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Hello all, I am new to the board but I've been coming here for quite a while to learn how to wrench on a 1978 GS 750 that I purchased in August. I don't have any experience riding and this is my first bike, but I wanted to buy an old Jap bike for the sole purpose of submerging myself into the world of motorcycle maintenance. It's been quite the learning experience so far, especially since my lack of knowledge about motorcycles forces me into the "guess-and-check" method of troubleshooting, but I still love working on this damn thing, despite the fact that I can't just go out and ride! If anybody can give me some advice on how to make that possible, it would BE GREAT!! 
So anyway, my original problems upon purchase:
- Cold start up takes forever. Electric practically unusable- it sparks but doesn't turn over. I get it to kick start after a 15 minute battle.
- Choke. Bike starts at half choke. Full-on and the bike bogs and dies immediately. When it is sufficiently warmed up I can turn the choke up all the way, but the initial warm-up has that problem and has me scratching my head.
- The Ride. Idles in "waves" at times, and is super boggy. Between 3000 and 4000 rmps it backfires like crazy. Under 3 and over 4 is strong. Took it out for a longer trip, got it into 5th gear, WOT, and I was only barely reaching 60 mph. A friend behind me said I was also blowing blue-grey smoke the whole time. I only average 18-20 mpg as well. I found this out by setting my odometer back at 0 with the idea of riding 100 miles then filling up and doing the math to see my mpg, and I only made it to 86 miles, died, and had to do the walk of shame and strap a portable gas can to my back to ride home. WOOF!
- When I rev the engine in neutral gradually, it accelerates fine. But if I jam on the throttle and open it up, it bogs and dies immediately. There is a youtube video of someone else with this problem. I will try to find it and post it here. This also reflects the ride. In first gear I can ease up to higher rpms, but going hard creates a sketchy, "about to die" feeling. This doesn't happen in higher gears.
- I need to give A LOT of gas to get moving. Other friends who have ridden it to help me troubleshoot always kill it because they are used to their fine tuned bikes and don't give it enough gas at the start.
- Gas. I can only run in "PRI" setting on the petcock. "On" and "Reserve" starve the carbs- I can physically see that no gas is coming from the tank while on these settings.
- Taillight doesn't work for the foot break.
The Previous Owner listed the bike as having a new clutch, new chain, new air filter, new tires. So that's good.
What I have done so far:
- Re-sealed the airbox
- New Intake boots (WHAT A MESS! Damn stripped screws, WOW!!)
- Carbs cleaned
- New O-Rings
- Static points timing
- Re- attached the foot break light wires. D'OH! If only all my problems were that easy!!!
Started it up today, same starting problem. Took forever. Idled really wild, could not find a good setting for the idle-mixture screw as I turned it below 2000 rpms it died. Same choke problem, died at full-on. Same throttle issue- revving slowly was aproblematic, hard throttle made it die. Filled my garage and street with smoke. Couldn't ever get it to come down from 2500 rpms without it dying. I elected it safe not to take it out for a ride.
I will remove the carbs asap and synch again. I did all of those aforementioned things in one 12 hour straight shot and worked on the carbs last. I will admit that at 3 am I was getting sloppy... just wanted the project to be done. In my hurried state I know I didn't do a good job on that.
Also to do ( please steer me elsewhere if I'm wrong) :
- I need a new exhaust. The PO put on these dumb Harley fishtail slip-ons and they don't fit correctly. There is a big hole where the muffler meets the pipe. I will photograph it for all to see. I will probably go with a 4-1 if I can find a good deal, but at this point, anything that fits appropriately will suffice.
- Pod Filters (?) Everyone I've talked to talks about how great they perform blah blah blah. The general consensus on here is that they are not necessary, although that opinion seems pretty split depending on where I look. We shall see.
- Electric ignition. I completely guessed on timing the points. If an electric ignition has me never doing that again then I am all for it.
-Valve clearance. I don't know exactly what that does at this moment but Clymer's Manual told me to do it, so it will be done!
- New Petcock? The only other bike I've ridden on (the yamaha 250 at riding school, HA!) only had "On" "Off" and "Res." I read that "PRI" is used as a 'to-gravity' option that is used to fully dump gas into the carbs with no control, or to clear the tank. With that knowledge, I do not think it's a good thing to be able to run only in that position.
-For way down the road, when all my riding problems are taken care of, I think I would like a new seat. There are no porblems with the current OEM one. The PO claimed to have had it re-upholstered a few weeks before I bought it. Right now when I sit on the bike without the seat on it, I like the feel of that better. I like it more than the upright, high-riding position I felt with the seat on. I don't think I want to do a complete cafe racer or bobber rebuild project (although I like the look of both!), but just some sort of slimmer seat would be great.
That is all for now. I just wanted to introduce myself, give my story, and hopefully get some real-human advice from some of the experts on the board. Thanks!
So anyway, my original problems upon purchase:
- Cold start up takes forever. Electric practically unusable- it sparks but doesn't turn over. I get it to kick start after a 15 minute battle.
- Choke. Bike starts at half choke. Full-on and the bike bogs and dies immediately. When it is sufficiently warmed up I can turn the choke up all the way, but the initial warm-up has that problem and has me scratching my head.
- The Ride. Idles in "waves" at times, and is super boggy. Between 3000 and 4000 rmps it backfires like crazy. Under 3 and over 4 is strong. Took it out for a longer trip, got it into 5th gear, WOT, and I was only barely reaching 60 mph. A friend behind me said I was also blowing blue-grey smoke the whole time. I only average 18-20 mpg as well. I found this out by setting my odometer back at 0 with the idea of riding 100 miles then filling up and doing the math to see my mpg, and I only made it to 86 miles, died, and had to do the walk of shame and strap a portable gas can to my back to ride home. WOOF!
- When I rev the engine in neutral gradually, it accelerates fine. But if I jam on the throttle and open it up, it bogs and dies immediately. There is a youtube video of someone else with this problem. I will try to find it and post it here. This also reflects the ride. In first gear I can ease up to higher rpms, but going hard creates a sketchy, "about to die" feeling. This doesn't happen in higher gears.
- I need to give A LOT of gas to get moving. Other friends who have ridden it to help me troubleshoot always kill it because they are used to their fine tuned bikes and don't give it enough gas at the start.
- Gas. I can only run in "PRI" setting on the petcock. "On" and "Reserve" starve the carbs- I can physically see that no gas is coming from the tank while on these settings.
- Taillight doesn't work for the foot break.
The Previous Owner listed the bike as having a new clutch, new chain, new air filter, new tires. So that's good.
What I have done so far:
- Re-sealed the airbox
- New Intake boots (WHAT A MESS! Damn stripped screws, WOW!!)
- Carbs cleaned
- New O-Rings
- Static points timing
- Re- attached the foot break light wires. D'OH! If only all my problems were that easy!!!
Started it up today, same starting problem. Took forever. Idled really wild, could not find a good setting for the idle-mixture screw as I turned it below 2000 rpms it died. Same choke problem, died at full-on. Same throttle issue- revving slowly was aproblematic, hard throttle made it die. Filled my garage and street with smoke. Couldn't ever get it to come down from 2500 rpms without it dying. I elected it safe not to take it out for a ride.
I will remove the carbs asap and synch again. I did all of those aforementioned things in one 12 hour straight shot and worked on the carbs last. I will admit that at 3 am I was getting sloppy... just wanted the project to be done. In my hurried state I know I didn't do a good job on that.
Also to do ( please steer me elsewhere if I'm wrong
) :- I need a new exhaust. The PO put on these dumb Harley fishtail slip-ons and they don't fit correctly. There is a big hole where the muffler meets the pipe. I will photograph it for all to see. I will probably go with a 4-1 if I can find a good deal, but at this point, anything that fits appropriately will suffice.
- Pod Filters (?) Everyone I've talked to talks about how great they perform blah blah blah. The general consensus on here is that they are not necessary, although that opinion seems pretty split depending on where I look. We shall see.
- Electric ignition. I completely guessed on timing the points. If an electric ignition has me never doing that again then I am all for it.
-Valve clearance. I don't know exactly what that does at this moment but Clymer's Manual told me to do it, so it will be done!
- New Petcock? The only other bike I've ridden on (the yamaha 250 at riding school, HA!) only had "On" "Off" and "Res." I read that "PRI" is used as a 'to-gravity' option that is used to fully dump gas into the carbs with no control, or to clear the tank. With that knowledge, I do not think it's a good thing to be able to run only in that position.
-For way down the road, when all my riding problems are taken care of, I think I would like a new seat. There are no porblems with the current OEM one. The PO claimed to have had it re-upholstered a few weeks before I bought it. Right now when I sit on the bike without the seat on it, I like the feel of that better. I like it more than the upright, high-riding position I felt with the seat on. I don't think I want to do a complete cafe racer or bobber rebuild project (although I like the look of both!), but just some sort of slimmer seat would be great.
That is all for now. I just wanted to introduce myself, give my story, and hopefully get some real-human advice from some of the experts on the board. Thanks!
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