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General Category >> Rubber Side Down! >> MAC exhaust installed, now a question...
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Message started by 911radioman on 02/22/06 at 14:48:41

Title: MAC exhaust installed, now a question...
Post by 911radioman on 02/22/06 at 14:48:41

Got the MAC muffler installed today. Went on sweet, no leaks, bolted right up. The sound is awesome! :D

Now I have a housekeeping question... I feel like this is probably a fine tuning issue, but I need the experts to sound off.

When I roll off the throttle down to an idle, sometimes the bike dies. I've set the idle up to compensate for this, but I'm wondering if a little fine tuning needs to be done.

What do you guys think?

Title: Re: MAC exhaust installed, now a question...
Post by pgolden on 02/22/06 at 14:51:41

Try adjusting your air/fuel mix. (The screw you uncovered). I adjusted mine til the engine idled up, then adjusted the idle speed.

Title: Re: MAC exhaust installed, now a question...
Post by Dynobob on 02/22/06 at 15:26:20

After I installed my Supertrapp I noticed the exact same thing. No tuning needed. Just turn up your idle speed slightly to the point where the engine won't die when letting off the throttle. It's normal and related to a change in engine vacuum or something ???

Title: Re: MAC exhaust installed, now a question...
Post by 911radioman on 02/22/06 at 15:44:02

Dynobob wrote:

Title: Re: MAC exhaust installed, now a question...
Post by bikingb on 02/22/06 at 18:49:13

I got my Supertrapp today. Doing the install on Friday. What kind of adhesive to you use? Something I can get at the auto parts store?

Title: Re: MAC exhaust installed, now a question...
Post by 911radioman on 02/22/06 at 18:55:11

On my MAC, I didn't use any adhesive. I used the gasket that was on my stock muffler. It is kinda hard to tell there is one there, but if you take a pocket knife and go around the circumference of the gasket between the muffler pipe wall and the gasket, it will loosen it up and you can then remove it from the stock muff gently and reuse it. It sealed very well on my new MAC.

Title: Re: MAC exhaust installed, now a question...
Post by Dynobob on 02/23/06 at 03:41:20

bikingb wrote:

I got my Supertrapp today. Doing the install on Friday. What kind of adhesive to you use? Something I can get at the auto parts store?

I had to remove some metal off the end of the header pipe so the mount would line up and I sealed the connection with high temp Permatex silicone sealant. You can get it from the auto parts. Just make sure you get the high temp version designed for exhaust manifolds.

http://www.holeshot.com/chemicals/permatex_prod.html

Title: Re: MAC exhaust installed, now a question...
Post by lancer on 02/23/06 at 07:43:34

I didn't know if I was getting into a pilot jet issue because of the dying or not. Hope not! :D I did turn up the idle a bit and it does fine. Actually, I only notice it when the bike is cold and hasn't fully warmed up yet.[/quote]

You have gotten into a pilot jet issue. When you put on the new muffler you CHANGED the air/fuel ratio throughout the entire rpm range, including the pilot circuit. Do the basic carb tuning routine. For the low range, where this particular problem is, do the following:

-Start and warm up the engine for several minutes.
-Turn up the idle speed several hundred rpm.
-Adjust the pilot adjusting screw so that you get the highest rpm possible.(if it is working correctly when you to go too far in either direction the engine should slow, or even die in the extreme)
-Adjust the idle rpm back down to the desired speed

At this point, your pilot circuit (low range) should be tuned correctly so that your engine is getting the proper fuel/air ratio, will idle and run well, and will not die when you roll off the throttle. If it does not, then there is another problem somewhere in the carb.

Title: Re: MAC exhaust installed, now a question...
Post by 911radioman on 02/23/06 at 11:30:19

Thanks, Lancer. I do know that the dying on roll-off throttle only showed up after I rejetted and changed the exhaust, so I figured it was a basic tuning issue. Just wanted clarification.

It is extremely strong through all the other ranges, just periodically wants to die when I roll off, and that more so when the bike is cold. Once it warms up it does fine.

I'll do what you suggested and see how it goes. Thanks again!

Title: Re: MAC exhaust installed, now a question...
Post by 911radioman on 02/23/06 at 12:40:16

Lancer, I did the basic low-end carb tuning and it seems to have taken care of it. I do still have a bit of what I'd call a "lag" when sharply rolling off the throttle, but in listening to the sound clips here of the bikes, it seems that they sound like they're going to die when you sharply roll off the throttle but then they recover. This is what mine sounds like.

Is this the norm after rejetting and upgrading the exhaust?

Title: Re: MAC exhaust installed, now a question...
Post by lancer on 02/23/06 at 21:31:02

The remaining symptoms you describe are normal for a large single cylinder, with just one cylinder and one mediocre carb the engine will drop rpm that way when the throttle is quickly rolled off. Be at peace, everything sounds like it is OK.
If you have the backfiring issue under control then you have done well, GRASSHOPPER.

Title: Re: MAC exhaust installed, now a question...
Post by 911radioman on 02/23/06 at 21:46:12

I still get an occasional pop out of it, but nothing like when it was stock.

Title: Re: MAC exhaust installed, now a question...
Post by Dynobob on 02/24/06 at 04:30:46

911radioman wrote:

YES. I turned up my idle speed just a bit and all is well. I have seen posts here about this issue. Since I raised my idle speed I have had 0 problems. Your jetting's fine.