Exhaust port/flange question

JM485
Profile picture for user JM485
Posts
5546
Joined
10/1/2013
Location
Davis, CA US
JM485
I'm doing a little port clean up on my cr500 cylinder, and I noticed that the exhaust flange is quite a bit larger than the exit area of the exhaust port. My question is, should I open the port slightly toward the end so transition is not so abrupt, or would it be better to leave as is? From my limited knowledge of gas flow this seems like it would disrupt the flow and pressure wave fairly significantly, but at the same time by expanding the port I would decrease exhaust gas velocity. For those with porting knowledge, how would you go about tackling this?



|
JM485
Profile picture for user JM485
Posts
5546
Joined
10/1/2013
Location
Davis, CA US
JM485 11/9/2016 11:58am
11/9/2016 11:58am
Awesome, thanks guys! Just out of curiosity, is this just something you have tried with success on your own bikes, or is there a theory as to when this is or isn't applicable to a specific situation? In other words, is there a limit to how far you would transition a port to fit an exhaust flange, or are there certain cases where this would be a bad idea?
F150Motocrosser 11/10/2016 12:31pm
11/10/2016 12:31pm
Are you aware of Jason Meyer at MSV Racing in Oregon, and the uber trick stuff he's coming up with for the 500s?? People are raving about his billet exhaust flange which apparently eliminates the classic "oil splooge" issue

I'm a member of a few CR500 groups on Facebook, and Jason seems to have a lot of street credit. If you're on FB, add him as a friend and shoot him a message (not sure how to reach him other than Facebook) https://www.facebook.com/msv.meyer







The Shop

See All »
JM485
Profile picture for user JM485
Posts
5546
Joined
10/1/2013
Location
Davis, CA US
JM485 11/10/2016 7:00pm
11/10/2016 7:00pm
F150Motocrosser wrote:
Are you aware of Jason Meyer at MSV Racing in Oregon, and the uber trick stuff he's coming up with for the 500s?? People are raving...
Are you aware of Jason Meyer at MSV Racing in Oregon, and the uber trick stuff he's coming up with for the 500s?? People are raving about his billet exhaust flange which apparently eliminates the classic "oil splooge" issue

I'm a member of a few CR500 groups on Facebook, and Jason seems to have a lot of street credit. If you're on FB, add him as a friend and shoot him a message (not sure how to reach him other than Facebook) https://www.facebook.com/msv.meyer







Interesting, I've never heard of him but there is a local guy around here who has been on 500s forever that makes something very similar. I think he uses your old flange and just modifies it to run O-rings for the pipe if I remember right. I tried your link but it only led me to "page not found", I don't have a facebook account though so I might just not be able to view it.

The chart you posted is interesting, is that mostly just a product of matching the flange with the port? I'm still hesitant to open up the port that much near the end, so I'm curious if he makes the flange slightly tapered so that it fits the stock port better, or if he would just open up the port to match the stock exhaust flange shape.
JWACK
Profile picture for user JWACK
Posts
2521
Joined
8/7/2009
Location
NM US
JWACK 11/10/2016 7:14pm
11/10/2016 7:14pm
You could also go the other way around and epoxy fill it if you don't want to take cylinder material off.
JM485
Profile picture for user JM485
Posts
5546
Joined
10/1/2013
Location
Davis, CA US
JM485 11/10/2016 8:19pm
11/10/2016 8:19pm
MSVRacing wrote:
Hey guys,

276 manifolds sold to customers in 12 countries with zero complaints.

http://www.ebay.com/itm/182326215956?ssPageName=STRK:MESELX:IT&_trksid=…
Thanks for the reply Jason, those definitely look like a quality product, especially since they are made from 7075. If you don't mind me asking, it states on your ebay page that there is a taper from the port, so does you flange start from the same inner diameter as the stock flange and taper out to the pipe, or is your initial inner diameter smaller than the stock flange as to match the port better without modification? In a situation like mine illustrated in the picture in the OP, would you recommend removing cylinder material to match the port or leave as is?

Post a reply to: Exhaust port/flange question