to crank long enough to
A: Open the fuel tap via vacuum
B: Allow enough fuel to flow and refill the bowl
C: Get a lung full into the engine and fire up.
30 seconds of cranking would seem a reasonable time frame for all this to happen.

I bet if you got rid of the vacuum operated tap and put a conventional petcock on it would be fine.

As a test maybe try to insulate the float bowl somehow and see if that helps.

Another just out of interest test would be drain your bowl when "Not so hot" and then see how long you have to crank for it to fire up. I’d bet about 30 seconds ….
 

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A: Open the fuel tap via vacuum
How do you propose the OP develop the vacuum to open the fuel tap, 270win?

Don't see how the fuel volume of the float bowl evaporates entirely from the carburetor as you suggest, through the small-diameter (about 1/4" I.D.) carburetor breather hose in 20 minutes. The petcock closes automatically when the engine is off, and no manifold vacuum exists to extract fuel through any carburetor jets. The fact the engine was running when he turned the ignition off indicates fuel was in the carburetor, and no path exists to drain it.

Turning the engine over with the starter buttom immediately creates manifold vacuum, opening the petcock and releasing fuel in the fuel line and tank to replenish the fuel in the float bowl if needed, up to the limit of the float valve.

The Keihin CVK40 carburetor is gravity-fed; whether a vacuum-actuated (i.e., stock) petcock or a maually-actuated (modified) petcock is in play, fuel flows when either type petcock is open.

Thus, doubt a dry fuel bowl is the problem.

The 20-minute stand-down mentioned in the IP may be long enough to require application of the choke to start readily, IMHO. The complaint arose from starting a cold engine, i.e., after the engine had not been running for a while, in contrast to starting the engine immediately after running, seemed to me. Don't think the "hot start lever" is therefore relevant. I'm unaware of any sin associated with utilizing the starting enricher ("choke") to start an engine after it's been at rest, approaching ambient temperature.

How about it, JJNyborg? Do you find your bike starts more readily, if you apply the choke?

Again, backing out your fuel screw to 1.75 turns or so may enhance your starting/idle air/fuel mixture.
 

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When I said OP I meant ”Original Post”, I do not know what you interoperated OP as?

I proposed the engine be cranked over to produce the vacuum to open the petcock. That’s why it would take time as explained, does not start flowing till it’s started cranking.

As far as evaporation / escape paths go, all float bowls have breather lines to vent the bowl. Fuel vapours from hot evaporating fuel expand and hence, will exit via the carbi breather tubes.

I do not believe that an engine operating at say 220 deg F on a 100 deg F day would cool to what could possibly be ambient temperature or called a cold start state in 20 minutes, hell you could still cook an egg on it after that time frame in those conditions and IMHO would still be a “hot start” situation in only 20 mins.

Please don’t think I’m trying to discredit your responses mate I’m just throwing another train of thought at the original question.

Cheers!
 

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I see you edited your post while I was responding, therefore if my response seems a bit strangely worded that’s why, but you can still get the drift.....

Edit: Oh and dont mind my typo "interoperated"
 

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If the entire fuel bowl content evaporates in 20 minutes, through the foot-and-a-half long 1/4" I.D. carburetor breather hose, I'd be surprised. I doubt a demitasse filled with the float bowl volume of gasoline, fully open, would evaporate completely in a day.

Regardless, if that much fuel disappeared that quickly, wouldn't take long for an open petcock, and the hydrosatic head of fuel in the tank, to replenish it, IMHO.

While I doubt a dry float bowl is the cause of hard starting, I respect the theory.

I take the nomenclature, "starting enricher," at its word, using the "choke" to provide a combustible mixture to the engine for starting, regardless of engine or ambient temperature.
 

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When I said OP I meant ”Original Post”, I do not know what you interoperated OP as?

I proposed the engine be cranked over to produce the vacuum to open the petcock. That’s why it would take time as explained, does not start flowing till it’s started cranking.

As far as evaporation / escape paths go, all float bowls have breather lines to vent the bowl. Fuel vapours from hot evaporating fuel expand and hence, will exit via the carbi breather tubes.

I do not believe that an engine operating at say 220 deg F on a 100 deg F day would cool to what could possibly be ambient temperature or called a cold start state in 20 minutes, hell you could still cook an egg on it after that time frame in those conditions and IMHO would still be a “hot start” situation in only 20 mins.

Please don’t think I’m trying to discredit your responses mate I’m just throwing another train of thought at the original question.

Cheers!

I commute in hot weather and my bike stays out side 10 hours during the day in the sun. It's been bumping 110 F (43 C) here. The asphalt temp has been measured to be +50 F hotter than the ambient. My bike starts easily. Ancedotal but hot weather doesn't evaporate the gas out of the bowl.

Float bowls don't have a vent tube they have an overflow tube. The carb has vent tubes and the gas in the bowl does vent through the jets but the rate is slow.

There's enough gas in the bowl to start the bike without pulling more from the tank. The bowl is full if it can get gas. The jets stay submerged in gas. You would have to turn off the supply of gas and run the bike until it quits to empty the float bolt (short of opening the drain of course!).
 
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