From:Rob R
Subject:ST165 bogs at higher RPM - Why? Date:Wed May 14 01:27:22 2014
Hi all - new to the list. My brother and I just completed restoration of a 1958 ST165 that has been in my wife's family since new. Visually, it's stunning. We are test-riding it right now, and a unfortunately a little stumped by it's behavior. Starts easily and runs well, but when it reaches medium-high RPM, just seems to bog... Doesn't want to rev any higher. So far we have checked that the factory timing marks are correct, with .020" point gap. We haven not yet pulled the head to check the timing in the recommended (precise) way. We started with the carb needle in the uppermost position. Just tried lowering it one notch (leaner); that seemed to make it pull a little better, but still not liking higher RPM. Doesn't seem there is any real way to adjust float level... I havent read the spark plug yet. I should do that.

What else can I tell you? The voltage regulator is new, and voltage is right where it should be. Lights and horn are very strong. The entire exhaust is new, and somewhat louder than the old system. Might have less back pressure... Oil is mixed at 25:1 per the manual. Using modern Bel-Ray two-stroke oil. Compression feels very good when kicking it over. Engine was not rebuilt be me. It supposedly has about 500 miles on a fresh rebuild.

If any of you have any ideas, I would love to hear them. I am much more familiar with Harley flatheads. I have a '38 Big Twin and a '42 WLA. This is my first foray into two-strokes... If you are curious, there are some pictures of our ST165 here:

Thanks in advance for the help.