Topic: Rebirth of paulages' cb735

[fastbroshi]

...so i did the math.... 736cc.  

so i'll have a 736cc cb550 that will run circles around a (736cc) stock cb750. what do i call it not to confuse it with the big brother? i wouldn't want to give him a complex...

  How ironic, what are the odds?  You shoud see about getting some 750 badges fixed on somewhere.

[paulages]

...so i did the math.... 736cc.  

so i'll have a 736cc cb550 that will run circles around a (736cc) stock cb750. what do i call it not to confuse it with the big brother? i wouldn't want to give him a complex...

  How ironic, what are the odds?  You shoud see about getting some 750 badges fixed on somewhere.

that would be funny.

[johnsy]

Slick! Excellent craftsmanship.

[greasy j]

that's pretty cool.

are you worried about the extra hp and the lower end bein cool? I know the 750 was seriously over engineered strength wise in the bottom end, crank and rods and bearings and stuff, so it can handle twice as much hp. Soichiro was adamant about it not failing. wondering if it's the same story with the 550?

[paulages]

that's pretty cool.

are you worried about the extra hp and the lower end bein cool? I know the 750 was seriously over engineered strength wise in the bottom end, crank and rods and bearings and stuff, so it can handle twice as much hp. Soichiro was adamant about it not failing. wondering if it's the same story with the 550?

at this point, the rods are the only thing i worry about. trans and clutch should be bullet proof. primary chain? i wish i had installed a tensioner... we'll see. i might get a wild hair and pull the cases back apart to do so.

[fastbroshi]

  My neighbor used to drag a 550 and he said all the ever did to the bottom end was shot peen the rods.  He used to run it to 12k all the time.  Then again, we're talking a quarter at a time so, take it for what it's worth.  I think it's safe to say the 550 has a safe margin for overrev.

[paulages]

  My neighbor used to drag a 550 and he said all the ever did to the bottom end was shot peen the rods.  He used to run it to 12k all the time.  Then again, we're talking a quarter at a time so, take it for what it's worth.  I think it's safe to say the 550 has a safe margin for overrev.

the 550 race bike i have has stock rods and the guy that raced it back in the '70's says he ran it to 12K every race. maybe he was one race away from total destruction? 

[fastbroshi]

  Guess we'll never know until you flux those rods, eh?  Isn't x-raying a good tactic for finding cracks too?  I always thought cryogenically treating parts like this was a good idea, given what's on the net about it.

  I know you're getting ready to bore, thought you might find this interesting, from http://www.sme.org/cgi-bin/find-articles.pl?&ME08ART40&ME&20080601&SME  :

Finally, Schaefer points to a lesser-known honing process in North America which has been used since 2002 in over a million gasoline and diesel engines worldwide: laser structuring. Situated in the standard honing process between rough honing and finish honing, laser structuring uses a laser incorporated in a conventional honing spindle to burn microscopic pockets inside the engine cylinder.

Schaefer describes laser structuring as a technology that allows engine builders to further improve engine oil effectiveness. Creating a kind of enhanced crosshatching, the process produces a homogeneous "engineered surface structure" that reduces friction in the cylinder wall. This structure cuts emissions, and enhances gas mileage by over 6% when the entire cylinder surface is treated (according to tests cited by Gehring). The process can also be used for bushings and piston rings—"or wherever we need to optimize the lubrication and surface conditions," says Schaefer

[traveler]

Damn Paul!  Cool to hear about the motor going larger!

I would imagine the big difference will be the extra torque at lower RPM's....of coruse you will get a 3-5 hp bump all the way across i suspect.

Will be interesting to hear what you will have to do in regards to jetting.

~joe

[bwaller]

Paul, sent that scan in an e-mail.

[greasy j]

when I finish mine up, in 4-6 mos. maybe, I'm still planning the trip up to seaWA. might have to wait for next summer or spring to avoid too much rain.

anyways I could stop by and you could try your 736cc 550 out against a stock engine 750. perhaps you know of some semi-private unused streets with no children or pets. or a track. it'd be a blast. I'm sure you'd pull ahead with less weight and all. but then you'd have some proof in your pudding. it'd be rice pudding, too. my fave.

[paulages]

when I finish mine up, in 4-6 mos. maybe, I'm still planning the trip up to seaWA. might have to wait for next summer or spring to avoid too much rain.

anyways I could stop by and you could try your 736cc 550 out against a stock engine 750. perhaps you know of some semi-private unused streets with no children or pets. or a track. it'd be a blast. I'm sure you'd pull ahead with less weight and all. but then you'd have some proof in your pudding. it'd be rice pudding, too. my fave.

i've had fun with some stock 750s already, but sure! what i've really had fun with is SV650s, which are nearly the exact same HP and torque. their handling and braking blows my bike away obviously, but it always surprises people on new bikes when my little 70's honda blows by them at 100MPH. 

[Pinhead]

Luckily, Soos saved the day. He had a set of 64.75mm pistons that appear to be ready to drop in, and we traded. His are in the mail already, so i'll be able to mock up and check compression ratio and valve clearances this week. I was curious what that extra .75mm would do to the displacement, so i did the math.... 736cc. 

You're going to be running Soos pistons?! (Reminds me of Foose.) Can't wait to see how the engine turns out!

[Soos]

woohoo! new pistons from Soos came in the mail today! these look dramatically different, with higher domes and different valve cutouts. i'll take pictures side by side when i get the old pistons back from the machine shop tomorrow. i'll have them bore the block for the new pistons, then mock up for valve clearances and compression ratio. 

Just got back from Chicago today(a few hours ago in fact) WHEW......


Anyways, good to hear you got those pistons!
Let me know what(if any) you end up needing to remove from those valve pockets.

My guess (from the other cb350T overbore pistons I have done) you will need to touch the exhaust more than the intake for proper clearances.
But with your cam I dunno. You might need to cut both the intake and exhaust.

If you find yourself a set of 66mm KZ750 pistons, send them my way and I can cut them for your cam.... if interested in having your next overbore on the shelf.  $50 to mod them for cb650 and cb550/650hybrid specs.(that includes return shipping)

 





l8r

[paulages]

ok, finally some progress. i have the new pistons that Soos sent me, and the cylinders are bored and ready to go. i double-checked the machine shop's work, and have just over .001" clearance. i specified .0012".




Bwaller sent me some drawings for the primary tensioner bracket he made, and I made my own out of a chunk of 7015 aluminum I had lying around. I'm using the 650 tensioner.



now i just need to get the bottom end together and clay the pistons to check clearances, and CC a cylinder to find the compression ratio. the valve cutaways are deeper than the old pistons and the shoulder is little lower, so I'm not too worried about the clearances.

[fastbroshi]

Paul, correct me if I'm wrong, but given the same combustion chamber size, an increase in bore increases your CR correct?  What was your old CR?  Those pistons look pretty awesome too.

[bwaller]

Paul you may want to use that copper washer on the outside of the case to seal that hole.


Good luck on the build.

[paulages]

Paul you may want to use that copper washer on the outside of the case to seal that hole.


Good luck on the build.

that hole has a copper washer too, brent.  the one in the picture just happened to be an used copper washer i put to use.

[paulages]

bottom end is together, and new HD studs installed (thanks A.P.E.!). i was going to measure the CR tonight, but my bottle of dyed isopropyl alcohol i use is too low. tomorrow.

[RAFster122s]

Paulage,
So how did claying the piston turn out?
CR in range of what you expected? What's the score on the clearance...going to have to grind on those pistons?
Are you going to have the pistons balanced...ideally something done from the crank on down to the pistons.
Definitely going to be a premium fuel bike with that setup if it wasn't before...some serious "domeage" on those pistons.

Wonder what a white fairing with red pinstriping inset from the perimeter would look like...
a mirror of the tank treatment...
It would definitely change the looks of the bike again.  Looks fabulous the way it is now.

David

[traveler]

This motor is going to pick up some torque.

~Joe

[paulages]

Paulage,
So how did claying the piston turn out?
CR in range of what you expected? What's the score on the clearance...going to have to grind on those pistons?
Are you going to have the pistons balanced...ideally something done from the crank on down to the pistons.
Definitely going to be a premium fuel bike with that setup if it wasn't before...some serious "domeage" on those pistons.

Wonder what a white fairing with red pinstriping inset from the perimeter would look like...
a mirror of the tank treatment...
It would definitely change the looks of the bike again.  Looks fabulous the way it is now.

David

i haven't had time to get to either yet. actually, i did run clay through once, but forgot to oil the head side of the chamber so the clay wouldn't stick to it. i threw a birthday party for my lady friend at the shop last night, which ended up taking up the whole day. hopefully i'll have time to do it this weekend.

joe- yeah, i hope so. i really feel this engine is capable of breaking mid-70's for HP. hopefully the displacement/compression bump combined with a set of CR carbs will get it there...

[Soos]

VERY interested in what the CR is going to be




L8r

[paulages]

VERY interested in what the CR is going to be




L8r

me too! i hope to have time for this today... i'll post results as soon as i get them. i'll send those pistons out as soon as i get the new ones sorted out, ok? for now it's useful to be able to measure off of the old ones if the valve pockets aren't deep enough on the new ones.

[traveler]

okay....I didn't know you were going to move up to CR Carbs!

My guess is low 70's HP with those carbs, GOOD fuel, and timing full advanced.

Heck, my 550 feels about 50 HP, and lightened up she really screams until I hit the brick wall at 5,000 RPM's, but that will be fixed with the 125 jets I just ordered. 

Anyway, you bike must REALLY scoot!

~Joe