Author Topic: Getting an old bike running (Read 4750 times)

void909 · « **on:** July 18, 2008, 08:10:01 PM »

So a friend of mine (a certified mechanic) and I (a backyard tinkerer) are slated to take my 74 cb750 k4 to his house on Monday to use his lift and see if we can get this thing started. Just a little background info... I have no background info. The bike has been sitting for who knows how long but it kicks over and has not got any signs of a leak. The throttle is stuck along with the carbs which we plan on cleaning. Besides that the bike seems like it wants to run. So do you guys have any tips or pointers to keep in mind on Monday? Anything Important to remember? Ill let you guys know what happens. Wish me luck!

Void909

my78k · « **Reply #1 on:** July 18, 2008, 08:45:53 PM »

1- a full case of beer!
2- fresh plugs
3- fresh gas
4- fresh oil
5- fully charged battery
6- ear plugs to drown out the swearing! Doubly so if the starter doesn't work and you hurt yourself kicking it over....and over .....and over

Other than that you should be good to go!!

Oh yeah an internet connection may help so you can read through all the posts of guys who have done the same things and had entirely different causes as to why it won't start

Dennis

void909 · « **Reply #2 on:** July 18, 2008, 09:05:59 PM »

1- Check cold beer of his choice (he is the pro) bud light
2- Check new in box D8EA's
3- Check will fill can on the way
4- Need to get a few quarts but what kind... just kidding
5- Check Brand new Autocraft battery part # 14LA2
6- No ear plugs but we got rock n roll... Oh and we are taking my parts bike so if it is the starter we have a spare. Hopefully it works.

I'm sure he has the internet.

Thanks Dennis

mystic_1 · « **Reply #3 on:** July 18, 2008, 09:49:49 PM »

If you don't have a manual, download one and print the sections you think you'll need, or take the file to a print shop and have the while thing printed. OR if you're like me, download your reference directory into your garage laptop and tote that along.

I'd also recommend:

A gallon of carb dip with basket
Multimeter
Carb jet cleaning supplies (brass or copper wire)
Electrical tape
Basic shop chemicals (WD40, Liquid Wrench, Carb spray, degreaser)
Assorted brass and plastic cleaning brushes
Patience

Enjoy!

mystic_1

bryanj · « **Reply #4 on:** July 19, 2008, 06:14:14 AM »

Extra on the patience
Contact cleaner for the ponts
swear box----should have enough for the next box of beer by the time you finished

Johnie · « **Reply #5 on:** July 19, 2008, 06:54:24 AM »

If you want to give that bike the best opportunity to start, I would do everything the guys mentioned plus, install new points and condensors. But I suppose you could just clean them up a bit with emery, check the gap and hope for the best. I sure hope the gas tank and fuel line is clean for you. If everything else fails, just drop that 74 off at my house...

BobbyR · « **Reply #6 on:** July 19, 2008, 07:40:54 AM »

I would put a bit of Marvel Oil in the cylinders to if not free the rings a bit, but also prevent a dry start. The other ideas are also spot on.

shoemanII · « **Reply #7 on:** July 19, 2008, 10:03:45 AM »

a cold compression check might be in order first, just to see what you're in for. if all is ok, have at it!
bobp

mystic_1 · « **Reply #8 on:** July 19, 2008, 11:21:53 AM »

Quote from: shoemanII on July 19, 2008, 10:03:45 AM

a cold compression check might be in order first, just to see what you're in for. if all is ok, have at it!
bobp

+1

Good call.

mystic_1

void909 · « **Reply #9 on:** July 19, 2008, 04:44:06 PM »

Quote from: mystic_1 on July 18, 2008, 09:49:49 PM

If you don't have a manual, download one and print the sections you think you'll need, or take the file to a print shop and have the while thing printed. OR if you're like me, download your reference directory into your garage laptop and tote that along.

I'd also recommend:

A gallon of carb dip with basket
Multimeter
Carb jet cleaning supplies (brass or copper wire)
Electrical tape
Basic shop chemicals (WD40, Liquid Wrench, Carb spray, degreaser)
Assorted brass and plastic cleaning brushes
Patience

Enjoy!

mystic_1

Got a haynes manual.
what is carb dip? Ive got carb cleaner.
I need brass and copper wire brushes
im sure he has a multi meter
got the basic shop chemicals
ill see if I can scrounge up some patience somewhere

void909 · « **Reply #10 on:** July 19, 2008, 04:45:18 PM »

Quote from: mystic_1 on July 19, 2008, 11:21:53 AM

Quote from: shoemanII on July 19, 2008, 10:03:45 AM
a cold compression check might be in order first, just to see what you're in for. if all is ok, have at it!
bobp

+1

Good call.

mystic_1

how do I do a cold compression check?

mystic_1 · « **Reply #11 on:** July 19, 2008, 04:48:39 PM »

Remove the plugs, hook up a compression gauge, and kick it over several times. Read the peak value. Repeat for each cylinder.

You want similar numbers but they don't have to be identical. Post your results and people here can tell you a lot about the condition of the engine.

mystic_1

void909 · « **Reply #12 on:** July 19, 2008, 05:01:23 PM »

Quote from: Johnie on July 19, 2008, 06:54:24 AM

If you want to give that bike the best opportunity to start, I would do everything the guys mentioned plus, install new points and condensors. But I suppose you could just clean them up a bit with emery, check the gap and hope for the best. I sure hope the gas tank and fuel line is clean for you. If everything else fails, just drop that 74 off at my house...

I have some sand paper for the points. every time I think about points it reminds me of that movie Slingblade. Great movie. The parts bike I have has a dyna s ignition and three ohm coils so if the points don't work I guess I will have to hook it up.

void909 · « **Reply #13 on:** July 19, 2008, 05:02:21 PM »

can you buy a compression gauge from the auto parts store?

shoemanII · « **Reply #14 on:** July 19, 2008, 05:23:49 PM »

yes.

bring a plug with you to make sure you have the right threaded end on the gauge. you may need an adapter, but easily had. threading in the center cylinders is always a pain for me, my tester hose is U-shaped. always thought a rubber push-on type might work better, but am too cheap to buy one.

bobp

fmctm1sw · « **Reply #15 on:** July 19, 2008, 06:03:44 PM »

Quote from: void909 on July 18, 2008, 08:10:01 PM

The bike has been sitting for who knows how long but it kicks over and has not got any signs of a leak.

Void909

What's the over/under on how long it takes to leak guys? Seriously though, there's no feeling like bringing a bike back to life... Have fun!

my78k · « **Reply #16 on:** July 20, 2008, 12:34:33 AM »

I am on two minds about the compression check at this point...reason is, if it reads low even on one cylinder what does that tell us? If it has been sitting for a while and the rings are stuck it won't give a good reading...and then what? Do a rebuild based on potentially faulty readings? On the other hand a base number may not hurt...I just wouldn't read too much into the numbers just yet....but that's just me.

Dennis

quietlikeachurch · « **Reply #17 on:** July 20, 2008, 01:05:34 AM »

I second (and third) all that has been said before and wish you good luck. Six years ago I resuscitated my 750 after almost 20 years of inactivity and it still starts first kick and doesn't smoke. I would skip the cold compression check for now. Absolutely use penetrating oil in the cylinders beforehand to free the rings, set the ignition and carbs, and after it's running change the engine oil and change the engine oil and change the engine oil...if it doesn't blow up you're good to go.

P.S. - Spend the time to clean and set up the carbs the FIRST TIME...it took me about 10 carb rebuilds before the damn thing ran right which can be alot of fun or heartbreaking depending on your mood.

-Ian

Oh, and beer.

void909 · « **Reply #18 on:** July 21, 2008, 03:18:41 PM »

UPDATE TIME BOYS!!!!

So we got the bike to his garage which was tons of fun with no front brake and an ATV ramp but we were careful. We got the carbs off the engine after fighting with the boots (which are in good shape) for a while. The carbs were really stuck and the old gas inside them looked like syrup and stunk to high hell. It didn't take too long to get the carbs apart and once we did we soaked them in carb dip. My buddy was freaking out about the old technology, he says this is the oldest thing he has ever worked on. We were both so pumped about the start of the project we wanted to work on it all day but a lack of tools brought us to a screeching halt. He is going to bring home some tools on Thursday so we can get a lot more done. While we had the bike on the lift we found what looked like an oil leak. He thinks its just a gasket but I'm not sold on that yet. He is brining home his compression tester to so I will give you boys some readings soon. This is the most fun Ive had all month.
thanks again for your help
void

Hush · « **Reply #19 on:** July 21, 2008, 04:06:11 PM »

Everyone missed the most important article of all!!!
A camera, for Godsake how can he post horror photos on here without one?
Oh and on that oil leak, my 650 was dripping oil everywhere from sump, I dropped sump and cleaned out half inch of black gunk and deglazed the sucking strainer thing and slapped it back together, hasn't leaked since!
So do that and change oil/filter and you may find oil leak is no more.

TwoTired · « **Reply #20 on:** July 21, 2008, 05:45:03 PM »

Quote from: void909 on July 19, 2008, 05:01:23 PM

I have some sand paper for the points.

Don't be using sandpaper on the points. Sand is silica and an insulator. It will leave some grit in the point material and diminish conductivity. OK for emergencies, but usually you will have to replace them soon after using sandpaper on them.

void909 · « **Reply #21 on:** July 21, 2008, 07:05:46 PM »

Quote from: Hush on July 21, 2008, 04:06:11 PM

Everyone missed the most important article of all!!!
A camera, for Godsake how can he post horror photos on here without one?
Oh and on that oil leak, my 650 was dripping oil everywhere from sump, I dropped sump and cleaned out half inch of black gunk and deglazed the sucking strainer thing and slapped it back together, hasn't leaked since!
So do that and change oil/filter and you may find oil leak is no more.

Sorry hush, I will take the camera next time I promise. I was so excited I left the house without it. I will remove the sump for a good cleaning too. I got one of those trick screw on filter conversions as well so that will go on Thursday after the cleaning. Hopefully that will fix the leak. I'm trying to stay optimistic.

Quote from: TwoTired on July 21, 2008, 05:45:03 PM

Quote from: void909 on July 19, 2008, 05:01:23 PM
I have some sand paper for the points.

Don't be using sandpaper on the points. Sand is silica and an insulator. It will leave some grit in the point material and diminish conductivity. OK for emergencies, but usually you will have to replace them soon after using sandpaper on them.

Thanks im glad you said something before I messed that up. What would you recommend?

NGL_BrSH · « **Reply #22 on:** July 21, 2008, 07:16:45 PM »

i just got a "points file" from vip auto parts down the road for $2.80.. worked great!

TwoTired · « **Reply #23 on:** July 21, 2008, 08:36:27 PM »

Yep, points file is "the bomb".

But, I've also used a good quality fingernail file, when in foreign territory.

Cheers,

dboblet · « **Reply #24 on:** July 21, 2008, 09:03:59 PM »

My '78 750f sat around for 21 year before I got it. The engine still kicked over but when I got it the carbs were off, no exhaust, mismatched set of plugs came with it. It took 5 carb rebuilds (I only replaced the bowl o-rings) before all 4 carbs ran properly (set them up on the bench with a 1/8 drill bit as a guage). All the jets were clogged shut when I first took them apart. I found some stiff fishing line worked perfectly to clear them all out.
I change the oil twice before I got serious about trying to fire her up.
There was crap in the fuel tank and after two cleanings... well, some s*** was still getting into the carbs. I added a cheapo in-line filter and cured that problem!
I also found that although the points LOOKED fine, and I could set the gap perfectly, they didn't open properly and two of the cylinders were hardly fireing at all. I had another used set and when I dropped them into the equation, the darned thing fired up and scared the crap out of my dog who won't even come near the bike at this point.
After that, I put the exhaust pipes back on.
The story is a lot more involved and has a lot more convolutions that that, but what a rush getting it back on the road again. My first 'real' trip on her is tomorrow. I've got the new reg and title at last and the road beckons...
So, best of luck and have fun. and a beer. How cool you've got a bud to work on it with. I did all my work in the back yard with my wife yelling at me that my dinner was getting cold.... again.

Johnie · « **Reply #25 on:** July 22, 2008, 06:42:25 AM »

Quote from: void909 on July 21, 2008, 03:18:41 PM

UPDATE TIME BOYS!!!!

So we got the bike to his garage which was tons of fun with no front brake and an ATV ramp but we were careful. We got the carbs off the engine after fighting with the boots (which are in good shape) for a while. The carbs were really stuck and the old gas inside them looked like syrup and stunk to high hell. It didn't take too long to get the carbs apart and once we did we soaked them in carb dip. My buddy was freaking out about the old technology, he says this is the oldest thing he has ever worked on. We were both so pumped about the start of the project we wanted to work on it all day but a lack of tools brought us to a screeching halt. He is going to bring home some tools on Thursday so we can get a lot more done. While we had the bike on the lift we found what looked like an oil leak. He thinks its just a gasket but I'm not sold on that yet. He is brining home his compression tester to so I will give you boys some readings soon. This is the most fun Ive had all month.
thanks again for your help
void

Void...you for sure have the right attitude. I can hear the excitement in your text. Have at it and have a great time. Just don't forget the pics for us. Plus, once you get that done you will be glad you have the old pics of the new bike...Good luck with it.

void909 · « **Reply #26 on:** July 22, 2008, 10:33:24 AM »

Thanks TwoTired Ill go get a points file first thing.

Thanks dboblet, thats a great and inspirational story. It is really cool to have some help working on my bike. Up to this point it has just been me on a 8' x 8' slab called my back porch so being able to get this thing up in the air has been cool.

Thanks Johnie, I am very excited about this project. After seeing and hearing all the success stories on this forum I really want to be able to contribute one myself. I will be sure to bring my camera from now on for anything that comes up.

I really appreciate the support of everyone here. You guys have help a guy who doesn't no sh!t about anything feel like he can tackle just about any project that comes up. Once again this forum is the best!

void909 · « **Reply #27 on:** July 26, 2008, 01:37:16 AM »

Alright boys I have some reporting to do.

So we got the carbs back together tonight and got them mounted on the bike after about 30 min of turning the boots and pushing them on. It was a b!tch. We got the air box back on but we didn't get the air box boots up tight around the carbs. They were ridiculously hard. The battery I just bought didn't come with enough acid to completely fill it so my friend is going to take it to his work and top it off tomorrow. We decided to try and kick it over anyway. As soon as we hooked up the gas lines gas started pouring out onto the floor. I think it was partly due to the hoses being old so we pulled them and inside the T shaped tubes leading into the carbs (sorry I don't know the proper name)was still clogged. No fuel even drained into the bowls. SO as of today we got beat up and we really got nothing accomplished.

We gave it a couple of kicks for good measures. Nothing. I work all this weekend so Monday we are going to charge the battery, pull the air box to figure out why it wouldn't seat Properly, pull the carbs back off and clean out those T's. He is getting some new fuel line from his work so we can start fresh. I really feel like after seeing the carbs get taken apart and put back together I could do a better job of cleaning them then he did. He is more experienced than me and knows way more than I do but I am A stickler for detail. I have that 75 parts bike, I think I am going to pull the carbs off of it and try it myself. So far 74 cb750 2 - rookie 0. I will get it though if its the last thing I do.

Johnie · « **Reply #28 on:** July 26, 2008, 06:10:16 AM »

Well, you are finding out that is what it is all about. Fix it, put it on, take it off and fix again. Great learning experience and you will feel good when you get it right. I also am a stickler for detail and it sometimes takes me longer to do stuff because of that...but if you like the detail it will all show in the end. Good luck and keep us posted.

TwoTired · « **Reply #29 on:** July 26, 2008, 09:04:19 AM »

Quote from: void909 on July 26, 2008, 01:37:16 AM

... but I am A stickler for detail. ... I will get it though if its the last thing I do. ...

Both statements are assets for carb work.

Patience, perseverance, and practice.

If you buy new carb boot rubbers, you'll wonder why you ever bothered with the old, hard ones.

Cheers,

dboblet · « **Reply #30 on:** July 26, 2008, 09:23:19 PM »

of course, there's a nice thread on making the old hard rubbers soft and supple again.... worked with mine anyway. And once I had them treated, it made a world of difference... Took all the sweat out of re-seating the carbs, literally.

void909 · « **Reply #31 on:** July 27, 2008, 02:53:19 AM »

It wasn't the carb boots that were giving me the trouble. It was the air box boots. mo matter what we did they just wouldn't go back up snug on the carbs. I can see why so many people go with the pod filters. I thought about using them but after reading so much about getting them to work, I decided I would just go with the stock box until I was more comfortable jetting and tuning.

Do you guys know if you have to have the battery hooked up to get the bike running? I was pretty sure you had to but he swore that it would start with the kick start even if the battery was disconnected.
thanks again guys
void

mystic_1 · « **Reply #32 on:** July 27, 2008, 07:22:34 AM »

You cannot run a CB750 without the battery. The alternator requires power in order to make power.

mystic_1

BobbyR · « **Reply #33 on:** July 27, 2008, 07:34:26 AM »

Quote from: mystic_1 on July 27, 2008, 07:22:34 AM

You cannot run a CB750 without the battery. The alternator requires power in order to make power.

mystic_1

Mystic is correct. We do not have magnetos as they did in the past. You need to power the coils to get a spark. The alternator also requires power.

void909 · « **Reply #34 on:** July 27, 2008, 02:25:09 PM »

Thats what I thought. So we did a lot of kicking for nothing.
Thanks guys

my78k · « **Reply #35 on:** July 28, 2008, 08:29:52 AM »

Well....not really for nothing...consider it practice!! You will have much more kicking to do before you are through!!

Dennis

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Author Topic: Getting an old bike running (Read 4750 times)