Topic: Stroker build- '76 cb750k6

[EnginebyAdam]

Hey guys great site. I build performance engines for a living and have been working on the dohc 750's for a while but I have no experience with the sohc's. That has never stopped me all the same

I have been digging through the posts here and have come across a lot of different approaches on the stroker builds. I am not looking to go max effort, but I need some impressive times on the strip. This is a drag only bike, we plan on a slick, wheelie bars as well as a custom frame.

I am still gathering information on all this but as of now I have the cb900 crank, cb900 rods (shot peened) with cb1100f rod bolts. I also have the cb900 sleeves. I have had Cometic make me a footer before so I'll go with them again for that part unless things change. I have a GL1000 in mind to donate the drive gear.

I have found a few posts by jweeks on this subject but where I am not familiar with the process I was hoping you guys might have a few book marks you could pass along.

I will be breaking down the '76 shortly so once I get in there I'll be able to see what needs to be done with the chain tensioners, primary and cam. Chances are I'll have lots of questions after I get in there.

On another note my buddy offered me a F top end so I'll have to size up which head to use once I get into this.

Well that's all I got right now, basically research mode. One of the guys over on the cb1100F site used to drag race these and the dohc's I'll have to get in touch see if he can have a chat.

[turboguzzi]

check memeber's mec mega thread on a stroker

[EnginebyAdam]

check memeber's mec mega thread on a stroker

I'll look into it now. Thanks.

[jaguar]

In to see how this turns out.

[dragracer]

Welcome to the forum Adam. Looking forward to your build. Check in with Jon Weeks and Bear. The thread by Bill Benton on   "a bike is born" has tips from both of the guys I mentioned and is specifically about the 900F striker build using off the shelf parts. Pistons, crank, rods and cam chain.

[jweeks]

     Remember that the crank ends are opposite for the DOHC 900 crank from the SOHC 750 one. You have to machine away the taper end of the 900F crank to match the points recessed end like the 750 one. The metal is relatively soft and machineable. You have to use the 900F seals in the 750 cases to prevent oil leaks. You have a splined end with a threaded hole in the center of the crank at the other end. That's what you use to attach a nut for external starters or some form of kick starter gear/one way clutch from a 750 on that end of the crank. It will be a total loss ignition system. HyVo primary chain from the crank will need early Goldwing parts to connect to your transmission. Tensioners for the primary chain can come from many various places. Using the stock 900F tensioner with a custom mount has been done by several forum members. Bear is a good source of information on this stuff.
     The 900F cranks still clear your cases in most places. Some clearancing of the crank throws to case webbing will be needed. It's a minor amount of filing/grinding. The 900F cranks can be lightened a fair amount. They can also be welded up and stroked another 2-3mm, depending on rods used and case clearances. You will find that your cylinder head will be the limiting factor as the displacement goes up. You've got to get the air through the motor to make power. Without significant increasing intake port size, valve sizes, carb sizes, etc., you'll limit the motor's power. I've got an 1180cc Hondamatic that I drag race that needs more head work, not more stroke. I've moved the powerband down with the stroker crank, but haven't got a normal power curve on the chassis dyno. It's limited by the cylinder head passing more air through. Cycle X has done the best job of reworking a 750 head to handle the big cc displacements available that I've seen. Speed costs, how quick do you want to go? Stock crank 750's can go 10's easily. Add a stroker and 9's can be had. Get a good reworked head like Cycle X has, and high 8's might be possible.
     If you're looking to bracket race it, the Hondamatics will be much more repeatable than their clutch equivalent. Tell us what you're looking to do...

                                                     Jon Weeks

[Bill/BentON Racing]

Welcome,you've come to the right place! Yes Bear,Jon Weeks,,Mec, and others have experience in what you are building. There's another member here who probably could be a big help......if you want more CFM! The CB750F77-78 over here,is the best head if available. Bigger valves,better ports,combustion chamber,etc.Head is stamped"410"
on upper backside.Kenny has the best Ive seen....,but was a very highly modified stock head.  Intake ports relocated straight shot,38 mm intakes,34 mm ex valves. See fellow member Mike Rieck for your porting needs,he's in touch with Kenny weekly. We are all meeting in Bradenton in Nov. for the World Finals.Nov. 8-10th. Come join us,Bill

[EnginebyAdam]

Wow guys thanks for the responses I will dig into the thread mentioned promptly. I have a 77-78 F head from a buddy for pennies I will confirm it is the one mentioned.

I am defiantly looking for an off the shelf build if at all possible, trying to use what I have in my garage I have this piece that I hope to use from the Captain over on the 1100F site that I bought for my 985cc dohc build if it can work. Will have to see when I get there, not sure on the internals of these yet so I'll take it as it comes.

[EnginebyAdam]

Well it's nice to be digging into research mode again, and there is lots to read here. I have read mec's thread as well as "stroker cranks and big motors...", "a bike is born..." completely.

I can honestly say I have a lot of the parts on hand, I also have the guide and tensioner for the primary chain. In the dohc realm we like to use the 1100F set up, tensioner and guide, because it is wider and supports the primary chain more, but the 900 setup seems to be more common here. I also just ordered the GL 1000 primary for the conversion.

I guess my first major question is what piston should I use? I am limited by the 15mm pin for the 900 rods. I also know these engines can run higher CR's than the DOHC's as well but where is a good range for a dependable low 10's bike? I have seen threads for the gpz750 pistons which looked good but they are 66mm I think stock and the domes are very large. Also the RC 45 pistons but they are 17mm wrist pins. I am looking for the max piston size of 67.5mm which would give me the 1000cc. The cb900 liners I plan to use only like up to that bore size anyway, or so it seems with the dohc's.

I am also having a hard time finding info on the kicker set up, or external starter for the cb900 crank set up.

The plan is to spend the major money on the cams/head, transmission and clutch as well as any oiling mods that need to be done. All this is besides the drag frame, slick and bars.

Cheers, Adam

[dragracer]

Bill Benton's thread outlines the type of off the shelf pistons recommended in his build. If i remember correctly they are stock Honda forged pistons with the correct pin diameter- take a thorough read on his thread.

[EnginebyAdam]

Bill Benton's thread outlines the type of off the shelf pistons recommended in his build. If i remember correctly they are stock Honda forged pistons with the correct pin diameter- take a thorough read on his thread.

Looks like he used VRF 750 pistons but they have the 17mm pins. I would jump on a set of 1100F rods to use the 17mm pistons but they are like hens teeth even on the 1100F site.

[Jerry Rxman Griffin aka MuthaF'er]

Aren't the CycleX 915 pistons 67.5mm?

[jweeks]

Rick Stetson recommended to me to keep it at 12:1 max if you are planning to drive your bike back to the pits after your quarter mile pass. If you tow back, the sky's the limit or at least the octane rating of your fuel.

                                                            Jon Weeks

[Bill/BentON Racing]

Well,I got my answer.....still need a set of 1100F rods!  915cc Kenny's kit Wiseco pistons weigh 155 grams.Jay has 1000 cc kits,J&E will make what you want.Lots of 15 mm kits. Good Luck and find "us" some rods!  Bill
I'm using XL 250 will post a pic tomorrow. Bear very big help,he's sent me in the rt direction more than once.Jon also.Kenny,Mike,Jay, all willing to help.Alongvwith most anyone on this awesome forum!

[jweeks]

Wouldn't a 915 kit with a +6mm stroke get you around a 1,000cc motor? Yes, the 900F cranks were out in the early 80's. Lockup clutch, as much compression as the pistons will allow, a good top end cam, a well ported head, undercut transmission,  and you're on your way to a mid/low 10 second bike.

                                                                   Jon W.

[dragracer]

I wish i could find a multi stage lockup for mine.

[EnginebyAdam]

I read in Bill's thread he was having a bit of trouble after he started running a lock up clutch. I am going to dig into transmission mods next.

With all the extra pounding of a clutch drag bike versus the auto bike's I'm wondering if the cb900 rods will hold up even shot peened and good bolts. Although I have read good things with the midget racers. Went thru the options for pistons and there are lots. Would like to go 68mm to give me the 1002cc if I can. I'd like to shoot for 12:1 maybe 11.5:1 depending on the head.

The stock cb900 pistons weight 230.3g on average with rings, clips and pins. Plan on using the cb900 rods if I can, they weight 390g's. From what I got off cycle x's site there pistons are 155g's and four grams lighter than stock. That is over the 50g rule unless that is just piston weight not dressed which would be a bit better. I have to look at balancing I saw that Mec sent his out for balancing. I hope a buddy of mine can help me out here to get this part right.

I still have to look into the kicker/starter setup. If I plan on running 11.5:1 - 12:1 I'll want the starter for sure.

[Medyo Bastos]

i may be willing to part with a set of 67mm arias pistons with new rings from total seal, new wrist pins, decked jugs with new sleeves, freshly bored and honed, just waiting for a motor to drop into...  head is polished, opened up to 67mm, ported, cc'd, new guides, springs, anodized retainers, etc... (11:5:1)

[evan77]

i may be willing to part with a set of 67mm arias pistons with new rings from total seal, new wrist pins, decked jugs with new sleeves, freshly bored and honed, just waiting for a motor to drop into...  head is polished, opened up to 67mm, ported, cc'd, new guides, springs, anodized retainers, etc... (11:5:1)

Hi Medyo,
I might be interested in this setup. The pistons are 15mm pin I would assume? I was planning on using a spare set of CB1100F rods that I have but I suppose I could bush the small end to 15.
Let me know if you are really interested in selling.

Thanks,
Evan

[Medyo Bastos]

yes, 15mm wrist pins.

let me do some brain storming, and number crunching.  i will let you know.

[Sam Green Racing]

i may be willing to part with a set of 67mm arias pistons with new rings from total seal, new wrist pins, decked jugs with new sleeves, freshly bored and honed, just waiting for a motor to drop into...  head is polished, opened up to 67mm, ported, cc'd, new guides, springs, anodized retainers, etc... (11:5:1)

Hi Medyo,
I might be interested in this setup. The pistons are 15mm pin I would assume? I was planning on using a spare set of CB1100F rods that I have but I suppose I could bush the small end to 15.
Let me know if you are really interested in selling.  Bill here,Would trade you some MTC alum rods or RC H/D with bushings installed, shot peened, etc. Both 15mm pins.

Thanks,
Evan

[EnginebyAdam]

I found a lot of info regarding undercutting and who can do the process. I am still looking for info on either a four or three speed transmission. I found with my DOHC 810cc that I would of much preferred a properly geared four speed if it was a drag only setup for the 1/4. We do not want an automatic, thinking air shifter or electric shift. I have been going through jweeks posts all the same

Thinking I will bump up to aftermarket rods in the 1100/900 length for the better ratio. By the time you get a set of 1100 rods now you are half way to a set of aftermarkets. I'm sure the cb900 rods I have are fine but I'll save them for my DOHC 985cc as was planned.

The head my buddy has is an F head but is a '75. Will take a look at it all the same.

Looking into the ignition system now. I run a Dyna 2000 system on my DOHC 810cc find it great. Might try to go the MSD route with this one, cycle x looks good too.

Any recommendations would be great guys, thanks.

[jweeks]

My opinions:
Air shifter with CO2 bottle. Get an auto shift electronic box to shift at a given rpm. (either way, you're building an automatic) A lockup clutch to launch with less worries.
MSD MC-3 ignition (used if on a budget, MC-4 if you want to extract the most possible from the motor on the dyno) Usually the only option that you can get contingency money for using at big drag events. Yes MSD is going through bankruptcy. Product is still available.
The rod problem is that inexpensive aftermarket steel 1100F rods don't exist. Carrillo's are expensive to most build budgets.
Cylinder head is where the money should go. F heads are a good start, but check how you are going to mount the carbs to that head. Manifolds are difficult/impossible to find. A good set of 34/36 mm carbs aren't cheap purchased in the Honda spacing. Used has it's advantages for us on a budget.
Don't even look for a 3/4 speed for your SOHC Honda. Too rare/too expensive. Won't get you much of any improved performance. Quarter Jr. software can check the tranny theory you're using and give the changes in ET. That's the cheap way to find out what really works. If you think that the 3/4 speed tranny will help with lower ET's, save a lot of $$ and add nitrous. You'll run quicker for less $$ spent.

     What class/category are you trying to build for? Most all bikes at the local dragstrip level are bracket racing. Heads-up racing on an index would have your Honda at a disadvantage. (9.90/8.90 usually are the slowest two) Air cooled motors are at a handicap to the water cooled higher horsepower Suzuki/Kawi's that are out there. They would be always chasing you with more horsepower than you can build. They vary less round to round than your oil cooled motor will. It would be a challenge to start to compete at that level.

     Another question for your build theory- What bike type has one rider won the most rounds of motorcycle bracket racing in New England drag racing history? answer: my Hondamatics. I know that they're not as sexy as the clutch equivalent, but they sure do win a lot. Don't use Sam's Hondamatic build as a guide. Until you launch consistently off of the back brake, the bike is a random number generator. Sam's bike isn't there yet. My 1180 'matic runs high 10's at 124 mph in the quarter mile. Not as quick as you can build a clutch equivalent, but still respectable for a 70's Honda motor.

     Good luck with your build.

                                                        Jon Weeks

[EnginebyAdam]

My opinions:
Air shifter with CO2 bottle. Get an auto shift electronic box to shift at a given rpm. (either way, you're building an automatic) A lockup clutch to launch with less worries.
MSD MC-3 ignition (used if on a budget, MC-4 if you want to extract the most possible from the motor on the dyno) Usually the only option that you can get contingency money for using at big drag events. Yes MSD is going through bankruptcy. Product is still available.
The rod problem is that inexpensive aftermarket steel 1100F rods don't exist. Carrillo's are expensive to most build budgets.
Cylinder head is where the money should go. F heads are a good start, but check how you are going to mount the carbs to that head. Manifolds are difficult/impossible to find. A good set of 34/36 mm carbs aren't cheap purchased in the Honda spacing. Used has it's advantages for us on a budget.
Don't even look for a 3/4 speed for your SOHC Honda. Too rare/too expensive. Won't get you much of any improved performance. Quarter Jr. software can check the tranny theory you're using and give the changes in ET. That's the cheap way to find out what really works. If you think that the 3/4 speed tranny will help with lower ET's, save a lot of $$ and add nitrous. You'll run quicker for less $$ spent.

     What class/category are you trying to build for? Most all bikes at the local dragstrip level are bracket racing. Heads-up racing on an index would have your Honda at a disadvantage. (9.90/8.90 usually are the slowest two) Air cooled motors are at a handicap to the water cooled higher horsepower Suzuki/Kawi's that are out there. They would be always chasing you with more horsepower than you can build. They vary less round to round than your oil cooled motor will. It would be a challenge to start to compete at that level.

     Another question for your build theory- What bike type has one rider won the most rounds of motorcycle bracket racing in New England drag racing history? answer: my Hondamatics. I know that they're not as sexy as the clutch equivalent, but they sure do win a lot. Don't use Sam's Hondamatic build as a guide. Until you launch consistently off of the back brake, the bike is a random number generator. Sam's bike isn't there yet. My 1180 'matic runs high 10's at 124 mph in the quarter mile. Not as quick as you can build a clutch equivalent, but still respectable for a 70's Honda motor.

     Good luck with your build.

                                                        Jon Weeks

As of now motorcycle racing is not very big here so we'll be racing against all the newer factory bikes. The front runner is a 1400 ninja, slightly modified, runs 9.32@146mph. If the bike can do mid 10's on engine and lower with the squeeze if I go that way, I am happy. I am thinking I will have to go with the 73mm pistons and 11:1 CR min to get reliable 10's out of the bike. Doing this on an old Honda is way more impressive than doing those numbers on a nearly stock super bike. This will be a first of it's kind around here and that's the big thing, beating up on some crotch rockets would be good too

The head spacing on the sohc vs dohc is very similar. I plan on pulling the CR31 specials off my 810cc if they can work here. Alternate mounting techniques for non traditional carbs have been used on the 1100f site with good success if the spacing is not correct. I also have a set of 36mm CV carbs as well, that might be an option. I have looked at undercutting on the transmission so I'll go that route with a lock up clutch. I plan on building this engine so it could take nos if need be. 

I have a lot of the parts already for the engine side of things so I am thinking I can spend $5000 on this project doing most of the work my self and have a solid mid to low 10's bike with a light rider (I have to lose weight ). The frame is another thing but a friend is a Tig inspector and has offered to weld it up once we get it designed.

I like MSD and hope I can find one at a good price when I get to that point.

[EnginebyAdam]

I took a trip out to see a buddy of mine this past weekend, the same guy who gave me my '76. We have been trading parts for a while now and he has quite the collection so I try to get out as much as I can. Anyway I sold him a 1982 kz1100 spectre a while back for a parts bike and I went out to see if he still had the pistons, and he did.

They are a little grubby for high performance use but for now I'm just looking for measurements. The compression height is 25.5mm on pistons which are 72.5mm bore, they also have the 17mm wrist pin. I also measured a set of stock 750 pistons and got 24.36mm compression height. Please let me know if I am off on the 750's measurement.

The obvious issue is the dome. I read a post here about machining the outer edge of the piston to get clearance for piston to head, then fly cut and shape the dome as needed. A little old school but I believe it will work with good CR numbers as well. From what info I have gathered if I were to use these pistons and cb1100 length rods with the cb900 crank I would be looking at a 8.64mm footer. Would that be too much of a foot plate under the cylinders?

The plan may change a few times before this makes it's first pass but I have to start somewhere. Cheers.

[EnginebyAdam]

I have decided to stick with an naturally aspirated build. I'll stick to what I know for this one and see how it goes. 

I have found a set of NOS 71mm and 73mm MTC pistons for a very good price. They look a lot like the one's on satanic mechanic though I believe this picture is a 12.5:1 piston?



I have read that some here still run these pistons. One issue I have seen is finding rings. If these are worth grabbing I was told that XN style rings could be fitted. The compression ratio is supposed to be 10.5:1 based on a K model head. 10.5:1 should still give good HP with the 69mm stroke. Chances are the head will be milled so a little bump in CR would be perfect.

Any reasons to stay away from these pistons? Was told 0.002"-0.0025" clearance on the skirts, but that seemed a bit tight to me. Any thoughts?

[Big Jay]

If the pistons still have taper in them, I wouldn't go over .002. max. MTCs did not need a lot of clearance.

How much taper do they have?

[EnginebyAdam]

If the pistons still have taper in them, I wouldn't go over .002. max. MTCs did not need a lot of clearance.

How much taper do they have?

I will ask that the next time I'm talking to the seller, which would be Monday. I won't have them in my hands till after I buy them, but I do trust that any measurements would be accurate. They are brand new pistons never installed so all original design and tolerance should be present. Providing they were handled right. That being said I'll double check that they mic the pistons on their end, although I'm sure they will anyway.

I have never run a forged piston this old before, thanks for the info Big Jay. I always go with the manufactures clearance unless I know it's horribly wrong. Edit: Had some bad clearance specs on a set of pistons, 0.00425" as opposed to 0.0025" proper spec. The cylinders were bore to the 0.0025" clearance

I don't own them yet but it is starting to look like I might

[EnginebyAdam]

Some pictures, 10.5:1 and 12.5:1 72mm bore.




The pistons will be double checked before being sent out, Big Jay. For my purposes the 10.5:1 should do. I figure I can mill the head some and get me in the 10.75-11.25:1 range. I have to get the head I want, 77/78K, dress up the chambers and cc them.

These pistons are being quoted at 10.5:1 and 12.5:1 for 71mm, 72mm, and 73mm. I will give up HP using the 10.5:1 pistons but I feel it will be easier to tune for my first go round. I will still get 10's with this
setup so it sounds good to me.

[EnginebyAdam]

I have been in contact with Jon over the last week, as well as HondaMan, both gave me a lot to think about.

The big factor with this build is budget. Going big, 71mm-73mm bore range, will take more money than I have to work with, as I am now aware of. The head work to support that size bore, combined with the cb900 crank, would run into the $2500-$3000 range. A used big bore block that would most likely need a bore/hone for the 71mm-73mm range most likely another $800-$1000.  No internals bought yet. I thought I had a money tree but it blew down in our last snow storm

One of the things that Jon mentioned was how well the F2/F3 head did on his 1080cc engine. The thought was that the stock F2/F3 head needs displacement, roughly 1000cc, to take advantage of the head. My thought is, why not build a bigger F engine? 67mm x 69mm stroke, 973cc, undersquare. This engine would be in direct ratio to the original F2, 61mm x 63mm. Pistons would be 12.5:1, so roughly 11:1-11.5:1 with the F chamber, without milling the head. The pistons are the same style of the 72mm piston pictures I posted.

I know that oversquare engines are typical for drag racing, I've built a few, but my theory is the natural midrange of the engine coupled with the right cam, would allow me to access the top end as well. HondaMan said this combo should make for a better launcher than a oversuare engine, I agree. What do ya'll think?

[joe p]

I check in to this to and no way I've got that much money. If I build a motor it will be a 970 or 1000 with a F head, super rod and thats about $3,000 and thats me doing eveything except the bored job. I had a motor like this in a street bike years ago and It would pull the front wheel off the ground with no problem .

[EnginebyAdam]

I check in to this to and no way I've got that much money. If I build a motor it will be a 970 or 1000 with a F head, super rod and thats about $3,000 and thats me doing eveything except the bored job. I had a motor like this in a street bike years ago and It would pull the front wheel off the ground with no problem .

If I went with 71mm-73mm pistons plus the cb900 crank, the issue is getting the engine enough air. The way I want to go now I should be at $3500 for the engine.

[joe p]

I had to go back and read all the post, I some time do not read thing right. It would cost me a lot of money to come up with the parts you have. and I'm not trying to go that fast. I sold my S/C 1428 KZ drag bike back in Oct. I have my old Honda drag bike that I raced years ago. I'm just looking at building a 11sec Pro ET bike. I agree with Dragracer go with the guys that know what there doing with this build Jon Weeks, Bear, Benton.

[754]

The pistons above, are not for stroker...correct?

[EnginebyAdam]

The pistons above, are not for stroker...correct?

No they are not stroker pistons, will be using a spacer/copper gasket under the cylinders.

[EnginebyAdam]

I had to go back and read all the post, I some time do not read thing right. It would cost me a lot of money to come up with the parts you have. and I'm not trying to go that fast. I sold my S/C 1428 KZ drag bike back in Oct. I have my old Honda drag bike that I raced years ago. I'm just looking at building a 11sec Pro ET bike. I agree with Dragracer go with the guys that know what there doing with this build Jon Weeks, Bear, Benton.

From speaking to Jon Weeks, the 973cc setup should yield a low 11's bike that can look at the 10's.

[TurboD]

Adam I have read through the posts and there is a lot of good info here. Now going back to your original post, what exactly are your goals (to fit a certain class, ET, MPH ,HP) etc?

Myself also new to SOHC Honda performace engines, I had posted up a thread asking about what could be expected in terms of both horsepower and cylinder head numbers flow wise. The cylinder head flow numbers will directly give an idea as to how much horsepower a given engine will produce. When it comes to the IC engine one simply cannot "cheat" the engine into making more power than the head will provide. Barring nitrous use or turbo.

A few years back I built a Kawasaki KZ 1428 with a completely stock head (head flowed about 70 cfm @10). It ran great with killer monster torque, but at the end of the day it simply was not very fast. That head was going to produce roughly 120 crank HP reguardless of how many CC's I put under it.

[jweeks]

Any pin height piston can be used with a more than stock stroke. It's a question of how you get the right deck height assuming that the combination makes sense to build.

Bill B. ran a 10.5 to 1 compression 836cc stock wheelbase Honda at the Manufacturer's Cup with 12.4 dial-ins. With 12:1 compression and a lockup clutch, he would be knocking on 11's door. 915cc?  11 second time slips.  A longer swingarm would help the launches. Yes, the head airflow limits horsepower, but the torque curve also has a big effect on ET.

There's very few surprises in building what has been done over and over for the last 30 years. Improved heads from better valves, better porting,  and more $$ spent welding up better ports to flow more air are most of the changes. The internet has made sharing build results far easier. There's a lot of answers on this forum. It should help your confidence when you start your next build. Remember, we want pictures!

                                                                            Jon W.

[EnginebyAdam]

Adam I have read through the posts and there is a lot of good info here. Now going back to your original post, what exactly are your goals (to fit a certain class, ET, MPH ,HP) etc?

Myself also new to SOHC Honda performace engines, I had posted up a thread asking about what could be expected in terms of both horsepower and cylinder head numbers flow wise. The cylinder head flow numbers will directly give an idea as to how much horsepower a given engine will produce. When it comes to the IC engine one simply cannot "cheat" the engine into making more power than the head will provide. Barring nitrous use or turbo.

A few years back I built a Kawasaki KZ 1428 with a completely stock head (head flowed about 70 cfm @10). It ran great with killer monster torque, but at the end of the day it simply was not very fast. That head was going to produce roughly 120 crank HP reguardless of how many CC's I put under it.

My goal has always been a 10 sec sohc Honda drag bike. I wanted something that would make the crotch rocket crowd at the drag strip give a second look to a 30 + year old bike that lays down similar numbers to their factory bikes. As I dug into the build I realized we don't have the cash to build this engine big enough to run 10's consistently. So racing heads up is out of the question.

We don't have a motorcycle drag community around here, it is coming and this build will be a big part of that. My partner and I ( I handle the engine design, he handles the FI and chassis) are racing our selves for the most part. One of the regular drag racers runs a extended swing arm, air shift, 1400 ninja. I know him fairly well, the bike has no engine work. 9.42 @ 146MPH. There are a lot of "drop in" in guys running factory bikes on average mid 10's due to lack of skill, not engine. Our goal is to see what we got in the 11's. This is all about pushing our selves to see what we can come up with design wise.

A 1996 GSXR fell in our laps this mourning, I just finished striping it down, looks like we got a swing arm, front end, wheels and brakes to work with. Have to dig into it more tomorrow to see if we can use it all. The swing arm can defiantly work and that rear wheel gives us a 180 size tire to start with

On the point of the head flow, this F head can support a 1080cc engine flow wise. So flow wise it should support the 973cc. The 67mm bore should work nicely to unshroud the large valves in the F head. Large valves and in the case of the F head, nice intake ports, are not typical of a undersquare engine. The natural characteristics of the undersquare engine combined with a head that flows on a undersquare engine, in my mind, should produce an engine capable of 100HP and low 11 sec passes on a good chassis.

As Jon said, the torque curve should be the ticket here. HondaMan also mentioned that with a undersquare engine, as these were stock, a turbo charging effect comes into play in the stock engines around 6500 RPM with the 28mm carbs, and about 7700 RPM with the 31mm. He also mentioned that as the intake valve gets bigger so can the carbs. So with the stock valve size of the F head being 34mm this should move this effect even further up the rpm range. We will be running gsxr throttle bodies so will have to see how this relates.

Cheers,
Adam