Thanks. Lesson learned.i would go vm32 i just got one for my own xl250
NICE INFO! Thank you!A CV carb doesn't flow as well as a simple slide carb because things like the butterfly valve and shaft disrupt flow. I read somewhere years ago that a rule of thumb when replacing a CV with slide carb is that the slide carb should be 85% of the size of the CV it replaces.
That's 85% of the area. Not the diameter, so that works out to 31mm more or less.
But if you want more performance, you can go larger than that "rule" which takes you to the 32 that CXman recommended.
An example of a poor flowing CV carb is the BS40 fitted to the GT750 Suzuki. The CV carb is 40mm outlet but has a lot of restrictions and it supposedly equates to a 32mm slide carb and not 36mm which the rule would suggest
I will definitely be taking the path of Trial & Error, as evidenced by my purchase of the VM34. The whole header length/diameter/RPM thing is a different bag of magic beans, yes. I plan on running the stock header that I have, (the silencer has been already hacked off by the PO.) and a glasspack muffler. I don't plan on racing any GSXRs, etc. !The exhaust is another completely different can of worms. There is so much misinformation and straight up BS about 4 stroke pipes that it makes my head hurt. The best answer I have come up with on my racebikes is to just try different pipes and see what works best. I have found a few items which seem to be consistent, but not yet quantified by me. Most exhaust header pipes are too big and too long to put the power where it is usable. Combine that with too big of a carb and you have a bike that is boggy everywhere and won't clean up on top end.
My suggestion based on just my gut feeling would be to go with a VM30-32 and a head pipe which is only slightly larger diameter than stock, stock length with a Supertrapp muffler that you can tune with the discs.
Thank you! So much that can be done to these things. A new header would be sweet. That will go on my Wish List. I'd also love to go 18" rims front and rear, but that is WAY above my budget. I don't know how the folks in Australia can afford this; I've read the forums for a bit now, and it seems they pay a lot more for stuff... yet some of the coolest rides come from there! My hat is off to you.The issue with the stock pipe is that it is double walled with the inner tube being just above an inch in size.
4 stroke exhaust gets complicated when you start looking at header length and pulse reverb timing.
I would go for a 1.25" header and have it run the way you want without worrying too much about length.