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Author Topic: Spark Plugs  (Read 610 times)

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Offline Jayson Hill

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Spark Plugs
« on: November 02, 2017, 08:53:43 am »
Hi Chaps

I took the BMW for a nice long ride and when it heats up at slow speeds it tends to cut out, then wont start, starter turns over but does not fire. A quick push start gets me going again. First port of call was to check the spark plug, i see it has a CR9EK , but the interweb suggests CR9EKB.....could this be an issue?

Open to any suggestions?

Thanks chaps
Jayson
 

Offline katana

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Re: Spark Plugs
« Reply #1 on: November 02, 2017, 09:58:50 am »
The spark plug will work just fine.  Valve clearances?
If you want to haul ass, you gotta mix gas.
 

Offline Jayson Hill

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Re: Spark Plugs
« Reply #2 on: November 02, 2017, 02:32:19 pm »
No sure, will send it in if this does not resolve the issue. Would valve clearances cause the bike to cut out???
 

Offline katana

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Re: Spark Plugs
« Reply #3 on: November 02, 2017, 04:12:04 pm »
More than a sparkplug - unless it is really worn out on the electrode.
If you want to haul ass, you gotta mix gas.
 

Offline Jayson Hill

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Re: Spark Plugs
« Reply #4 on: November 02, 2017, 04:22:28 pm »
Mmm, will see, engine is basically new, so will swap plugs this eve and see. Thanks!!!
 

Offline LanC

Re: Spark Plugs
« Reply #5 on: November 03, 2017, 04:28:46 pm »
I doubt it's the spark plug. Are starting it in neutral? Does the starter sound like it is under strain or like the battery is weak when trying to start?
I would also guess valve clearance or a worn decompression lever. Mine at one stage also cut out when hot and rolling off the throttle. Would not hot start but bump started quite easily.
A quick fix I found when this happens was to pour some water over the cylinder head to cool it down. Something in the valve or decompression lever area would loosen up when it was cooler it would start fine.
My valve clearances were in specification but i changed the shims anyway to next size, still in spec, and that solved my hot start problem in the end.
 

Offline Omninorm

Re: Spark Plugs
« Reply #6 on: November 07, 2017, 12:09:49 pm »
I doubt it's the spark plug. Are starting it in neutral? Does the starter sound like it is under strain or like the battery is weak when trying to start?
I would also guess valve clearance or a worn decompression lever. Mine at one stage also cut out when hot and rolling off the throttle. Would not hot start but bump started quite easily.
A quick fix I found when this happens was to pour some water over the cylinder head to cool it down. Something in the valve or decompression lever area would loosen up when it was cooler it would start fine.
My valve clearances were in specification but i changed the shims anyway to next size, still in spec, and that solved my hot start problem in the end.

Hmmm damn, I was with Jay when this was happening...it did sound like the battery was under strain when trying to start.

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Offline LanC

Re: Spark Plugs
« Reply #7 on: November 08, 2017, 08:49:47 am »
Hmmm damn, I was with Jay when this was happening...it did sound like the battery was under strain when trying to start.
To confirm this I would suggest carrying a multimeter with you and when it starts giving that starting issue measure the battery voltage while the bike is off. Battery should be healthy >12.8V since the alternator should have been charging it. Now keeping the multimeter on the battery, start the bike, voltage should not drop below 10V (i think, just measure your bikes normal cold start voltage drop to confirm). If is dropping below 10V then there could be too much resistance/compression from the exhaust gases still in the cylinder because the decompression level is not opening the exhaust valve enough.
 
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Offline Omninorm

Re: Spark Plugs
« Reply #8 on: November 10, 2017, 11:45:29 am »
Hmmm damn, I was with Jay when this was happening...it did sound like the battery was under strain when trying to start.
To confirm this I would suggest carrying a multimeter with you and when it starts giving that starting issue measure the battery voltage while the bike is off. Battery should be healthy >12.8V since the alternator should have been charging it. Now keeping the multimeter on the battery, start the bike, voltage should not drop below 10V (i think, just measure your bikes normal cold start voltage drop to confirm). If is dropping below 10V then there could be too much resistance/compression from the exhaust gases still in the cylinder because the decompression level is not opening the exhaust valve enough.

I think he actually took it in to have someone look at it. But thanks for the explanation, good to know.  :thumleft:
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Previous:  KTM 690 Enduro R , BMW G310GS, BMW 1200GS LC, BMW F800GS, Suzuki Vstrom 650, Honda Transalp XLV700, BMW Xchallenge, BMW Xcountry, Yamaha WR250F, Honda NC750X, Honda XR150, Kawasaki KLX450R, Yamaha YZ250, Kawasaki KX450, Yamaha YZ250F,  KTM 250 XCW, Yamaha DT125, Yamaha DT50, Honda NSR250, Yamaha RZ 50.