GT750 Drag Bike

[water cooled]

Thanks Jeff. The air was excellent that weekend. At one point the morning of Qualifying, the altitude was below sea level but didnt stay there long. Still, it hovered around 700-800 ft for a little while. While some jetted up..... I went down one more size on the MJ for Sunday and it certainly seemed like the right direction for me....though I did get a few looks and a raised eyebrow or two.

The rain was actually helpful as it gave me "blocks of time" to work on the bike in the trailer. The motor had been fully torn down and rebuilt over the winter. As a result, there are always a few things to chase. I can never seem to get blocks of time to work on the bike at home, but once at the track, I can work around the clock if needed to take care of many things.

Jeff, I think you need to come to the track and join us. You would probably like it. Great group of guys that like to have fun on these old 2-strokes. Take your bike to Capital and see what it does.....then consider joining us this year. We have 3 more races and would love to see you come to at least one of them. What bike to you have....?

[jeff kushner]

I haven't a doubt in the world that I'd have fun....and that's what scares me<LOL>! Back in the 70's, we took our GT750 road racer to Capital raceway so we could learn how to get good starts in the races. We were two terrified teenagers but we arrived and asked for help instead of acting like we knew everything. THAT was the best move we could have made. The guys there, like you guys, took us under their collective wing and really helped us. By the time we left on Sunday afternoon, we were both getting consistent starts and both had gained a world of knowledge in the little things to go fast. They were all strangers Saturday morning when we arrived but friends by the time we left. In my 50's now, I can probably pretty accurately guess that it wouldn't be any different today, except it would be the younger guys helping me now!

I bought a 74 H2 locally several years ago and formulated a build plan for it over the next 3-4 years that I finally put into play last year. My goal was to keep the bike appearing as stock as possible other than the carbs and pipes, but went pretty radical on my port timings. A friend of mine, John Ritter ran the numbers for me on his program and Jon Easton built the pipes to match my porting. It took a bit to get my final jetting tidied up but now it runs pretty nice. I like narrow, explosive powerbands because that's what I raced with so while this isn't the bike I select for a 50 mile ride, it's great for zipping up and down the highway for some fun.

I'm taking my sweetheart out to Mid-Ohio Vintage days this year. It will be her first trip, my 4th. I usually ride my Vstrom 1000 out but she's a new rider and not used to a 1000 mile weekend so we'll drive out. Are you guys going? I'd love to take a long weekend and ride out to one of your meets and come down to see how you guys do it but I think I'll watch for now.

jeff

[water cooled]

Jeff,

lm probably not going to mid Ohio although I dont live far from there. There might be some guys on this board that do go....

We have one more race at Indianapolis in July, then the remain two will be at Martin, MI US-131. The last one at Martin will likely be the best attended. Its part of the AMSnow races so there are about a thousand sleds (many of them two-stroke and 20 or so triples (bikes). Its a ton a fun to watch or race...hope you think about dusting your bike off and coming out. There is a class for stock bikes which is the entry level or you could pick one of the other subclasses based upon how much your bike is modified or altered. We always like to have new guys come to help expand the class. All the guys in our group are great and will help anybody getting back into it.
Great event. Martin is just south of Grand Rapids

[water cooled]

Super Eliminator Dragbike Series is for multi-cylinder two-stroke motorcycles.

SE bikes 9.99 and quicker are required to have either IHRA or NHRA Competition License.

Cross-over and delay boxes are prohibited on bikes competing in Super Eliminator.

All entries are required to have a front fender or fork brace.

Nitrous Bottles need to be mounted on the inside of the frame rails for protection.

The use of any oxygenated fuel or any type of fuel additives are prohibited.



RECORD CLASSES:
The record / index classes will be loosely based on the old IDBA SE rules which accommodated more than 80 different classes. The following table shows the displacement ranges assigned to the groups. To claim a record, time slips for the record run and one time slip with a one percent backup run during the race weekend (Sat and/or Sun) must accompany the claim. Record certificates will be issued by SE committee for each record set and claimed.
INDEX CLASSES:
Note: MPH can not be claimed until the ET Index is turned into a National Record.



ENGINE TEAR-DOWN:
If the Super Eliminator rules committee determines that a tear-down is necessary, it will be done under the order and supervision of the rules committee with findings reported to track tech officials. Competition rules including tear-downs and Fuel Samples are governed by the Super Eliminator rules committee.


CATEGORIES BREAK DOWN AS FOLLOWS:
Any engine modification allowed in all categories except stock class.
All of the Suzuki GT-750 bikes are allowed to enter the FF classes.

ENGINE SIZE:

CC / = 810cc & UP
DD / = 780cc to 809cc
EE / = 740cc to 779cc
FF / = 490cc to 739cc
GG / = UP to 489cc

BIKE CLASS:

S = Stock Factory mass produced two-stroke street bikes. Must have stock wheelbase, working rear suspension (no struts) and DOT street tires. Stock or Aftermarket street exhaust with baffles and stock carburetors required. No lockup or slider clutches allowed.

M = Modified Lightly modified frames using the stock engine cradle. A minimum of one-gallon fuel capacity required. Backbone fuel tanks prohibited. Struts, wheelie bars and slicks allowed. Extended swingarm allowed but must use the stock pivot point. Front foot pegs must be located within six inches from stock location. Use of rear foot pegs prohibited.

A = Altered More extensive stock frame modifications allowed. Raked steering head, weld on aftermarket tail sections instead of swingarm. Rear set foot pegs allowed. 15-inch car type rear tires prohibited.

D = Dragster Lay down aftermarket frames. 70" Minimum wheelbase. 15-inch car type rear tires allowed.

G = Gasser Sit up modified stock or aftermarket frames. 15-inch car type rear tires prohibited.

XG = Experimental Gasser Sit up or lay down frames. 15-inch car type rear tires allowed.

XGN = Nitrous Any one of the above engine sizes using nitrous oxide.

PS = Pro Street : Must have working rear suspension (no struts), DOT street tires and no wheelie bar.

HH = Heavy Hitter: Rider must weight a minimum of 200 lbs. in full race gear.

[captainpooby]

I think this story is awesome and I've read every post in this thread, congrats to you and those involved in building your bike. It's truly an amazing journey you've taken.


I'm new here but I'd like to put in my two cents.

I think you're missing one part of the equation and that's aero. You're so close to the 9s I think a little good aero will put you over and then some. Check out this graph of horsepower vs top speed with motorcycles.



If your bike is making 120 HP and you're hitting 130 in the quarter(if I remember from the thread correctly), your drag coefficient is somewhere around 8.6 by my eye. That's terrible. A modern faired sport bike is somewhere near or under 5.

If you could drop your CD down even one point, it would free up probably 10-15 horsepower. Drop it down 3 points and you're looking at a pile of almost free HP. Remember, drag increases with the square of velocity. From 120 to 130 mph is 120x120 vs 130x130. Those are huge numbers.

Right now you're struggling to drop weight and add ponies and admirably achieving those goals but at great effort and cost. A proper fairing for your bike would probably cost you under 500 bucks.

Here's some interesting reading:

http://www.borynack.com/xr650r/Horsepower2speed.htm

I'm no expert, I just stayed at Google Express last night.

[tz375]

You are right that drag is an issue but the graph is off I think.

Our RZ350 hit 99 with around 56HP and my GT hit 107 with big high bars, and tall suspension (lots of area) with less than 80HP. None of the period drag bikes uses much of a fairing and some of the triples are getting over 140 per at the 1320 stripe.

Reduction in area is probably more important than Drag Coefficient in the scheme of things - low is fast...

[ja-moo]

It doesn't loo too far off, no scale can cover everything precisely.

Also, there are a few major factors effecting CD. Being low is more effective with cars, as there is a lot of area to create turbulence. Then there is the the way air goes around the vehicle and comes back together that is also very important, again, to reduce turbulence. Another factor, and a big one is frontal area. Motorcycles do a lot better there, but not flow-around with the rider and all the fiddly bits sticking out. Unfaired bikes have the aerodynamics of a bus because of this.

There are a lot of factors, but, we all know, most all hp gose to just pushing the bike through the air.......

[tz375]

You are right John. It's CD (coefficient of drag) x Frontal Area to get CdA. I was being a little glib when I said lower it to reduce frontal area.

Drag bikes typically have a lower frontal area than the equivalent street bike because they are lower and more importantly, the rider sits lower into the chassis. Even back in the day, very few drag bikes ran much of a fairing which is interesting, but a more aerodynamic overall package would have to help more than hurt.

[ja-moo]

I think a lot of drag racers "back then" looked more at weight, than aero's. It wasn't really understood as well as it is now.

[captainpooby]

It's true, most drag racers back then didn't look at aero. Look at the top fuels cars then vs now. Back then, they were all naked, now they are all covered in bodywork.

The back of the bike is very important. John Britten, RIP, was very aware of this. His bikes, while they didn't use a lot of body work at the front, channeled all the bad air that went through the radiators and engine was channeled out through back. It was very effective. Race cars today use diffusers for the same reasons.

I'd bet a small fairing to hide behind and cover the steering head area would drop you in the nines.

[Cyzygy]

[quote="water cooled"]First S/E meeting of the year. The race was held at Indianapolis - Lucas Oil Speedway. We had (8) 2-stroke bikes. Six Kawasaki H2's and two Suzuki GT750s. Bob Prior flew from Australia to compete on the Michigan (Dave Derrick) built GT750 Altered. During testing the week before, the RH piston and connecting rod let go damaging the cases and Flannery ported block. Crew Chief - Dick Fortino and Bob Prior worked around the clock to get another GT750 motor ready and six days later they were in the staging lanes at Indy. "End quote"

I would like to say that the engine blowup, I believe, was totally my fault. I blewup the engine, it had nothing to do with Dave's engine assembly, Doug Flannery's porting or Richard Fortino's bike preparation. Dave sold me a very good bike and was totally honest with everything about the bike, I'm very pleased with the deal we made. What watercooled didn't say was that without him supplying us with a doner engine we would have not made it to Indy, thanks so much Kevin. I'm trying to get back for the final meet of the season at Martin in Septenber but finances may prevent this, if not there is always next year. 20,000 miles, 40 hours sitting in planes, a week long thrash on the engine for a first round lose and no record. The excitment of racing in S/E all two-stroke drag racing, PRICELESS:-))))). It was worth every minute and dollar I spent.
Keeping the dream alive. Bob Prior

[water cooled]

Captain

Here's some interesting reading:

http://www.borynack.com/xr650r/Horsepower2speed.htm" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

This is a really good link.....Im really glad you posted the information! Any chance we can convince you to come race with us in the Fall? I understand that S/E might be considering a 2-Stroke Street class to get more of us to the track.

[water cooled]

Here is a picture of a picture....taken by Steve at Pro Photos.

[Suzukidave]

Looking bad ass there Kevin

[water cooled]

Hi Dave....I was thinking the same thing! LOL

Im also trying to figure out how to get you and few others on this forum to come out to the track to join us. S/E might be forming a "2-Stroke Street class" to encourage guys to come out for the first time or....to come back if its been a few years since they last raced in the 70's and 80's. Im sure there are at least 4 or 5 guys on this board that might be willing to dust off a 500 or 750 in time for the race. Maybe we could even pop up a Suzuki-Sundial canopy tent in the pits for all the forum guys to share.... offer free food and community cold beverage

Here's the challenge:

The S/E-3 race is August 22-24 in Martin, MI. How many guys on this forum are interested in tuning up their bike and coming if S/E offers an entry level 2-Stroke Street class which would include some Basic Instruction, group practice time in the pits and two pre-Qualification passes during the morning Test N Tune.... if interested, post below...