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Discussion Starter #1
Hey, guys.

I wanted to share my build with you, and hopefully get some information as I need it.
Whatever I can contribute to help anyone else I will try my best.

I don't know if I'd consider this a "cafe"... it's just a motorcycle at this point, and I think it's coming along alright.

As it stands now, I need to wire it up and do little odds and ends.

The goal is to have a stout and reliable bike that's somewhat tame enough for a newer rider. (I'm gifting this bike to my girlfriend.)

If you see anything, please stop me and let me know I goofed.

History of the bike:
Found an AD on CL for the bike, about 2 hours drive from me.
The bike was basically is severe disrepair. Missing several pieces.



Got her home in several pieces. :)



The engine was locked up, so we prepared to strip the bike down, yank the engine, and inspect it.



Made a little engine cradle to hold the engine when inspecting.


In the mean time, I picked up a CB900 bike and prepped it to strip.


After removing the head from the 750, it was obvious I'd be wasting my time trying to repair this one.




So, all attention went to the 900.
Cleaning it up on the exterior with soda blasting and stripper/wire brushes:



Sandblasted and re-painted some parts:

















Cont. next post:

- - - Updated - - -

Updating:
 

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Discussion Starter #2
The brakes were in sorry condition.
After soaking them in chemdip for a while, I ended up using elbow-grease.










Cleaned the pistons as carefully as I could as not to remove material staying in spec.


New seal kit I used: (Let me know if this brand is ok, or w/e.)





Stripped down the frame over the course of several days working in the evening:
Primed:


Loading the engine into the frame.
I swapped some rubber mounts that I didn't think were that big of a deal, apparently there's a difference in the engines that mean installation headaches for some.
I know there other 900 configurations, but this one was almost a direct swap.



Cleaned up carbs, I'll have to go back and swap jets around for the 900 now. (may use the stock sizes, unless someone has any tips. I'm pretty comfortable with experimenting with jets and what not.)



Measured, and ordered custom brake lines for the front:






Fabricated a gas tank bracket, that I welded into the frame: (also the seat pan brackets)





 

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Discussion Starter #3






Cleaned and stripped the wheels, and aired the tires down and inserted index cards between the lip and the tires. Painted:






I'll have to go get some new pictures, but this is how she sits now:
 

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Ok, so let me get this straight.....you started with a cb750 c,k, or nighthawk, and a cb900f engine and you decided it would be smart to keep the shitty 750 chassis and suspension instead of the supersport stuff (which is way better than the cb750 stuff). Is that right?

i can maybe understand the frame since titles might be hard to come by, by why didn't you swap over all the better bits from the 900? You probably didn't get the stock shocks from 900f but the prospect of 39mm non leading axle forks should have appealed to you at least a little. That 16" rear wheel is the epitome of garbage, esp with that drum brake. Throw those stock shocks away, the fact that you even wasted time sandblasting them boggles my mind. They weren't good when new, they sure as shit aren't good now. They aren't even the dual range ones the 750f came with.

regarding the motor mounts, the stock setup uses two rubber bushings captured in a dogbone hard mount. If you have those pieces then the engine slots in. If not, it can be a pain in the ass. I assume you used the stock dog bone.

The rear seat might clear under full compression, but I wouldn't bolt anything underneath it.

Since it it is clear you don't care about performance, a little tip someone gave me years ago about the 900f motor - run the cb750 carbs. The stock Honda carbs are garbage and their response can best be described as lazy. If you don't mind giving up a few ponies, the 750 carbs give better throttle response because the engine is pulling more vacuum than the passages were designed for.
 

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i really hope those forks arent that pitted anywhere the seal runs.
 

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can you weld? access to a metal shop? If I were you I would create a hoop that reinforces the back of the bumpstop. Not a hoop that runs parallel to the ground but one that acts as a support for the seat and ties the shock mounts together (since you deleted that brace too with your frame hack).

look at this rickman frame, the rear most hoop:
 

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Discussion Starter #11
Ok, so let me get this straight.....you started with a cb750 nighthawk, and a cb900f engine and you decided it would be smart to keep the shitty 750 chassis and suspension instead of the supersport stuff (which is way better than the cb750 stuff). Is that right?
Wrong. Started with the 750 nighthawk.(engine trashed)
Thought I was buying another non-title CB750(unknown trim) but after pulling the engine noticed it was a 900.
The frame it was in stated on the VIN name plate it was a 82' CB750. (Someone swapped an engine into it at some point.)

i can maybe understand the frame since titles might be hard to come by, by why didn't you swap over all the better bits from the 900? You probably didn't get the stock shocks from 900f but the prospect of 39mm non leading axle forks should have appealed to you at least a little. That 16" rear wheel is the epitome of garbage, esp with that drum brake. Throw those stock shocks away, the fact that you even wasted time sandblasting them boggles my mind. They weren't good when new, they sure as shit aren't good now. They aren't even the dual range ones the 750f came with.
I have a clean title for the frame I swapped everything into.
If I had a 900F bike, I would have used it. The parts bike with the 900cc engine was a Franken-Bike.
Concerning the wheel, I agree. Working on a caliper vs. drum will make for a nice swap in the future after getting bike running.
Plus, getting an 18" rear would be nice.


regarding the motor mounts, the stock setup uses two rubber bushings captured in a dogbone hard mount. If you have those pieces then the engine slots in. If not, it can be a pain in the ass. I assume you used the stock dog bone.

The rear seat might clear under full compression, but I wouldn't bolt anything underneath it.
I was concerned about that also. I will have to test it out, and determine what I could do.


Since it it is clear you don't care about performance, a little tip someone gave me years ago about the 900f motor - run the cb750 carbs. The stock Honda carbs are garbage and their response can best be described as lazy. If you don't mind giving up a few ponies, the 750 carbs give better throttle response because the engine is pulling more vacuum than the passages were designed for.
Which stock carbs are you referring to? Non-vacuum? (use mechanical carbs)
Both of these engines had the vacuum slider type, both identical. Some different jetting of course.


Throw the carbs away. For the price of rebuilding those and especially for the time, just get CR's. Thank me later.
I'll thank you now... :)
Is the spacing on the mechanical carbs identical to the vacuum type? Or will I need to make some new brackets and fuel passage tubes?

i really hope those forks arent that pitted anywhere the seal runs.
They're clean past the dust seals. But I will replace these forks in the future.

can you weld? access to a metal shop? If I were you I would create a hoop that reinforces the back of the bumpstop. Not a hoop that runs parallel to the ground but one that acts as a support for the seat and ties the shock mounts together (since you deleted that brace too with your frame hack).

look at this rickman frame, the rear most hoop:
Yes and yes. That is the plan.
I am going to loop the rear to outline the seat.
If the rear tire interference issue is a non-issue, I plan on getting a seal battery in the cowl, and put in a under tray that covers up the electronics where the stock battery used to be.

Thanks for all the input so far.
 

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regarding the frame: ok, didn't realize the 900 donor was a franken bike. was it an F franken bike? because it would have a bolt on rear disc setup if it was.

The Kehin CR carbs are the mechanical hot street/racing carbs that are a popular replacement for the stock vacuum operated CV carbs. You would buy a set specifically for the CB900F spaced appropriatly (31mm inlet). They ain't cheap but bob dog is right - rebuilding and setting up those CV carbs to work without an airbox will probably end up costing you around $100 a carb ($400 per rack) and then you are still stuck with shitty unresponsive carbs.

DYNOMAN PERFORMANCE - Austin, Texas


The 750 carbs on a 900 motor refers to Stock CV carbs. THERE ARE NO stock mechanical carbs for the DOHC cb 750 or 900. The stock 750 CV carbs are smaller and have smaller vacuum passages than the 900. The 900 has slide lag - you twist, count to 1, and then the motor goes. If your riding enviornment is a lot of commuting and not a lot of WFO, then putting the smaller 750 carbs on the 900 mill will cause them to snap open and give you a really crisp throttle. It's not the best mod, but seriously, ride the 900, if you are smooth you might hardly notice the throttle lag, if you are agressive it will piss you off.

The stock honda CV carbs hate pod filters. Shitty emgo cheapies (like dime city sells) will actually block the vacuum ports and the bike will never rev. Even good quality K&Ns are hard to tune for. you are better off with Kehin CR's if you really want pod filters.
 

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you will need CRs designed for the dohc engine.

oops didnt refresh. his post is much more comprehensive than mine :)
 

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btw....if you find used DOHC CRs that dont make you gulp and swallow hard, youve done good.
 

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Discussion Starter #15 (Edited)
regarding the frame: ok, didn't realize the 900 donor was a franken bike. was it an F franken bike? because it would have a bolt on rear disc setup if it was.

The Kehin CR carbs are the mechanical hot street/racing carbs that are a popular replacement for the stock vacuum operated CV carbs. You would buy a set specifically for the CB900F spaced appropriatly (31mm inlet). They ain't cheap but bob dog is right - rebuilding and setting up those CV carbs to work without an airbox will probably end up costing you around $100 a carb ($400 per rack) and then you are still stuck with shitty unresponsive carbs.

DYNOMAN PERFORMANCE - Austin, Texas


The 750 carbs on a 900 motor refers to Stock CV carbs. THERE ARE NO stock mechanical carbs for the DOHC cb 750 or 900. The stock 750 CV carbs are smaller and have smaller vacuum passages than the 900. The 900 has slide lag - you twist, count to 1, and then the motor goes. If your riding enviornment is a lot of commuting and not a lot of WFO, then putting the smaller 750 carbs on the 900 mill will cause them to snap open and give you a really crisp throttle. It's not the best mod, but seriously, ride the 900, if you are smooth you might hardly notice the throttle lag, if you are agressive it will piss you off.

The stock honda CV carbs hate pod filters. Shitty emgo cheapies (like dime city sells) will actually block the vacuum ports and the bike will never rev. Even good quality K&Ns are hard to tune for. you are better off with Kehin CR's if you really want pod filters.
Thanks for the info, geeto.
No, the parts bike looks like the same as my clear title bike. The forks are 35mm, single brake steelies front and back. 16" rear wheel drum brake also. Bought the whole bike for $100, and had good CDI's, carbs, and other parts too.

I have a mint air box on the shelf, I was planning on using. Should also help with slide lubrication from the crankcase vent being connected to the box for PCV.
I'm not totally sure where this exhaust came from, looks like a vance. 4-1. (but mine has a bit tighter radius on at the head. )

All I did was clean it up a little. Baffle still installed.

If I cut it out, I can mess with the jets a little.

btw....if you find used DOHC CRs that dont make you gulp and swallow hard, youve done good.
Hah, yeah no shit. I've seen a few sell that were pretty pricey.
I think a pair for about $300 were for sale on a CL ad somewhere mid-west, and someone posted it on another site... people were going crazy.
 

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I have a 900c I am parting out. Have almost everything. Let me know if you need anything. Good to see someone with a thick skin taking good advice. :)
 

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Discussion Starter #17
I have a 900c I am parting out. Have almost everything. Let me know if you need anything.
I might have to take you up on that at some point.
Thanks.

Good to see someone with a thick skin taking good advice. :)
Thanks, you'll never learn anything if just keep living in a fantasy world bashing knee dents into your motorcycle gas tank thinking you're cool.
 

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Discussion Starter #19
This might be fun.
Last year a project at work required some testing with amphenol/circular interconnect cables.
In the end, I had several left over that were heading for the trash can.

Maybe I can use them for the bike.
Some might be shielded, which would be nice for ignition wiring.



 
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