That was when I did it with my 09. I wanted the cams out so there was no chance of dropping a bolt down the cam tower for sure.

KLXter is right, removal of the spring from the KACR apparently is fine. I pinned the shoes out on mine because it just made two less moving parts. When I do the valves next I will probably press the whole mechanism out. Neither Honda nor Yamaha have a compression release on their 250s when there's electric start. Now with the mechanism disabled I've never had problem one with starting.

Read the MCM article, but take a look at the condensed version linked in my sig when you go to do the work. It pretty much is step by step without the background information in it. The original could get a bit confusing as written, when you see the actual process it's pretty easy, other than the headache of getting the cams on the right teeth to align - a point where I kept ending up a tooth off or moving the wrong way... but maybe that was just me. The actual verification is quite easy once you see it.

 

Someone try tack welding a short divider into the typical bigger OD aftermarket head pipe and see if it perks up low end but still gives you better top end. You can always take it back out if you don't feel a difference..

 

What is in the science that would help the low end? I recall something similar for carbs but that was to "match" the partial opening of the slide with the air flow from the air box.

Ride on
Brewster

 

ill definately have to read both versions of the mcm. i get the comcept bull all the steps arnt clear to me yet.

 

If money alone was a big issue and I was to start again I'd still do the BB for slightly over $500 bucks and chop and rework the stock exhaust (free), buy a few jets ($25), pull the snorkle (free). Do all the work yourself with this forum alone and you would have a bike that was pretty damn impressive.

 

Dividing a large ID .header pipe into 2 smaller D-shaped sections that could boost exhaust velocity in that section. Maybe encouraging better cylinder filling too boot as the increased velocity evacuates the cylinder more efficiently.

Or, as you read down the hot-linked page, consider a sort of very short/tapered anti-reversion cone sandwiched in between the engine and .header pipe..


Or


I used to weld up something like this hoping for anti-reversion on my XT500 decades ago... (bomb pipe?)

 

+1
Definitely best bang for the buck in transforming the characteristics of the bike.