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1985 KLR600
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Discussion Starter · #1 ·
Twice this happened: Runs spectacular, then out of the blue POP/CLUNK, engine instantly starts to brake itself, pull clutch, rpms instantly go to 0, pull over, right away without cooling down starts fine as if nothing happened, continue riding.


I think/hope it is just a flake of paint/fuel tank junk blocking my petcock intake (there’s a lot. it’s bad)... but I’m paranoid, and since I already drained the oil out of the system for my doohickey now would be the time to disassemble anything to check for other schtuph.

Carb is clean and have fuel filter in the line. Left side engine clean, timing set, valves set. Happened in 5th gear between 55 & 65 warm engine.

Only has 7,000miles, but shows signs of setting at some point in its life and is 36yo.


Any thoughts?
 

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Mystery noise with deceleration, I assume that you immediately checked the engine oil level.
Does the vibration level change at all?

Have you checked the valve tappet clearances on this engine yet?
Which would give you the opportunity to inspect the cam chain tensioner, camshaft bearings & the KACR.
Chances are high that the previous owner had never inspected them.
 

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1985 KLR600
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Discussion Starter · #3 ·
Mystery noise with deceleration, I assume that you immediately checked the engine oil level.
Does the vibration level change at all?

Have you checked the valve tappet clearances on this engine yet?
Which would give you the opportunity to inspect the cam chain tensioner, camshaft bearings & the KACR.
Chances are high that the previous owner had never inspected them.
Oil level good. Drained and found no metal or burnt smell. All of the above were checked and passed with flying colors 2 weeks or so ago.

Vibration doesn’t change beyond normal with the power band.

I do have a mmmmMMMMMmmmmMMMMM sound in 4th that changes to a quieter mmMMmmMMmmMM in 5th. (Both around 4000+rpm) but I don’t know if that’s related. Sometimes I can kinda feel that.
 

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I do have a mmmmMMMMMmmmmMMMMM sound in 4th that changes to a quieter mmMMmmMMmmMM in 5th. (Both around 4000+rpm) but I don’t know if that’s related. Sometimes I can kinda feel that.
I've had tires & chain/sprocket sets that have made odd or even pleasant road noises on various bikes in the past. :)
 

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2013 KLR 650/692, 2017 HD Electraglide Ultra
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If you haven’t already, check the heat shield on the exhaust pipe, muffler, and that all those are tight. Check body panels too. The heat shield on my 1998 was loose and would vibrate at certain RPM and conditions.
 

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1985 KLR600
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Discussion Starter · #6 · (Edited)
Yeah, I’m not too worried about that. Every vehicle I’ve owned with a manual gearbox had weird noises either inside or sympathetic.🤣

Tires are old but the noise isn’t directly related to speed as it is rpm and gear.

The biggest thing right now is making myself confident it wont die permanently on a road trip. 👍
 

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2013 KLR 650/692, 2017 HD Electraglide Ultra
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Then getting back to the original problem: if it suddenly shut itself off, that would be a symptom of an ignition electrical problem. Crap in the carb would result in sputtering and dying, not instant off. I had this problem on my 2013 too. It eventually went away as I worked my way through cleaning the connectors throughout the bike. I cleaned them by pulling apart and plugging together a couple times and squirting silicone spray or grease into the connectors to prevent future corrosion.

So I suggest you do the same, starting with the connectors in the ignition circuit. Also watch carefully to see what else stops working when the engine dies next time. That will give you further clues.
 

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Discussion Starter · #8 ·
Then getting back to the original problem: if it suddenly shut itself off, that would be a symptom of an ignition electrical problem. Crap in the carb would result in sputtering and dying, not instant off. I had this problem on my 2013 too. It eventually went away as I worked my way through cleaning the connectors throughout the bike. I cleaned them by pulling apart and plugging together a couple times and squirting silicone spray or grease into the connectors to prevent future corrosion.

So I suggest you do the same, starting with the connectors in the ignition circuit. Also watch carefully to see what else stops working when the engine dies next time. That will give you further clues.
Awesome! Didn’t think of that:^)
 

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Discussion Starter · #9 · (Edited)
Update:
The noise was just a unusual misfire. Problem is getting more frequent. Killed 4 times on an 15 mile drive today. Time to take the tank off (yet again) and try to hunt down that bad electrical connection.

This time I didn’t pull over. Just clutched to let fully stall, then let it out again to restart. (pleasantly I didn’t lose more than 10mph doing it this way. I could just keep going) Stalls too long to ride out the bucking without pulling the clutch.

Daytime so I couldn’t tell if the lights or anything else cut. It’s just momentary, so pulling over and checking would be fruitless.
 

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Figure out a way to rig a plastic bottle to get gas to the carb with the tank off. Have a fire extinguisher handy. Run the bike and poke/wiggle things to try to make the problem occur.
 

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So, by letting the engine completely stop turning over the problem rectified itself?
And immediately restarted upon letting the clutch re-engage?

I'll suggest that your carburetor has got junk in the float bowl and that junk is getting sucked up into the main jet, restricting its fuel flow. When the engine stops turning over, therefore stops sucking fuel, gravity allows that junk to fall back to the very bottom of the main jet well.

Have you not yet drained the carb float bowl into a clean glass jar to look for junk? Or maybe that object is too large to flow out of the drain hole?

People have had ants or other bugs crawl into their carburetors via the float bowl air vent hose attached to the upper LH forward plastic nipple. They are light enough to be sucked up, heavy enough to fall back down and large enough to not pass thru the drain hole.
 

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Discussion Starter · #12 ·
So, by letting the engine completely stop turning over the problem rectified itself?
And immediately restarted upon letting the clutch re-engage?

I'll suggest that your carburetor has got junk in the float bowl and that junk is getting sucked up into the main jet, restricting its fuel flow. When the engine stops turning over, therefore stops sucking fuel, gravity allows that junk to fall back to the very bottom of the main jet well.

Have you not yet drained the carb float bowl into a clean glass jar to look for junk? Or maybe that object is too large to flow out of the drain hole?

People have had ants or other bugs crawl into their carburetors via the float bowl air vent hose attached to the upper LH forward plastic nipple. They are light enough to be sucked up, heavy enough to fall back down and large enough to not pass thru the drain hole.
Yeppers. Sparkling clean. It’s never been immune to misfiring on occasion, so I’ve already checked that specifically twice in the past two months.

If I recall right, I had it also had it apart before it happened the first time to repair the float, and several days after to adjust the float. That was last month.
 

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Discussion Starter · #13 ·
*It has always kinda half misfired sometimes at slower speeds. It is minor and my plug hasn’t fouled so I have been ignoring it... but now imagine it’s related.

Is it normal for a thumper to fully misfire when revved under no load? It does that too. But not when riding. Coincidence?
 

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Discussion Starter · #14 ·
Another update:

I tried to wiggle everything around I could with the tank still on and the engine running, which is nearly everything. I found a couple unconnected wires that blew my fuse, but nothing that cut spark to the engine.

I also replaced the fuel filter and checked the tank in case a little piece of that paint got in there.

still can’t replicate it, and thereby fix it

I tell you this thing is driving me nuts. Love the bike, and seems to run good except for this one stupid little issue.
 

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Discussion Starter · #16 ·
Paper fuel filter or metal screen?
Well, the original metal screen in the tank is missing, but there’s an in-line fuel filter. There was a lawn mower paper type one which I removed and tore apart (no blockage), and replaced it with a high-performance see-through filter.
 

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1985 KLR600
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Discussion Starter · #17 ·
Maybe something in the petcock getting stuck? It never turns fully off, but I’m kind of scared to take it off and replace it since the tank is pretty rusty in that area
29927

29928
 

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After running the engine about 10 - 20 miles down INTO the reserve fuel supply, one can lean the bike far right with the petcock turned to ON and remove the 2 phillips screws to replace the 4 holed packing gland / fuel selector disc and the o-ring for the external handle seal, and barely drip a drop of gas.

I usually lightly 'resurface' the face of the handle on a sheet of 220 - 400 wet/dry sand paper. Lubricate the rubber parts lightly with dielectric spark plug boot grease prior to reassembly.
 

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1985 KLR600
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Discussion Starter · #19 ·
After running the engine about 10 - 20 miles down INTO the reserve fuel supply, one can lean the bike far right with the petcock turned to ON and remove the 2 phillips screws to replace the 4 holed packing gland / fuel selector disc and the o-ring for the external handle seal, and barely drip a drop of gas.

I usually lightly 'resurface' the face of the handle on a sheet of 220 - 400 wet/dry sand paper. Lubricate the rubber parts lightly with dielectric spark plug boot grease prior to reassembly.
I’ll have to try that
 
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