New Member Build

[Lindy]

New member here, thought Id share my build. I built this bike to drag race with, both locally and nationally in a Super Eliminator class. Its a 79 750F, converted to monoshock using Hayabusa linkage, motor is 1220cc, MTC rods, Megacycle cams (mild cams with shim under buckets) slightly oversized valves, ported head, 33mm smootbores, MSD MC-4 ignition. Second motor is starting to go together, 1220cc (custom CP pistons) Carillo rods, big megacycle cams, 38mm flatslides. Battery and ignition is located in the front (behind 1100F fairing) everything on the bike is purpose build and has such faetures as removable backbones (so you can remove head in the frame)

 

[Medyo Bastos]

Looks great! What swingarm is that?

 

[Lindy]

the swingarm was originally built for a Hayabusa (by a company called Evil Swingarms, so I had to make bushings to reduce the larger pivot down to Honda size (I actually increased my pivot to 17mm and had a titanium pivot bolt made)

 

[amc49]

Kinda wondering about that swing arm setup although I am no expert on drag bike, I HAVE run plenty of drag car including over 200 mph. Wondering at wall thickness of swing arm stock, I know they run the arms pretty minimal but big power can change that, and most arms with no boxing or triangulation run struts to stiffen them up. The mono will cover up some stress there by spring absorbing some hit but why when most go to solid rear suspension (struts) that stiffens up the swingarm by itself. And they are lighter than the shock. The arm can now warp from side to side in its' length, double struts stop that. And why do we have suspension in back with virtually none up front? Looking at how little travel front has before striking the bottom of triple. That seems somewhat backward if bike needs some handling down on the big end. Much easier to drive (control) with some front travel on bumpy tracks and big power and speed tend to make ALL tracks seem bumpy.

I may be totally full of it though.

If you already don't know him, you will likely want to contact Brent (online name 605brent? something or other) at the CB1100F.net site about how to make the cam chains live much longer than they commonly do and he makes the ultimate early DOHC CB head in the world if you have the cash. You can't port that head beyond a certain point, they are flawed in the basic casting and need the entire intake port just about cut away for any power easily over 150 hp., otherwise the motor hits a limit around there regardless of how big it is. He's pushing 180 hp. on an engine with no primary chain at all, he created a gear primary drive for his. Big $$$$$$$$$$.

Really nice work there from what I see.

 

[Lindy]

Thank you, and not to be a jerk, but since you said it, you're full of it...

You dont want much suspension travel in the front, its stored energy, when you release the clutch that energy will push the front end up (and on a bike with no wheelie bar, naturally this is undesirable) even on a bike with a wheelie bar, its not warranted either. Most racing organizations "recommend" a minimum of 1" of front fork travel, this bike has 1" (and it cant hit the lower triple, I put internal limiters in them) you only want enough travel so on bumpy tracks, so as to not upset chassis, thats it. There is nothing new here, this is the way its done, and been done for quite some time, current record for a street tire no wheelie bar bike is 6.38 at 224ish, so Id say its a proven method.

On the rear suspension, I dont know what the wall thickness of the swing arm is, I can go measure it if you would like. If the bike was going to make bigger power, I wouldve had one built with additional bracing, as its a Honda, no need (and please remember it was built for a Hayabusa, and the exact swing arm has already been proven to high 7s) NO ONE runs struts on a street tire bike, and hasn't for the last 30 years (they dont run struts on slick, no wheelie bar bikes either) then is tremendous technology and tuning to be had with the rear shock, its a way to control wheelies and traction, absolutely no one is going fast these days on a non wheelie bar bike that doesn't utilize a shock.

I do know Brent, I have his cam chains and all his cam chain guides/tensioners in this motor. Ive also spoken to him about his superheads and started on a version of a straight port for myself. (by the way hes over 200hp now). I have no desire to make that kind of power with this bike, there simply isnt enough return on investment, in the class I want to run in, the national record is around 10.80ish, since ive already went faster than that on a 810cc DOHC Honda 30 years ago, im pretty sure we can take that record at 1220cc, and this simple combination will do all the things I want it to do.

 

[amc49]

I was thinking in terms of maybe doubling the front to a couple inches, internal limiters can easily lose control in the rough exactly like hitting the triple when you hit them, the slightly extra damping length is better to me, a safety factor. If it weight transfers too much you add damping. You can make it widely variable enough to act like limiters are on it and not as abrupt at the hit as hitting an actual limit. I used to build car shocks myself that did that in much wider swings, the shock extended easily and fully at launch but settled down for less wind and tightened up at speed for control. Some of the tracks we had to run the 200 mph car at had POTHOLES in the slowdown area at end of strip! Lost the front spoiler more than once over that crap.

You don't need wheelie bars on a 10 second bike with street tire if launched correctly, used to do very low 11's myself with a stock (header, different bars) V65. Those tires were likely much harder rubber and easy to set up controlled spin without looping backwards though. 6.38 on a street tire? Not saying anyone is a liar AT ALL, but is there any web video of that, I'd certainly like to see it. Probably will shatter my mind just like seeing a basically stock Mitsubishi turbo 4 AWD going in the 8's and wondering why we spent all that effort to go as fast with 500+ inches as this stock car is going?????

I understand wanting adjustable shock(s) on back and have wondered at tire problems from shake on the much faster bikes than 10 second. I just don't pick up on why the effort to go to one shock only when two stabilize the swing arm more, and on only a ten second bike. If it came with monoshock fine but going to the trouble of adding it? You've done it though and it looks nice. I questioned the swing arm as most are (or used to be, a good while since I looked at drag bike swings) made with no shock mounts but at least used to be intended for two not one. If the one there is intended for monoshock able then again I am full of it.

Two different ways to get to the same place I guess. I can accept being full of crap, progress tends to do that. Whether one likes it or not. I grew up thinking somewhat out of the box anyway, our start with drag cars was American Motors and we had to do quite a few things somewhat differently to get them into the nines in the mid '70s.

I'm surprised there is still a class record at that 10.80 time slot that somebody hasn't bombed the living crap out of into the nines, is it restrictive in some weird way?

 

[Lindy]

There is zero benefits to running more front suspension, if there was everyone would be doing it, 1" has proven safe. No where did i say you need a wheelie bar to run 10s (I have personally been in the 7s on a no wheelie bar, street tire bike) nor did I say the bike would only run 10s either, what I said was the goal for the bike was to run 10.80s and set the record, by doing so with a realistic goal, it will give me lots of room, to set and reset it over several times, and hopefully provide some low qualifiers and a favorable position on the ladder and possibly win a race or two (super eliminator is very tough) The motor combination in my bike has already ran in the high 8s in another chassis.

Yeah there is plenty of videos of fast street bikes, the first street bike in the 7s did it in the year 2000, 6s in 2011, Jeremy Teasley went 6.38 this weekend at MDIR, I was there. Oh and by the way the 3rd fastest street tire bike in the country, a 1980 GS1100, been 6.40 at 220 with guess what? a monoshock! https://www.youtube.com/watch?v=RZzAEC-55N8

Why go to a monoshock? well if you built shocks and messed with race car suspension, then you will under stand this. Compress the suspension 4", how far did the shock move? correct answer is 4". Now connect a shock with a linkage (the way a bike swingarm is) compress the suspension 4", how far did the shock travel? answer is a whole lot less. So which is easier to control? which alows more suspension movement, easier to set up ride height etc....etc... There is a reason that ALL performance bikes have went to it, there is a reason I went to it. There is zero advantage to two shocks, not in rigidity, not in control, zero, nada, if there was you'd see 6 second bikes converting to it.

I posted my bike here becasue im very proud of it, I couldve built any bike I wanted (and in fact sold my hayabusa when i started building this) the first bike I ever owned and raced was a 79 CB750K. So I decided Id do something different and build a old Honda. Just becasue its a old bike doesnt mean it has to have old technology, and I dont write or give explanations based off poor information, I do it based off experience, as Im at the track weekend after weekend.

 

[Medyo Bastos]

I’ve got an sohc monoshock build with an extended arm on the back burner. 1”, or less travel up front; chicanes on the ground.

 

[amc49]

Are they still having to offset the pins in rod on 1220 DOHC big bore engines? Assuming you're running 69 mm. stroke (count the cylinder fins).

 

[Lindy]

on my 1220 no it isnt offset, they are on standard bores. The motor in the bike is in a stock block, the 2nd motor im building is in a magnesium block. My friend is having a 1252 built it is offset, and I sorta wished I did it this way, (the centers in the case between 1&2 and 3&4 are gone) but he started with a blank magnesium block so it was easier.

The motor in the bike is based on a 1100 crank, I had no intention of using the big primary chain, but I had a brand new crank and set of steel MTC rods fall in my lap that had a lot of work done to them, so I had to use them. My second motor is a 900 crank and Carrillos.

 

[Lindy]

I’ve got an sohc monoshock build with an extended arm on the back burner. 1”, or less travel up front; chicanes on the ground.

would love to see it, I have several sets of Chicanes, would love to do a SOHC next

 

[JFG316]

Freakin Awesome!

 

[Wickedfast17]

Not sure if anyone here still responds but im new to the 750 engines but i have an 80 dohc 750 and im looking to build the motor here soon when i redo all the leaking seals and gaskets, can i buy a 900 engine and swap the crank and top end? Then find some 1000cc jugs and pistons or are they different pin sizes for the connecting rods? Ideally id swap an 1100f engine but im on a tighter budget and im trying to get as much power out of this engine for 1500

 

[loxley007]

Sweet bike.