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Blood Sweat Tears and Grease => Projects => Cafe Racers => Topic started by: lostinmiself on Feb 18, 2017, 18:29:50

Title: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 18, 2017, 18:29:50
Building my first cafe bike, figured this might be a good way to keep track of my progress and keep things organised if I start having questions rather than posting on each sub as needed. First bike was a cm200t rode that for a season off and on, but really felt like a monkey F-ing a coconut on it (im 6'2" that bike seemed to fit in my pocket). Sold it and was on the search for another bike more my size. Came across this 81cb750 early spring of 2016 and the guy wanted 2900 or something. I sold the cm200t for 1200 and thats what i was willing to invest into another bike. Im very...frugal...to say it P.C., and dont really like to spend more than i have to on things i want. That being said we couldnt reach a deal and i kept looking throught the summer. Nothing really caught my fancy, started to get in to the shitty months and low and behold the same bike came back up for sale. So i got back in touch and worked out a price of $1350. Has 18k and a cam seal leak, 4-2 pipes, other than that bike seems to be in good mechanical condition.
(http://i64.tinypic.com/2cs87ci.jpg)
(http://i66.tinypic.com/2zqhamt.jpg)

I pulled the rear chrome rack, fender, lights, and on the shelf they go to collect dust, removed the front blinkers as well. threw on some clipons and bar end mirrors and i can start to see where im headed.
(http://i65.tinypic.com/2h6ramx.jpg)

Of course i have to hide all the electrical harness, so that was next. While cleaning the garage i came across a skid plate from a 89-98 silverado from an old pickup i sold, as i was walkign to toss it in the trash i happen to get the wild idea about using it as a tray for the harness. Tossed it under the seat on the frame and it was like a gift from the cafe gods! Fits as if was meant to be. Had to notch the front so the harness could fit in to the tray (i probably could have done a better job at it but it was more of a spur of the moment cut, cant see it so im not really worried anyways.
(http://i63.tinypic.com/10xagdd.jpg)
(http://i65.tinypic.com/veu3av.jpg)

Thats where i am at currently. Painting it so it doesnt rust, but i figured i would make one of these while it drys. I also have some 90s cbr600 coils, and am going to do the resistor mod as well. I picked up a ducati integrated LED tail light i hope to use, seems like the lines would fit well with a tail piece when im to that point. Also plan to use some velocity stacks and if that wont work, ill get a cognito moto filter box. Still need to get a 4-1 exhaust as well im not really digging the 4-2 split style that much. I have some rear sets i also plan to use at some point i need to get some hime joints and get the linkage made. Until then this is the direction i want to build towards.

(http://i67.tinypic.com/10zy235.jpg)

Cheers!
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 21, 2017, 19:15:54
Finished up the harness tray, threw some rest prevention primer with a black semigloss paint and bolted everything in for a final test fit. Tossed the seat and tank on, looks good from where im standing!
Happy with the free tray mod. Hopefully it works for someone else.
(http://i66.tinypic.com/2ccl9vo.jpg)

After i got the tray all done, i went to start with the coil relay mod and cbr600 coil swap when i noticed one of the stator cover bolts was missing. After finding a replacement to thread in and continue on with the coils it wouldnt thread in. Got down and noticed it has been broken off, and someone tried to drill it out. I gave it a try with an eazy out and decided to order another one rather than trying to fix it. Found one on ebay for $15 shipped and was good enough for me.
(http://i67.tinypic.com/10ho8c8.jpg)
(http://i67.tinypic.com/bgzlfc.jpg)

Got to run and grab some spade ends and can get back to the coil mod. Seems easy enough and if the interwebz are correct will help out tremendously.

Still need to order some velocity stacks, but im unsure what ones i want to pull the trigger on, there is a nice set on dime city (http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-carburetor-parts-polished-aluminum-keihin-honda-velocity-stack-cb750-dohc-carbs-pft-sd-cb750dohc-pft.html) im still shopping around to see if thats what i want to get. I know there is steel dragon performance as well, any other vendors make a decent quality stack?

What about shocks what direction do yall think i should look? DCC has a set of universals on sale today for $59 with a weight at 365lbs per shock. That sits at 730lb with a roughly 500lb bike and 210lb rider.
 http://www.dimecitycycles.com/catalog/product/view/id/1831/s/13-2-inch-black-chrome-eye-to-clevis-rear-motorcycle-shock-absorbers/category/1836/?source=hp-daily
Title: Re: 81CB750c build first time here goes nothing
Post by: BigNickel on Feb 22, 2017, 10:57:19
I'm currently working on a '81 750C as well. I'm really liking what you're doing so far with this bike - I'll be following this build.

What online link did you use for the coil mod? I was also thinking about doing this while I have my bike apart. Also, where do you plan on putting your battery? Some more detailed photos of your harness tray once you get it finalized would be much appreciated.

Cheers.
Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Feb 22, 2017, 11:58:04
I used the cb750c forum. An absolute TON of information relative to the 79-82 cb750c on that site. It's run by a group of surly, old guys, but they know their stuff! Here's the link:
http://cb750c.com/modules.php?name=Forums&file=viewtopic&t=2740&highlight=relay+mod
You may have to register with the site to access it, but I'm also going to attach a schematic of how to wire it up.

I used 10ga wire and a 70A relay from a Land Rover air suspension system that I had lying around. You don't need to go that heavy duty, but for me it was a free upgrade. I wouldn't use smaller than 12ga wire.
Title: Re: 81CB750c build first time here goes nothing
Post by: teazer on Feb 22, 2017, 12:18:01
Any modern i.e. new 20-30 amp relay is more than enough.  You can get one form your local auto parts store or on line form places like http://www.cycleterminal.com/accessory-relays.html  I like the 20 amp micro relays and use them for dip and main headlamps and the ignition circuit.

You will be fine with the same wire gauge as the stock system, or even lighter gauge on the switching side and keep the power side from battery to relay as short as possible/practical.  The idea is to stop trying to push all the ignition power through old main switches and kill switches which are really not designed to take that much power, and to reduce the voltage drop through long leads.
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 22, 2017, 14:09:25
I'm currently working on a '81 750C as well. I'm really liking what you're doing so far with this bike - I'll be following this build.

What online link did you use for the coil mod? I was also thinking about doing this while I have my bike apart. Also, where do you plan on putting your battery? Some more detailed photos of your harness tray once you get it finalized would be much appreciated.

Cheers.
I'll get a link up for ya when I'm back on my pc, but basically like they said above bypasses the OE harness and runs a new one for the coils. One lead from power to relay, one lead from relay to coils, one lead from relay to kill switch at controls, and one ground. Remove the power and  ground from the coils and use the new power lead from the relay, and the relay has its own ground. Anything specific photo wise with the tray?

http://gstwins.com/gsboard/index.php?topic=62039.0
thats the link i went off of

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Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Feb 22, 2017, 14:19:27
Any modern i.e. new 20-30 amp relay is more than enough.  You can get one form your local auto parts store or on line form places like http://www.cycleterminal.com/accessory-relays.html  I like the 20 amp micro relays and use them for dip and main headlamps and the ignition circuit.

You will be fine with the same wire gauge as the stock system...

I agree wholeheartedly. I only used the super-duty stuff because that's what I had lying about. I have about a half dozen of those big Land Rover relays. The ignition coils will never pull 70A (the fuse is 15A and the main fuse for the bike is 30A), but I just didn't want to have to buy anything. Same goes for the heavy gauge wire. I had like 8' of it coiled up in a corner of my toolbox, so I figured, 'what the heck'? Perhaps I'll redo it if I happen across a spare mini or micro relay, but for now I'm happy.

The point is, it works.
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 22, 2017, 14:30:25
Anyone have any experience with Li batteries rather than AGM? I'm going to have to get one or the other, with minimal electronics I figured spending the extra on an Li that's lighter, and smaller wouldn't hurt. Makes it easier to hide as well.

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Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Feb 22, 2017, 14:51:58
I put a Shorai into my friend's CB125. Their Li batery is the same as the unit that my 650 Tempter used.
Teressa's 125 has sat outside all of this winter, and in her shed all last winter; still fires up like it's brand new.
Conversely, the 15lb standard lead-acid battery in my '79 750F lasted 3 weeks of non-use in the summer before I had to rush out and purchase a Battery Tender (couldn't justify another battery so soon after the last one).

I plan on acquiring a Ballistic 8-cell for my 750C, once I can come up with the extra $$$
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 22, 2017, 16:08:12
I should figure out what my idle output will be before I invest in a new battery. I don't want to spend some bucks and ruin the battery with sub standard charging. 13.1v+ seems to be the necessary voltage at idle and no more than 15v at max. I have a good wet battery but of course those don't hide well, and all the work on the tray would go to waist if I had to hang a battery back there. I saw some putting it on the swing arm but I don't like that idea having it connect to moving parts, worst case scenario comes to mind.

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Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Feb 22, 2017, 23:30:28
DOHC CB750's don't typically "break even" until about 3000rpm. Basically at anything below that you're discharging the battery.
IIRC the shop manual specifies 14v at approx 5000rpm
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 23, 2017, 00:07:37
Well i wont opt for the top dollar Li battery then, i dont feel like spending the money and watching it discharge down the drain in a couple months. Maybe an AGM will be more forgiving with the voltage cycles. If they can handle 40k watts being charged and discharged over and over in sound comps they can handle some rough cb750 charges ey!

http://www.dimecitycycles.com/deltran-battery-tender-lithium-battery-12v-120-cca.html

Maybe this one?
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 25, 2017, 19:52:48
Help me troubleshoot

Wired in the relay mod, just as the site i linked says. One part from coils to the relay, one part from the relay to the positive on the battery, one part from the relay to a ground, one part from the relay to the kill wire (yellow/red) leading up to the kill switch in the hand controls. When i gave it power nothing happens, the relay clicks but thats it. It clicks weather its in the run position or in the stop positions (when you press the red start button) so obviously i did something wrong. Hopefully someone can help me? I really dont know how i could have screwed it up.
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 26, 2017, 14:47:32
Well even with the power from the battery to the relay disconnected the relay still clicks. I am assuming it's getting external power somewhere. Finding that I hope will help the issue, but I don't see where it would be getting power from

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: esmoojee on Feb 26, 2017, 20:10:44
You don't use the kill switch wire... you run a power line to the battery from the relay.  A line from the coil wire black/white to the relay and a wire back to the coil from the relay and a ground.  Also, look into a lucas three phase charging system. 
Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Feb 26, 2017, 21:33:08
As esmoojee said, thereferring is no yellow/red wire involved. The wire from the switch that feeds the coils is white with a black stripe.

1. Remove the white/black wire from the coils, connect to the control side (pin 85 or 86) of the relay. Connect the other side of the control to ground.

2. Run your coil power wire from the battery positive terminal, (preferably through a 10A fuse) to the switched terminal (pin 30).

3. Run the remaining wire from the output side of the relay (pin 87) to the terminal on the coils that you disconnected the white/black wire from.

4. Test the system: put a test light into the wire that feeds the coils to ground. Key on run. The relay should click and the test light should light up (indicating power to the coils) with the kill switch in 'run' and click off/light go out when you flip the kill switch to either of the 'off' positions. Likewise the test light should be out when you shut off the key.
Hook up that feed wire and make some noise.

Hope this helps!
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 27, 2017, 10:36:41
I must have misunderstood the directions from the link, but when I get back from my meeting this morning at work I'll get back out there and rewire it. Thanks for the info gentlemen, much appreciated!

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Feb 28, 2017, 18:28:36
Got it, got spark at the plugs, ill get it all perma-wired once my plugs and wires get here in the next couple days. Thanks yall!
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 07, 2017, 00:49:56
So a little update, got the bike running smoothly, ordered plugs, wires, and some velocity stacks. They sure are shiny :)
(http://i65.tinypic.com/11j0xfr.jpg)
Installed everything and the starter wouldn't crank. So after some quick work with the test light i have deducted it was the starter relay solenoid. Power going in from the battery, but nothing coming out to the starter. Yet the fuse is in tact, and bi-passing it cranks no issues. Im more curious as to what would cause it to go out? Regardless ill order a replacement and be on my way hopefully. Pulled the front wheel in order to paint them.
(http://i65.tinypic.com/2u97hxj.jpg)
Figured keeping the dual disks would be a wiser choice than trying to go with laced wheels. So i figured a quick rust preventative primer, and some nice gloss black might do the trick. Im not setup to use a gun yet, so rattle can should work a-ok. Also id LIKE to spring (guiltless) for some new suspension, but i think i will use what i have and get something later down the line. Came up with cutting some of the sleeve off the OE setup to give it an aftermarket look. Hopefully the paint holds up decent, its no show bike it will be ridden as much as im able to.
 (http://i64.tinypic.com/24ch5k9.jpg)
Ill be picking up a battery tomorrow on the way to work on my pops 32 ford, he had some surgery a couple weeks ago so ive been throwing that together as well in my spare time for him. I also have narrowed down my choices as to what exhaust i want to run but i have yet to hear them. I really like these they LOOK awesome but im again unsure how they will sound.
(http://i67.tinypic.com/35akolz.jpg)
(http://i65.tinypic.com/2lbl3qg.jpg)
I also like carpys Exhaust 4 into 1 CB750 SOHC Yoshimura style https://carpyscaferacers.com/shop/shop-our-store/motorcycle-parts-accessories/honda-cb500-cb550-cb750-parts-upgrades/cb750-4-into-1-exhaust-sohc/
so thats where im at lately.
Cheers yall!
Title: Re: 81CB750c build first time here goes nothing
Post by: esmoojee on Mar 07, 2017, 10:49:46
I have the cycle x 4-2-1 and its nice but itís loud. I have a V&H on my nighthawk and it too is loud but not as loud as the cycle x. 
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 07, 2017, 23:20:31
https://www.amazon.com/Starter-Solenoid-Honda-Motorcycle-1979-1983/dp/B008LX9GKI

what do you think about this replacement?
Title: Re: 81CB750c build first time here goes nothing
Post by: Cookie on Mar 08, 2017, 06:48:43
The price is right, it even comes with a proper fuse.
There's also vintagecb750.com

http://www.vintagecb750.com/products/5/electrical/49/starter-system-parts

A bit more money but all they sell is cb750 parts, so you know it's correct.
Title: Re: 81CB750c build first time here goes nothing
Post by: J-Rod10 on Mar 08, 2017, 06:57:37
The 4-2-1 sounds great. Is super loud. I run a Ballistic 8 cell on my 750. Hasn't failed me yet.

I run a solenoid off of a CBR600F2 on mine. Had it laying around the shop, it worked.
Title: Re: 81CB750c build first time here goes nothing
Post by: esmoojee on Mar 08, 2017, 17:10:42
+1 on the cbr600 solenoid... You can find them on ebay for $10.  I wouldn't use that one off of amazon. 
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 08, 2017, 17:49:53
Here is an OE one for $8 so that should do it yea?

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 08, 2017, 17:53:48
The 4-2-1 sounds great. Is super loud. I run a Ballistic 8 cell on my 750. Hasn't failed me yet.

I run a solenoid off of a CBR600F2 on mine. Had it laying around the shop, it worked.
I want to get something local battery wise, for any issues I want same day replacement.  A guy on here nateb picked up one in town here in Spokane by the battery tender brand with 240 cranking amps and a li charger for $140 here is it next to the stock sized one 😂😂

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: esmoojee on Mar 08, 2017, 18:54:16
Here http://www.ebay.com/itm/1994-honda-cbr600-f2-starter-relay-solenoid-/262879623407?hash=item3d34d8b8ef:g:XywAAOSw8w1X6bvA&vxp=mtr
Title: Re: 81CB750c build first time here goes nothing
Post by: Sonreir on Mar 08, 2017, 18:55:10
Yup. Love me some LI-ION.

I'm currently running one in my car.
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 09, 2017, 10:35:01
Here http://www.ebay.com/itm/1994-honda-cbr600-f2-starter-relay-solenoid-/262879623407?hash=item3d34d8b8ef:g:XywAAOSw8w1X6bvA&vxp=mtr
Ordered thanks

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: J-Rod10 on Mar 11, 2017, 11:45:14
Give you an idea what that exhaust sounds like.

https://youtu.be/-MIH8exuZGM (https://youtu.be/-MIH8exuZGM)
Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 12, 2017, 19:36:27
Give you an idea what that exhaust sounds like.

https://youtu.be/-MIH8exuZGM (https://youtu.be/-MIH8exuZGM)
I like it! Sounds nice and throaty, almost a little pissed off

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 12, 2017, 19:38:08
Is that your bike? I noticed the 2 into 1 carb adapters how do they work

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: J-Rod10 on Mar 12, 2017, 21:50:25
It is. They work great.
Title: Re: 81CB750c build first time here goes nothing
Post by: Cody.linhart on Mar 12, 2017, 22:33:18
Give you an idea what that exhaust sounds like.

https://youtu.be/-MIH8exuZGM (https://youtu.be/-MIH8exuZGM)


Which exhaust was this again? Sounds absolutely incredible! Good work as always


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Title: Re: 81CB750c build first time here goes nothing
Post by: J-Rod10 on Mar 12, 2017, 22:38:27

Which exhaust was this again? Sounds absolutely incredible! Good work as always


Sent from my iPhone using DO THE TON (http://r.tapatalk.com/byo?rid=89466)
The 4-2-1 Tri-Y that the OP linked a bit higher up on the page.

Sent from my SAMSUNG-SM-N920A using Tapatalk

Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 13, 2017, 13:45:40
It is. They work great.
Have you happen to use them on a stock frame? I saw a couple different styles, but both say that they aren't for use on a stock frame. I'm not about to cut up my frame for a set of carbs, I'd spend the extra coin on a set of 4, but I think the 2 into 1 look awesome. What's your incite on that? I will also email the site and ask directly but hoped this may give me a better result.

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: J-Rod10 on Mar 13, 2017, 13:47:18
Have you happen to use them on a stock frame? I saw a couple different styles, but both say that they aren't for use on a stock frame. I'm not about to cut up my frame for a set of carbs, I'd spend the extra coin on a set of 4, but I think the 2 into 1 look awesome. What's your incite on that? I will also email the site and ask directly but hoped this may give me a better result.

I'm here for a good time,  not a long time.
This particular set up works with the stock frame. These are cxman's (username on here) setup.

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Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Mar 13, 2017, 14:18:14
Perfect those are the ones I was looking at, price seemed good and said it was complete ready to bolt on.  Glad I already bought the velocity stacks haha

I'm here for a good time,  not a long time.

Title: Re: 81CB750c build first time here goes nothing
Post by: lostinmiself on Jun 16, 2017, 15:37:29
Well it's been a little bit since I've worked on the bike. Work picked up, and so has a divorce (that means more time for the bike :). Going to get my 4-1 ordered today, figure out something about a seat. I tried to fiberglass a pan for it, but we can say that my glassing skills are sub par for a photo finish. I did however get a rear hoop welded on and made progress there. This weather has me itching to ride, hopefully I can soon.

I'm here for a good time,  not a long time.