Shorter Exhaust Header Mz65?

[Sumsloppymeet]

Will cutting like 1 1/2 inch of the header tube to pull it closer to the frame and making the ID a few MM Smaller for the first few Inches of the header effect or damage it to much? Basically cut the original header about 2" behind the flange and then took the header from a stock exhaust and whack it in snug with a sledge hammer

 

[FNTPuck]

Will cutting like 1 1/2 inch of the header tube to pull it closer to the frame and making the ID a few MM Smaller for the first few Inches of the header effect or damage it to much? Basically cut the original header about 2" behind the flange and then took the header from a stock exhaust and whack it in snug with a sledge hammer

It will move your RPM range higher up, noticably so, but don't reduce the header diameter byt using the stock pipe to join them since its already too small.

Top speed may slightly increase at the expense of acceleration.

 

[CrazyDan]

You won't lose acceleration overall, it just won't accelerate in the same rpm range as before when it "got on the pipe". If you do lots of stop and go, you may not like the end results. If you do country roads without many stops, you would love having the pipe kick in at higher rpm, will help push against the wind better.

 

[Sumsloppymeet]

Your right runs great after 20mph I need to down jet its 4 stroking like crazy I think I'm gonna swap pistons out and use one with a smaller window see if it'll help with the acceleration and what not currently my window is about as big as it can get so hopefully it'll make a difference this is what I'm riding again lol rebuilt for the 3rd time

 

[Sumsloppymeet]

So it's not necessarily a bad thing at least that's good cause I just can't ride without at least an mz65 on it all my motors just overheat and bog down without it lol

 

[HumanPerson]

So it's not necessarily a bad thing at least that's good cause I just can't ride without at least an mz65 on it all my motors just overheat and bog down without it lol

Hi,
Would your pipe be the same size as a kx65 pipe?
Not sure where to get the dimensions.

 

[Sumsloppymeet]

Another idea what if I just put the original header back on but insTead of weld it use this to hold it till I can get use of a welding machine

 

[Street Ryderz]

Been studying this myself. Recommended header diameter should be 1.05-1.125 of the port width. Shortening it from a properly designed pipe can reduce the on the pipe rpm in return for a shorter sharper range and vise versa. View attachment 90823

I use this pipe design software it's from Iwt racing and is based on Blairs works.The biggest problem with these is that both Jennings and Blairs works were based on 70's knowledge and these formulas have since been refined.You'll find that following these diamentions it will be too long and off by about 2k the above pipe will peak at 6k and run out to about 6.8k then go lean if you try to push past its run out.The FOS pipe calc (free software) is much more accurate and has more relevant features.

 

[FNTPuck]

Your stinger length looks perfect but the diameter seems a tad much. You could benefit by increasing the stinger pressure to get more stronger hit when on the pipe if it lacks it.

Correct, MZ65 suffers from too small header and too large stinger. There was no real R&D done for it, although it is a true expansion chamber and the best performance bolt-on pipe for these motors.

 

[Sumsloppymeet]

Ok so I'm gonna use the original 65 header and decrease my stinger ID a few MM and do a piston swap once I finish cutting it should I put the window high or low I've got a 3rd transfer cut already