High Rev Issue KLE500 '93

[Badger74]

Firstly...Hello!

As usual, i am one of those who have been loitering in the background awaiting my confirmation email so i can get stuck in with asking questions and generally enjoying one's self which brings me onto my first question issue/question relating to my bike.

It is a 20 year old Kwack KLE500...i purchased it with this problem ( reflected in the price i might add ) and was keen to get my hands dirty sorting this, and a few other, issues out.

In a nutshell, over 6-7k revs in any gear it will run as intended for about 20 seconds, then will pop, buck, fart, lose speed, throttle response and all manner of PITA running...if i ease back on the throttle it'll calm down slightly but if i was to pull over she'll just happily die on me for 5 minutes before starting back up again...if however i continue to ride along at a lower rev then she will still backfire/pop/fart etc until i stop and she conks out ( see the waiting 5 minute rule ).

Now then, i do know abit about bikes ( how many have said that !! ) and from her behaviour i would say it's a cylinder not firing at the point she goes all wobbly on me, but is this a carb related issue or electrical?

I stripped the Carbs last night, gave them a clean although they were looking in pretty good shape ( one did have traces of rust in the float bowl, very minor and an old issue by the looks of it ) and installed back on today, i checked the coils and got 3.2ohm and 18k ohm on both and checked and maintained the air box was correctly fitted.

So any ideas my fellow KLE owners? Most point to the carbs but I'm chin scratching as to why it happens at high revs AFTER 20-30 seconds and not straight away...

[MadM]

Hey!

Welcome to the forum. I really can't help you with the specific problem, but I can supply you the service manual if you wan't to dig deeper in to the problem.

Cheers!

[Badger74]

Originally Posted by Ghosty_SLO

Hey!

Welcome to the forum. I really can't help you with the specific problem, but I can supply you the service manual if you wan't to dig deeper in to the problem.

Cheers!

Hey Ghosty

That would be a great help!

[Jameseye]

Lift the tank, make sure none of the hoses under the tank are pinched, route them so that they do not pinch when you put the tank back on; enjoy....

Cheers
Ian

[Badger74]

Originally Posted by Jameseye

Lift the tank, make sure none of the hoses under the tank are pinched, route them so that they do not pinch when you put the tank back on; enjoy....

Cheers
Ian

The tank has been off and on so many times over the last week and each time the breather pipes are routed cleanly away, i wish it was such a simple remedy!

To date i have now done:

Valve clearances
Cleaned carbs, full strip down, checked jets were clear
New air filter
New plugs
Checked coils


I've also attempted to balance the carbs...i say attempted but the results were quite good but not perfect. Using a Souriau 2440 Indiana i was getting 1085 mbar on carb 1 @2k revs but a fluctuation of 1045-1062 mbar on carb 2 and no matter how i adjusted the pilot screw, it continued to fluctuate.


I don't hold much faith in the airbox tbh, the seals between it and the carbs are quite frankly, crap. I'd rather be looking at individual K&N style air filters for each carb and needle/jet set up as well, this is something to ponder.

The fuel tank isn't in great shape, the fuel tank cap area is rusted, i assume from years of being outside and a bad seal around this area...saying this the fuel in the float chambers has always been clean, no signs of contamination as such ( old rust spots from an issue some time ago, i imagine she was stood for some time ) but on a run yesterday i opened up the filler cap to make sure the tank could breathe and eliminate that thought.

So fueling wise i'm nearly 100% happy with the results...other than the 2nd carb not playing ball, the difference at 2k revs is minimal and i can live with it ( the bike is beautiful to ride up until the issue kicks in @7k revs ) so where do i go from here?

Replace the fuel tank as it's an easier option than repairing.

Electrical issue...coils are the first thought but why only at high revs?

to be continued.....

[leonator]

That is a real good one...Could be something to do with your timing. I would check compression too. Im not sure if the looming is the same but I have had a few electrical issues myself. Mostly due to corrosion and dirty connections. Get some contact cleaner, unplug, spray, plug, unplug, plug. Might need some cotton buds for some terminals. If your in Melbourne, Aust. I have a compression tester and timing light I could lend you.

Best of luck!

[Badger74]

Originally Posted by leonator

That is a real good one...Could be something to do with your timing. I would check compression too. Im not sure if the looming is the same but I have had a few electrical issues myself. Mostly due to corrosion and dirty connections. Get some contact cleaner, unplug, spray, plug, unplug, plug. Might need some cotton buds for some terminals. If your in Melbourne, Aust. I have a compression tester and timing light I could lend you.

Best of luck!

I'm looking at electrical issue atm...i'm going through the whole shebang and checking all the connections...as well as riding her daily with no issues below 7k revs..she's a real fun ride!

I'd love to take you up on the offer of the compression test but i'm UK based so it would be a fairly long ride...but tbh i reckon the ol girl would make it!

[leonator]

There is no question. She'd love a ride like that! Have you had any break-throughs?

[Badger74]

Indeed she would

I've done a 200 mile trip today and not an issue with her a all...over 8k revs in top gear for nearly 20 minutes and not even a hedgehog sized hiccup from the engine...

I did 'open' up the exhaust slightly to allow her to breath outwards more and she is better overall although still abit sluggish in the low range still but I'm looking for a replacement tank as it needs some tlc especially around the filler cap area...

[jjrider]

My guess is something to do with the pulse generator or cdi., mostly the cdi. They have a tendency to do goofy thing when they get hot, then cool down and work good for a bit. As for running , even though crappy, till you idle it down then puking it definitely sound s cdi issue. Most of these cdi have 2 advances, one at 8-12BTDC for starting(low rpm) and then switch to 28-39BTDC(depends on brand/model/year). As they fail sometimes one advance quits and it'll run, somewhat, on the other. In this case it sounds like the start advance(low rpm)has quit and the normal one is failing as it heats up.
Try tapping on the cdi when it acts up to see if anything changes.
My other guess is the pulse gen not sending all signals when it gets hot.