Topic: Rebirth of paulages' cb735

[Soos]

The original owner of the cb750 those pistons came from has been asking me quite often if those piston have been used in a new motor yet or not.
I finally have an answer.

To say the least he is a serious Honda nut, and LOVED that cb750 that those pistons were in.

[paulages]

HOLY #$%*ING HELL!

I've had no time at the shop this week at all, so I've been putting in 15 minutes or so at a time putting it back together. anyway, I got it on the road tonight, and WOW, does it pull hard. It could be that I haven't ridden it in a while, but it really feels like it has lots more power than before. The dyno will tell, but i'm betting on breaking 75 HP with the displacement/CR bump and the CR29s..


Several times I accidentally pulled the front end up, simply grabbing a fistful of throttle... not little wheelies either, more like WOW I SHOULD SET THE FRONT END DOWN NOW wheelies. damn, I can't wait to get the loose ends sorted out. hopefully this weekend...


 

The original owner of the cb750 those pistons came from has been asking me quite often if those piston have been used in a new motor yet or not.
I finally have an answer.



Glad you are able to easily pull a wheelie.
75hp? I wouldn't be surprised, considering that the cb650 gets nearly 10cc:1 hp in stock configuration.
And you have gone a ways past that to say the least.


I have really enjoyed your build paulages, you have made a work of art IMO.
Now go finish the final touches, and ride the piss outta it!
 


How is the kick start? a bit hard, or not too bad?



l8r

the kicker is easy... the first/primary gearing on the 500/550 makes for a very easy kickstart. i'm using the 650 clutch gearing, but it doesn't change it all that much.

as for wheelieing... i was doing so on accident just grabbing a fistful of throttle in 1st and 2nd gear. I imagine doing so on purpose would be a breeze, not that I really run around pulling wheelies all the time.

[coldright]

I take it your shoulder and thumb are feeling much better  

Glad to hear you've got her back on the street.

[paulages]

I take it your shoulder and thumb are feeling much better  

Glad to hear you've got her back on the street.

well... sort of. head gasket's still leaking. 

[pdxPope]

Yours or the bike's?

 

-JP

[RAFster122s]

Have you torqued it to spec a couple times or just the one?
What sequence are you using (pattern) when torquing it? Per manual method I presume?

If it's been torqued down a couple times and is still leaking then it makes me wonder, and I hate to say it, if the head is warped or cylinder height or something else is off causing the leak?

Hopefully it is just the multiple torquing required of copper gaskets initially as another poster with copper gaskets mentioned.

[paulages]

Have you torqued it to spec a couple times or just the one?
What sequence are you using (pattern) when torquing it? Per manual method I presume?

If it's been torqued down a couple times and is still leaking then it makes me wonder, and I hate to say it, if the head is warped or cylinder height or something else is off causing the leak?

Hopefully it is just the multiple torquing required of copper gaskets initially as another poster with copper gaskets mentioned.

i torqued it twice before the first head cycle, but haven't again yet. I will certainly do so before pulling the head again, but the leak was immediate upon the first start up. it is puffing exhaust smoke from between the 3rd and 4th cylinders, and the other head gasket proved that it was leaking over to the stud hole. i thought it was only because of the loose stud, but it's tight now... worried it might have warped the head.

[RAFster122s]

Well, have you torn it back down to have a machine shop check the head for flatness yet?
Having access to a certified flat surface to check is 1/2 the battle as most don't have access to that type of precision measurement tools.
I hope it isn't warped.

David

[paulages]

Well, have you torn it back down to have a machine shop check the head for flatness yet?
Having access to a certified flat surface to check is 1/2 the battle as most don't have access to that type of precision measurement tools.
I hope it isn't warped.

David

i haven't even spent more than five minutes in the shop for a week, so sadly no. i hope to this week.

[paulages]

OKAY!  she's alive again... without leaks! so far...

I had to have the deck and head re-surfaced, and went back to the composite gasket (though with .007" total removed and the piston shoulder now .004" above the deck, I think the CR ratio is still in a good range). The bike starts first kick, and feels absolutely fantastic. Butt dyno is happy, real dyno to come soon...

 

[Soos]

 


I wanna see that dyno sheet!!



l8r

[traveler]

OKAY!  she's alive again... without leaks! so far...

I had to have the deck and head re-surfaced, and went back to the composite gasket (though with .007" total removed and the piston shoulder now .004" above the deck, I think the CR ratio is still in a good range). The bike starts first kick, and feels absolutely fantastic. Butt dyno is happy, real dyno to come soon...

 

How does the power feel compared to the 714 build?  More mid range punch?

~Joe

[paulages]

OKAY!  she's alive again... without leaks! so far...

I had to have the deck and head re-surfaced, and went back to the composite gasket (though with .007" total removed and the piston shoulder now .004" above the deck, I think the CR ratio is still in a good range). The bike starts first kick, and feels absolutely fantastic. Butt dyno is happy, real dyno to come soon...

 

How does the power feel compared to the 714 build?  More mid range punch?

~Joe

I haven't had a chance to really ride it hard yet, but yeah the midrange is where it wants to pick the front wheel up.

[cdoggy81]

"I haven't had a chance to really ride it hard yet"

What about now??? :-)

[paulages]

"I haven't had a chance to really ride it hard yet"

What about now??? :-)

I'm sorry to say I haven't been riding it at all... It's been a frustrating summer/fall for me, as far as the motorcycles go. I broke an HD cylinder stud off in the case a few months ago, and was too mad to even look at it. Then, my Norton stripped the threads in one of the exhaust ports. I went on tour in Europe for a bit, spent a lot of time catching up on other people's projects, and am only now caught up enough to start thinking about it. I sent the Commando head to Raber's in California for repair, and it is now on the lift and will be running today, I'll have my rings and gaskets this week for my new KLX650 R, and the Honda will finally get some more attention again.

Funny, it's December and rainy as hell outside and I'll suddenly have all three bikes on the road soon. 

I've begun work on the new hybrid engine for a customer though, which should be fun... 66mm pistons, etc. It'll benefit from all the lessons I learned from mistakes I made with this one...

[sinister902]

I am just totally blown away with your builds. I may contact you with my tax return check to build me a 740cc 550 setup for my cafe racer, it's been fun but I would LOVE more power......all my buddies ride rockets, and I have ridden with them borrowing rockets so I can keep up and whatnot, but totally prefer riding my SOHC.....would be FANTASTIC if I could have enough power to just ride my 550 around with them all the time!

[paulages]

I am just totally blown away with your builds. I may contact you with my tax return check to build me a 740cc 550 setup for my cafe racer, it's been fun but I would LOVE more power......all my buddies ride rockets, and I have ridden with them borrowing rockets so I can keep up and whatnot, but totally prefer riding my SOHC.....would be FANTASTIC if I could have enough power to just ride my 550 around with them all the time!

PM me if you're serious. I'm just starting another now and it would be easy to do parts of the process/machining concurrently. otherwise, I'll have a good estimate on cost after this one.

[sinister902]

I really wanted to be able to accomplish it on my own, but after all of your small modifications inside the cases and whatnot I am afraid I won't be able to figure all of that stuff out......such as your primary chain tensioner, and IIRC you swapped in a modern bike's cam chain tensioner as well. I was planning on locating a 650 parts bike for cheap and grabbing 750 liners off fleabay, as well as the $110 836cc kit for the cb750 that terry in australia started a thread about.....however the 836kit is out of stock until the end of january.....

[paulages]

I really wanted to be able to accomplish it on my own, but after all of your small modifications inside the cases and whatnot I am afraid I won't be able to figure all of that stuff out......such as your primary chain tensioner, and IIRC you swapped in a modern bike's cam chain tensioner as well. I was planning on locating a 650 parts bike for cheap and grabbing 750 liners off fleabay, as well as the $110 836cc kit for the cb750 that terry in australia started a thread about.....however the 836kit is out of stock until the end of january.....

TurboGuzzi used the CBR cam chain tensioner, but I'll likely use the same on this next engine. It's not too tough to figure out, but there are lots of little important details.

[sinister902]

TurboGuzzi used the CBR cam chain tensioner, but I'll likely use the same on this next engine. It's not too tough to figure out, but there are lots of little important details.

yeah, and I feel it's rather unfair to ask you to literally make a step-by-step write-up on those little details complete with specs and whatnot considering you have basically pioneered them. I'll probably have to wait until you are finished with this one, and I would be EXTREMELY interested in a cost estimate once done. At the very lease, I could swap the liners and do that sort of machine work myself to save some bucks....but it's the rest of those fine details that I know are imposible for you to document every little thing that I feel are super important for reliability with this thing

[paulages]

Ok... with spring here, I decided to tackle the broken cylinder stud issue. I managed to remove the broken stud, but the insert came out with it, also somehow destroying the outer threads for the insert. My options were: weld the hole up and re-drill/tap, find an over sized insert (couldn't find a single supplier of big-certs in the area), or the option I decided to choose...

First, I drilled the hole out to be tapped for a 1/4" NPT pipe plug. I ran the plug in nice and tight with red loctite just for good measure. After cutting the head of the plug off, I had to carefully file it flush with the case half.

Here it is ready to be re-drilled:


I made a drill guide out of some scrap aluminum stock I had lying around and drilled the new hole, and tapped it for the stock 8 X 1.25 bolts.









I bolted the barrels/head to the case to be sure, and the cases went into the parts washer to be ready for new paint. Now I just have to put it back together!

[paulages]

I painted the cases this morning, and found a spare couple hours this evening to put the bottom end together. However, I committed a serious rookie move, which will necessitate I re-split the cases tomorrow. I won't admit to what I did unless someone can guess it...


Anyway, before the last tear down, the shift fork shaft had pushed itself outward towards the clutch side, bending the retainer out a bit that holds it in place. The shaft rests in a hole, and I think what was happening was that air was getting trapped behind it, then expanding when the engine heated up, pushing the shaft out until the pressure was released. I think I mentioned this back in this thread somewhere. Anyway, I decided to fix this problem by drilling a relief passage in the end of the shaft.

First I chucked the shaft up in the lathe and used an end mill to hollow the end of the shaft:



Then I cross-drilled a relief that would vent into the inside of the case:







After I fix my brain fart from today, I just need to track down a base gasket and I'm ready to reassemble... finally. 

[fastbroshi]

You dropped a sardine in the case.  Yup, that's it.

[MasterChief750]

did you forget to put in a shift dog?

[paulages]

Nope, aaaaaaaaaand.... nope.