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when you short the multimeter in resistance mode, does the needle/display 0 ohm? if not, say 0,2ohm then you deduct that from your readings on the primary circuit (in the >1kohm its negligible).

4.8k or 5k makes bugger all difference so that's fine.
the secondary resistance is within range zo that's ok.
the primary is still odd. however if you search where the same coil is used on the 660, it goes from the 400LC4 in 1997 upto the 250SX in 2020, so a pretty common HT coil...
 

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Discussion Starter #22
When I connect the multimeter leads together it reads 0.4
So if I subtract that from my primary figures they are all in spec?
Thanks for that tip, it’s all starting to make sense now.
 

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that should be about right. both could will be in spec then.
possibly the problem is somewhere else then...?
 

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Discussion Starter #24
As I said I couldn’t get a reading on the old plug cap at all either before or after I removed it. It looked to be the original too so maybe just maybe that could be the culprit right?
It’s difficult to test it out properly under the lockdown restrictions, sometimes I ride for a while before it starts giving me problems but I’ll try and get it out tomorrow and see
 

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Discussion Starter #25
I took the bike out for a short ride today. The problem is still there. Any idea where to go from here?
 

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Discussion Starter #26
I have been looking through the web for other answers to this. Is it possible I have a bad/ dodgy earth somewhere?

just to clarify the issue, the bike runs fine most of the time. Sometimes Just after picking up the throttle in low to mid rpm the bike will hesitate repeatedly. it will backfire sometimes very loudly. It also dies occasionally on idle or low rpm gear changes. when the bike isn’t acting up it will idle indefinitely. The bike will start again seconds later. There is no noticeable power loss and using more than 50% throttle and high rpms the bike has never misfired. also seems to happen only when properly warmed up after 5-10 mins riding.

please help
 

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could be earthing. these lumps do vibrate even with the balancer shaft...
now you mention it happens when properly warmed up: have you checked the pickup distance to flywheel? just for fun: put it at TDC, put the lock bolt in to lock the crank (careful here! just follow the manual I sent you). check the distance with feeler gauge and also position.
then again check all the connections with multimeter in continuity mode.

its difficult to diagnose from behind the keyboard when all other items have been covered.
 

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Discussion Starter #28
could be earthing. these lumps do vibrate even with the balancer shaft...
now you mention it happens when properly warmed up: have you checked the pickup distance to flywheel? just for fun: put it at TDC, put the lock bolt in to lock the crank (careful here! just follow the manual I sent you). check the distance with feeler gauge and also position.
then again check all the connections with multimeter in continuity mode.

its difficult to diagnose from behind the keyboard when all other items have been covered.
Right I’m back on this today. I will get that checked and let u know what I find. So I am checking the gap for the pulse generator and flywheel?
The manual says 0.75mm +/- 0.2mm

I do have the crank tdc lock bolt and know how to use it but is it necessary for this? does the pickup and pulse generator even align with tdc I thought it would be before?

thanks
 

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I had to use lock bolt with the SEM ignition on my 620 to set the timing with the cover; I presume the same for the kokusan.
 

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Discussion Starter #30
It just says in the manual to rotate flywheel till the pickup aligns and check gap.
I have managed to do it without the lock bolt, through the small inspection cover. The gap is 0.8-0.85, the manual says 0.55-0.95mm is ok. It’s a bit high but in spec.
To make these continuity tests I will need to remove the cover and just test each wire on the pulse generator up to its connector under the tank?
Thanks again
 

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Discussion Starter #31
I think I should remove the cover so I can inspect the stator windings while I’m there and try and eliminate that from the equation too. What am I looking for other than broken copper windings?
 

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Discussion Starter #32
Ok so I have tested the stator. Here’s what I found:

Pulse coil (red-green)
Manual spec: 100 +\- 20
98.3

stator (black/red-red/white)
Manual spec: 12.7 +\- 2.54
14.8

charging coil (ground-yellow)
Manual spec: 0.65 +\- 0.13
0.6

charging coil (white-yellow)
Manual spec: 0.16 +\- 0.032
0.1
my multimeter can only measure 0.1 ohm increments so I can’t accurately measure this one

so everything seems ok there. what else can I look at?
 

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those values look al right to mee too.
due to changes in temperatures and expansions, I would put the pickup at the 0.6mm personally...
 

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Discussion Starter #35
those values look al right to mee too.
due to changes in temperatures and expansions, I would put the pickup at the 0.6mm personally...
ok I will do, surely that can’t be my culprit though as it’s in spec?
It’s a bit tricky with the kokusan 4K-3 system on this bike. The pickup is inside the the cover so you have to adjust it blind, then re-fit and check
 

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same with the SEM, but that's a dry system. its got a plastic inspection hole with a marker behind it so you can align the cover (with the pickup/coil inside it) with the relevant dot or line (350/400 is the most advanced mark, for the 600/620 its the least advance mark).
loosen the screws a bit, lock the crankshaft, rotated the cover accordingly and tighten the 4 screws, all done!

but on your bike there should be an inspection glass, yes? there was on m y 640 engine...
 

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Discussion Starter #37
I thought I would check the throttle valve sensor readings. In the manual it says you must adjust the idle speed correctly before doing checks. My bike idles perfectly and it has been dyno tuned so I presume that’s ok.

blue - black= 4.21k
Yellow - black= 760

the manuals says the yellow and black measurement should be within:

4210 x 0.15 = 631 +\- 50

All the other figures are within spec but this is not. What would a bad TPS do?
 

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How about the regulator/rectifier?
I suspect your multimeter will show once its more than 0.1 increments, so if its 0.16 ±0.032 (so technically between 0.128 and 0.192) your meter will show as 0.1 as its between 0.1 and 0.2
 

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from my understanding:
fuel injection bikes: it uses the TPS for selecting the correct ignition timing advance, and injector duration.
carved bikes: mostly for tempering the ignition only.

some say you can ride with the TPS disconnected and it livens things up a bit (because not delaying the timing).
never had a TPS on a carbed bike before so can't comment on this.
does raise the question: if your bike starts without the TPS connected, how does it react/behave compared to the issues you have currently?
 

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Discussion Starter #40
same with the SEM, but that's a dry system. its got a plastic inspection hole with a marker behind it so you can align the cover (with the pickup/coil inside it) with the relevant dot or line (350/400 is the most advanced mark, for the 600/620 its the least advance mark).
loosen the screws a bit, lock the crankshaft, rotated the cover accordingly and tighten the 4 screws, all done!

but on your bike there should be an inspection glass, yes? there was on m y 640 engine...
no inspection glass on the stator side of the engine just a plastic inspection cover u can peek through
 
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