Austin MotoGP & An RD400 Update

Just returned from the Austin MotoGP race and yes, it was a blast. Marques dominated MotoGP, the track was beautiful and Austin is still a great party town! The racing was great and the MotoGP "grid girls" were bang'in hot!

Now the RD update..... After countless jetting sessions, with little to no improvement, I turned my attention to my beloved MZB ignition system. It appears that my issues are being caused by an ignition fault. Now I am in the process of ripping out the MBZ ignition and installing a Gen 2 Newtronics unit. This is no easy task since the wiring harness is a custom built unit just for the MZB. I'll debug the MZB ignition issue later. Right now I just want to get the bike running properly throughout the whole powerband.

I should start the ingition transplant this weekend... Stay tuned for updates.

The RD Curse

Today I finished up in the garage and started prepping the RD for a test run of the new carb jetting, until my wife came out to the garage. She was heading out and refused to let me test ride the bike if she was not at home. Confidence inspiring it's not, but in reality my wife's attitude is a reaction to a long string of crashes, wipe-outs, break-downs, and even a dry fuel tank. When I head out on the RD things happen and my wife has taken note.

In the not so distant past I have really pushed on the RD. I also accomplished 1 "I can see my house from up here" high-side, 2 low-sides, and 1 wipe-out that I still don't know what happen, "bringing the bike upright, wacked the throttle WFO and then next thing I remember was sliding on my back on the side of the road". The RD is fun to push...... Its light, its tiny, its got a brutal power-curve when it comes onto the pipe.... Just can't resist.

Need to chill on the RD, or else I'm going to get hurt again.

Jet Test 2 - "Baseline"

• Way too rich - loading up until 6,000 - 6,500 rpm
• Sluggish
• Cyclic thumping in chambers at idle
• Never really comes onto the pipe
• Knew this would be too rich, but I thought it would be at least a tad closer!

• Main - 170
• Slow / Pilot - 48
• Needle - CEL
• Clip Position - #3 (middle)
• Float Height - 19mm

Pre-Work / Testing

• Pulled heads to visually inspect top-end
• New head gaskets
• New reed-block gaskets
• Case Leak Test completed - 6lbs for 6 min.

Next Test

• Double check ignition timing (dial indicator)
• Check plugs & wires 
• Main - 170
• Slow / Pilot - 48
• Needle - CEL
• Clip Position - #1 (top)
• Float Height - 19mm

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....