Topic: 1977 CB750F

[ornj]

New to the forum and already I've had a couple questions answered just by browsing. Awesome! I'm new to riding and I picked up a 1977 CB750 Supersport. A lot more bike than I should probably be starting on but I'm a pretty big guy and the weight/size feels right. Couldn't pass up on the deal. You will be seeing her in the Project forum starting this winter as a friend and I cafe it out.

Anyways I sort of pieced together some info from the forum and wanted to make sure I'm right in my thinking. The 4 cyl obviously needs time to warm up. During that time should I not worry about idle speed? Seems like this should be idling around 1200 rpm from what I've read here. How long should I warm the bike up before I adjust the idle speed?

[Johnny5]

Do some city driving for about 15-20 minutes. After that your bike should be plenty warm enough to set the idle. Then you shouldnt have to touch it anymore. You'll just need to either keep blipping the throttle to keep it from stalling during warmup/keep choke engaged. Cool thing about PD carbs is that they have a mechanism that helps add some throttle when the choke is engaged.

[Johnny5]

Oh, and welcome to the forum. Great place!

[ornj]

Thanks! Do you have any suggestions for how long I should let the engine warm up?

[Johnny5]

When it's cold out, 50 degrees or so, I let the bike warm up a good 5 minutes before heading off. Sometimes if Im in a hurry, I'll ride with the choke half on, then shut it off when it's good and warm.

[cycleman]

These year bikes are cold blooded & like their choke.  Theirs really no way to apply a set time, just use the choke until the bike runs fine without the choke on.

Bike should be well warmed up to set the idle and 1100 is probably a better idle speed. 

[ornj]

Awesome. I'm sure it will all fall into place when I get better acclimated. The bike is in very good condition, could probably do well with a tune up but my friend is going to go over it for me so I can start learning how it all works. I've just been sitting with the front wheel against a brick wall so I can get used to the weight and practice shifting into first gear without it lurching on me. Going to hopefully head out to a parking lot this Thursday and I'm registered as an alt for the MSF course starting a week from tomorrow.

[Slayer]

Welcome. Nice choice on the bike. You will do fine learning on it, especially with a MSF course. Make sure you notify your insurance company, they usually cut the cost down a little bit. It technically should be idling at 1,000 RPM but a little more juice for the cold weather is probably good. Once you drive around for a few minutes it should warm right up. The guys on this forum are pretty sharp and have saved my ass plenty of times. Make sure you post pics!

I am currently working on a 77 750F myself. The best tool someone shared with me is this manual http://www.mediafire.com/?5ttzdg9yyuz I hope to see the progress 

[ornj]

Nice, I bought the Clymer manual and read through that pretty much cover to cover. Downloading that shop manual too. Here is the bike in it's current untouched state. My buddy and I will likely build a companion site to track our progress when we begin taking it apart.

Here it is currently.

[kslrr]

Nice 750F!  You're sure you want to cafe' that beautiful specimen of late '70's motorcycle tech?

[Slayer]

Yea dude, nice one. Very clean. What kind of exhaust are you running?

[IAmCitizenMe]

Nice, I bought the Clymer manual and read through that pretty much cover to cover.

Yea, be careful with that Clymer. I just had to buy a new tappet cover because it gave me back valve-adjustment instructions.

That is a sick looking bike, though. That's for sure.

[BobbyR]

New to the forum and already I've had a couple questions answered just by browsing. Awesome! I'm new to riding and I picked up a 1977 CB750 Supersport. A lot more bike than I should probably be starting on but I'm a pretty big guy and the weight/size feels right. Couldn't pass up on the deal. You will be seeing her in the Project forum starting this winter as a friend and I cafe it out.

Anyways I sort of pieced together some info from the forum and wanted to make sure I'm right in my thinking. The 4 cyl obviously needs time to warm up. During that time should I not worry about idle speed? Seems like this should be idling around 1200 rpm from what I've read here. How long should I warm the bike up before I adjust the idle speed?

I have a K8 so they are essentially the same. You always set the idle speed when the bike is fully warmed up and leave it there. The tachs are not that accurate so most reports here are about 1200-1500, smooth is the key, so unless we all used inductive tachs, the actual speed is unknown. If you go too high you lose a lot of your engine braking, you will feel that. A carb synch helps these at idle a lot.

They way I work the choke I start it and give it enough time for me to get my helmet, jacket and gloves on. At the end of my street is a sweeping corner so I donl;t want to stall so I get on the road uo to speed and push in the choke. If I don't hit a light she is fine after a mile or soot  choke. If I stop sooner I play Harley rider and blip the gas.

Keep us posted on your progress.

[bender01]

Please let me be the first to buy your seat if you decide to lose it. Thanks
   Ben

[mikeb4]

If you open up the mixture screws a half or full turn that can help the cold running, also for more bump up one size on the pilot jets it will run a lot better cold and fine when warm.  You can then fine tune with the fuel mixture screws.

I went from the stock 35's to 45's on a velocity stack application, you could try 40's with a stock airbox.

http://www.siriusconinc.com/carb/parts.asp?category=2&supplier=1&id=1&curp=19&conn0=&conn1=&conn2=&conn3=

[ornj]

Nice 750F!  You're sure you want to cafe' that beautiful specimen of late '70's motorcycle tech?

I'm not sure exactly what I'm going to do to it but I have ideas. I actually want to dial back the clock on it a little bit.

Please let me be the first to buy your seat if you decide to lose it. Thanks
   Ben

Ha, I will keep it in mind. Anything that gets taken off will be made available.

[BobbyR]

Nice 750F!  You're sure you want to cafe' that beautiful specimen of late '70's motorcycle tech?

I'm not sure exactly what I'm going to do to it but I have ideas. I actually want to dial back the clock on it a little bit.

Please let me be the first to buy your seat if you decide to lose it. Thanks
   Ben

Ha, I will keep it in mind. Anything that gets taken off will be made available.

I have always figured the more stock I kept it more time and money I could spend on making it run well.

[ornj]

I have always figured the more stock I kept it more time and money I could spend on making it run well.

I can appreciate that.

[ornj]

I got out on the bike today, have to say I love this bike more than I thought I would. After it warmed up I seemed to have a little trouble though. I think maybe I didn't put the right fuel in. What octane do people suggest.

[TwoTired]

Regular grade gas.

Is your air filter clean as new?

[ornj]

Probably not. Going to go over the whole bike next week hopefully. I'm sure it needs a new filter and the throttle is a bit sticky.

[Slayer]

I hate to be captain obvious but make sure you change the oil and oil filter.