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Still working the bugs out of my 81 YZ 465. I know those old big bores were famous for their run-on type surging on deceleration, but want to correct this. The overall jetting condition seems somewhat rich, but low rpm range seeming lean. When I rev it in neutral, it takes several seconds of the old "ting ting tings" before it idles down normally. I am thinking that the slide may need replacing, as the chrome looked fairly worn when I cleaned it. Does that sound like the probable cause? The air screw doesn't seem to have much impact on this. I've already eliminated the probability of any air leaks, and besides, if there was an air leak it should surge at all times, and be consistently lean. Only other guess could be a timing issue, I don't know where else to look. Any help is greatly appreciated. Thanks.

What exactly does it have for a carb?

I have one of those bikes too, I think its a 38mm round slide mikuni but I am not staring at it right now.

Yes, Mikuni round slide. Under further inspection, I think my carb boot is leaking. Wasn't at first, but was cracked and may have given out after a couple of runs. Just my luck, those bastards aren't cheap!

jbsleddin wrote:Yes, Mikuni round slide. Under further inspection, I think my carb boot is leaking. Wasn't at first, but was cracked and may have given out after a couple of runs. Just my luck, those bastards aren't cheap!

www.hotfootmoto.com

Owned one back in the day. As I recall, the quote from then was, "If it ain't pingin', it aint RUNNIN!" They were a nasty machine to jet and I seem to remember, if you could get rid of the pinging, then it was too lean.