1977 GS750 carb woes

[AmGr8ful]

I recently disassembled my carbs to clean them good... in being a bit overanxious to get it fixed and get riding I failed to count the number of rotations on the jets and screws and I cannot seem to get the bike started... I have searched the forum as well as other online sites but cannot seem to find the right document for undoing the damage I have done... with $ very tight right now, taking it to a professional mechanic just isn't feasible. Can anyone offer any advice? I am willing to do the work but have no clue where to start... I just wanna ride!!

[KEITH KRAUSE]

Don't know what you mean by "the number of rotations of the jets", but the main, needle jet/bleed pipe, and pilot jet are simply tightened down firmly.
If your concern is just the pilot fuel screws (underneath) and the side air screws...
It's of course possible to re-set them as the factory did but without the test equipment, it may take some tinkering.
Remember the sharp tipped pilot fuel screws must be seated only LIGHTLY or you can break off a tip in the carb body. If you can remember, replace them in the same order as they were.
Be sure all o-rings are in good condition.
The pilot fuel screws are generally 3/4 to 1 1/4 turn out from the factory and if the bike is stock. I'd try 1 turn out for starters.
The side air screws are to be adjusted using the highest rpm method.
Initially set them to 1 1/2 turns. Start the bike and warm up fully. On the centerstand/level, adjust idle to 1,000 rpm's with the idle adjuster knob. Starting at any carb, slowly turn a screw in either direction until you hear the rpm's max out. Fine tune. It should end up about 1 1/2 to 1 3/4 turns. Now re-set the idle to the base 1,000 by using the idle adjuster knob. Repeat with each carb.
For pilot circuit plug reads/performance test, chop off after a couple miles at minimal throttle riding. Cruising around at a steady 35/40 mph in top gear is a decent test. You want a minimum throttle setting to assure you're on the pilot circuit. Be sure the bike is fully warm before starting the test. Turning the pilot fuel screws CCW (outward) richens the mixture. They should end up between 3/4 and 1 1/4. Because of differences in each cylinder, you may find the perfect setting for each cylinder to be a tad different. But they are normally within 1/4 turn of each other, if not closer. Plugs should burn a nice tan color. The bike should warm up well and with a normal amount/time of choke. There should be little or no decel' pop. When hot, the rpm's should return to idle normally. If after revving it the rpm's drop below the set idle momentarily, that's a rich condition.
Do not re-adjust the side air screws after setting by the highest rpm method. If you're positive the pilot fuel screws are finally where you want them *AND* you've moved them beyond a 1/4 turn from the initial setting, then you may want to re-check the side air screws using the highest rpm method. You may find the sweet spot has changed a tad but somewhere between 1 1/2 and 1 3/4 is usually right.

[KEITH KRAUSE]

Also, keep in mind the slides must be bench synched for the fully closed and fully opened positions. This should be followed by a vacuum tool synch to get ACCURATE plug and performance reads.
At the very least, the bench synch must be done correctly.

[petelardo]

Keith Krause is one of the most knowledgeable people you'll find ANYWHERE, so please read his posts thoroughly, because his advice is outstanding...

If you need to learn more about carburetion basics (who doesn't?), check these links, starting with one of the best basic sites I've EVER seen:

http://oldmanhonda.com/MC/Rcarbs.html

Next, check out these links:

http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html

http://justkdx.dirtrider.net/carbtuning.html

http://www.motorcyclecruiser.com/tech/motorcycle_jet_kits_carburetion/

http://oldmanhonda.com/MC/MC.html

That last link to OldManHonda is a GOLDMINE of information, not only about carburetion... when you've read through the other pages, check it out...

This link can help to point you in the right direction about MANY motorcycle repair subjects:

http://www.dansmc.com/MC_repaircourse.htm

Check these pages:

http://www.dansmc.com/carbs.htm

http://www.dansmc.com/carbs2.htm

If you read anything you don't understand, make some notes, then contact the links provided on those websites, and feel free to post general questions here.

Keep in mind that I'm NOT posting ANY of those links to contradict ANY of the advice Keith Krause has given you; I'm ONLY trying to help you learn more about what you're trying to accomplish.

You "just wanna ride"... well, we ALL do, but if you're going to RIDE, you have to know some specifics about WRENCHING, especially if you need to save money! I HATE paying people to do things I can learn to do myself; I wasn't BORN with a wrench in my hand, in fact, I didn't own ANY tools until after I learned how to ride, and realized I couldn't afford to keep throwing my hard-earned money at other people!

That being said, you CAN learn how to do this to SOME degree, but time and patience are virtues here. If you have any mechanical sensibility at all, seeing daylight through pistons should make you mad as hell; there is no excuse for anyone ruining a good engine because they didn't want to take the time to learn... As long as you take the time to learn some basic skills, you'll probably never kill an engine while trying to tune or repair it.

YOU have taken some excellent first steps by asking for help here; you found this website, and now have one of the most knowledgeable members here advising you. I hope you'll want to take advantage of that, but doing so requires some level of commitment on your part. Carbs can't tune or repair themselves, so it is up to you to start reading and learning... Print out those pages so you can refer to them as you look at your carbs; that will also allow you access to the information 24/7, which means that even if your computer dies, you'll STILL be able to work on solving your problems...

This is up to you now, AmGr8ful; there are too many time zones between us for me to be able to help you turn those wrenches, but you CAN learn a LOT in a short amount of time, if you take the time to read through those webpages, then RE-read the advice Keith Krause has given you. You write well, which tells me you're intelligent; you already have a motorcycle that needs you, you've now got PLENTY of reference material to learn from... I think you're a LOT closer to solving those carburetor problems than you might realize...

Whatever else you do, do NOT work on the motorcycle if you think that simply turning a few screws will solve the problems; getting everything right will require more effort than that, but you're NOT alone in this... If you don't believe me, just search the forums and see for yourself... there are a MULTITUDE of people with the same problems you're facing, and they're no different from you or me. They need help, they have questions, THEY all just want to ride... if you approach this the right way, it won't be long before YOU'RE helping others with the exact same problems...

Well, here's hoping your NEXT post will be to tell us you've made some progress. Many people consider carburetion something of a black art, but I don't agree with them. When I first learned to ride, I didn't know (or much CARE) what a carburetor was, or what it did.. I got motivated to learn how to do basic repairs ONLY because I got tired of being broke all the time... My (cheap, broken-down) motorcycle needed a LOT more help than I could give it, so I had to let it sit and rot DURING RIDING SEASON while I saved enough money to pay for MORE repairs... My girlfriend hassled me all the time about not being able to go out on the weekends; my friends all thought I was NUTS to work two jobs, then just throw my money at the dealership mechanics... you get the idea. I finally bought some hand tools (Craftsman, on sale at Sears), and a Clymer manual. The guy at the parts counter told me I'd do MORE damage by trying to fix things on my own, but I ignored him and went home to start learning...

Keep punching, OK? We're all in this together, and you owe it to yourself to give this your best shot... Good luck; check those links, learn as you go, and post any questions you might have here, so someone can try to keep you pointed in the right direction...

[KEITH KRAUSE]

petelardo, well said and thanks for the atta-boy.
Lots of info out there. Some good and some not as good. Some may conflict with others. You have to study and learn for yourself. Most common incorrect info I see is jetting recommendations that are on the lean side, sometimes very lean. This is from some well known sites too.
I just give the best help I can, based on my experience and I do keep records of what works. I try to help others from my own trials and errors over the years.

[AmGr8ful]

Thanks guys!

Well, I have some studying to do... my problem has been getting the bike started... the #1 and 4 carbs are fouling plugs quickly (black and sooty, not wet and oily)

I do really appreciate the info and will have to learn some terminology but in time I will get this thing rollin again!

thanks again!:-D

[frosty5011]

Keith Krause is one of the most knowledgeable people you'll find ANYWHERE, ...................

(Till it comes to his knowledge about torque wrenches..........\\/:-D)

[KEITH KRAUSE]

If 1 and 4 plugs are dark/sooty, and you cleaned and set up each carb the same way, then it may mean you have a weak coil.

[chef1366]

I second the coil.

[KEITH KRAUSE]

If your bike still has points, you might want to check them too. If worn/uneven/dirty/pitted, that can cause a weak spark too at 1 and 4. They may be able to be cleaned and re-gapped, but serious pitting means they need to be replaced and sometimes serious pitting means the condensor is bad too.