A different KLR 650 Petcock Mod

This Saturday, late in the day, after believing I fixed the "stuttering" problem months ago, the fuel starving symptoms came back.

Original Thread, (http://www.twtex.com/forums/showthread.php?t=81713)

Since it was Sunday and I'm broke anyway, I took apart the petcock and seemed to successfully do my own Hurricane mod but without buying anything. (I've ruled out other stuff so it was time to look more closely it the petcock)
I took the diaphragm assy out, removed the o-ring from the plunger and took the spring off of the vacuum side of the diaphragm and moved it over to the plunger/fuel side of the diaphragm and reassembled the parts in their new configuration back into the petcock.
The cutting out at 4-5k steady rpms seemed to all but disappear, but since I felt it ever so slightly a couple of times, I'm left wondering. I didn't plug the vacuum port on the petcock, just on the carb sideof course, so I would have thought that if the diaphragm had a hole in it, it would be leaking a little bit of fuel through it, unless the fuel side is tight and the air side is not. But, no fuel leaking past the diaphragm, which made me wonder if the petcock is really the problem...
Time will tell and I will post again if I feel like I've fixed the real problem.
I had previously found little black bits in the fuel when I drained the float bowl, so I kinda wondered about the integrity of the petcock internals. Added a EM fuel filter to help keep crud out and all had seemed good, until now...

with a pet cock that stays open all the time you are at risk for a cylinder full of gas or a crank case full of gas.

the vacuum line from the carb to the diaphragm is known to break down and get soft allowing them to collapse under high suction. this lets the petcock slowly close down some restricting flow.

also the later model KLR's come stock jetted well on the lean side and a size bigger on the pilot and a shim to the needle can work wonders.

With the petcock in the stock configuration, vacuum line connected & petcock set to ON, disconnect the fuel line from the petcock & install a long section of clear tubing onto the petcock fuel port, directing it to a suitable container.

With the engine off: Does fuel flow into the container? It shouldn't.

Start the engine: Does fuel flow into the container? It should.

Set the petcock to PRI: Does fuel flow into the container? It should (engine running or engine off).

I would probably go ahead & replace the diaphragm assy. It should be about $20 or less from the dealer (~$12 at some of the on-line places).
The petcock diaphragm is one of things that I kinda wonder if it gets ruined by the ethanol in gasoline?

In the end, I'd prefer to have a functional vacuum operated petcock. I like not having to remember to turn the petcock valve off and on manually.
I was happy to have found a way to temporarily bypass the vacuum operation that didn't cost me anything.
The goofy thing is that over the almost ten months I have had the bike, this symptom keeps coming back. I replace the vacuum line between the carb and the petcock and the symptom goes away... for a month or more. I purge the float bowl of little tiny black bits and add a EM fuel filter and the symptom goes away... For a month or more. Now, I bypass the vacuum operation on the petcock, and the symptom goes away... So I will leave it that way until I have reason to believe the problem is solved and then I'll rebuild the petcock and hope again that the symptom doesn't come back.
One of these days I should probably get into the carb, but when the bike runs, it runs great as it is, even without the 22 cent mod, etc.

Livin'TheDream said:

In the end, I'd prefer to have a functional vacuum operated petcock. I like not having to remember to turn the petcock valve off and on manually.
I was happy to have found a way to temporarily bypass the vacuum operation that didn't cost me anything.
The goofy thing is that over the almost ten months I have had the bike, this symptom keeps coming back. I replace the vacuum line between the carb and the petcock and the symptom goes away... for a month or more. I purge the float bowl of little tiny black bits and add a EM fuel filter and the symptom goes away... For a month or more. Now, I bypass the vacuum operation on the petcock, and the symptom goes away... So I will leave it that way until I have reason to believe the problem is solved and then I'll rebuild the petcock and hope again that the symptom doesn't come back.
One of these days I should probably get into the carb, but when the bike runs, it runs great as it is, even without the 22 cent mod, etc.

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I got a bag of them SS washers if you need a couple, actualy I have 98 of them.

DaveC said:

I got a bag of them SS washers if you need a couple, actualy I have 98 of them.

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Cool... are you a nice ride away from Leander...? How much do you want for one of those sweet babys...?

martin-csr said:

Set the petcock to PRI: Does fuel flow into the container? It should (engine running or engine off).

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Unless I am mistaken, I don't think the KLR has a "prime" position on the stock petcock. Mine only has on/off/reserve. Is this something they added for the new models?

Livin'TheDream said:

In the end, I'd prefer to have a functional vacuum operated petcock. I like not having to remember to turn the petcock valve off and on manually

Click to expand...

You have to turn the manual petcocks on and off? Dang, I don't think the manual one on my KLR has been turned off in a few months.

DFW_Warrior said:

Unless I am mistaken, I don't think the KLR has a "prime" position on the stock petcock. Mine only has on/off/reserve. Is this something they added for the new models?


You have to turn the manual petcocks on and off? Dang, I don't think the manual one on my KLR has been turned off in a few months.

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Ha! Good to know. I kinda figured it wouldn't actually be a problem unless the float valve got stuck or something.
BTW DFW Warrior, don't feel like you always have to be funny but, you often crack me up. Thanks for your contribution to TWT. You've been helpful, AND made me laugh, both things much needed and appreciated If I knew you better I'd have used this emoticon

Livin'TheDream said:

Ha! Good to know. I kinda figured it wouldn't actually be a problem unless the float valve got stuck or something.
BTW DFW Warrior, don't feel like you always have to be funny but, you often crack me up. Thanks for your contribution to TWT. You've been helpful, AND made me laugh, both things much needed and appreciated If I knew you better Id have used this emoticon

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Well thank you. Nothing I ever post on here is intended to be mean by any stretch. Most of the time I am chuckling when I type it, so I just hope it comes across that way.

On a side note, I had my stock petcock on the KLR throw in the towel while riding around at Animas Forks in Colorado. It started to leak fuel out of the middle of the petcock where everything screws together. I quickly limped it back into town and headed to a hardware store. They had a sheet of thick rubber gasket, so I picked it up for a few bucks. Back at camp I gutted the petcock, and cut a sheet of that gasket to act as a filler. It held up fine for months until I made an aluminum plate to serve as a filler. That thing will never leave me stranded again!

But if you ask me, I do pick the most scenic locations for a break down. LOL After taking this picture I walked back to my bike which was leaking fuel all over the ground.

Livin'TheDream said:

Cool... are you a nice ride away from Leander...? How much do you want for one of those sweet babys...?

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They are part of a "pay it forward" project. Let me relocate them and when I find them I can mail them, $0.42 versus a gallon of fuel, but burning fuel is more fun

DFW_Warrior said:

Unless I am mistaken, I don't think the KLR has a "prime" position on the stock petcock. Mine only has on/off/reserve. Is this something they added for the new models?

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My mistake. Older bikes have PRI. I ride an old bike.
If there is no PRI, then I'd probably get a simple vacuum pump.
Or just go ahead & replace the diaphragm assy if it's much more than a couple of years old.

I finally had some free time when it wasn't raining or too cold, so I went out on a ride this afternoon. Seems as though bypassing the vacuum operated petcock solved the problem. No more popping on deceleration, and no more stuttering/choking/starving for fuel randomly while on the freeway or cruising at 4K+ rmp at whatever speed.
I suspect that every time I had this problem in the past, it was probably the petcock going bad, and/or related to the petcock. I added some SeaFoam and it got better one time. I replaced the vacuum hose and it got better one time. I cleaned little black bits out of the float bowl and added a EM fuel filter and it got better one time. Now that I finally bypassed the darn stock petcock and it got better again, I guess I shouldn't have any great confidence that it is THE cause, but if the problem doesn't resurface within a couple months, I'll be thinking it's been that vacuum operated petcock all along and I'm gonna become a huge manual petcock fanboy!

Don't forget the inline filter, if it is empty then your out of gas, system of fuel monitoring.

Yeah, it was helpful to have that clear fuel filter in there this last time when I was having problems. In the past, I just had to wonder what the fuel flow looked like when I pulled over because of the choking and stuttering. This last time, I had the filter inline so I could see that there was just a small dribble at idle. Don't know if a dribble at idle indicates a problem necessarily. I forgot to look again at that after bypassing the vacuum operation of the petcock.


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Livin'TheDream said:

Yeah, it was helpful to have that clear fuel filter in there this last time when I was having problems. In the past, I just had to wonder what the fuel flow looked like when I pulled over because of the choking and stuttering. This last time, I had the filter inline so I could see that there was just a small dribble at idle. Don't know if a dribble at idle indicates a problem necessarily. I forgot to look again at that after bypassing the vacuum operation of the petcock.


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Since my dealings with the petcock are part of the overall ongoing stuttering and cutting out issue that I started a post on awhile back, here's the link to that thread, which will hopefully serve others with similar issues in the future...

http://www.twtex.com/forums/showthread.php?t=81713

Whats the spark plug color? It should be a light tan, any blackness is either a miss fire or to rich. Whiteish deposits indicate a to lean condition, this is also found by running it up to about 2500 to 3 grand in idle for a minute or two, the header well turn cherry red.

DaveC said:

Whats the spark plug color? It should be a light tan, any blackness is either a miss fire or to rich. Whiteish deposits indicate a to lean condition, this is also found by running it up to about 2500 to 3 grand in idle for a minute or two, the header well turn cherry red.

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Early on in my troubleshooting of this problem I replaced the plug. The one I pulled out was probably fine, but it was pretty white, so yeah, lean I reckon. Are you saying the header gets real hot after revving as you described, when there's a lean condition...?

I had mine jetted lean, 145 I believe, and started it ran it steady throttle open to between 2500 and 3 grand, pipe turned cherry red. Did not take but a minute or so. Plug read was clean new plug so nothing showing. I think I ended up with a 150 in it. The PO had goobered it up pretty bad with some needle with no numbers or markings and a 155 main, it was getting 30 to 35 mpg and leaving a big gob of soot on the fender. The new owner gets around 45 mpg.