RLV Can Support for Yamaha KT100

Bill Snow · Joined: 22 May 2012 Posts: 9

Has anyone used a support for an RLV Can muffler on a KT100?

This past weekend my RLV can fell off as a result of one exhaust stud snapping off and the other being pulled out of the head. Or, vise vera.

I read somewhere that this happens from time to time, but it doesn't seem like a common problem for most can racers.

My thought is that a support for the can muffler might lessen the chances of both studs breaking or pulling out and the muffler falling off.

Thoughts? Is a support too much?

Dan Rudd · Joined: 15 Oct 2009 Posts: 198

Interesting, never heard of that happening. Never seen a can supported.
I suppose if the can was to become loose it could continue to bounce until it pulled a stud.

Dan

Jim White · Joined: 21 Jul 2001 Posts: 994

I too think it came loose and then just beat itself to death. On my exhaust nuts I use 2 head bolts drilled out for saf-t-wire. Then you don't have to over tighten them (messes with the roundness of the bore if you do) and they won't back off either.

Ron Gordon · Joined: 27 Dec 2009 Posts: 150

Why not just double nut both sides or use a lock washer under the nut on each side...

Does sound like the cans nuts were torqued a bit much to cause a stud to pull out of the cylinder. As most people know a loose exhaust can get you a DQ as fast as one that falls off.

Ron
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Bill Snow · Joined: 22 May 2012 Posts: 9

Both studs were double nutted. Maybe they were torqued too much.

I am going to give it another try without a support. Double nuts and safety wire as well.

Kent Metcalf · Posted: Fri Jun 08, 2012 6:31 pm Post subject:

Have you checked to see if the holes in the head might have worn larger and the studs might be slipping past the threads and popping out of the head?
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Walt Gifford · Posted: Sat Jun 09, 2012 6:01 am Post subject:

An SAE flat washer, a lock washer and nut is all I ever used. Tighten it until the flange starts to bend a little.

Gif Cool

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Frankie Schaffier · Posted: Sat Jun 09, 2012 6:55 am Post subject:

It came loose.

Folks either over tighten them, causing the alum around the hole to "ant hill" and end up pulling the studs from the cylinder. Or under tighten them being afraid of causing the "ant hill" and pulling the threads. Walt pretty much nailed it. I suppose there is a torque, but it just becomes a feel thing.

Rather then risk a DNF after spending the money it costs to run nationals, I also cross drilled the nuts across the flats, or though the point of the nut if you will. Then safety wired them in a manner that the wire is pulling the nuts tight, they can't spin in the dirrection to loosen.
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Walt Gifford · Posted: Sat Jun 09, 2012 8:15 am Post subject:

120 inch pounds but you need a crows foot wrench and some math skills on a can muffler.

Also, the Nord loc washers seem to work well. http://www.nord-lock.com/default.asp?url=2.16.37

Gif Cool

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FAA certified jet engine and aircraft technician
Nicholson Speedway class champion 2001
Yamaha KT100 Service Center
40 years karting experience

Frankie Schaffier · Posted: Sat Jun 09, 2012 6:50 pm Post subject:

Gregory Dzielinski · Posted: Sun Jun 10, 2012 8:06 pm Post subject:

We've bn running a can support for years on our laydown yamahas.
My brother built one for both of us. After the can came loose, pulled out the studs and broke the EGT probe wire; end of race.
Very simple to build.
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George Clausen · Posted: Mon Jun 11, 2012 5:17 pm Post subject:

Couple of mentions of Nationals and DQ's. A can support would be an issue, rule says no attachments. Have seen several instances where the studs had marred threads so the nuts ( that were left loose on purpose ) could only unscrew so far. 2 8mmX1.25 studs are more than up to the task of securing the muffler
George

Jim Fry · Posted: Wed Jun 13, 2012 8:02 am Post subject:

Can supports were the hot setup a few years ago in road racing, because guys figured out that if you left the can a little loose, it was faster! Therefore the rule change for no attachments.

Like most we double nutted and had no problems. Jim

patrick slattery · Posted: Thu Jun 14, 2012 9:42 am Post subject:

Nordlock washers are great.

We just use a nut, no washers and no problems. My Engine supplier only ships with the nut and doesn't recommend the washers or the double nuts.

For me, the key to getting the muffler on correctly is to run both nuts up tight by hand and then rotate back and forth from left to right and slightly tighten each nut untill they are snug tight. If you tighten one side and than the other you put the studs in a bind and is a potential for the stud to pull out or one side of the nuts to start backing off.

If your running double nuts, you will get a close look at by the tech man by the way. Smile

John Mulvihill · Posted: Tue Jun 19, 2012 5:45 pm Post subject:

Two nuts are better than one. (There's a bad joke there somewhere.....).

Make sure that they are tight enough not to have any exhaust leakage around the gasket (that is what tech is looking for). Shocked

But not tight enough to distort the cylinder bore.

If the threads in the cylinder are damaged take a look at Pete Muller's web site for the brass insert fix.

Over the years the weight of the can on the studs wreaks havoc on the stud threads. Another good reason to do away with the cans.

John
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