Topic: 1978 CB750A HEAD MILLING ???? MR. HONDAMATIC MAN

[POPS 911]

MR.WEEKS [ HONDAMATIC MAN ] :  How much can you mill off a stock 750A head to pick up a point or two for compression and still start with the OEM push button starter .  My friend has a machine shop and works on big car motors for the racers in Ohio and surrounding states [ 25 years in that trade ] and does my work for free , er er er I cook the whole shop " A FIREHOUSE MEAL " and the bill is paid in full .

POPS BK911 ST/ET NHRA

[Sam Green Racing]

Rich, I don't know the answer but it will depend on the cam and pistons you are useing.

Sam.

[jweeks]

Pops
     You can aim for around 11:1 and use the stock starter. The Honda starter can be aftermarket rewound for about another half a compression point if you've got a good enough battery to crank it over. Stock starter limit is around 11.25:1 in my past testing (really slow cranking). You can't get there with head milling alone. The valves will be unhappy bouncing off the top of the piston for a revolution. I can do the math for the theory, but the real world, it won't get you where you want to be. Maybe a half point increase in compression from head milling would be my goal limit.(I've never tried over .040") You get into needing deeper valve pockets for clearances (with not enough thickness in the tops of the stock pistons) and eventually a link smaller cam chain.
     The motor loves compression. Your torque curve is better as the compression goes up and your ET's go down. The increase in oil temperature from the compression increases the need for more oil cooling to be consistent. All my drag Hondamatics run external oil coolers. I cover the cooler when it gets under 50 degrees F.
     The solution to your question is to use different pistons. I've seen 14.5:1 in all out clutch CB750 motors. Yes, there is more horsepower there, but you loose consistency from the heat generated. I use 12:1 as my building limit to allow my external oil cooler to keep me consistent and to be able to drive the bike back to the pits (no tow bike) My big bike runs about 11.25:1 with a F head and an external starter. The quickest Hondamatic (in Texas) runs quicker than I do using more compression but they are unhappy with the consistency. There's a lot of topics here in this forum that cover DOHC pistons in SOHC motors along with the Cycle X cast 836 pistons, etc. available for little $$. I'd use Ebay Motors for a set of Wiseco used ones. Sam's hondamatic runs lower 12's with the Wiseco 10:1  836 pistons (yes I know they're a fraction of a point higher) and a ported K head. That's a fun ride. The next step in motor size requires sleeves and machining. 900cc and you're kissing the 11's on a cold day. Aftermarket blocks for 1080cc and middle 11's will happen. Stock pistons and you'll stay in the 13's. The stock Honda design won't give you much for a hour or two in a machine shop.

                                                                       Jon Weeks

[MRieck]

I would work on decking the cylinder as the pistons sit deep in the holes. Either that or do not run a base gasket and deck it a smaller amount. I have milled over .050 from the K head but you get into the intake seats pretty good.

[dragracer]

I would work on decking the cylinder as the pistons sit deep in the holes. Either that or do not run a base gasket and deck it a smaller amount. I have milled over .050 from the K head but you get into the intake seats pretty good.

Mike, is that the case with all of the SOHC motors? Negative deck height i mean.

[POPS 911]

So .020" would be safe with stock pistons and cam , as the piston are in the hole deep enough with NO cam chain changing ?  We put our BUSA race motors 6-8 in the hole with a 243 hp motor and a race head = learned not to squeeze the motor with rod strech [ Falicon rods w/special MTC pistons that Tony made for the motors  ]  and had many motors last a lot longer running big numbers =  Ask Boo Brown , Johnny Locklear,  Mad Dog Bruce  about the many MSP BUSA motors at 68-72 " long that chopped heads at Rockingham a few years back with SHINE RIDING.

POPS BK 911

[jweeks]

Yup.

Happy New Year.

Jon Weeks

[MRieck]

So .020" would be safe with stock pistons and cam , as the piston are in the hole deep enough with NO cam chain changing ?  We put our BUSA race motors 6-8 in the hole with a 243 hp motor and a race head = learned not to squeeze the motor with rod strech [ Falicon rods w/special MTC pistons that Tony made for the motors  ]  and had many motors last a lot longer running big numbers =  Ask Boo Brown , Johnny Locklear,  Mad Dog Bruce  about the many MSP BUSA motors at 68-72 " long that chopped heads at Rockingham a few years back with SHINE RIDING.

POPS BK 911

I would slot the cam sprocket (or buy a slotted one) and degree the cam if you take that much off.

[POPS 911]

MRIEK:  So this means that .020 off the head moves the valves  closer to the piston and retards the ignition by the timing chain making up the slack, rolling cam back ??  So the slotted cam gear you could roll the cam foward for advance     What is best a low end or a high top end ? This is a 400cc motor with ported head and sidewinder and carbs worked , with me 215 lbs. in leathers ,helmet, boots,   1 1/2 gallon SUNCO fuel [ 6.5 lbs ]  geared for 1320' with shift light [ 7100 RPM ] on in DRIVE right at the 12" mark of the 1320". We have a DYNO and could put bike on and move the gear back or forward.  Do not need speed on this TURTLE as I kill them on the lights [ .100 to .017 ]  same MPH everytime.  Head winds kill the ET and dial in off of a weather station .  I do not look back and never lift , laying on the tank , feet on rear pegs with a link shifter.

POPS BK911  ST/ET NHRA

[POPS 911]

Is the answer :  Advance or retard when you mill 20 off head ? Roll cam back or forward ?  The car engine builder [ in business 23 years ] gives me the story that milling head 20 and leaving stock sprockets on cam will give me a better [ same power ] run every pass = what say you-all wrench spinners. He can grind my cam and harden it back to spec's for free !!!!!  What safe numbers for this CB750A 1978 CAM for a little more lift ??

POPS BK911   ST/ET NHRA

[Sam Green Racing]

It would be retarded Richard. The tensioner pushes further on the back run of the chain pulling the cam sprocket in the opposite dierection that it would turn. That in turn would make the cam get to the rocker that little bit later.

Sam.

[POPS 911]

With this heavy TURTLE I do not need the low end power  [ advance ], but at the 1319' mark I need the top end [ retard ] to make the folks in the other lane to break out trying to catch me !  Me at 112=118 mph and they Busa,GSXR, KZ 14 will be coming at 132-144 mph and cannot lift , brake or set up in 12" as I will be leaving first with a great light and they watch me fade down the track with their side vision and they chase with all they have , somtimes they  wheelie, red light, break outs, hitting rev limiters = I shift once on a shft light and the special narrow glasses my Eye DR. made for me to only see that bottom YELLOW bulb only cheats the tree.............. .100 - .012 lights give you the edge.

POPS BK911 ST/ET NHRA

[lucky]

MRIEK:  So this means that .020 off the head moves the valves  closer to the piston and retards the ignition by the timing chain making up the slack, rolling cam back ??  So the slotted cam gear you could roll the cam foward for advance     What is best a low end or a high top end ? This is a 400cc motor with ported head and sidewinder and carbs worked , with me 215 lbs. in leathers ,helmet, boots,   1 1/2 gallon SUNCO fuel [ 6.5 lbs ]  geared for 1320' with shift light [ 7100 RPM ] on in DRIVE right at the 12" mark of the 1320". We have a DYNO and could put bike on and move the gear back or forward.  Do not need speed on this TURTLE as I kill them on the lights [ .100 to .017 ]  same MPH everytime.  Head winds kill the ET and dial in off of a weather station .  I do not look back and never lift , laying on the tank , feet on rear pegs with a link shifter.

POPS BK911  ST/ET NHRA

Sounds like you just need a 20 year old rider that weighs 110lbs.

[POPS 911]

LUCKY :  I BEAT 5 of them 110lbs. 20 years old in a row and they filed CHILD ADBUSE CHARGES against me after the final win.  It's a bracket race and just like the UPS MAN I bring the package right on my time.  Do you think ELMER  or SPIDERMAN or HOGAN weight 110 lbs. and are 20 on those TF BIKES ?  I have grandsons that size and age but they want to be SNOW-BOARDERS like Shaun White WHO EARNS MILLIONS and not a motorcycle drag racer who earns $175 on a SUNDAY !

POPS BK911 ST/ET NHRA

PS. You-all come to Valdosta and I'll BRING MY PACKAGE, you better be dead on , see you at the 1319' mark

[MRieck]

You could put an elephant on a TF bike and it would still run in the 7's.

[Sam Green Racing]

Are you looking for a ride Jumbo

[Bill/BentON Racing]

Ouch!,Sam says he'll win the 1320,1319...well .Pops come on down,77 years young,yeah we impressed,wanta see it live,guess I'll have to run you w/Calendar Girl(clutch CB750)and yes TF bikes don't even know you're there! Bill

[MRieck]

Are you looking for a ride Jumbo

I've lost about 45 lbs since you last saw me Sam.

[Sam Green Racing]

I spent 45 pounds in the pub the other night.

I've put a few lbs on since I packed in smoking, coming up to 5 months Mike.

Sam.

[MRieck]

I spent 45 pounds in the pub the other night.

I've put a few lbs on since I packed in smoking, coming up to 5 months Mike.

Sam.

Excellent news Sam!!! Good for you!

[bwaller]

Good on you both.

[dragracer]

I guess i'll load my 1973 Honda SL125 single in the trialer and see what kind of package i can come up with too. Oh wait, its not a 4 cylinder, i suppose it means i'll have to ride 4 of them at the same time.

[POPS 911]

BELLCOW:  I'm 69 an will be 70 Sept.19 -2012  racing that night at National Trails Raceway Park  in the Wed. nite points race.  Will bring my "Little Turtle 400ccA " South to Valdosta as it will take me the rest of this year to get 750A dialed in at many dyno's pulls and track rentals.  I can bring a 2009 BUSAMATIC Auto shift 10mm stroker for you to ride as the owner is away for 5 years making license plates.  If you need NHRA license to run quicker that 10.00 at these CUP races this 68" all motor bike runs 8.05.  But we can get a lane with that ladies 750 for HONDA racing. Fastest car I ever beat was at NORWALKS NO-BOX weekend [ three days of Drag racing ]  he ran 177 mph at 7.77 and never lifted = he lost but the side draft of him passing me at the line was like the NASCAR sucking you loose from your lane.  Lost to a guy with a perfect .000 light dead on dial in his street car that he drove to the track  [ found out he was a ST/ET champ from Michigan ].  PACKAGE = 72 MPH   18.25 - 18.28 DIAL IN   .012 - .072 REACTION TIME.

POPS BK911 ST/ET

[Bill/BentON Racing]

Pops,cool,come on down,bring the L'il Turtle this year,big un next year.Keep us posted on the 750A build.Still plan on bringing Samauto CB750A,Sam to ride,I'll try again on Calendar Girl,you and Sam can run each other in the over 65 class!!!!! ..Think we can hang with the R/T's,dial ins up to Jon!!! Sam's package rt now not as consistent as yours,he did run a 12.99 on a 12.98 dial in @ 115.xx mph,R/T.......being worked on! ;)Bill
Inherited a couple license plate bikes over the years! ;)Bring you the bike,some money and disappear...oh well.

[Sam Green Racing]

Hey Rich, would love to see you at Valdosta, bring the little turtle and I'll race you for $5 
Just joking Richard, but would be real good to meet you, your mate Chad will be there.

Sam.