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Piss poor manufacturing or part failure damage over time?

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Please take a look at the attached picture. This is the sparkplug well for a '99 Yamaha XT350 dual sport. I was shocked to see this and don't know if this is a result of just plain bad manufacturing (crappy casting mold?) or if it is from sustained failure around the sparkplug etching away the surface area.

 

The Story:

 

The factory clutch cover gasket failed at the top (as this model is want to do) and oil was spraying out of it.

 

I replaced the gasket but in doing so, I damaged the decompression link assembly when re-installing the cover, but did not realize it. The bike started on a half kick and ran great, per normal and per an earlier jetting of the carb.

 

While on a short ride, the bike would not start after sitting for a few minutes. The kick-starter seemed to be just a little too easy and no number of kicks would start it. I was able to bump start the bike.

 

The bike ran smooth, then rough and stalled after a few miles. Again, I could not kick start it, but could bump start it. This happened a few more times (smooth running, then rough and stall) but I got it home. I tried to start it again and nearly broke my ankle when the kick-starter rebounded.

 

I noticed the external decompression assembly was not moving the cable. I disassembled the clutch cover and found that I had, earlier, broken the decomp link assembly. I replaced it with a new one, replaced the gasket and reassembled the bike. Again, it would not start. Additionally, it also now would not bump start.

 

Thinking that the decompression valve might have been opening when it was running and running rough and that possibly the spark plug got fouled during these stints, I removed the spark plug, which came out way too easy, and was bummed to see that it was not fouled so the non-starting issue is not the plug.

 

I was about to re-install the plug and noticed the black area in the sparkplug well. I have never seen this before.

 

Any ideas about this "damaged" area would be appreciated as would any comments/ideas as to how/if the non-working decomp link assembly could have caused the run-rough-stall issue, leading to the current non-startable/non-running issue.

 

Thanks!

 

Close Up.JPG

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Sounds like mechanic issue, not bike

 

.

I have never seen that clutch cover gasket fail.

If the decomp was set up wrong, all it will do is eityher not work or hold an exhaist valve open. Iver time, it is pobbile to do damage to the cam or lifter bucket, but you have to remove the colve cover.

 

Most likely you suffered a cam chain tensioner failuer and have subsequesntly caused valve isses. Only way to know is to look at the clearances.

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I can't comment on the fowling in the spark plug well, but on starting difficulties I can tell you my bike was a bear to start due to a severely stretched out cam chain which was altering the timing  . After I replaced the cam chain and guides my bike starts no problem .  Just something for you to think about .

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