Muffler Insert


On the 250F with a vortip it ran weird until I went lean on the jetting especially the mid (needle) and the main. I ended up rich on the pilot. Then it ran like a raped ape. I think if you play with the jetting you'll get it to run the same.

I feel now I lost nothing in power compared to the stock open exhaust. Jetting is everything you just have to adjust it until you get it right, no matter what exhaust or air combo your running.

The part number is GYT-5TJ93-75-00. My dealer didn't have it in the computer, called Yamaha, and that is the part number they gave him.

We all want a quiet bike. :)

can someone that has an insert lay out a couple of dimensions so i can make one, diameters and lengths of tubes etc


Thanks for the info. I ordered my insert this morning to be shipped 2nd day to CA. Well worth the $16 shipping to get the part before I get a ticket! Local dealers say possibly mid April - No thanks!

:) I just bought the last insert at Snake River. Thank you for the information. It will arrive next wednesday.

I am so sick and tired of SNOW!!! I need to take a trip down south.

I needed to thank you as well. I got either the first or second one this morning.

Too bad my local shop has a Cranial Rectal Inversion. Wish mine was more like your shop. :)

called snake river today, all gone!

I guess I was lucky too. Ordered mine on Feb 18, and got it about 10 days later. Just under the wire. :)

Just got back from riding and I had to laugh when I read all the replies about you guys making a run on the muffler inserts at my local dealer! They're probably wondering what happened... :)

vmaxcbr900wr426, JJboys and Md450f....glad it worked out for you guys!

Storch is going to home brew one this weekend using the dimensions from the GYT-R insert. Good luck and make sure you get us some photos!

Thanks Dave, made up the sketch tonight, will try to play Sat on the lathe and mill. You other guys who want a copy of my sketch, send me your email address. Do understand we measured this over the phone.



I have never seen a GYT-R Insert. The sketch was made over the phone with another TTer and from pictures he provided. It is not an engineering drawing! Based on the phone call I believe the tubes to be 5/8 and ½ OD with .062 walls. I used 5/8 x .035 and ½ x .028 wall 4130 tubes and 6061T6 for the plug. This should be almost 4.5 times the stock exit area and 75% more than the estimate of the GYT-R. I bored the plug from the exhaust end with a 1.125 drill to just short of the depth shown. I then used a boring bar to bring the diameter out slightly and flatten the bottom of the hole. This left a conical projection from the 1.125 drill bit into the forward portion of the plug. This is important. After boring from the front for the 3 tubes the small triangular piece of aluminum between the tubes will fall out. This is good.

I then pressed the tube in place. At the rear face of the tubes, I TiG welded the ends together and filled in the missing triangle between the tubes. Notice by doing this you can trap the tubes from moving forward due to the conical shape of the plug (1.125 drill). The tubes are constrained from moving aft by the undercut from the boring process. I then clamped the 3 tubes together and welded a small amount of bead to stabilize the tubes.

I also tried lathe spinning the long tube to give it a bit of a bell mouth like the GYT-R. As I was doing this, I suddenly felt stupid, pulling on the end of an oiled steel bar shoved up the spinning tube in the 3 jaw chuck. I’ve never tried this with 4130. Wish I had a torch to heat it to at least red-hot first!

My part should weigh less than the GYT-R since it does not have as much steel in it. It took 3 hours to make, but I’m just a hobbyist. The drawing and pictures can be found soon at courtesy of ddialogue.

Good Luck, if you can get a store bought one It's a bargain!


Finaly found a plaice that say's they can get them but just my luck the dam thing is on back order . MAN IM SICK OF THIS NEAR 0 STUFF

I got mine today from Snake River Yamaha. Thanks for the info. :)

I'd order from them again.

I might actaully get to try mine out Sunday. Supposed to be 65 here Sunday. Wooooooohoooooooooo, spring may be here. :)


I am making one at work tomorrow. It seems as thought the GYT-R unit is just bored all the way through and held in place bt a set screw. I am a machinist by trade. I am figuring 2-3 hours for the first one then about 1/2 hour each after that. I will try and get some photos. I may take a bit of creative freedom on the design. I hope my tubing shows up. If any body wants one of these made let me know, I might be able to help you out. Cheap. ----Mike

I chose not to bore it all the way through. This reduces the part count by 2 plus one fastener is eliminated.

The GYT-R looks like it needs 2 steel disks bored for the steel tubes and turned to the ID of the aluminum plug. A lot of welding is needed to secure. This is not required with my design.

Best of luck, I had a blast making mine.


I rode my WR450 with the homemade insert Sunday and I'm very happy with it. I had ridden the bike up and down the street with the stock insert removed and my wife got very upset. My wife says the bike is now very acceptable, but that I'm not. Still have some work to there!

Did loose a little off the top end, but the carb seems happy with no jetting changes so far.


Just passing along some info I got from deep inside big blue.

The GYT-R muffler insert works for all 4-stroke WR models from 1998 to present and the correct part number is GYT-5TJ93-75-00.

The insert provides 96 dBa (on both 250 & 450F) per SAE J1287 (same as USFS Test) which is 20" @ 45 deg.; engine run at 1/2 of max rpm.

My source doesn't know the current back order status.

Hope this helps.

We currently have six (6) of these inserts in stock. Please e-mail me and I'll reply with a cost ($ 40.00) plus tax and shipping. Contact me at:

These inserts are made here in Huntington Beach, CA. for YMUS. I've tested a couple of versions just before the new WR's were released to the public. I'm impressed with the sound levels (meets the new 96 dbA) that are about to be enforced here in California. I've yet to feel a problem with the jetting and power output. I guess it depends on where you ride.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now