Part 6: Post Dirtbag
In the weeks after Dirtbag I wanted to find out why it wasn't running properly on the last day. I also wanted to swap out the old crappy SpecII expansion chambers for a new set that my friend Brian Turfery had made. So that would be step one.
With the SpecII pipes off of the bike I could finally see that the GP styled cross over pipe (lowest point on the bike) had been badly smashed on the ride to and from Usal Beach. Did I mention that the road was severely rutted in some areas. I suspect that this was why the bike was running so oddly on the last day. Now on with the Turfrey pipes. The new pipes were designed specifically for an RZ350 chassis with a TZR250 3XV swingarm swap, which happens to be the same swingarm my frame is designed to use. Brian's pipes were a perfect fit and look amazing! But wait, how do they ride? The mid-range power is noticeably better. Much better! So much so that the bike is now slipping the clutch on hard acceleration. Turns out my clutch didn't have much free-play, but that wasn't an issue with the SpecII pipes. Now it is.
20201029_091030 by
andbike, on Flickr
I also wanted to get feedback from another rider. This is always a good idea for any new product... motorcycle or otherwise. As the designer I will always have some biases so wanted to get some sucker, uh, I mean my friend Ken to try the bike and get his opinion. Ken not only rode the bike, but documented his ride in this short YouTube video. Thanks ken! Oh, almost forgot to mention, Ken is
KPKE here on BARF.
Here's his video...
https://www.youtube.com/watch?v=9nIu62JAmuc
As Ken mentions at the end of the video, the bike rides "different" than a stock RZ, is "stiffer" and "more upright". All are reactions that I would expect. It is more upright because I wanted it to be as comfortable as possible for my 500 mile Dirtbag ride. Because it uses GSXR forks, its very easy to convert back to clip-on bars for a more aggressive (less upright) riding position. As for stiffer suspension, well yes it is and that is mostly intentional. The bike is really designed as a high performance sport bike. It is set up rather stiff considering the GSXR forks on a bike much lighter than a GSXR and rear shocks that are now over damped for the lighter springs that have been installed. But all of this falls under normal suspension tuning that can happen later. So overall I'm happy with Ken's evaluation, especially that he had fun and wants to build one of these bikes for himself
There is still engine tuning to be done as the jetting isn't as good as it could be (I think its still lean on the pilot and possibly rich on the main). I have lots of time to come back and fiddle with jets.
With the pipes swapped and the bike running well, the next step is to remove that fugly looking utility rack and build a proper rear sub-frame and race tail. About 30 minutes into building a fixture off of the old sub-frame my welder decides to die... WTF!!! I have a big "blue box" TIG welder and its been problem free for the past 25 years, so now it decides to die? Oh wait, 2020! Of course it decides to die now
The sub-frame build will need to continue later...