Topic: CB750 Racing

[turboguzzi]

haybus, been there before, arrived to my race with my first build after starting the bike for the first time on friday before loading on the trailer!
 but in your case the pan looks like it could cause you trouble to pass the tech check .... but indeed, maybe wait till you get there.

[JohnN]

Me too, I arrived at my first race session with an oversize pan because I was afraid to fail tech. I quickly ground holes in it even though I was not going fast. At that time I had standard length shocks and fork tubes. The chin fairing design should not be a problem but the overall width may be a problem.
John

[Haybus]

Got my calipers put back together with all new parts. Definitely a sequence for the install, which got me thinking about lock wiring. The rules say caliper mount bolts. Is that the 2 socket head cap screws that bolt the two halves together, or the 3 bracket bolts on the fork leg, or all? There isn't much room for doing any of that, especially with the twin caliper setup. I wired up the socket head cap screws off the bike just for practice. Not looking forward to that with the calipers on the bike. Also wondering about the oil reservoir lines. I can see drilling the bolt heads for the fittings at the motor and wiring them together. Do you also have to drill the fittings at the tank and wire them to each other? What do you wire the fork drain plug to, the pinch bolts? Anything on the rear drum have to be wired?

I'm debating what to do about electronics. Dyna 2000, CycleX/C5 optical setup, or that GSXR setup. I'm kind of running out of time, so maybe tackle it after the first race. Is it completely stupid to just throw the old coils (stock) and points back on? I'm not looking to tear up the track first time out, just hoping to make some laps and have fun. With a completely stock motor, are any of those electronic systems very beneficial to me at this point?

Alan

[JohnN]

Alan:
 I safety wired all five bolts on the calipers. You can complete one side then install the wheel, followed by the caliper to minimize the wiring with wheel in place. It is cumbersome with the dual disk setup! I made a simple loop with one wire through all three of the bolts that attach to the fork leg and it was accepted. Tech has not scrutinized my oil lines. I have AN fittings and wrap a wire around the base of the supply fitting to keep it from unwinding should it become loose. Fork drain bolt can be wire to the unused fender mount lug at the bottom of the tube, and pinch nuts wired to each other. WMRRA also requires the rear brake adjuster to be wired, and hoses clamped onto the exposed axle adjuster bolts. Vintage has a designated tech inspector who understands the old machinery and he will work with you, especially first time out. Bring a drill to the track just in case!

 I ran my first season with a stock engine, including standard points ignition. I focused instead on chassis setup and developing skills, and the wider power band of a street motor makes this easier. I found gearing at Pacific, for instance to be of little concern compared to my current setup with a narrow power band. I'd say don't worry too much about the engine for the first season. 
John

[Jerry Rxman Griffin aka MuthaF'er]

Dyna 2000 has 2 distinct advantages over Dyna S etc. Advance curves and rev limiter. Plus other potential functions if you need them. May be overkill for a CB750 unless you need these options.

[Old Scrambler]

The rev-limiter is key..........we all miss a shift or find a false neutral now and then

[Haybus]

John, thanks for the excellent explanation. Could I trouble you to take a picture of your axle adjuster. Not sure what you mean by hoses clamped onto the exposed axle adjuster bolts. Wasn't sure about the rear brake adjuster since it doesn't cover it specifically in the rule book, so good to know. I'm going to use the stock oil lines for now. Doesn't look like a lot of room to drill the fittings. Did you reuse the 90 fittings on the engine side when you made new lines? I would imagine they're a barbed fitting the hose is swaged onto. I think Troy does most of the tech for the newer bikes (?), didn't know someone was designated for vintage. I have the NRS classroom next Saturday, and I think all the track workers meet right before. Maybe I can sneak in a few tech questions before the class. But you've mostly answered everything I was wondering about.

I feel better with your recount of your first season as it matches my plans. Race Tech springs and emulators should be here Thursday so maybe I can get the front end buttoned up this weekend.

Alan

[JohnN]

Alan:
 It's not in the rulebook but they have called both of these on two occasions, so they are still looking for it. See photo below of adjuster bolt, but I don't have drum brake any longer. It was simple to wrap a wire around the wingnut on the actuator rod and tie it forward ahead of the spring. No drilling required so you can add this at the track in a couple of minutes if this does not make sense.

 I have the 90 degree fitting for oil lines at the engine and safety wired the bolts that secure the fittings to the engine. Jim usually techs the vintage entries; If you pit with the vintage folks at Pacific (behind the grand stands) he will inspect in your pit so you don't have to stand in line with the modern bikes; it's very convenient!
 John

[Haybus]

Seems like all I do is work on this bike. Got all the lockwire holes drilled and most everything wired up, except maybe a couple I'll do last minute. Need to do some more work on the right disk. The fork leg mounts are screwy and tips the caliper a bit side to side. I guess the shims I made for the upper mounts aren't quite right, or the lower mount boss needs some attention.

Took it for a ride last week. My road was a bit muddy and the street was wet so it flung mud everywhere. Ran like crap between 1/4 and 1/2 throttle. Seemed to pick up after 1/2 throttle, but I only did it a couple times cause I was getting mud all over me. Suspect the carbs were a bit dirty so I tore them down for cleaning. Slide heights and air screws were all over the place. Back to what I think should be tuneable now.

Those pipes I made were unbearably loud without baffles. So I ordered up some parts from Cone Eng and made baffles. Just the baffles didn't seem to tame it much so I wrapped them with fiberglass packing. It sounds reasonable now. I think the clamps at the header and the baffle tips contrast nicely with the black pipe.

The seat is firm to say the least. Contours pretty well to my hind end. It's not perfect, but it will do for now.

2 weeks before I need to get her on the track at the new racer school. Hopefully paint next weekend, weather permitting.

Alan

[JohnN]

Alan:
 The caliper does not need to be perfectly parallel to the disk and a couple of shims should get it close enough. I like the detail on the exhaust. How did the paint turn out?
 Weather does not look great for Saturday; watch turn 3 in the wet as it takes out a lot of racers on dry pavement!
John

[Haybus]

Didn't get the paint done, just primer. But the primer almost looks like it's painted  Good enough for the track day. I only have one weekend between the track day and the first race to finish the paint. Hoping for good weather that weekend, or at least fairly warm. Takes forever to get my garage up to 60 and it's going to take 2 days to paint.

Got the fork brace made and on. Pretty happy with how it turned out. The pan was put on a healthy diet and had to rethink the mounting. Got about 4.5" clearance at the nose. First thing to hit now would be the alternator cover, but that's what the slider is there for. On the right side it would be the peg, then the exhaust, but that's well over 60 degrees in both cases. I got about 55 degrees before the alt cover hits. Mounted the stock tach, just cause it seems like I ought to have a tach.?. Was going to order a tach from Speed Hut, but they take a few weeks so I'll see how the stocker works for now. It's kind of big a goofy looking.

Spent a good bit of time tuning on Saturday. Runs pretty strong now. Had to go up to 110 on the mains, was 105. Lots of false neutrals. I'll need to be pretty positive on shifts. But otherwise it seems to shift perfectly. I think I'm ready for the track day.

John: I plan to take it slow the first time out. I ride all year round to work, but I'm still not a fan of wet. Could the weather man be wrong? I hope so.

Alan

[JohnN]

It looks like you have the fork brace and pan dialed in. When I first installed open exhaust and stacks on the stock motor it also ran too lean; I worked my way up to 125's before settling on 120's that season. The track really makes a motor run hot so you need the extra fuel for cooling when running hard. I'll be at the Ridge as well this weekend and can bring some jets if you don't have any.

The forecast is looking much better today, with the heavy rains now expected Friday instead of Saturday.

John

[Haybus]

Thanks John, I have jets covered up to 140. Looking forward to meeting you.

Alan

[bwaller]

Have a good weekend guys.

[JohnN]

Likewise Alan, and thanks Brent!

[Haybus]

Weather was all over the place yesterday. We actually had some snow/hail while on the track, but they red flagged that session. Gale force winds taking EZ-ups everywhere. Then the sun would come out for awhile and dry the track, but only briefly before the rains came back. Crazy day, but super fun.

Bike ran awesome. It's a good thing because there wasn't any time to work on it between the track and classroom sessions. Had an exhaust hanger bolt rattle out, slider rattled loose but stayed on and my tach died about mid day. I felt it was useful, at least I did pay attention to it a bit, so I'm thinking a digital replacement will be in order. Add a few more bolts to the lockwire list and I think I'm good.

Really great meeting you John. It's going to be a great season.

[JohnN]

Easy stuff to fix, not bad for first test on the track!
John

[Haybus]

Finished up the painting, for now. Had a lot of bleed under the tape. Tried the green 3M, the green Frog tape, and the blue poly fine line (it mostly worked the best). I could see the tape lift after the first dust shot. By then it's too late. Maybe the surface isn't clean enough for the tape to stick, though it's freshly painted. Tried using gloves while applying the edge tape and that just doesn't work. I only ended up with a couple problem areas in the end, but of course they're right on top of the tank. Perfect spot for "uh, what happened here?". Maybe some white pinstripe tape to hide it, or just forget about it and race. I think the biggest problem is.....I suck at painting.

Waiting for the paint to dry a little more before I put on the numbers. Then I'm ready to roll. 

Looks like a wet race this weekend  John, are you coming or play it by ear? I'll be there rain or shine. I'll just tiptoe around the track if it's wet. Never been to Pacific, so I'm a little cautious anyways.

Alan

[Roach Carver]

Marked.

[Jerry Rxman Griffin aka MuthaF'er]

Looking good!

Did you just fine mist the tape on the first pass to barely wetten it to activate the chemical blocking agent before coming back at it with more? I haven't used Frog Tape on a bike but have around the house and on irregular wall surfaces with good results.

[JohnN]

The paint looks good in the photos! I have had good luck with fine line tape from Sherwin Williams automotive division. One in a while I'll get some bleed but it can be removed with 1500 wet or dry prior to clearcoat if you are using that process. Anyway, these are race bikes so they don't need to be museum quality!

I'll definitely be there, but won't race on Sunday if it is raining. I broke my shoulder in a wet round 3 last year and had to make a deal with my wife; no more racing in the wet or no racing at all; I chose the former! She will be at the track as well so no cheating for me.  Pacific warrants more caution when wet compared to The Ridge- we can talk on Saturday.
John

[Haybus]

I'm just doing a single stage acrylic urethane, in case I have to repaint for some reason  . So not much opportunity to fix mistakes. I thought I was dusting on the first pass, but maybe I got too aggressive. Only happened in a few places though. I know it doesn't have to be museum quality, but I still like to be proud of what I have. John, your bike is beautiful so I'm just trying to get close to your level of class.

I don't think the weather could be much worse than the Ridge last weekend, so hopefully I'll be ok. Look forward to any words of wisdom on riding Pacific. See you Saturday.

Alan

[bwaller]

Racing in the rain is interesting, some guys are really good and enjoy the rain, others refuse to race.

Our last race last season was dismal on the Saturday. I was out a few times and struggled so parked it. Dave Roper told me he couldn't understand why people don't race. I felt guilty...... for a split second.  Like John, my wife is always around and we have a deal too.

If it rains, play it cool guys, it's still only April!

[JohnN]

Maybe our wives are smarter than us? We get too competitive and want the points, but racing in the rain just isn't as much fun.
I also crashed in 2013 trying to keep up with Roper on his 350- but that was on a dry track!
John

[bwaller]

He's a real wiley veteran for sure, plus he's still just plain fast on whatever he rides. He's one of those guys who learns tracks quickly and never forgets what he's learned. Drives me nuts.  I guess if we keep at it thirty more years guys might talk about us this way!