Author Topic: CB550 Track Bike (Read 40936 times)

Rocketman · « **Reply #100 on:** July 24, 2014, 06:24:06 PM »

Had my CB550 back on the dyno Tuesday. Worked my way from 150 mains, to 140, and finished at 130. The needles are from the 77 CB550, F205IE, started with the clips in the middle and ended with them in the lowest slot. It is amazing what getting close to the ideal air/fuel ration will do. There were some 20 HP holes in the power curve after the dyno runs a couple weeks ago.

Here is the air/fuel (bottom lines) from the 140 mains & clips in the middle(red line) and 130 mains clips in the bottom (green line) today and HP (top lines). Still lean in the midrange, will try shimming the needles first before changing them.

Here is the HP for the 120 mains (blue line) during the first dyno session and today's runs with 140 mains (red line), and 130 mains (green line).

Time to sort the suspension and get out on the track.

bwaller · « **Reply #101 on:** July 27, 2014, 09:13:18 AM »

RM, I know you mentioned JE pistons, what bore size? Are there any other jobs to complete before you do a trackday?

Rocketman · « **Reply #102 on:** July 28, 2014, 01:15:45 PM »

Hoping to do a track day at Nelson Ledges August 30. The only "must do" is the swing arm pivot. When I installed the brass bushings the total swing arm width at the pivot ended up wider than the pivot tube. May need to have a new pivot tube made or come up with spacers for the tube. The fairing is still in the works at this point. I want to put cartridge emulators in the Red Wing forks, but that will need to wait until winter. I guessed at 150cc of 20 wt fork oil and ended up 7" below the fork top when collapsed. A steering damper and catch pan are on my list, but think I can do a track day even if they do not get done.

Trad · « **Reply #103 on:** July 28, 2014, 01:50:08 PM »

What is causing the lean spots? It seems like 120 and 130 mains are really rich. Also, wouldn't the increased cylinder bore size cause more vacuum, in turn needing to bump down the main jet? Clearly my assumptions are wrong judging from the dyno info.

Rocketman · « **Reply #104 on:** July 28, 2014, 05:04:34 PM »

Trad, I was thinking exactly the same thing. My best guess, and comments from the dyno operator, is that the larger diameter of the CB750 carbs has slowed the air flow down resulting in less gas being pulled through the jets. I am really shooting in the dark though. I have added .020 shims under the needles to see if that helps the lean spot in the midrange. My have an opportunity to take in a test and tune night at the local drag strip before hitting the track at the end of August. It was an extremely hot day on the last dyno run, so may need to bump the mains to 135 on a cooler day.

Trad · « **Reply #105 on:** July 28, 2014, 07:03:19 PM »

RM, I must have missed that you are running 750 carbs, it makes a bit more sense now. Well, the bike sure sounds great! Good luck with the next dyne run. Excited to see the results.

Rocketman · « **Reply #106 on:** September 01, 2014, 07:31:28 AM »

Did my first track day on the CB550 this past Saturday at Nelson Ledges. Being the first ride I took it easy in the corners trying to get a feel for the suspension. The track surface has deteriorated since I was last here and is rough. The new management is trying to catch up from past neglect. I am still lean in the mid-range, but once it is on the mains it pulls pretty good. Will need a 18 tooth front sprocket as I was running out of gearing. Did 5 laps the first session and was looking forward raising the needles and picking up the pace. Then someone asked me if the front tire was flat? What the heck! Flatter than the proverbial pancake. Was able to pump it back up, but could hear the air leaking back out. Wiggling the valve stem confirmed the leak was at the tube/valve stem junction. No spare tube or tire irons. Plus it took two of us on a tire changing machine to get these Heidenau tires on even if I had a spare tube. Packed up and headed for home. One very expensive track day. Have not take the tire off to see what happened yet. Still planning to do the Ohio Mile September 27 for top speed.

bwaller · « **Reply #107 on:** September 01, 2014, 12:25:40 PM »

Expensive track day....I had one of those ten days ago so I feel for you. At least mine was weather related.

There are some tires that are a bugger, I find the Avons easier to deal with, but they are more money. I wonder where the tube was made.

Sorry for your trouble, we have to fight for every advancement sometimes huh? Better days ahead.

SOHC4 Cafe Racer Fan · « **Reply #108 on:** September 01, 2014, 02:12:01 PM »

I can attest to the Avons. I just road the piss out of them through the canyons between Malibu and the Rock Store. Nice and grippy. Worth the $.

Retro Rocket · « **Reply #109 on:** September 01, 2014, 02:32:10 PM »

Really good reports on the new conti race attack tires as well...

SOHC4 Cafe Racer Fan · « **Reply #110 on:** September 01, 2014, 02:38:44 PM »

Martin,

I don't think we've seen any "finished" pictures of the track bike. Don't keep secrets!!

Rocketman · « **Reply #111 on:** September 02, 2014, 02:27:08 PM »

I used some cheap tubes on the Honda as I was in a hurry! Was swapping tires on my 82 BMW last night which has Metzler tubes. The difference in quality was dramatic. Had planned to take some pictures and maybe a video at the track day. Planning to do the Ohio Mile later this month and will post some pictures. The winter goal is to strip the frame again, have it powder coated or painted with high quality enamel, and be ready to roll in the spring.

SOHC4 Cafe Racer Fan · « **Reply #112 on:** September 02, 2014, 02:37:10 PM »

Would still love to see some pictures, even if it is in mock-up stage without fairings!

Last seen as (which may be the present look):

Rocketman · « **Reply #113 on:** September 21, 2014, 07:12:37 AM »

It seems the track photographer did capture a few shots at the Nelson Ledges track day.

Adding a steering damper as one is required by the ECTA for the Ohio Mile next weekend. Was able to source some richer needles from Sudco and hope to get back on the dyno this week to see if they help with the lean spot in the mid-range. Will post my trap speeds and some photos from the Ohio Mile.

SOHC4 Cafe Racer Fan · « **Reply #114 on:** September 21, 2014, 09:47:26 AM »

The bike looks gorgeous! I bet it makes a wicket banshee howling sound with those unbaffled reverse megaphones!! Awesomeness!!

Rocketman · « **Reply #115 on:** October 13, 2014, 07:11:43 PM »

I made the Ohio Mile the last weekend in September. For those not familiar with the Ohio Mile it is a top speed run on one of the 2 mile runways at the Wilmington, Ohio airport. The event is hosted by the East Coast Timing Association. Bike prep is similar to what is required for road racing. A tethered kill switch is required.

I made a total of 4 runs over 2 days. The first run was slowed by the shift lever not being adjusted correctly for my new boots. I missed a couple of shifts and ran through the traps as 116.2791 mph. The second run was the best of the weekend. With the stock gearing and pulling 10,500 rpm through the traps, my speed was 121.0980 mph. On Sunday I lowered the rear sprocket 2 teeth and could only pull 9.500 rpm. My speeds were 117.9864 and 120.7405.

All in all I was pleased with the performance. I sourced a set of richer needles and they seem to be very close. Hope to get on the dyno one more time this year to see where my jetting and HP is.

Here are a couple of pictures and a link to a video on You Tube.

http://www.youtube.com/watch?v=79WrUqr_ZYM

SOHC4 Cafe Racer Fan · « **Reply #116 on:** October 13, 2014, 07:17:29 PM »

121 on a 550!! Awesome. I'm sure you'll go even faster if you mount a fairing. The bike sounded good from behind on accel. What's the deal with the billet linkage in the video?

The bike looks fantastic.

SF · « **Reply #117 on:** October 13, 2014, 07:36:16 PM »

That's awesome

congrats!

Lostboy Steve · « **Reply #118 on:** October 14, 2014, 07:11:55 AM »

I just want to say, that bike looks amazing. I love the front drum. Very cool. Congrats.

Rocketman · « **Reply #119 on:** October 15, 2014, 05:55:27 AM »

The billet linkage is a splitter for the front brake cable. The single cable from the front brake lever is split into two cables as the front brake has 2 shoes on each side. The brake is a Grimeca 4 leading shoe. This was state of the art before disc brakes.

Thanks to all for the feedback.

bwaller · « **Reply #120 on:** October 15, 2014, 07:25:02 AM »

How did it feel at speed? Did you try any crazy maneuvers to upset it at 121?

Now that you've "loosened" it a bit, a few more pulls on the dyno should gives some real numbers. Good luck.

Rocketman · « **Reply #121 on:** October 15, 2014, 05:30:49 PM »

I was doing my best to crawl under the paint and make myself as small as possible.

Lots of wind resistance in 5th gear. So nothing crazy, just looking for that extra mile an hour or two. It did seem very stable and tracked straight down the course. I cleaned up the mismatch between the intake manifolds and rubber connectors this week. There was nearly a 2mm step. The manifold on the left is the after and the before on the right.

I'm curious to see how much horsepower it was robbing. Hope to get on the dyno in the next couple of weeks and will post the numbers.

bj · « **Reply #122 on:** October 15, 2014, 07:03:03 PM »

Beautiful bike. Hope to see you at some WERA events next year.

Tews19 · « **Reply #123 on:** October 16, 2014, 07:07:10 AM »

Rocket you have nominated for bike of the month. Please head over to that thread and accept. You have 3 backers already!

luceja · « **Reply #124 on:** October 23, 2014, 07:17:53 PM »

Thanks for posting your work here. I am getting into cb160 racing, but I've got a couple of untitled 500/4's to bump up to in a couple of years, so finding others' sohc4 race builds documented is very valuable for me. We have a good road racing class for the 550/500 here in Oregon, but not enough participants, so looking forward to that.

By the way, I made the exact same mistake with the shift fork rod retainer on my 550, except it caused the transmission to lock up between 2nd and 3rd and destroyed much of the transmission and the primary chain. I found a shift fork in the pan as well... along with a lot of teeth!

The bike is beautiful, by the way.

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Author Topic: CB550 Track Bike (Read 40936 times)