Inconsistent idle?

[gw204]

I was hoping you all may be able to help me track down an idle problem I'm having with my '85 150 Black Max. I rebuilt the carbs and put in new BU8H plugs and noticed that when idleing, she seems to drop 50 or so RPMs and then pick up again repeatedly. I now have the heads off to replace the head gaskets (in real bad shape) and noticed excessive carbon buildup on top of the pistons and light scoring on the no. 2 cylinder walls. No shavings or debris was present so I think it's been there a while. Compression is still even on all six cylinders at 125 lbs. Could this excessive carbon be causing the problem? I plan on doing a shock treatment once I get it back together to remove what carbon I couldn't get with the heads off. If not, what should I look for next. Repowering next spring with a new powerhead or a new motor so I just need this to run a few more weeks to fish out striper season.

Thanks.

[vector mike]

I not really sure about your idleing problem but if you used synthetic oil in your gas it would prevent alot of your carboning up problem. Just something to think about when you go to your new powerhead. :)

[Burke Kilgour]

Check all your bleed lines and check valves.

[stvhelm]

one thing that commonly gives trouble is the cold start enrichening valve. its that little dohicky that lets fuel from the top carb drain into the middle carbwhen you push in your key. It can be allowing fuel to pass with out hitting the key switch. there is an adjustment on it that could be out of whack.

[QUICKSILVER]

I had a stator that was causing that once. At idle it would drop a couple of cyls., and then pick them back up. It only did it sometimes.

[Tom D.]

Vacum(sp) leak maybe?

[Clams Canino]

I've got a similar problem and it's caused (in my case) by loose / worn bushings in the throttle arm / trigger department. I'm gonna deal with it in the spring either correctly - or by adding a small tensioner spriing to the trigger to keep a little pre-load on it.

-W