|
|
12
|
|
I acquired a cb750f a few months ago and have started to dig in and modifying the bike. This is my first motorcycle project, so I'll have a lot of questions for you experts!
The bike's carbs where pretty mucked up when I got it, it ran - but not well! I knew I wanted to add pods, so I opted to just upgrade the carbs (cr29 specials).
I am going to check the valves this weekend and try to get off some of the covers that the screws seem the be stuck on (any tips for getting these off would be great, my impact driver isn't doing a good job!) to get out the scratches.
The frame looks to be in good shape, with only a tiny bit of rust here and there. I'm going to wait to paint/powder coat it until I take out the engine to paint (maybe next year?). Any suggestions for removing the small bits of rust?
So far I have added a 4-2-1 exhaust, cr29 specials to the bike, and have moved around the wiring some with a smaller battery under the seat. I plan on adding a rear loop, different speedo/tach, new handlebars (something lower/sportier), repainting the tank (it might need to need rust removed, even though the previous owner told me it had been seal coated), and probably quite a bit more!
When I got it:
 How it sits now:
 I'm all open for suggestions of things to check, add, remove, etc! Obviously I want to bike to look good, but there is no point of it looking good when it's not running correctly!
|
|
|
Well unfortunately it looks like there is rust in the gas tank. I drained out some of the fuel into a clear container and there were a few small rust particles. Fortunately, I've had an in-line fuel filter on it! I'm going to try the electrolysis method this weekend.
Another strange problem has occurred, the engine won't rev past 5k. This wasn't a problem before I switched to the CR29s. Although, I also swapped out batteries at the same time, I am using a Shorai battery underneath the seat to conceal the wiring. From what I've read the lack of rev past 5k could be due to the charging system or incorrectly jetted carbs. I have my battery on a charger so it seems like it must be the carbs? Or could it still be something in my charging system?
As you can probably tell, my knowledge of electronics and carbs isn't anywhere close to expert!
I'll do more digging this weekend to see if I can rule out anything. Any tips would be great!
|
|
|
Can you pull your plugs to see if you're running rich or lean?
I've never worked on CR's, but incorrect jetting could definitely be the issue.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
My cb750 video site
|
|
|
Sees, will do. I actually have a new set of plugs coming since I didn't replace the current ones after I purchased the bike.
|
|
|
I think that not being able to rev to high rpms is still an indication of a poor charging system. To test mine i just hooked up a voltmeter to my battery and revved to about 4k and saw that it was at about 14.2V.
My bike wouldn't rev past 7k for the longest time because my main jet was WAY too big. What jetting do you have for your bike right now?
I also switched my coils out for F3 coils(F3, F2 and cbr900rr coils work too), iridium spark plugs and i got procom igniters and now my bike starts ridiculously quick and revs like it always wants to go just a little faster. The electrical system helped a lot, but I'd check your charging system before.
1981 SS with Kerker 4-1 exhaust and extremely attractive rider.
|
|
|
I checked the plugs, they are all black and dry. I also have a set of F3 coils that I'm going to put on when they arrive.
I will start checking the charging system to see what is weak. I saw some info in the manual. Are there any other step by step guides I can use? Anything that can help a newb!
I believe my CR29s came with a 120 main jet. I haven't played around with the jets yet as I wanted to make sure my valves were set and my charging system were good.
|
|
|
I believe seestheday has a few good videos up, I have a starter clutch rebuild video too. I saw somewhere where a guy played with the jets for his CR's and ended up putting in 100's... I'll check that, but I'm pretty sure. If you dont have one a clymer manual and reading up on all these guys builds really helped me. They're all pretty smart 
1981 SS with Kerker 4-1 exhaust and extremely attractive rider.
|
|
|
Well I checked my valves and there are quite a few off, but fortunately it looks like I can make them all between .004 & .006 by swapping the around. I don't have the valve tool, so I used a flat head screwdriver as I read it worked on another site. Unfortunately, it was extremely difficult and I only got 2 moved. I ordered the motionpro tool so ill continue when it get it.
I installed my F3 coils, incorrectly connected my wires the first time and got a horrible backfire and assumed I blew up something haha! I then connected the wires correctly and it fired up really fast!
I checked the battery voltage and it was only around 13, not at 14.4 or whatever it should be. So I assume my not revving above 5k are due to charging issues. Ill have to look more into that this week, not looking forward to it haha.
Thanks for all the tips and offers to help so far. More advice is always appreciated!
|
|
|
Any tips/tricks on removing the center stand and footpeg brackets? I purchased a set of the factory sportkit rearsets from Wout, and I have to remove my center stand as my new exhaust have to bracket to stop it so it comes in contact with the chain.
Gas tank is currently undergoing an acid bath by a local guy who came recommended and has very reasonable prices. I currently have a "fancy" setup rigged with a tube and plastic container/funnel in order to fuel the carbs for testing, hah!
This week/weekend I'll be testing my charging system and cutting up an aluminum sheet to mount my electronics under the seat/gas tank.
I'll try to take some pictures for you guys in order to spruce up the thread!
|
|
|
Do you want to keep your center stand? You can make it not hit your chain by just sticking a bracket on the rear passenger footpeg. Here is a pic of it on mine. It's kind of hard to see because it's immediately behind my rearset peg, but it's there. Just a piece of stainless steel, that keeps the chain an inch and a half away from the center stand (it looks like it's closer in the pic, but that is not the case).
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
My cb750 video site
|
|
|
Interesting, I hadn't considered that! My plan was to just remove it but keep it handy to slide back into place (without the spring) when I needed to do some work.
Did you weld the piece of steel on? I am not a welder, no equipment or expertise, but will have someone weld on a rear loop at some point so I could have them do that at the same time.
|
|
|
No need to weld anything. Just get a piece of metal, drill a hole, and put it on. Here is a pic from a different angle.
 I have a few extra washers in there because the bolt I used to mount my rearset peg was a little long.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
My cb750 video site
|
|
|
Thanks for the picture. That's a great idea!
|
|
Administrator
|
What the ...?! Everyone can find these bike but me! Did they not sell F model DOHC's on the east coast or what?
Awesome bike bud. I love the style of these things. Dying to get my hands on one....someday.
|
|
|
Thanks Shinyribs! Funny story how I even got into custom motorcycles, I saw this awesome Triumph built by Vintage Racers ( http://www.vintage-racers.com/p/by-ats-original-idea-for-this-bike-was.html), and wanted to build that one, but instantly realized Triumphs were out of my price range. Then I saw a bunch of really cool cb750 'brats', and had to build one. I searched craigslist all over the state (and surrounding states) of Texas for a few months before I finally found one at a reasonable price!
The nice thing is there was pretty minimal rust on the frame, so I will not worry about that for now (I'm sure I will remove to engine to paint it next year or something, and I'll powder coat the frame at the same time).
|
|
Administrator
|
shinyribs wrote
What the ...?! Everyone can find these bike but me! Did they not sell F model DOHC's on the east coast or what?
Awesome bike bud. I love the style of these things. Dying to get my hands on one....someday.
No. They were all sold in Kansas City. I'm so sick of seeing these things.  Why don't you come and haul some back to the coast?
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
|
|
Administrator
|
TOOLS1 wrote
Why don't you come and haul some back to the coast?
TOOLS
Let me get Opie on the road and I may just do that.
We now return you to your previously scheduled build...
|
|
|
Well it looks like my rotor is toast. Any suggestions for where to get a quality one? I don't want o be changing it out every year!
I measured my valve clearances and have some off. Need to buy a micrometer tomorrow to measure my shims. While iwas in there I noticed the 2 blk rubber pieces in the pics below. Are these broken, or Is this normal? Also, should there be rubber pieces on the other two sides? Sorry I'm sure this is a noob question!
|
|
|
Whoops, second pic:
 You can see both rubber pieces in this pic, and how the bolt on the other side does not have rubber over it.
|
|
|
Those are oil deflectors and yes you should have four in total. Pull your oil pan and see if they're in there.
They're still available from honda.
Without then your camshafts may not get the oil the need. Check your lobes to see if they're still in spec. Might be a good time to get some 900 cams and drop them in.
Sent from my BlackBerry device
Whoops, second pic:
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
My cb750 video site
|
12
|
Locked
