A couple of questions.

[Bigfoot]

I have a 80 MNS that I have been working on. Today I was finally able to take it for a short ride. It ran with plenty of power and handled very well. I do have a couple concerns though.

1. The idle was slightly rough but the carbs have not been sync'd yet and I am still running some seafoam through the system. The choke does not work, when I use it during a cold start, it will not start. It will start without it and I need to throttle up a little until it is warmed up.

2. After cruising for awhile, it takes a long time for the idle to come back down. It will stay at 2000-2500 for awhile before slowly backing down.

3. At around 5k there is a pretty bad buzzing sound. I have not been able to find anything loose externally that could be vibrating and am just concerned that this could be something internal that indicates a larger problem.

I would appreciate any comments, suggestions, or insights into these issues.

[DGXSER]

As to items one and two, have you checked for a vacuum leak? I know it can cause the hanging idle issue. Although if it starts with no choke, that sounds like a rich condition. throttling up would let more air in so that may still be a rich condition.

I got no idea on no 3.

Sure there will be better ideas coming, JMHO.

[CatatonicBug]

I'm no expert, but it sounds to me like there is an issue with the mixture screws. Have you checked/moved them lately? Adjusting those screws then sync-ing the carbs may be the best solution.

Without hearing the rattling noise, or knowing where it's coming from, it's going to be almost impossible to tell what that is caused by.

[Ken Talbot]

Until the carbs have been properly sync'd, you will continue to experience that hanging sensation, being slow to retuurn to idle.

[Bigfoot]

Thanks for the ideas.
Tomorrow I guess I will pull the plugs and see if it seems to be running rich. I have only put about 30 miles on it since I got it running.
I did adjust the mixture screws when I cleaned the carbs. I will check the screws but I am sure that I set them as per the manual.

[CatatonicBug]

I am sure that I set them as per the manual.

Remember that the manual only tells you the standard setting. Each carb is different, and may require very slight changes or adjustments.

[motoman]

I can remember back in the day when I had my Venturer new, that the idle wouldgo a little erratic like that. Would do the cam chain slack adjustment while hot and it was back running and idling normal. Ironiclly, during that ten year of ownership, never did have carbs sync. and it always run fine. Guess ignorance is bliss. Selling it in '91 and getting it back 3yrs. ago, lots more knowlege, it holds me accountable now. Just a thought, and may explain the noise your getting too. Worth doing to avoid a diaster top-end.

[oseaghdha]

Check the exhaust shields. That's probably where the buzz is.

[trbig]

If it won't start with choke on, the little jets in the float bowls are probably dirty. Either that, or it's already running really rich.

If it's a buzz you're hearing and not feeling, then yeah, I agree that it's probably heat shields on the collectors.

Tod

[boyat68]

Just like all the above posters are telling you, it will not idle right untill you synch the carbs. Look at it logically, carb No. 3 is what you synch on. If carb No. 1,2,4 are idlying higher or lower than 3 the vacuum on those carbs will drag 3 higher or lower. The ideal situation is to get 3 idlying at 1100 rpms and adjust the others to that exact vacuum. It is a touch and go situation where you have to get all the carbs pulling the same vacuum and then lower or raise the idle with the main idle screw. Once you do this then you can adjust the air screws individually to suit the color of the plugs. I think that Ken Talbot has a routine on how to adjust the air screws for the "sweet Spot"

[XSPastor]

Check the exhaust shields. That's probably where the buzz is.

If the exhaust shields are tight, you might have a loose baffle in one of the mufflers, a loose clamp on a header or the crossover pipe (if you have the stock exhaust), out of sync carbs cause more vibration than usual, worn motor mounts, loose muffler hanger bolts, cracked muffler or weld where the mufflers join to the header pipes... Check all the bolts and nuts and tighten anything that's loose, sync the carbs and your vibration will most likely go away.

Loose is pronounced luce.
Lose is pronounced luze.

Pet-peeve of mine. People switch them a lot. Yeah, I've got issues.