'78 SR500 street tracker

[hoffman900]

Out of the post from the exhaust forum:

A little background:

I'm a broke, full time college student. Grew up riding dirtbikes and bmx'ed. Towards the end of high school, I bought a Miata and started autocrossing, which I did for a few seasons. In addition, my father road raced a Yamaha FJ600 in the early 1980s. Friends of ours race and I grew up helping out on their cars.

The first is a '63 Triumph TR4:

The owner/driver/builder of this car has been racing since the late 1950s. He owned repair shop that did race car building / dyno tuning as well. He was the only privateer to take it to and beat the factory backed Triumph teams in the 1960s. He was leading the national championship race in 1965 when he lost the overdrive (essentially 5th gear) and had to settle for 5th. He later raced Shelby Cobra's (2nd in the nation to a factory backed 'Vette in 1970), did some F5000 racing, race IMSA, and built the first Toyota to win a professional race in North America. He retired from racing in the early 80s, but bought his old TR4 back and restored it and has been tearing up the track since. This is one of, if not the fastest, TR4 in the world right now.

Here is some in-car. Qualified 2nd oa of about 50, but had to start mid-pack due to some problems in the qualifying race. He is 76yo at the time of this video:

Second is GT-Lite Toyota Tercel:
The driver/owner grew up in the Triumph driver's shop and has worked for racing schools as a mechanic before starting a real career. The car is a tube chassis, silhouette, racer (fiberglass Tercel body draped over it). It is rear wheel drive and is badass fast.

Here is a qualifying lap which put him first overall:

Friends of ours also have Spec Miata, which is an uber competitive road racing class.

As for the bike:

I picked this bike up a year and a half ago for a steal. I don't know all the details, other than it was built by a Yamaha shop just outside of Reading, PA as a "street legal flat track bike". The kid I bought it from inherited it from his uncle, so all he knows is that it "wheelies and belches fire". It was advertised as having a 'White Brother's engine'. It had Progressive shocks and fork springs, and the rear subframe was also chopped and a flat track tail was installed. I've had it for about a year, but I didn't get it running until this past June. When I finally got it running, I ran it hard through the gears hard and parked it until August (full time student, work, other hobbies that were more pressing).

 

[hoffman900]

Late summer, I finally got some time to work on the bike and started transforming it into one of those Kenny Roberts replica's that Richard Pollock makes fun of . I painted the body work up in some generic yellow paint I got from Summit Racing and slapped on some decals from an ebay seller.

I then finished out the rear subframe and mounted the Supertrapp that came with the bike (someone called the cops within 5 minutes of me firing it up with just the megaphone). This was my first welding job, and I have since gotten a much nicer gas mig welder, and have gotten better.

After this, I rode it around all fall. Hurricane Sandy pretty much put an end to the riding season around here (we were close to, but luckily didn't take any water),

 

[hoffman900]

Not happy with the exhaust and having a 'vision' for this bike, I set out acquiring parts so I could build the bike over my winter break.

Using the knowledge I have gained through being around top notch race cars for most of my life and some modeling software, I spec'ed out the exhaust and called up Full Circle V-Twin to throw a kit together for me. The owner is a flat track racer and a very good fabricator. There was no way I could afford an exhaust like this assembled. Basically I got the kit, and had to build the head pipe and tack it together - I got everything to the lengths that I wanted, and was then was able to mount up the muffler.

The specs are as follows:
spigot port matched to the exhaust port. tapers up slightly to exit.
1.625" od pipe for 15"
1.75" od pipe for 16"
megaphone/reverse cone (the muffler can slips over the reverse cone) that is spec'ed out to be pretty close to optimum by the fabricator (kind of keeping that one a secret, sorry ).

I then sent it back to be tig welded together. Today (3/7/13) I shipped it out to H.M Elliott to be ceramic coated (they do a lot of NASCAR work and are the company that coats engine bearings for many of the bearing manufacturers).

The exhaust still isn't the cheapest option when you include ceramic coating, but I've saved hundreds of dollars by doing a lot of the work myself and I'll put it against the best anyone can come up with for my motor's particular combination of parts.

 

[hoffman900]

I also got in touch with a AHRMA racer who is building up a new bike. He had some parts laying on the shelf and cut me a great deal.

Shortened Radian swing-arm. (with the rake of the SR, it puts the wheelbase at 55", right where I want it). The shock mounts were also relocated a little bit, and it put the shock angle right where it should be. With me sitting on the bike now, the swing arm angle is about 4 degrees - perfect, imo.

Also a RM250 rear hub, disc brake caliper, rotor, and sprocket. It's a non-cush drive, but the old set-up is off a XS650 which isn't either. This bike is a little too wild to ride too far so I'm not worried about it.

I ordered the cheapest of the 19x2.15" Excel rim I could find, but the place was out of them and upgraded the order to a much nicer SM Pro Platinum rim for no charge. I then went over my buddy's shop and sand blasted them (he grabs sand off the beach, sifts, and then dries it ) . I sourced out bearings that would work with the rear hub and the 17mm Radian axle. I also put new bushings in the swing arm and painted everything up. The hub and caliper are painted with Eastwoods aluminum paint.

 

[hoffman900]

I then had to get everything to work on the stock frame (drum brake version). I had to move the brake pivot a little bit and make a mount for the master cylinder. I then stripped the frame, sand blasted it, made an aluminum splash guard and mounted it with dzus fasteners. My buddy with the shop was also a top shelf crew chief and engine builder for a fast dirt modified team. So he has aluminum paneling laying around, dzus mounts, and a bead roller which he let me use. He also builds really cool 'street' cars for himself (he's retired). Here is his daily: http://www.corvettereport.com/the-worlds-only-4wd-hemi-powered-corvette/ .He also has a Studabaker with a NASCAR chassis underneath, and a Keith Black Hemi out of the dirt modified he built motors for. He was also into turbo charging motors back in the 70s, well before it caught on with the rest of the V8 establishment. I then painted the frame in Eastwood's Vintage Racing Wheel silver paint.

 

[hoffman900]

I then reassembled the bike. I cleaned up the wiring and made a soft mount for the electrics on the splash guard. The whole thing is soft mounted with rubber grommets and rubber washers. It gets things out in the air a little bit to keep things cool. This is a bit of a carryover from my car racing experience. Everything is on a panel, gets some air, and is easily removable. I also put taper head bearings in the front. I also called up Barracuda Racing and ordered some #240 bend stainless handle bars. Some mis-communication on the phone had her thinking I was Bryan Smith (she was expecting a call from him) of AMA Flat Track fame. We both had a good laugh about it, and her and Bryan did later too. I also ordered some Heidenau 4.00x19 K34 tires. They were a good deal, I feel, and look the part. Pretty much an exact replica of the flat track tires before they became 'grooved road racing slicks', and they're built with modern construction. I pinched the front tube - I have a replacement one, but haven't gotten around to changing it yet. That's why the front caliper is not mounted in the photos. I also rebuilt the forks with new seals and changed the fork fluid level / weight to where I think it should be after riding it all fall.

So, now. I'm waiting until I get a chance during my spring break to make new cables, some rear axle spacers, install the chain (and modify the panel a little bit for clearance), and brake lines. When the exhaust gets back, I'll fill her up with some oil, adjust the valves, and ride. It's not the best tracker, but I'm a broke college student and built it for me and within my means/abilities. I've lurked on this site for a while getting some ideas in addition to looking at photos and talking to racers. I'm looking to buy a 'framer' to go racing with as soon as I can afford to.

Note: the photo of the electric panel, I made a new capacitor mount and the whole thing looks much better. With the body work on, you can't see much.

 

[racerdave]

Looks like a nice tire

 

[hoffman900]

Looks like a nice tire

They come in two compounds - a real soft racing compound that some AHRMA flat track racers are using and a harder street compound. The soft compound is a bit more expensive. I couldn't find any information on these tires when I bought them, so I took a bit of a gamble. They look good, I still don't know how they'll handle or ride, yet.

 

[Tron]

Awesome build. I love the swingarm man it looks great. I bet it will really help this thing shine on the corners.

 

[hoffman900]

Thanks, Tron. Can't wait to ride it!

Just got the exhaust back from H.M. Elliott. They do a lot of NASCAR and NHRA work. Coated inside and out, for a reasonable cost. Here it is mocked up.

 

[SINKING78]

Can't wait to ride it!

Ha, I bet! I would be sleeping in the garage! good lookin bike

 

[hoffman900]

The bike is up and running, so that's a relief. Still lots of little stuff to do, but it's getting there.

It sounds "bassier" in person.

 

[scabber]

The bike looks great. Nice Job.

 

[hoffman900]

Thanks, Scabber.

Just have to connect the chain and tidy up / bleed the brakes, and it's good to ride!

Here is the same view, yet again.

 

[racerdave]

Any problem with the rear tire hitting the plat on full compression? Exhaust much better.

My fav Yammie paint scheme.

 

[deadchef]

that is a sweet bike! i always like the yellow with the yama decals but the overall stance of this bike really sets it apart from the rest.

what's with the bracket by the right shock going to the swingarm?

 

[racerdave]

that is a sweet bike! i always like the yellow with the yama decals but the overall stance of this bike really sets it apart from the rest.

what's with the bracket by the right shock going to the swingarm?

exhaust hanger

 

[hoffman900]

Thanks, guys.

racerdave,

No issues. I only weigh 155lbs, so I had my uncle who is about 85lbs heavier than me sit on it and jump up and down on it. No issues there. It looks closer in that picture than it does in person.

To be honest, it was stiff before and would skip over bumps with me on it. The rear shocks are less angled now, so the wheel rate should be higher. Of course, the tires have a larger sidewall... that should help a little. We'll see. The big mystery for me is how it will ride, now. I'll hopefully get it on the road tomorrow.

 

[hoffman900]

Yesterday morning I made a chain slider out of a cutting board. I had the bike out and about that afternoon. So far, no issues. It rides, runs, and sound great. The only issue is that it feels like it's running lean at WOT. I Had a new plug laying around and had some time tonight so I did a plug chop to confirm.

I warmed the bike up with the old plug. After warming it up, I changed out to a new plug. I'm lucky I have a nice, long, straight of road nearby with pull offs, little traffic, and no one around but fisherman. Wacked the throttle wide open at 3000rpm in 4th gear and took it to 7000rpm. It took longer than I wanted to, especially up high. Some of that might be the gearing (larger circumference tires), but it doesn't pull at WOT like it does at partially open throttle positions. At 7000 (~84mph), held it out for a two count, and killed the ignition / pulled the clutch in.

Here is the plug:

Granted, it's unleaded fuel, so it won't color as fast as leaded, but it should still show something. Looking at it with a magnifying glass shows nothing. There are some black speckles on the electrode (can't see them in the picture), which is a sign of trace detonation.

I checked everything over, no air leaks anywhere.

For giggles, I lowered the needle one notch. It takes five minutes from start to finish to do, so why not? I knew right away it didn't like it, so I changed it back. It felt good on needle circuit before, but it doesn't hurt to try. I might go the other way when I go up bigger on the main.

I have 230 and 240 main jets on their way. I'll start with the 230 and see how things look.

 

[hoffman900]

Put a couple hundred miles on it. Still need a rear brake hose (ordering one at the moment). The bike handles like a dream. With the old swing arm, the bike squatted in the rear. Getting the wheelbase correct, the swing arm angle, and lowering the forks some really transformed the bike - it just falls into corners now. I'm digging these tires, too; they feel like a modern tire and seem to be wearing pretty well too. The bike feels pretty good on the highway (80mph). It felt a little twitchy, but nothing my dirt bike wouldn't do at speed, so I was comfortable with it and am happy with that. I thought I hurt the motor though as it was spinning very fast and the old dirty plug was white after, but it seems okay.

I put a 240 in it and it's still too lean (up from a 220), so I have a 250 and a 260 on their way. I think it will like the 250. That means I'll be up 3 jet sizes from the old WB Supertrapp set-up.


Cheers,
Bob