Reply To: Big twin service bulletin

[Don]

We have had a similar discussion regarding 15/18hps that seemed to have hot exhaust housings. We found that there was a relief hole from the lower cylinder cooling jacket that sprays into the exhaust housing. Oftentimes these cooling relief passages get plugged up with carbon. I’m wondering if your Bigtwin has a similar relief hole…Wish I had a crankcase around to check, but do not… I would prefer having the relief hole coming from the block, then reducing cooling water pressure by drilling into the inlet cooling tube. I will try to find a picture of this relief hole on the smaller engines and post it for you…………Don