Westie1 29 #1 Posted October 27, 2018 So after some googling I bought a new plug for my k341 yesterday. I went for the NGK B6L as the B4L is on all the lists but is apparently a little too hot. I've looked at what came on it just now and it's a NGK B6S which is rated at best for 8hp. What effect will this have had on my engine and could this be the reasoning for the head warp or the carbon build up? Just curious really but glad I ordered a new one yesterday now. I thought the plug sat a little far back in the head I will compare them. Thanks Share this post Link to post Share on other sites
Stormin 4,458 #2 Posted October 27, 2018 The head warping is most likely due to the head not being bolted down correctly. But if it's been running to hot, that also could be the cause. Though if that was so, I would think the valve seats would be burnt. Carbon build could be to never been de-coked or worn rings. Share this post Link to post Share on other sites
Westie1 29 #3 Posted October 27, 2018 (edited) Apparently the rings are good as I've had no oil washing the carbon from the face of the piston, so I have read anyway. I haven't looked at the valves/seats, to be honest I was surprised that the valves were alongside the piston as I've never seen a flat head before. Only messed with my Honda ohv pushrod pc50 up to now (and that hasn't ended too well lol) Edited October 27, 2018 by Westie1 Share this post Link to post Share on other sites
Anglo Traction 1,016 #4 Posted October 27, 2018 28 minutes ago, Westie1 said: So after some googling I bought a new plug for my k341 yesterday. I went for the NGK B6L as the B4L is on all the lists but is apparently a little too hot. I've looked at what came on it just now and it's a NGK B6S which is rated at best for 8hp. What effect will this have had on my engine and could this be the reasoning for the head warp or the carbon build up? Just curious really but glad I ordered a new one yesterday now. I thought the plug sat a little far back in the head I will compare them. Thanks B6L versus B6S . Both have the same heat range, but the B6S has the shorter reach (screw thread into C/head) which is only 3/8" and so would not be able to dissipate tip heat away and into the C/head. B6L (correct equivalent to Champion RH10C) has a reach of 7/16", so more thread engagement in the C/head which will bring the heat dissipation rate back to where it should be for that part of the Spark Plug. You have probably deduced that the lower the number on NGK Plugs, the hotter it runs (the plug that is, not the engine). Champion = higher the number, the hotter it runs. As you/we will never know what conditions were when the previous owner was running it (with/without Filter etc), it is difficult to say. For your situation, once you've got it back to how it should be with a good A/Filter and what you've done C/head & Carb-wise, it will run fine. Not burning Oil yet and will have efficient cooling. Share this post Link to post Share on other sites
Westie1 29 #5 Posted October 27, 2018 Ah so the 6 is the heat range, embarrassed to say I hadn't made the connection but seems obvious now thanks. It did look very short, I've been reading up on how they changed plug placement to above the exhaust valve and it seemed silly the plug was so receded. Thanks guys back to my sanding Share this post Link to post Share on other sites
