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Cylinder 4 plug carbon fouling

What was the problem that time? What brand of parts did you use?
So It's a little hard for me to get parts here in south africa don't have a local import store for it and when I have ordered from overseas they tend to get lost or stolen.

So 9/10 times it's finding doner bikes scrap yards referbing parts.

so the last service I changed the cdi units because I fried one. But now I'm wondering if my coil packs are good I'll need to test the one running to 1&4.

If the float level are off on 1&4 or if they are running richer the 2&3 could theu be flooding and they only fire when it get up to temp because it's evaporating the excess?
 
I've seen coils start to fail when they get hot, but not the other way around. Swapping them will at least tell you if that is what is happening. Also do a swap on the CDI units, but do one thing at a time.
 
Not yet. Hoping to get to it tonight.. I was having the same problem and I think my plugs were so carboned up they wouldn't spark.

Put new ones in and it was day and night... except for cylinder 4 that fouls instantly.
Update.. no gas coming out of the exhaust with the wire off the plug.
 
Did you swap the coils around? Did you then swap the CDI's around? Does that cylinder have good compression?
 
Did you swap the coils around? Did you then swap the CDI's around? Does that cylinder have good compression?
Coils are brand new so no, I haven't swapped coils. Yes, swapped cdis and no difference. Compression is 130. Same on cylinder 3 and I haven't tested 2 and 1 yet. I'm also going to do a leak down test.
 
I'm still leaning towards oil. Maybe head gasket is bad. If the plug is black and you can't smell gas, that would be my guess. I wonder if you pulled the plug and held a paper towel or rag over the plug hole, then ran the bike for 10-15 seconds, if you might catch some of what is happening in there.
 
I'm still leaning towards oil. Maybe head gasket is bad. If the plug is black and you can't smell gas, that would be my guess. I wonder if you pulled the plug and held a paper towel or rag over the plug hole, then ran the bike for 10-15 seconds, if you might catch some of what is happening in there.
I will try that. I am also leaning towards oil at this point... last night I had the pilot screwed in until it was seated and still black on the plug. Anyone have recommendations for a specific leakdown tester?
 
Leakdown test results.
Cylinder 1: 2% leakage
Cylinder 2: 5% leakage
Cylinder 3: 7% leakage
Cylinder 4: 3% leakage.
Cylinder 4 is the Cylinder I have been discussing in this thread. As I understand, leakage below 10% is acceptable with a variance of 5% between cylinders. If I am wrong on this, I would appreciate some insight. When opening the throttle on Cylinder 4, I was able to hear some air escaping but seemed to be minimal.
 
Have you changed the caps? There are 6 connections being made in those resistor caps that can corrode and make a bad connection. Once those connections corrode they are impossible to clean.
 
Can anyone tell me if the butterfly is open too far? Can see most of the first hole where the bottom of the butterfly is.
 

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Can anyone tell me if the butterfly is open too far? Can see most of the first hole where the bottom of the butterfly is.
Butterfly valves can be set via a bench sync, but true carb syncing is fine with the bike running and vacuum gauges attached. Plenty of YouTube videos show this process (some vids better than others). Look for brick house builds, he may have one or two despite seeing more SOHC bikes on his channel.
 
Butterfly valves can be set via a bench sync, but true carb syncing is fine with the bike running and vacuum gauges attached. Plenty of YouTube videos show this process (some vids better than others). Look for brick house builds, he may have one or two despite seeing more SOHC bikes on his channel.
I have bench and vacuum synced these a few times. I'm just concerned that the butterfly is binding up and not closing far enough.
 
Have you had to do it a few times because one carb is not returning properly? Are the throttles smooth or tight?
No, just because I've had the carbs off a ton of times trying to troubleshoot it running rich. I usually don't end up having to vaccum sync it as the bench sync has been close enough. Throttle is decently tight
 
I just realized you have 2 threads going for the same problem. I'm not going to keep answering both.
 
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