Topic: yosh cam cb 750

[222CT]

i have an old yosh cam.  decided to throw it in my motor.  motor has been rebuilt in the spring.  this cam was in it previously with 63 mm pistons.  when i took the motor apart initially, when i lined up the T 1-4 marks the cam key groove was not at the 12:00 position...more like 1:00.  i put the old  yosh cam back in it and lined it up at the 12:00 position like a stock cam and the bike will not run right off idle to about 4000 RPM.  after 4000 though the acceleration is out of this world cause im used to the stock cam.  below that 4000 RPM though she just wont idle right...wants to stall and float.  i know the cam is off.   carbs are clean and set and synced for the 250 time valve lash is good my question is where do i line the marks up at.  like I said before it was at the 1:00 position with the T 1-4 mark on target before my rebuild.  seems like the cam should be set up using the advance timing marks...the 2 just to the right of the T 1-4 and F mark.  anyone have any advice.  that is what it seems to me and that will be about at the 1:00 position i think when i line up the T 1-4 after resetting this cam. but any advie is greatly appreciated and thanks.   

[Jerry Rxman Griffin aka MuthaF'er]

222,

Which Yoshi cam is it? Road Special or Daytona? I have all the info for the Daytona cam if you need it. May already be posted somewhere on here too. In gallery somewhere?

Jerry

[222CT]

its a daytona.  i read and studied everything on the yosh cam gallery page.  so basically just set the cam advanced 10 to 15 degrees?  assuming my TDC is really right on TDC.  i got a degree wheel printed.  i figure...ill put the cam at 13.5 degrees advanced.  that way ill lower the risk of the piston to valve hitting.  am i right in guessing this??  then that in turn will slightly give me a lower max power range??  cause im not taking the head off.  and i dont want the piston to hit the valve by advancing it too far.  but having it advanced all the way to 15 degrees would give me a higher rev max power?  once i get the cam in ill turn the motor over to check and listen for any clanging.  will this basically work without doing it all the way the correct way??  i just dont have the time to take the head off and there is a little more nice weather still here in Pa.  i jsut want it too work basically and give me more power.  cam really makes a difference.  this cam was in my old motor.  it had a yosh kit in it i guess.  the pistons were 64 mm.  wow i would have like to have ridden my bike when it was fresh in the 70s. 

motor has new 62 mm honda pistons and new rings.  well new at the beginning of the summer.  runs really good but with this cam man all i can say is wow.  even though she was not running good in the low once the rpms were above 4000 say man the power.  im going to get this right tonight. 

[bryanj]

The way that runs is typical of a yosh cam, utter crap at low revs and a scalded cat at high revs, remember it was designed for reacing not street

[222CT]

any way to make it idle better?? a carb mod or someting.  maybe bigger pilot jets or different carbs.  im using the early carbs.  seems like when she would idle she kinda float and want to stall out if i turned the idle screw.  seemed it worked better when she was warm.  i have a dyna s ignition maybe run it in the full advanced position?  even at idle.  just throwing some ideas out.  id really like to use this cam and i know it works at the 0 degree position. should run it advanced 10 to 15 degrees.  but i cant cause i got stock pistons.  man this cam sure does make the motor fly.  wish i had the cake for some racing pistons.  i was comparing the stock pistons to the pistons that i took out of the motor and they have deep valve reliefs in them.   AP pistons.  they are scored pretty bad.   would it be possible to put deeper valve reliefs in a stock piston with say a dremel??  anyone ever modify stock pistons to run a hot cam??  just some ideas i was thinking and wanted to throw around cause that speed bug caught me.  im almost ready to float the cake via credit card to get some 850 pistons and a bore job.     just to use this cam. 

[Jerry Rxman Griffin aka MuthaF'er]

Bryan,

My Daytona cam is REALLY nice once it gets above 7000 rpms all the way up to 10,000 rpms. It'll run through my 8500 redline and back into the blue area in about half a heartbeat. Kinda doggish at lower rpms. It gets it's name from the Daytona 200. Not likely those engines went below 7000 rpm on that big long track. Just keep the rpms up. :-)

Be damn sure to use high performance valve springs too!! It will hit those high R's QUICK and if you miss a shift like I did you just ruined your engine when the valve can't close fast enough and kisses the piston. Otherwise just follow their installation/setup instructions and you shouldn't have to worry about clearance.

My bike has their 64mm pistons. The deeper pockets are needed due to higher domes and higher compression ratio. I never degreed my cam but wish I had. Next time for sure.

I can set my idle down to 600-700 with a proper tune up, sync and my Dyna III once it warms up. Non-pumper carbs too. Carbs suck. Make sure they are cleaned well and definitely synchronize them.

I'm out of town until Sat but will try to remember to get the information I received when I bought my cam from Yoshimura to you. Specs/installation/clearances. It is supposed to be advanced above stock but I don't remember how much. Be patient, good things are to come.

Jerry

 
 

[MRieck]

 Just about every Yosh cam (except some Stage 3) used 105 lobe centers

[Jerry Rxman Griffin aka MuthaF'er]

Here is some of the info I've posted:

http://gallery.sohc4.net/main.php?g2_itemId=5543
http://gallery.sohc4.net/main.php?g2_itemId=5543

Can't link due to the computer I'm using.

I have 1 more piece of info at home that has the timing specs on it so you'll know how much advance to use. I think it's +5 over stock. I know I punched a new timing mark just past the T1-4 mark. Wish I was at home.

[bryanj]

I remember putting a cam in a 500 years back and the ignition went to about 38 deg and the rear sprocket up about 6 teeth as it would not go "on cam" till 7,000 and below that was a real dog on the street

[Jerry Rxman Griffin aka MuthaF'er]

222,

As promised for everyone's viewing pleasure. Click the link below. Perhaps this should be saved to the site. Hope this helps.

Jerry

[paulages]

kinda silly to run a nice cam like that and not degree it properly... don't just use the degree wheel to "adjust"  13.5 degrees. find your lobe centers properly and let the cam work its magic.