vacuum? carb? help - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 18 Old 02-07-2011, 12:57 AM Thread Starter
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vacuum? carb? help

hello all,
chris from santa rosa ca needs some help! my 04 klr just had valve job, put in new spark plug, and new trugel batt .... there are some new problems that were either not apparent, or didn't exist before my mechanic friend got into it. the bike performs great for about 15 min at full throttle (freeway), and then starts to cough and max out at about 5000 rpm's. the bike used to do 75 comfortably, 80 - 100 if i needed it no problem... now it coughs and will not do more than 65-70 at full throttle on flat ground w/no headwind! help please! i keep stripping the bike down, troubleshooting, cant seem to figure it out

i'm leaving for baja in 3 weeks, 2500 miles in 14 days! hoping to sort most of my big issues out before departure

Thanks!
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post #2 of 18 Old 02-07-2011, 08:07 AM
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Without more information, my initial thought is to check the vacuum line from the petcock for a kink or poor connection / damaged line. If the vacuum is restricted or weak, the fuel draw to the carburetor bowl wouldn't keep up with demand at high RPM's. Just a thought without more information. I doubt there is a valve issue, as the bike performs initially. Your problem seems to surface after enough time and fuel has been drawn to empty out the bowl. Thats where I would look first.

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post #3 of 18 Old 02-07-2011, 09:02 AM
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Make sure the carb vent line isn't kinked or blocked, too.

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post #4 of 18 Old 02-07-2011, 09:14 AM
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What does the MECHANIC say?

Is he in a position to examine/diagnose/repair?

Too many variables for long-distance diagnosis with reliability and precision, I think; fuel supply impediment/vacuum petcock problem possible; also . . . CLOGGED MAIN JET . . . but, there I go, into a realm of infinite possibilities . . .

Draining the float bowl would be a good starting point, on your own, IMHO . . .

Good luck!
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post #5 of 18 Old 02-07-2011, 12:01 PM
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Was the bike running hot? …… I would re-check the compression…
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post #6 of 18 Old 02-09-2011, 02:39 AM Thread Starter
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Bike wasn't running hot, just high rpm's at high speed? It's not petcock, as the bowl is emptied within first few minutes.. My problem starts about 15-20 minutes into riding? Checked all vacuum and fuel lines for kinks?! Still can't figure it out? Going back to mechanic tomorrow? Bike was fine before valve adjust, doesn't make sense!
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post #7 of 18 Old 02-09-2011, 08:47 AM
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Still not enough information. Once the bike starts to act up, does it straighten out when you slow down? Will it run OK if you ride at lower RPM's? The tank has been on and off a number of times. All it takes is a fleck of junk to get into the float bowl to hang up the float valve. And the symptoms of a hung up float valve are very similar to what you describe. I'm at a bit of a disadvantage, as I can't hear, see, smell or feel what is transpiring, and is why I am not making any declarations of certainty about your problem. The diagnosis could run from a fleck from a disintegrating petcock packing in the float bowl to the valves having been set to the tight side. Tight valves generally create problems on a hot engine, not a cold one. I have no evidence what so ever that either is the issue. Your mechanic may have done an excellent job, and you are experiencing the problems that go with running an ethanol blend gasoline in your bike, that has separated.

We all have our own methods of trouble shooting. When problems seem like they may be fuel delivery related, I like to drain the bowl and start fresh there. Maybe two and even three times. It's like clearing the bench off before starting a new project. You have stated that you have pulled the tank repeatedly to trouble shoot, but didn't tell us the method or direction of your troubleshooting. My thoughts now lean towards returning the bike to the mechanic. I'd be paying attention to what he does to correct this issue, as it may well repeat itself somewhere in the Baja.

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post #8 of 18 Old 02-09-2011, 11:30 AM
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Quote:
Originally Posted by bajabound View Post
Bike wasn't running hot, just high rpm's at high speed? It's not petcock, as the bowl is emptied within first few minutes.. My problem starts about 15-20 minutes into riding? Checked all vacuum and fuel lines for kinks?! Still can't figure it out? Going back to mechanic tomorrow? Bike was fine before valve adjust, doesn't make sense!

Sounds like fuel starvation, starts and runs good until 15 min, yes?

Try leaving the gas cap open (not locked down) and see what happens. There's 2 vent lines coming off the back of the tank under the seat. I guessing that they are switched or pinched. The lines are marked with a dab of paint, red and blue. Don't remember which goes where but they need to be on right and clear.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9

Last edited by Spec; 02-09-2011 at 11:33 AM.
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post #9 of 18 Old 02-11-2011, 12:29 AM Thread Starter
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Awesome suggestions all, thankyou! So, I emptied and cleaned carb, jets and bowl, checked tank cap and vents, bypassed entire ca emmissions system, and rechecked all fuel and air lines.. 15 hours later I'm stumped... Recheck valves? Exhaust? I'm running out of variables!
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post #10 of 18 Old 02-11-2011, 06:49 AM
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Curious why you had a valve job done? Any work done to the piston, rings etc? The adverse effect of only performing a valve job, on any four stroke engine, is this tends to bump the compression up inside the cylinder and if the rings are old or not up to the task then that newly increased compession will want to leak past the worn rings. But I'd think your symptom would be opposite, it would run like crap the first 15min then as the rings expanded then the performance would improve.

I like Crazy Jakes idea, test the compression, cold and at temp.

Good luck man and let us know if you find the culprit, before your trip hopefully cause this could be a show stopper.
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