Posted March 06, 2003 - 07:40 PM
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.
Posted March 07, 2003 - 12:54 AM
Posted March 07, 2003 - 09:05 AM
Posted March 07, 2003 - 10:46 AM
I am so sick and tired of SNOW!!! I need to take a trip down south.
Posted March 07, 2003 - 11:15 AM
Too bad my local shop has a Cranial Rectal Inversion. Wish mine was more like your shop.
Posted March 07, 2003 - 04:24 PM
Posted March 07, 2003 - 05:11 PM
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!
Posted March 07, 2003 - 06:48 PM
Posted March 09, 2003 - 10:24 AM
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 www.wr450.com courtesy of ddialogue.
Good Luck, if you can get a store bought one It's a bargain!
Posted March 09, 2003 - 04:16 PM
Posted March 11, 2003 - 02:05 PM
Posted March 11, 2003 - 03:28 PM
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 email@example.com
Posted March 11, 2003 - 04:44 PM
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.
Posted March 11, 2003 - 04:57 PM
Did loose a little off the top end, but the carb seems happy with no jetting changes so far.
Posted March 12, 2003 - 10:07 AM
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.
Posted March 12, 2003 - 04:55 PM
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.