THIS MONTH I have been shortening the muffler to improve gas flow and ramp up the power delivery of the RM-Z450.
This update was published in ADB issue #464 – May 2018
The stock bottom-end is soft and smooth, which is great for beginners or for someone a little timid on the throttle but I like hard-hitting torque to get me moving quicker.
I have the experience to control an aggressive powerband with the clutch and throttle so I like the power to come on strong. I felt the RM-Z450 engine had that punch but the exhaust just wasn’t letting it out.
So what I’ve done is cut the silencer down by 40mm and removed the baffle from the front of the silencer as well as the spark arrestor from the end cap. I have also reshaped the inside of the end cap to allow the exhaust gases to flow much more freely.
Once I got inside the silencer I knew it was going to be a big improvement but even I didn’t realise how much of a difference it would make. It’s like a totally different bike. It has much more bark off the bottom and the torque has been increased significantly.
I had been finding that, while idling through the pits, the RM-Z would tend to stall easily or hunt and not idle smoothly. Now that I have opened up the exhaust system I am able to run the lean map and it fixes that problem.
The bike no longer has the hesitation off the bottom and it cruises along through the pits on idle much more smoothly. Not surprisingly, I think the stock pipe was built to suit emissions standards rather than improve performance. Now that I have fixed the exhaust system the power of the RM-Z is very hard to fault.
The other thing I have done this month was add another 2.5mm of preload to the fork springs. This does not stiffen the springs at all, it just lifts the front of the bike a little higher as I was finding the fork to be riding too low in a few places. Now that I have done this, along with my work on the shock last month, the bike is much more balanced and handles much better.
The RM-Z likes to sit higher in the front than the rear but the standard suspension setup contradicts this. Once you can get the suspension set up higher in the front, it starts to handle and steer just as great as all the other RM-Z models we have come to know and love.
Apart from this tinkering I have been doing, the RM-Z is going great. It’s given me no grief whatsoever and has been performing well. The standard chain is starting to show some wear but we all know stock chains don’t last too long. The brakes are in perfect shape and the Pirelli tyres I fitted up a month back are still going strong.
Currently I am working on a sticker kit design with KustomMX graphics and we are hoping to have it on the bike ready to show you guys next month.
I also have a few other bits and pieces planned with a few tricks and hacks for you guys to try out. So check back next month to see where we are at. Tech Ed Mat Boyd
Mods this month: Modify exhaust
Mods next month: Kustom MX sticker kit