700 Magna Collector Box Rattle Problem

[arent_we_sarcastic]

I've been chasing a metallic rattling noise for awhile now that seems to resonate at about 2500-2700 rpm . I traced it to a broken/missing bolt that clamps the collector box to the oil pan. When I replace this bolt the problem goes away but I have had to replace it several times now as it keeps breaking. Is the collector box supposed to be flat against the oil pan or is there supposed to be a spacer of some type in there?
I looked online at an exploded view of that area and I don't see one there...anyone have any suggestions ?

[John Luttrell]

I don't see where it calls for a shim either, but I'd shim it with washers as required; it sounds like the collector is pulled into a bind when you torque the bolt down.
http://i2.photobucket.com/albums/y6/johnlutl/exhaust.jpg?t=1178754367

[MagnaDaddy]

Rattle seems to be a "feature" of my 86' as well.   Somebody had tried to cold weld the collector to the oil pan at some point in the past and really goobered up the threads for that bolt.....

[silveradocowboy]

Try crimping a few of the threads on the bolt in a vise or maybe use a hammer to flatten them slightly. Too much and you won't be able to screw it in and not enough is...well you know.

[arent_we_sarcastic]

I went to Brafasco and got the "strongest" bolt they had in that size. It seemed to last longer than the others. Problem now is the other bolts were hex head and they broke right at the head so it was a simple task to remove the broken stud. The stronger bolts are socket head and it broke halfway down. So, now I have to lay the bike down on some grass so I can get a screw extractor on it.

[John Luttrell]

Shim it with washers or it will continue to break bolts.

[arent_we_sarcastic]

Well I gently laid the bike down on the front lawn so I could get access to get the broken bolt out. I measured the gap between the collector box flange and the oil pan, got a couple of washers as close to that thickness as I could and bolted it back together again. The rattle is reduced but not completely eliminated as it is when the collector box is flat against the pan...still working on trying to completely eliminate it.

[MagnaDaddy]

I went through a similar exercise and finally decided that it gives my Magna character  

[ThomasMagna]

I'm not sure if this would help, but if you try again, get a couple of rubber washers. Put one on the bottom and one on the top of the rest of the spacers. Like I said, don't know if it would help.

[arent_we_sarcastic]

Thanks for the suggestion.
The same thought has occured to me as well but with the collector box getting hot I passed on that idea.
Everytime I hear the rattle it reminds me of the old heat shields on the first generation catalytic converter equipped cars that came out in the mid 70's. There are heat shields on the Magna but they appear to be tight...still searching...

[Charles S Otwell]

Just out of curiousity have you had the collector box off ? I've only had one off and it had quite a few cracks on the top side of the box , this could cause the metallic rattle , and the heat from the cracks could be weakening the bolts, Just a thought..

[arent_we_sarcastic]

I haven't had the collector box off but I have given it a good once over and didn't see any issues with it. One thing I did try that seems to be working is to shim the collector box away from the oil pan. The original gap was about .140" so I gathered some various thickness washers and tried increasing the gap in .020" increments. The rattle seems to have completely disappeared with a shim of about .200".
Will keep you posted.

[John Luttrell]

yeah, shim it with washers............who'd a thought?  he he