Yamaha pipes

Depends on what engine. Gas or alky. Flex length is critical also. Now we will wait for Jack or TTown to fill in the answer your looking for.

Tsow probably the best all around for stock to mildly modified gas or alky. For a high modified with LOTS of intake duration added i like the KBY-97 that Kermite is now making again. It comes on at about 10,000 and pulls like a freight train to 14,500 on alky. Jon and Sjg22 should know something about cylinders this week.
Yes jack. The pipe bulldog let me borrow at Daytona. Was a TSOW but he had a hole he drilled in it (??????) so I don't know. But I did set it at 9 1/2 flex. Think I was over Erving thou. Turned 14800 in race

Have u heard of a L4 ? What is it?
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But I did set it at 9 1/2 flex. Think I was over Erving thou. Turned 14800 in race
I have heard of the KT100 turning 17,000 RPM with direct drive, and 15,300 with a clutch, so 14,800 is not over revving for the KT100, but maybe it is for that pipe. And that's in stock configuration.
Steve, the L-4 is a RLV pipe, top end like on enduro karts, it's 1 of a series , like L-1, L-2, L-3 and L-4, it too like the T.S. pipes have at least 1 spl. header, which to me look identical to the L series pipes I have.
I dont like turning mine over 15,000. I know they are capable of turning much more but that sure wears them out quick and is asking for the big BANG. Of course My builds are designed to make torque lower in rpm band. I mostly run smaller tracks 1/8-1/6 mile to. Dont think the overrev helps much in that format. Geared right they accelerate super quick and pull real hard out of the corners.
My favorite pipe from RLV is the L-3, It will pull on bottom with the L2 and doesn't have a flat spot like the L4. I set mine at 7 3/8" for the 3 and 7 1/2" on the L4. I have not had an L2 on a kart in 5 years
Can anyone second this without a doubt? I tried running the L-2 pipe at 9.5 flex length today sand had all sorts of trouble. Thanks for any feedback.
you know, RLV includes a setup sheet with their pipes. If you don't have one I'm sure a call to RLV will get you the information you want.
I'm pretty sure you had the wrong header length, by a bunch!!! Give them a call.
One other thing, watch your clutch stall RPM coming out of the corners, it could change and you'll need to adjust for it.
You'll also see changes in the carb settings.
Comments compliments criticisms and questions always welcome.
Your cylinder head temp will be low with a long flex if jets are set correctly. This is a good indicator flex is to long also. CHT should be around 450 max on gas and about 350 on alky with a new style cylinder. Al is the EGT man he can tell ya those temps better than me. Also longer flex brings the max torque down lower in the rpm band. But this is effective only to a certain point then proformance drops off big time.Try changing the flex in 1/4" increments and run it till ya get best preformance out of that pipe on your engine set up. Dont change final gear ratio. As Al said check clutch stall and jetting with each change in flex and adjust accordinally.