After having a stupid amount of fun completing a CornerSpin school for the first time this year, I picked up a 2011 Honda CRF100 as a playbike and learning tool. Since I can never leave anything stock, a K&N air filter, Renthal bars and Acerbis hand guards went on first, quickly followed by a FMF Powercore 4 exhaust.
Now she's a beast, but two days of hard riding with my nephews over Thanksgiving revealed a few things:
1. The FMF exhaust is the shit! Really uncorks the torque of the little 100cc mill.
2. She's running really, really lean with the stock jetting and the K&N & FMF mods.
3. Re-gearing would make better use of the gears, as I rarely get above 3rd in general riding.
4. The suspension is woefully inadequate for my, ahem, adult-sized body.
So, up on the workstand she went. Here we go, in a partial state of disassembly/reassembly:
First up was the jetting. Stock is a #35 slow and #95 main, so in went a #40 and #105, respectively, sourced from jetsrus.com. I fully removed the carb for this, but it really wasn't necessary. Just drain and remove the float bowl, and there's plenty of easy access to the jets. The job was so easy, I forgot to take pics. Sorry.
A new rear tire was next. After removing the wheel from the bike, out came the Motion Pro tire irons. I only have a set of two, 11" irons, but will be ordering a set of their (longer) tire spoons shortly, as soon as my bruised knuckles allow me to type again. Here's a great video on how to change a tire and/or tube, from the experts at Dirt Rider, who make it look so easy:
Of course, I tried to re-use the original tube and pinched it on installation, and it leaked. Off again came the tire and a new, heavy-duty tube installed. Sure, the heavy-duty tubes are tougher to work with, but IMHO they're worth it on dirt bikes. While the wheel was off, I installed the new rear sprocket. Ain't she pretty?
I wanted to change the gearing to better handle adult riders. Factory is a 50:14 (3.571), and I’ve installed a 49:13 (3.769). This should result in a lower top speed, but should make better use of the power available. We’ll see. It’s a different animal since installing the FMF exhaust!
Changing the front (countershaft) sprocket required removing the left crankcase cover. Of course, I'd not purchased a replacement gasket, so one is on order now. BikeBandit is my friend!
Next up was the rear suspension. I purchased a BBR rear spring and fork springs that're supposed to be 30% stronger. While I was on the back of the bike, I started there.
Removing the rear shock requires taking at least one bolt out of the suspension linkage. Not a big deal, but you need to support the frame of the bike enough to let the swingarm sag. Got the OEM shock on the bench and...
First, there’s no (obvious) way to take the spring off the shock. No threaded collars for preload adjustment; no split top ring. Maybe, once I get some spring compressors on there, something will make itself apparent, but I can’t see anything at this point. Second, that aftermarket spring has about one half more wind than the OEM. That means the preload will be a lot stronger, and the travel distance (to the spring binding) will be shortened. Not good. There are aftermarket adjustable shocks available, but I’d prefer to not spend that money (yet).
Okay, spring compressor ordered (after the one I have for automotive springs wouldn't fit, darn it), and shock re-installed in the bike for now. Time for the new chain.
And f#%^$&%^%^#%#!!! The chain I bought, per the manual, is wrong. Manual spec's a 420, but a 428 is needed.
The 420's for sale on eBay, by the way, and a new 428 is on the way to me.
Next time...
Stay tuned. In our next episode, we'll install:
1. The proper size chain, and
2. The left crankcase cover with new gasket.
Plus, we'll attempt a disassembly of the OEM rear shock.
Cheers!
- Rob.
Post Script, links of interest (as promised)
K&N Air Filter
Renthal Playbike Bars
Acerbis Hand Guards
FMF Powercore 4 Exhaust
