my 900f on the dyno, part 2

Posted: Fri Nov 16, 2007 6:19 pm

original thread- http://www.cb1100f.net/modules.php?name=Forums&file=viewtopic&t=37333

had a little more free time this am and the comp baffle arrived for my VHR meg system.

this is the difference between the street baffler that comes in the pipe and the $25 comp baffle.

red = 1.75" comp baffle
blue = 1.25" street baffle

im extremely pleased for 10 minutes worth of work and $25.

Posted: Sat Nov 17, 2007 3:47 am

Thats a really nice pick up. Even at 6 grand its picking up faster. I did notice every thing comes to quick end at 9 grand with max torque at 8k. Fine by me. One more reason to shift a bit early. Keep the posting coming. Really glad to have you around. Very Happy

Posted: Mon Nov 19, 2007 4:20 pm

What would really be useful is to degree the cams and rerun the dyno pass.

In fact the single largest variable in any bikes performance is the cam timing. What is listed in the book and what works the best and what your engine has is rarely if ever the same.

The effect of chain wear/stretch is to retard the timing on both cams. This opens the exhaust valves later than optimum so you have less exhaust pressure to work with,probably the main reason for the big HP change. It also delays opening the intake valve till the piston is well down the bore and this really affects the total charge it can breathe since the valve is a restriction to flow for a longer period.

The 900 had cams degreed poorly from scratch and the wear really made it off from correct. The book says 5/5 on overlap,but checks at close to 0 on intake and 10 on exhaust,the chain wear can easily make it be past 0 when the intake finally opens. You get no breathing at all until the intake is open.

The trend on these motors is the breathing really falls off with revs. You can put in any cam you want,degree anywhere you want and still get no power above 10,000 RPM. The only way to gain is to get as much breathing as possible early in the rev range. The timing I find that works is about 100 lobe center on intake and 105 on exhaust,which relates to about IO 10 IC 30 EO 35 EC 5.

All the engines I built and drag raced I tried many different variations of engine size and cams. No real "dyno" numbers only the ET gain(or loss) until I ended up at these numbers. At dyno shootouts with my "numbers" I made power,but the Honda limitations still prevail. The work that would get 200 HP on another brand only gets 150 HP on these,they just do not breathe at big revs. Ported heads are my standard cut and end up at the same power. The 1220cc sizes are not as fast as the 1187cc version and the 1123cc seems to run just about as well. You just get to the flow limit sooner,ie the RPM is lower,so the higher torque of the bigger engine does not offset the RPM loss and the HP= T X RPM/5252 is a smaller number.

Making different numbers on the cam timing and your dyno would give us needed information. The only real trend is the overlap works best not "split",ie equal overlap,but better with the 5 degree stagger,ie intake opens 5 degrees sooner than the exhaust closes,until the cams get wild enough that either piston or valve to valve contact can occur. The maximum numbers I know will clear are at 25 degrees on intake and 20 on exhaust,obviously using some version of aftermarket cams,either .375" or .400" lift cams. The stock 1100F cams,or close aftermarket,degree to IO 15 IC 35 EO 40 EC 10 and perform quite well.

Posted: Mon Nov 19, 2007 4:54 pm

this motor definately needs to be done.it runs perfect,but is alittle smokey on hard decel.

my plan for the build-

985 kit,sonicrete style port,valve job and some stock 1100F cams or closest aftermarket version.

give me a list of the different lobe center settings you would like to see.

once i do the testing with the stock carbs,i will round up some carbs.

maybe some one would be willing to lend me a set for testing?

im hard pressed to give up the driveability of the stock carbs.it lets me be lazy and i like it.

on a side note,did a 300 mile ride on it yesterday.ran flawless once again.

ultimately i would be happy with 100hp.that what a stock zrx makes.

Posted: Mon Nov 19, 2007 5:16 pm

burned wrote:

once i do the testing with the stock cabrs,i will round up some carbs.

maybe some one would be willing to lend me a set for testing?

The opportunity to test stock carbs versus CR's with real Dyno data doesn't come up all that often and it would be a great bit of information to have.

I have a spare set of CR31's with 70mm stacks that I would be willing to send to you. I have not run these carbs, but they appear to be jetted for a 900F. I also have a set of untouched stock carbs that you could try if you wanted a baseline comparison. There'd be some conditions on this obviously, but if you're interested drop me a PM and we can work out the details.

Posted: Mon Nov 19, 2007 5:46 pm

id be interested in testing the 31's even as the motor sits now.

pm sent.

Posted: Mon Nov 19, 2007 7:58 pm

Sonicrete, would the cam timing of 100 degree intake & 105 degree exhaust work for the 750F as well? I have V & H Supersport and GSXR 34mm carbs. Stock engine.

Posted: Mon Nov 19, 2007 8:01 pm

burned, you have PM

melchiro, you should find a set of 900 cams for that 750 and time them up in it. Wink

Posted: Mon Nov 19, 2007 8:11 pm

replied!

Posted: Mon Nov 19, 2007 10:04 pm

genesound wrote:

melchiro, you should find a set of 900 cams for that 750 and time them up in it. Wink

Would 1100 cams not be advisable in a 750?

Posted: Mon Nov 19, 2007 11:12 pm

burned wrote:

replied!

back at ya!

motomoon wrote:

genesound wrote:

melchiro, you should find a set of 900 cams for that 750 and time them up in it. Wink

Would 1100 cams not be advisable in a 750?

1100 cams have considerably larger lobes and would take considerable more work. The lobes would not clear the head around the buckets, and would require some head machining, and you might need to check other clearances as well, like piston to valve. Sonicrete would no doubt know about that off the top of his head.

Posted: Mon Nov 19, 2007 11:36 pm

Read between the lines.

I have tried just about everything from stock cams to really hot grinds. These motors seem to like the 100I/105E cam timing. It does not matter the carbs,these work on the 1100 where it was first seen and lead me to using these short numbers with the hot grinds and direct lift carbs.The hot grinds "suggest" longer numbers like 108/108 on the timing tags,these did not work as well.

Honda made no sense in the timing numbers they used per models. The 750 had the same 5/5 overlap as the 900 cams per book but the longer duration of the 900 was all at the bottom,so the lobe center in effect becomes longer. The effect on power is the 900 makes no power down low but seems to turn on and run up high. This is deceptive. People "feel" the change in acceleration but not total power,the reason is it goes from "dead" to running compared to pulling all the time. The 1100 has it correct and not only that but they actually degree close to the book,the 900 was off and got worse due to the chain wear. By using the 5 degree stagger it then moves toward "split overlap" by the chain wear. Degreed split to start goes the entire wrong way.

There are two ways this is bad. The intake MUST open early or the valves are not open when the conrod to crank angle is 90 degrees to achieve maximum piston speed down the bore,ie maximum draw. It is also bad because the exhaust valve is open on the overlap at the critical early part of the draw,it just draws in exhaust. Another way to look at it is consider the overlap as one event occuring at TDC. My version the piston is still rising at the center of the event helping this along. The reverse is the overlap center occurs while the piston is decending,ie the volume is getting larger. This version plain does not work.

Now add the fact that these motors do not breathe at high revs. The reason I think is the port angle compared to bike centerline. The flow favors the outside valve of the pair,with the inside valve effectively in a closet off the main hallway. At slow airflow/crankspeeds the air can turn this corner,but at high speeds it does not. The effect is the torque,ie cylinder fill,drops off as the revs rise. The HP=T X RPM/5252,so the RPM makes up for it some but eventually the total power is less.

Depending on the valve sizes and how far into the seat they are sunk eventually you will run into collision of valve to valve or valve to piston,thus ending any further "tuning". This is only using aftermarket cams,since these have enough duration to move them around some to test the effect of the actual opening/closing numbers and not just the lobe center.

As I said intake opening at 25 degrees is the maximum I use and 20 degrees for the exhaust,I know these clear. You may go to 26 or 27 degrees but everything is getting close at this point.

Stock 1100 F cams degree to IO 15 IC 35 LC 100,EO 40 EC 10 LC 105.
.375" lift cams degree to IO 25 IC 45 LC 100,EO 50 EC 20 LC 105 and the nicest choice.
.400" lift cams degree to IO 25 IC 55 LC 105,EO 60 EC 20 LC 110 the motor feels similar and "maybe" gains 500 RPM over the .375" lift,but these require shim under buckets.

You need to do this work with the existing motor condition to see the actual change. Going to 985cc and freshing the bore or porting or valve job makes previos runs not relative to what was done before. The classic making two changes and not knowing which worked. This is after all a learning experience to validate my work.

Posted: Mon Nov 19, 2007 11:47 pm

you dont need to validate your work.youve already done it.

are there any slotted sprockets available or are you doing them by hand? or mill?

Posted: Mon Nov 19, 2007 11:52 pm

To answer the last post.

The 1100 cams are the best of the bunch REGARDLESS of engine size. The stock 750 cams are plain junk,no lift/no duration. The stock 900 cams at least have decent lift/duration. This is of course ignoring the "soft cams" wearing away of the peak lift.

Had Honda "planned ahead" they would have made the clearance at the bucket hole the same on all the heads. If it cleared the gasket flange it could fully rotate. The 750 head has a ledge there and 1100 cams will hit,the 900 cams may or may not clear.

On built engines the big cams like the .405" lift Andrews also have a larger base circle so the entire cam is larger and the lift will hit the radius on the bottom side of the tach drive. You need to relieve this part and actually break through into the area under the seal,which makes no difference the seal keeps the oil in.

On any of the stock cams 750/900/1100 the base circle is the same size except for small variations so basically can be interchanged if they would clear the head. The aftermarket cams are all over the map on base circle so need to check to even see if you are in the shim range and require the engine apart. The combination of sinking the valves to do the valve job and the larger base circle can get to the really thin unobtainable range of shims.

Posted: Tue Nov 20, 2007 4:09 am

There are no aftermarket slotted spockets. The pictures seen in catalogs for bikes like a Z-1 Kawasaki show a spocket with a slot about a mile long. The maximum amount of slot needed is from 1/2 tooth before to 1/2 tooth after a tooth,since you can jump the chain to be on the other side of the number. I usually only cut what I need so it is at one end of my "slot" and if it would move it would end up where stock was anyway. I never had one move even with hot cams and heavy springs even though I never liked the slot idea.

Basic information is to mount the wheel on the alternator rotor bolt and the pointer from one of the alternator mounting holes. Use a positive stop to accurately find TDC. Check the cam timing where it is now and write it down. By measuring the distance between the mounting holes you can calculate the amount of slot you will need and in which direction to cut,usually to advance the timing since the chain wear retards it. At these small of changes the sin and tan of the angle are close to the same,so it is the radius times the sin of the angle change you need. Say .080" is quite a bit of timing change,but it depends on where it is now and where it needs to go.

Posted: Tue Nov 20, 2007 12:05 pm

i degree cams everyday.i just couldnt find any sprockets.your right,the slots are a mile long in aftermarket sprockets,but they save me alot of time.

if its slow this week at the shop i will at least see where im at currently for lobe center.

Posted: Tue Nov 20, 2007 12:25 pm

I'm beginning to wonder if some of the chain stretch issues could be improved with new sprockets, especially on higher lift cams with HD springs. I have some old sprockets and they definately show wear compared to my NOS set that I will slot.?

I had a set of slotted sprockets that I bought from V&H many years ago come loose on me, then years later Ray put them in his bike and the same thing happened to him. Perhaps the slots were allowing the sprockets to be not quite centered, causing the bolts to loosten, or they were just off center a bit in the first place?

Posted: Tue Nov 20, 2007 3:26 pm

ok,i was super curious so i came in early and checked it out.

as my motor sits the intake lobe center is 106 and the exhuast is 103.

i did the ckecking at .050" with .004" valve clearance and got-

intake 37/5 37+5+180=222/2=111-5=106
exhaust 30/4 30+4+180=214/2=107-4=103

stock according to the 900f service manual would be

intake 102.5
exhaust 107.5

the cam chains in my motor look to be in good shape and the tensioners has plenty of room left.

some one kept on top of the adjustment of the valves and the chains as i havent touched either.

the LC isnt as bad/off from stock or 100/105 as i figured it would be.

if i get a chance i will slot the sprockets but i dont know if its even worth testing.im sure theres ia bit of power to be had but im not staying with this motor set up.

once i have sprockets slotted with this motor set up or the mod motor it will be asy to change the lobe center and test back to back.

on a side note 106/103 is very close to the sweet spot for the 4 stroke singles i build.that with a .356" lift and 277 duration cam that is my proprietary grind for +4mm bore +5mm stroke motor.

Posted: Tue Nov 20, 2007 4:47 pm

Under NO cicumstances regardless of motor should the lobe center on exhaust be a SMALLER number than the intake.

Think about what is happening. The intake MUST be open early for full air flow and after bottom center it depends on how high RPM you are risking to rev it to take advantage of the inertia supercharge. Turns out you really get no gain by this inertia deal above 10,000,this I found out by ET difference comparing the bottom number on "hot" grinds to say stock 1100F or similar. The rising piston on compresion at the beginning does not move much but at some RPM it really rises quickly,thus pumping the mixture back out and resulting in less trapped charge. A 4 valve Suzuki for example "seems" to take big lobe center and rev on up still making power.

The exhaust works under much higher pressure than the intake and this sudden release is a big tuning aid for it's effect by the pipe tuning. The sudden exit drops the cylinder pressure possibly below atmospheric,like Kadency discovered on 2 strokes with a quick opening port. Now on overlap is the next bad effect by hanging the valve open after TDC. As I said the combustion chamber volume is increasing at the same time the pipe is trying to get the intake flow started on overlap.

If you look up the effects in a book,I think it was in a Stifton catalog,the effect of the timing you gave is a weak engine early that "hits" hard. Split overlap is preferred,at least for most first guess settings,but on these they definetly work better with about 5 degrees (or more) stagger in overlap.

It is your choice but I would leave the exhaust alone,it is better to not have to oval the hole since you must take these bolts out to get the cams out. This is speaking from "shim under" maintainence deals. The intake though I would advance the crap out of,say 10 or 11 degrees for the IO number. As the chains wear the exhuast overlap number will get larger and the intake number will get smaller,thus getting closer to split,which is my "end line". Street bike wise this should give you a tractor from say 2500 to 3000 RPM on up,and probably not concerned with 10,000+ RPM operation. You could have some slot and make a mark to be say 8 degrees IO number so a dyno run with 11 degrees and another with the 8 to really tell the difference it makes. It "should" change the power band to a little weaker early and rev higher,but I think will only result in less total area under the power curve with peak power unchanged due to the head design. Just a few degrees can have a big effect,as little as 2 degrees. This is not a problem since after you find "the spot" the intake sprocket can stay on the cam even if it needs to come out. Not like the monkey motion you need to do on the exhaust.

By the way this overlap stagger is not new. ALL V-8 auto camshafts are ground this way. Installed straight up "on the dots" results in a cam at 4 degrees advance. Now of course the total lobe separation cannot be changed so you are stuck with what the cam grinder put in only to find the best spot,but on these you can have any lobe center or overlap you want.

I have a set of RSC (Racing Service Center) "factory cams". The intake cam looks like a square with the corners rounded off,the exhaust lesser duration and more "normal" looking. These plain made no power but made the bike really rev high,like to explosion range. In fact Honda called them motor destroyers. If you attemped to degree to short lobe center,the valves tangled and anywhere else made no power. The effect was really odd,the 60 ft time got slower,as in no power to carry the slick even though 7600+ launch RPM. The trap speed got slower and ET was even worse than the loss of 60 ft would indicate. These cams are in a box on a shelf. In fact stock 1100F cams worked better than these. Staggered cams wise you want a high lift short duration intake combined with a lesser lift longer duration exhaust. You put the extra exhaust duration at the bottom to give more "blow down" and still do the stagger on the overlap.

Posted: Tue Nov 20, 2007 5:04 pm

with the ex cam nonsense as it is im with you on leaving the holes as is.

on the intake i can tack the sprocket in place once ive done the testing and not have to worry about any possible slippage.ive never had any slipping issues on other motors,but no need to worry about it on this motors since the intake sprocket doesnt need to come off.

so with the stock 900 cams you would be ok with a 96/103 set up with testing the intake at 95 as well as 97?

Posted: Tue Nov 20, 2007 5:25 pm

HIJACK QUESTION....

So what is the best cam for a 750....if the 1100 cam is out. can a 900 cam be reground
for better improvements in a 750?

Just wondering.

Thanks

J

Posted: Tue Nov 20, 2007 6:42 pm

Basic information.

Extra duration only helps at high RPM(usually) but extra lift helps everywhere.

The opening at the valve bucket hole on a stock head limits the lift,it is that simple.

I have a CNC machine capable of profiling operation,so I relieve all the heads the same. That way if the peak lift will clear the gasket flange it can fully rotate. Wish I could get my CNC to run again,it worked fine at the last machine shop with true 3-phase,but does not like converted rotary 3-phase,then failed for I assume a ball screw failure. It was long about this time I quit racing so lost interset in working on it.

All of these heads,750/900/1000C/1100F are different in the clearance at the bucket hole,as strange as this sounds. It is really not a problem since usually you need to do a good valve job and better,read 1100F springs,to really gain with a cam swap,so it needs to be apart. The problem is the easy removal of a Z-1 Kawasaki head in the frame,is a time consuming back breaking job on these.

New bikes have decent cams,the hot rod 600's for example,and make more power everywhere,the 750 had very small bumps on a stick. Think women,nice looking but no figure.

The 1100F cams are decent,even compared to aftermarket,except some are soft and work on any displacement engine. The 900 cams are at least believable performance. I have a bushel basket full of stock 750 cams,only good for regrind cores,no performance at all.

What ever the lobe center comes out you need more intake overlap. I use .040" as degree point and .005" as clearance,so read the indicator at .035". The cams are not symetrical,ie equal lift and closing rate. They open quicker than they close and may begin to show this trend at the larger reading you use. I just did a motor using a 1000C top end and this uses 900 cams. These came in at 11/4 and made a strong feeling motor and uses CV carbs. As I said the effect of the delay due to the cam chain stretch could make it become 10/5,or where I wanted it to start,but this engine runs nice.

Posted: Tue Mar 11, 2008 4:35 pm

Did you ever get into degreeing your cams?

Posted: Tue Mar 11, 2008 9:48 pm

im will be installing my 985 kit and 1100f cams with in the next 2 weeks.

i decided not to bother with the 900 cams.

im going to give sonics numbers on the 1100 cams a go.