Got the 91 running Thursday night after swapping the CDI. While it was coming up to temp, I decided to bust out the multimeter and check the charging system just for giggles... imagine my surprise when I got 16.2v at 3k RPM. So a generic regulator/rectifier was spliced in, and all appears to be good on the charging front. I'm kinda curious now if the regulator letting go was why the battery was low on electrolyte (boiled off) and why it lost one side of the CDI (over voltage?)
In any case, it runs and charges, tires were brought up to pressure, lights all checked out, it appeared to have front and rear brakes, and some damping front and rear, so I took it out for a road test.
First thing I noticed, the stock exhaust is too dang quiet. Sounds like I'm buzzing down the road on a well muffled go-kart, and my race rules require me to keep the stock exhaust so I can't fix the sound. :P I take that back, above 5k RPM it develops a little character, which leads me to observation number 2.
The right hand cylinder gets a little loud above 5k when into the throttle. Haven't had a chance to determine if it's top or bottom end that's making the extra noise. It's not a distinct knock, I'd almost claim it was an exhaust leak but I can't find one. If it was constant I'd say it was a loose valve, but it's not. Oh well, I was planning on a tear down this winter to inspect the internals anyways, now I've got something to look for.
Third observation, front brake is well bled, but the brake line is tired (you can feel it expand). That still doesn't explain the uselessness of the front brake though. Looks like the inside pad is at about 80% gone, rotor is about 4.3mm thick but smooth, new pads and a new brake line should revive it, I should really put a new rotor on too I think. Back brake works great... guess coming off a Ducati I'm surprised by any back brake that works though.
Final observation, the suspension needs help both front and rear. I only weight 135lbs but I'm still getting way too much sag front and rear. The front especially is soft, and not damping up to par. Left tube is starting to pit so I'm going to have to deal with that. Going to see about having it re-chromed and / or Titanium Nitrided. :P Springs, emulators, general polish and clean up and the front should be good. (Anyone used Provalve emulators out of Australia? They use a shim stack rather than Racetech's spring valve setup, look like they could work pretty good.) New shock for the rear (Thinking Works although I guess Ohlins and WP Europe have offerings as well...) should get that sorted. The suspension is where I plan to focus most of my effort, if I can get it to ride right so I can push it hard in the turns, I should be able to offset some of the power differences between the GS and the EX500s I'll be racing. Loudon is a nice tight track, even on these little machines so I should have a fighting chance.
That said, buzzing down the road at 55mph, using large handfuls of throttle while haunched forward thanks to the clubmans on the lil 500 is a blast. : )
Hrrmmm... 30 mile trip, never above 55mph, there is definately noise coming from the bottom end. Goes away after sitting for 15mins to cool... :dunno_white:
Bottom end rebuilds are not that bad. They sound more intimidating then they really are. The first complete rebuild I did was with a motor I purchased which was taken completely apart and needed a new crank and rod bearings.
If you still are looking for a shock, I saw a Fox TC on ebay. I have had a couple of them and they do make a big difference. Plenty of adjustments.