Topic: StrongPerf CB550 Engine Build - Gentleman's Express Style

[HondaMan]

That much bore change will certainly take it into the 10s on compression.
I'm eagerly awaiting Strongperf's outcome here, as I have a whole BOX of stock CB750 pistons to use on something...

[rachet]

Just tagging this so I can follow along with your progress.

Rach~

[moham]

That much bore change will certainly take it into the 10s on compression.

That's what I figured, I qualified my response only because the article was insistent that the power increase was really "conservative"...

[cafe75-550]

That's what I figured, I qualified my response only because the article was insistent that the power increase was really "conservative"...

Well, they said the engine was conservative, not that the power increase was conservative. Realistically, the cam and compression are fairly mild for a motorcycle engine. That's not to say though that the engine wasn't a ton stronger than the original. It might not be up top in the form of a big horsepower increase, but based on the specs I would say that the low to mid range on the Express would be much stronger than stock. Not mind numbing horsepower, but a very strong pulling engine.

Keep in mind too that the big restriction on the 550's is the head flow. The cam and extra cc's will definitely make a noticeable difference, but for top end power the head is the limiting factor on the 550's. The 650 head flows much better, which is why all the hybrids come about. Still, I would think that with some port work, a hotter cam, and the compression and displacement increase a 593cc 550 would be no slouch.

[moham]

That's what I figured, I qualified my response only because the article was insistent that the power increase was really "conservative"...

Well, they said the engine was conservative, not that the power increase was conservative. Realistically, the cam and compression are fairly mild for a motorcycle engine. That's not to say though that the engine wasn't a ton stronger than the original. It might not be up top in the form of a big horsepower increase, but based on the specs I would say that the low to mid range on the Express would be much stronger than stock. Not mind numbing horsepower, but a very strong pulling engine.

Keep in mind too that the big restriction on the 550's is the head flow. The cam and extra cc's will definitely make a noticeable difference, but for top end power the head is the limiting factor on the 550's. The 650 head flows much better, which is why all the hybrids come about. Still, I would think that with some port work, a hotter cam, and the compression and displacement increase a 593cc 550 would be no slouch.

I don't want to turn StrongPerf's build thread into some semantic showdown, but perhaps we're both saying the same thing, in turn the same thing the article stated, to wit: "The very last thing you should worry about, in creating a Gentleman's Express, is how you're going to grab big chunks of horsepower."

I agree, the modified engine should certainly outperform the stock set-up, but probably not by tons...The article spends all but one page on handling and suspension improvements, after all...

[bwaller]

It's true, I believe Gordon's Gentleman's Express article strives for function over form or the like. Time spent on peg placement, bar width, handling making the bike more comfortable to ride being the key.

I rather followed this path, cutting overall weight to 395lbs. with improved handling & brakes. At that 61mm piston size I ended up with a CR of 10.1:1.

Someone on here a few years back Dyno'd his low mileage stock 550 and I think produced 36 or 37 rwhp. Mine with 61mm, mild street Webcam & mild porting with stock carbs reached 51rwhp and 34 ft./lbs of torque. No monster granted, but the difference is tremendous compared to a stocker.

[A Grove]

That is awesome to read, bwaller.  Exactly what I am going for, only a bit hotter cam and mriek port hopefully.

[StrongPerf]

If I remember right the article didn't mention porting the head. I did port mine...

Bwallwer's 37 rwhp to 51 rwhp is nearly 38%!  For an engine that still runs on pump gas and no power adder that's a significant change!!!! and that's what I'm looking for...

Can I say it's a beast? Not really. My ZX-10 makes 165 rwhp... But it's been a fun project so far and worth doing for me.

Big Jay at APE said he's done lots of these back in the day and they worked out well. I'll keep you all posted.

[moham]

Well, I may have misinterpreted the tone of the article a bit. In any case, I'm attempting a similar build at the moment with 60mm pistons bringing displacement to 574. Don't get me wrong, I hope it goes like crazy, for you and me both. The nature of my pistons, though, didn't increase compression but held steady at stock. But with 650 cam, ported head and a bunch of other crap it should still see an increase. Looking forward to the rest of your build, especially when you get to electrics...

[HondaMan]

That is awesome to read, bwaller.  Exactly what I am going for, only a bit hotter cam and mriek port hopefully.

And, boy, can that guy cut a port! 
Have you seen his 750 ports? They look like Carlsbad Caverns in there! Talk about flow. 

[B.O.X.N.I.F.E.]

Hows this one comming?

[MRieck]

That is awesome to read, bwaller.  Exactly what I am going for, only a bit hotter cam and mriek port hopefully.

And, boy, can that guy cut a port! 
Have you seen his 750 ports? They look like Carlsbad Caverns in there! Talk about flow. 

Thanks Mark....I just stumbled on to this thread. 

[StrongPerf]

I'm finally making some progress. Machine work is done (except the pistons). New primary chain and cam chain are in. The cases are back together.

New clutch time. The clymer manual says the clutch frictions should be greater than 3.0mm thick. My old were 2.70mm. I bought 7 brand new oem honda plates and they all measure around 2.7mm  .

What gives? My stack of 7 new ones measure slightly thinner than the old. They are not soaked in oil yet. They are part number 22201-286-010.

Any ideas?

[Ecosse]

been tuning in to this story with interest; sorry i can't help with your clutch query.

as a member of the sohc neophytes crowd i have a cylinder head question. i've read 650 heads have valve life issues, if so, i wonder if there are solutions to this such as better valve material. sodium filled valves run cooler, right? also, without going crazy with porting can a 550 head be made to flow comparably to a stock 650? my understanding is 650 heads are quite a bit better than 550's but i've seen what hondaman has done (via pix) to 750 heads and figure there's hope. i imagine if one were oranges=oranges, a cut 650 will out do a cut 550.

thanks for this thread sp. 

[FunJimmy]

StrongPerf

Since rebuilding my 550 I've noticed that I get just a bit of clutch slipage at higher RPM's now.
Me thinks that the MReick head work, 650 cam and fresh Yosh pistons are producing a bit more HP than the stock clutch is up to.

I’m going to pull the clutch and replace the thick spring plate with another friction plate and regular steel plate. It looks like there is enough room for it and that would add significantly more bite to the clutch while adding to the overall stack height. Added stack height should increase the spring pressure too.

Has anyone here done this?

Cheers
Jimmy

[StrongPerf]

FJ

I agree that more pressure can help. I don't think increasing the stack is the right way to do it. I think there needs to be enough free play when the clutch is disengaged. I think a thicker stack means less freeplay. I think stiffer springs or shimmed springs is a better way. It means more pressure and as long as you don't run into coil bind on the springs it would be the same freeplay in a disengaged clutch. I have done this on my 1200 and my 1000 and it worked great. It does give you a stiffer clutch lever though and more wear on pivot points and cables. A trade off that may be worth it...

Now can anyone tell me why the Clymer manual says 3.0mm min and my brand new Honda clutch plates are only 2.7mm?

[moham]

FJ

I agree that more pressure can help. I don't think increasing the stack is the right way to do it. I think there needs to be enough free play when the clutch is disengaged. I think a thicker stack means less freeplay. I think stiffer springs or shimmed springs is a better way. It means more pressure and as long as you don't run into coil bind on the springs it would be the same freeplay in a disengaged clutch. I have done this on my 1200 and my 1000 and it worked great. It does give you a stiffer clutch lever though and more wear on pivot points and cables. A trade off that may be worth it...

Now can anyone tell me why the Clymer manual says 3.0mm min and my brand new Honda clutch plates are only 2.7mm?

Clymer is wrong-ish. As far as I've been able to figure out in dealing with my Barnett "kit", 74-76 550 clutch had 7 plates, all at 2.7mm. Later models had six 2.7mm and one 3.2-ish. I discovered this after buying a Barnett kit that had the six and one thick disc included in the kit. They did not fit (I have a 74). Even if I had wanted a thicker disc, the tabs were too wide to fit the basket. Checking part fiches confirmed that the later models had the thicker disc. Why they made the change I cannot tell you, but maybe that's what Clymer is referring to.

[bwaller]

Jimmy, are you using Barnett springs? As StrongPerf mentions a little extra spring may help you.

[HondaMan]

Stiffer springs on stock clutch plates make a big difference on the mid-Four bikes. The stock springs were pretty soft. Also, many had the "slanted" clutch plates, where the cork cut pattern is slanted, not square cut. These had slip built into them, for a smooth ride and gentle clutch release: the 500/550 were all about smoothness at the time, and they lacked the sheer mass of the 750 to provide it, so Honda got sort of inventive about it all: the 500 felt like it had a torque convertor if you tried to do a clutch-drop dragrace start! If you accidentally installed the slanted plates backward, the oil would not ever sling out of the plates through the grooves, and a even brand new clutch set would slip like crazy.

The Barnett springs, without their plates, worked superbly, though. The Barnett plates, at least up until the 1980s, were no so good for these bikes: they tended to lose filaments of clutch material into the oil, pump, and oil passages in the engine.   

Strongperf: I don't know why the new clutch plates are 2.7mm. I just checked the 750 plates I have (same style, for the most part), and found the K7/K8 plates to be over 4mm thick, the K0-K6 style plates are 3.8 to 3.5mm thick. The Honda manual I have says 3.1mm is minimum thickness. 

[StrongPerf]

So the Honda manual says 3.1 but thier brand new oem plates are 2.7. Go figure. I'll mock up everything and keep you guys posted. Thanks for the help.

She's a real beauty so far. I can't wait to post some pics when I have time. I'm averaging 15 hours a week of overtime at work right now...

[MRieck]

Jimmy, are you using Barnett springs? As StrongPerf mentions a little extra spring may help you.

I agree with the use of Barnett springs....I wouldn't increase stack height

[moham]

So the Honda manual says 3.1 but thier brand new oem plates are 2.7. Go figure.

I guess I don't know what manual hondaman has, but here is clip from my 550 manual:

[HondaMan]

So the Honda manual says 3.1 but thier brand new oem plates are 2.7. Go figure.

I guess I don't know what manual hondaman has, but here is clip from my 550 manual:

Thanks for the scan, Moham: as I noted in my post, my manual is for the 750. I don't have a 500 or 550 manual.


Yet. 

[moham]

So the Honda manual says 3.1 but thier brand new oem plates are 2.7. Go figure.

I guess I don't know what manual hondaman has, but here is clip from my 550 manual:

Thanks for the scan, Moham: as I noted in my post, my manual is for the 750. I don't have a 500 or 550 manual.


Yet. 

I suspected you were talking 750, that's why I wanted to let Strongperf know what the 550 manual said, as he seemed unsure about the factory manual specs.

The goofy thing about the 500/550 manual is the addendum section covering the differences between 500/550. I guess if a guy was looking through the front half of the manual, he might not know to go to the addendum section for the later improvements.

I was surprised by the fact that Barnett seemingly had no clue about the difference in friction plate specs for different model 550s. I emailed back and forth several times with those guys about this issue and while they were extremely helpful and timely, they were misinformed. The experience just reinforced what I already knew: that the info and experts on this site are top notch.

[bwaller]

Well moham although I never liked the Barnett clutches, but don't be too hard on them.

We're all a little guilty of forgetting these bikes are 30+ and I'm sure they don't sell that many parts for these, so them not being current is forgiveable I recon!