Tuning,Tweeking & Confusion

I am still perplexed by the lack of performance from the RD!

I have experimented with several different carb setting on the Keihin carbs, but the overall performance of the motor is nowhere near what I know it should be. I have swapped jets, main jet & idle jet, testing a wide variety of options. I have also tested several carb needle combinations. My jetting is correct and power delivery is smoother with less of a "flat spot", but power just isn't what I want it to be.

The engine starts and runs fine, but the bike does not come smoothly "on to the pipe". When the RD does hits it's powerband it's VERY noticeable, but not nearly as powerful as I remember it being "back in the day". Maybe I have become jaded by the powerband of my Gixxer, but I remember the RD as having WAY MORE power than this (but it's been 30+ years)!

Time for a change in plans......

First.... I tried swapping the Keihin PWK33's for the freshly rebuilt Mikuni VM28's.... No dice! The Mikuni's are just too clapped out, so I trash this plan.

Second.... If changing the jetting is not working, maybe I have an air leak? I am in the process of building a "home-brew" leak-down tester and should have it ready for a test in the next two days. 6 psi for 10 minutes is the benchmark.

Third.... Return to a "baseline" jetting on the Kiehin PWK's ; CEL needles on clip #3, Main Jet of  170, Slow Jet of 48. Most of my sluggish throttle response is from 1/4 to 3/4 throttle, so the needle should be my focus. I know the Main Jet is rich, but I like to start rich and work my way leaner. I'll be burning VP C12 fuel mixed with Amsoil Dominator 50:1.

Stay tuned for test results.......

Do I have an air leak?
Burned or holed piston?
Too much carb to even expect a mid-range?

Shake-Down Rides

So I thought I would finish the "Project RD400 Racer" in one summer, what a joke. I'll never finish, I'll just keep tinkering!

I reset the MZ ignition back to 2mm BTDC and the bike runs fine on hi-octane pre-mix. The powerband is still as extreme as ever, but the 2mm BTDC seems to be a reliable compromise. The RD comes "onto the pipe" at about 4,500 rpm and explodes all the way up to the redline.

Next I'll play will the main-jets on the carbs.

The first couple of shade-down rides have gone well, without any major issues or failures. The bike is a blast to ride and the powerband is exhilarating! I have been keeping the rides under 60 miles in length and keeping the speeds down.

For Sunday's ride I installed some new knee-sliders on my leathers and focused on cornering and handling. The RD is very predictable in the corners and it's quite easy to get a knee down on the sweeping corners. I have a long way to go on the suspension setup, but the journey should be fun!

Fat Tires & Ignition Timing

Currently I have been spending the evenings in the garage trying to stuff the widest tire possible into the rear of my RD. This puzzle is all about finding just the right combo of rubber, chain length, sprocket size, and not have clearance problems between the tire and swingarm. Last night I dumped my box of chains and sprockets on the garage floor and started working out the best "combo". After trying several combinations, I have settled on 98 links, 17T front sprocket, and a 38T rear sprocket. This combo gives me about a 6mm gap between the new Pirreli "Sport Demon" 120/80-18 and the swingarm, but the gearing is not my favorite option. I would rather have a 40T sprocket on the rear! Now the ignition timing..... The 3mm BTDC on my MZ ignition is a bit extreme and I'm more than a little worried about frying a piston. This weekend I am going to experiment and test-ride settings between 1.7mm and 2.0mm BTDC. I just can't reliably get (or afford) the 115 octane leaded race fuel that I need for the 3mm advance. At about $12 / gallon, the race fuel really limits my riding options. I am planning an "epic ride" this summer and I want to complete the journey without melting a piston of seizing the motor! If I get the taxes done this week, I should be testing various ignition settings all weekend. Stay tuned for the results.

Rockers vs Mods 2011

Time flies and now it's almost time for the 5th annual "Rockers vs Mods" event in Dallas! April 1st - 3rd Dallas will be transformed into a cafe racer's gathering, with bands, rides, bar runs, bike shows and assorted shenanigans. I hope to attend, but it will probably be for just Saturday, April 2nd. The RD still looks pretty ratty, dented tank and I still need to get around to painting the bike. Sure hope to make the event!

UPDATE: 3/31/2011 Looks like I'll be in the garage working on the RD while everyone is partying at Rockers vs Mods! A rear wheel bearing failure and dificulty in procuring several parts have made the timeline undoable! Maybe next year....

Spring Is Here, Time to Ride!

Spring has officially sprung and I have sprung into action getting the RD Racer back on the road. This weekend I completed a tear-down of the carbs, charged the little micro-battery, and spent some time puzzling over the rear wheel alignment. Right now the rear wheel is my "big issue".

My quest for more grip led me to install a wider rear tire and now swingarm clearances are an issue. Hard cornering, my 180 lbs, and vintage 1970's chrome-moly all lead to some pretty substantial swingarm flex. After a hard ride with lots of aggressive cornering, I can see where the tire has rubbed the swingarm! I am moving the rear wheel back about 10mm to increase clearances.

Should be test riding this weekend!

Barcelona & MotoGP

Been away for awhile, but still having fun and working on the RD. Two weeks in Barcelona, with lots of time at the beach and the Circuit de Catalunya. The races were unreal and Barcelona is a beautiful city. Lorenzo won the main event while we sat with the Lorenzo Espania Fan Club. Very fun crowd.

I could so easily live in Spain! The Spanish are motorcycle CRAZED and the whole vibe is quite relaxed. Beaches, bikes and hot Spanish women... What's not to like?

I saw a wide assortment of 2-stroke sportbikes in Barcelona. Lots of CBR250RR's, Yamaha 250's and even a tricked out vintage Bultaco cafe racer.

I'm Healed!

Just over six months have passed since my collision with the killer dog and I am still hurting. Mainly it is my shoulder that hurts, but at least I am riding.


I have been riding my Gixxer, pushing harder and harder going on longer and faster rides. Now I'm ready to break out the "Punisher", my RD400. The RD is partially disassembled in the garage and this weekend I'll put all the lovely bits back together again.