Topic: CR750 replica for the street

[FunJimmy]

I've always had a fondness for CR750's and yours is awesome.

[SOHC4 Cafe Racer Fan]

Looking sharp, Vincent. I love the details on the bike. Even the kick start plug looks marries form and function. Even better than the Joker Machine plug. The motor is aesthetically beautiful and it is going to kick like a mule. Any chance I can get your friend Joe to machine me some stainless engine hanger bolts?
I really like the clean front end, too. Can you provide additional info on the more robust lower triple tree?

[Godffery]

   Some very nicely done work there Vincent..!

[scottly]

How will you drive the oil pump without the kick-start shaft??

[Vincent]

I'm speechless.

[iron_worker]

That engine should put down some power. Did you get any port/polish work done? I've heard that really unlocks some serious juice on the big bore builds.

IW

[lordmoonpie]

Nice work Vincent - coming along very well! Scottly is dead right though, you can cut the kickstarter shaft down like I did with mine and install the lovely plug you have machined but you need to keep the spindle and oil pump drive gear inside or you won't have any oil flow and it'll go pop very quickly. You can junk a lot of the kickstarter mechanism but need to keep these bits in...the picture shows my kickstarter shaft after it was shortened and turned down. I left the small section to go into the right side case to give rotational stability for the shaft - so it doesn't flap about!

[SOHC4 Cafe Racer Fan]

I was wondering how you got the kickstart spindle so flush with the cases.  Joker Machine makes a shaft cover/plug.  http://www.cyclexchange.net/index%20pics/Kickstarter%20Shaft%20Covers.JPG for $25 in clear anodized billet  http://www.cyclexchange.net/Machine%20Dress%20Up.htm
The JM product is clean looking but essentially covers the exposed kickstart spindle.  I kind of assumed (and you know what they say about the word assume) the spindle was machined or cut down, but not altogether removed -- but what the heck do I know.  This is why I do not rebuild engines and defer to experts.

[Vincent]

OK, I guess I'm not speechless anymore. It's been two days, but it'll take a bit longer than that before I stop feeling like a moron. Early on, I decided to eliminate the kickstart and just have the electric starter. I spoke with someone I considered to be knowledgeable about the bike, and he said I should just leave out the shaft. It wouldn't make a difference, and the bike would be a couple of pounds lighter. I failed to get a second opinion, failed to utilize the collective knowledge of the forum, and failed to understand the operation of the engine that I was working on. I was so proud of the aluminum plug that I made. The cool little bit that would disguise the fatal flaw I had unknowingly given the bike. What a humbling experience.

From time to time, I read a forum entry from someone who has put an engine together and then had to go back in to undo some mistake, and I always think, Wow, doesn't that guy know what he's doing? But now I'm that guy. And there are two things that I hope for. First, that the guys I felt scorn for went on to learn useful lessons and build strong, reliable, and fun bikes. And second, I hope that I can be as lucky and as smart as them.

I'm lucky to be on a forum where there are people who actually know what they're talking about. Scottly, your question about the oil pump practically gave me heart failure. Once I could move my hands again, a Google search for cb750 oil pump kick start led me to various descriptions of the relationship between the kickstart shaft gear and the oil pump (basically the same as the relationship between your nervous system and your heart). That led to a long night of imagining my expensive, lovingly assembled bike coming to a grinding, screeching halt as the bearings ran out of oil and the engine turned itself into junk.

I spoke with an old Honda mechanic here in Southern California. And then I spoke with another one. Between them, they've been inside of hundreds of CB750 engines, and they said that I could install the shaft by tipping the engine over on the workbench and removing the bottom half of the case. A pain to have to take it back out of the frame and put it up on the workbench, but hey...I guess that's how we guys who are still learning do it.

Thank you all for your time and your attention.

Vincent

[SOHC4 Cafe Racer Fan]

OK, I guess I'm not speechless anymore. It's been two days, but it'll take a bit longer than that before I stop feeling like a moron. Early on, I decided to eliminate the kickstart and just have the electric starter. I spoke with someone I considered to be knowledgeable about the bike, and he said I should just leave out the shaft. It wouldn't make a difference, and the bike would be a couple of pounds lighter. I failed to get a second opinion, failed to utilize the collective knowledge of the forum, and failed to understand the operation of the engine that I was working on. I was so proud of the aluminum plug that I made. The cool little bit that would disguise the fatal flaw I had unknowingly given the bike. What a humbling experience.

From time to time, I read a forum entry from someone who has put an engine together and then had to go back in to undo some mistake, and I always think, Wow, doesn't that guy know what he's doing? But now I'm that guy. And there are two things that I hope for. First, that the guys I felt scorn for went on to learn useful lessons and build strong, reliable, and fun bikes. And second, I hope that I can be as lucky and as smart as them.

I'm lucky to be on a forum where there are people who actually know what they're talking about. Scottly, your question about the oil pump practically gave me heart failure. Once I could move my hands again, a Google search for cb750 oil pump kick start led me to various descriptions of the relationship between the kickstart shaft gear and the oil pump (basically the same as the relationship between your nervous system and your heart). That led to a long night of imagining my expensive, lovingly assembled bike coming to a grinding, screeching halt as the bearings ran out of oil and the engine turned itself into junk.

I spoke with an old Honda mechanic here in Southern California. And then I spoke with another one. Between them, they've been inside of hundreds of CB750 engines, and they said that I could install the shaft by tipping the engine over on the workbench and removing the bottom half of the case. A pain to have to take it back out of the frame and put it up on the workbench, but hey...I guess that's how we guys who are still learning do it.

Thank you all for your time and your attention.

Vincent

Vincent,

I am SO glad you found this out NOW rather than when you were breaking the engine in -- and then breaking more than you bargained for.  Cheers to Scottly for the crucial catch!!  That man deserves a round or two of libations.  It'll be much easier for you to take out the motor at this point, versus having everything else (carburetors, headers, electrical, rearsets, etc.) all installed.  You can still relatively easily tip the bike on its side and extract the engine, and then do the inversion to take off the bottom case.

By no time, you will be back on track.  Don't beat yourself up, Vincent!  This is an AWESOME build.

Don

[Retro Rocket]

That was a close call....   Glad you got it sorted...

[Mr.Paynter]

You may need to buy Scottly a beer sometime!
Huge save!

This build is amazing!

As a random hark back to your challenges with the clocks, did you ever come right with that rubber mould around the trip-meter shaft? I am restoring a 500 and mine is shot, it basically fell off and now I am combing the internets trying to find another with no luck do far!

[lordmoonpie]

Hey Vincent, there is no failure, only feedback! The good thing is Scottly noticed before you fired her up and your feedback was the very expensive kind. To succeed you must first learn and you do that by making mistakes so there's no value at all in beating yourself up, just keep going and finish that lovely CR :-)

[Vincent]

Sheesh. I'm getting too good at taking the bike apart. My friend Mike came over and we lifted the frame off the engine and put the engine back up on the bench. Haven't split the case yet. I'm happy to have a job, but full-time work just shoots the hell out of your free time.

To respond to a couple of comments:

Joe says he made the stainless engine bolts as a favor and because he wanted to contribute something to the build, but he says he doesn't feel like making any more. Sorry.

The extended lower triple tree is something I saw on the CR750 that Yoshi (of Garage Company) owned. Here's a picture I took of it during the restoration that Kiyo performed.



When I bought the donor bike, the owner threw in another front end, so that lower triple was cut up and welded to the other one.

I didn't do any porting and polishing because, as I understand it, that mainly benefits the top end at the expense of the mid range. The bike is for the street, and I'm more interested in useable mid range power than in high-rpm power. For that reason, I had the crank balanced but not lightened. I wanted to retain the flywheel effect. Different people want different power characteristics, and it's useful to find out which engine modifications will best suit your riding style.

I haven't been able to find that tapered grommet that goes around the tripmeter shaft, so I'll probably end up altering a generic rubber grommet.

Thanks for the kind words and encouragement, and I hope to have an update here soon.

Last but not least: When I finally start the bike up for the first time, it's going to be pointed east. Towards Humboldt, Arizona. You may have saved me from going completely out of my mind. I imagine people passing by and saying Wow, nice bike. I wonder why that guy is just sitting on the sidewalk, staring at his hand and drooling, instead of going for a ride.

Vincent

[SOHC4 Cafe Racer Fan]

Sheesh. I'm getting too good at taking the bike apart. My friend Mike came over and we lifted the frame off the engine and put the engine back up on the bench. Haven't split the case yet. I'm happy to have a job, but full-time work just shoots the hell out of your free time.

To respond to a couple of comments:

Joe says he made the stainless engine bolts as a favor and because he wanted to contribute something to the build, but he says he doesn't feel like making any more. Sorry.

The extended lower triple tree is something I saw on the CR750 that Yoshi (of Garage Company) owned. Here's a picture I took of it during the restoration that Kiyo performed.



When I bought the donor bike, the owner threw in another front end, so that lower triple was cut up and welded to the other one.

I didn't do any porting and polishing because, as I understand it, that mainly benefits the top end at the expense of the mid range. The bike is for the street, and I'm more interested in useable mid range power than in high-rpm power. For that reason, I had the crank balanced but not lightened. I wanted to retain the flywheel effect. Different people want different power characteristics, and it's useful to find out which engine modifications will best suit your riding style.

I haven't been able to find that tapered grommet that goes around the tripmeter shaft, so I'll probably end up altering a generic rubber grommet.

Thanks for the kind words and encouragement, and I hope to have an update here soon.

Last but not least: When I finally start the bike up for the first time, it's going to be pointed east. Towards Humboldt, Arizona. You may have saved me from going completely out of my mind. I imagine people passing by and saying Wow, nice bike. I wonder why that guy is just sitting on the sidewalk, staring at his hand and drooling, instead of going for a ride.

Vincent

Hey Vincent,

Thanks for the write up on the lower triple clamp.  What a cool, period correct upgrade.  It looks like it was some kind of RSC/works upgraded part you could buy as part of the real CR kit.  That should help improve front end stability.  It's the little custom things on this bike that really take it up a notch from other CR builds -- the custom fabrication, the machined bolt heads, etc.  Once you have the kickstart shaft sorted, it will be right back on track.  What's next on the "to do" list after the kickstart shaft?
Don

[Retro Rocket]

I didn't do any porting and polishing because, as I understand it, that mainly benefits the top end at the expense of the mid range

You would get improvements all round with porting, it all depends on what you do and what cam you run, talk with forum member MReick about porting, most of the extra power in these engines is locked up in the heads....

[Mr.Paynter]

It's a pity about that grommet for the clocks, I will keep searching and keep you posted if I have any luck!
Good luck with the CR!

[Vincent]

Don, the next thing on my "to do" list is to put the engine case together and get it back in the frame. After that I'm going to put the instruments together. I had the tach and speedo backs cadmium plated and the cases powdercoated satin black, repainted the needles, and I should have new faces in a day or two, so I'm anxious to get that done. I picked up the calipers and disks from the powdercoater, so I'll put them on the bike. The way the shift linkage was set up, it has a one-up, four-down pattern, and I really want to change it to the stock pattern. When those things are done, there are only six or seven thousand other things to do. Make a wiring harness, have cables made, paint the fairing, tanks, fender and seat, have the seat upholstered, - oh yeah, and make a taillight. I can't imagine just buying a taillight and sticking it on. After all this time and trouble, it has to be unique. So I've made some drawings, and I think I have something worked out.

In the meantime, here are a couple of pictures.

New in the (tattered) box Smiths oil pressure gauge:



Switches for lights/horn and starter/kill:



Mirrors. Bar-end, but with minor parts substitution, they mount on the fairing and attach to the upper fairing mount for support:



OK, that's it for now. Night, all.

Vincent

[Terry in Australia]

I didn't do any porting and polishing because, as I understand it, that mainly benefits the top end at the expense of the mid range. The bike is for the street, and I'm more interested in useable mid range power than in high-rpm power.

For that reason, I had the crank balanced but not lightened. I wanted to retain the flywheel effect. Different people want different power characteristics, and it's useful to find out which engine modifications will best suit your riding style.

You're correct re: crank lightening, it's not that useful on a street bike, but your assumptions re: porting are incorrect mate, head work will give you more power and better accelleration throughout the rev range.

I've got one of Mike Reick's very early stage 3 heads on my 836cc engine, and even with a mild "street" cam (2mm more lift than a stock K cam with a little more duration) it wants to lift the front wheel under accelleration, with the stock carbs and airbox.

The difference between it and a stock engine is like comparing a Boss 429 to a stock 351. Cheers, Terry.

[buckett]

this build... ergh my gawd, this build. just wow.

[Godffery]

Hey Vincent,
What are you going to be doing for Rotors & Brake Pistons?   

Caution; shamless self permotion ahead:

 http://www.vinmoto.org/gallery/v/VinMoto-Garage/album03/Godfferys-Garage-123/95/

[Vincent]

Godffery-

I just recently learned about your phenolic pistons, and though they sound like a great idea, I had already bought a set made of stainless steel. As for the discs, I had the stock ones ground flat and then had the carriers powdercoated satin black. If I were planning on doing track days with the bike I'd consider having the discs drilled, but for the intended use, I think the rebuilt master cylinder, steel lines, ground discs, and new pads will do the trick. But thanks for thinking of me.

Well, reinstalling the kickstart shaft was a big pain in the butt, but it's finally back in. Getting the little arm on the kick start flange to go under the stopper pin isn't difficult, and getting the hook on the spring to go into the notch in the lower case half isn't difficult, but to do them both at the same time AND get the tension on the spring, now that's a job. Next I'll get out the Hondabond, seal up the case halves, and get the engine back in the frame. Stay tuned for further developments.

Vincent

[Terry in Australia]

Good job mate, don't go overboard with the Hondabond, like Threebond, it contains silicone and any blobs that break away and fall into your oil can potentially find it's way into your oil jets in the cylinder head and block oil flow. If you use it sparingly you'll have no problems, but like a lot of things, "less is more". Cheers, Terry.

[Godffery]

It looked like you may have already got yourself covered in the brake department, but I thought I'd offer anyway.

Bike is really looking great!

As for Terry's comment regarding Hondabond; as usual, he's spot on the mark here.
Too much can cause much bigger problems then not enough.

[SOHC4 Cafe Racer Fan]

Vincent,

I bet you're relieved to be done with the kickstart shaft re-installation. 

Those parts are pretty trick.  Pingel switches and a Smiths oil gauge!  Nice.

Don