Diagnosing suggestions? having more and more problems starting the bike. 81 GS750

[ktaylorm13]

Hey guys I'm riding a 1981 GS750E. It's my first bike and my first year riding. I was driving it at least 2 to 3 times a week for work all summer. Toward the end of August and through most of September it started having more and more problems starting. I bought a brand new battery for it at the beginning of the summer, at first it was just taking a long time to start after I hadn't driven it for a day or so. Most recently it wouldn't start most days after working a 4-8 hour shift I had to jump start it a few times. The last time I rode it I couldn't even jump it off of a running car's battery. Naturally through the process of trying later after my coworker left with his car I drained to battery. So I charged the battery at work over night then the next day after my shift it turned over after a couple times. It doesn't sound to abnormal when trying to start it. I've noticed a louder clicking sound at the same time but it's actively trying to turn the engine over and it just wont go. I don't know if it always made that clicking noise and I'm just more sensitive to sounds like that now that I'm having problems or it's something that just started. Either way I'd like to know what route I should follow as far as trying to diagnose the real problem. I'd like to get the proper parts ordered so that I can get some more riding going this fall. Thanks in advance guys!

 

[cowboyup3371]

What maintenance have you done on the bike? Do you have a multimeter and have you checked the voltages with no key on, key on, running, and at ~4000 rpm?

 

[ktaylorm13]

I've done some standard maintenance to get it running better. I also disassembled the carbs, cleaned them out and adjusted the floats. I can borrow a multimeter from work, Where should I put the terminals for the meter on the bike it self to test it? and what would the different readings mean? Is there a guide of sorts out there that can help me out with that? I don't have any prior experience with working on bikes and my car experience is mostly mechanical. I've done a limited amount as far as electrical work is considered in the past.

 

[jsandidge]

Sounds like your bike is not charging. Now that you've tried to jumpstart it with a running​ car's battery, you've likely killed the r/r if it wasn't bad already. Search for BikeCliff's site on your favorite search engine. There are guides there to help test and diagnose what's going on.

 

[cowboyup3371]

Basscliff's site will have a lot of good information (http://members.dslextreme.com/users/bikecliff) while Posplayer's signature block has information you need.

You're going to place the probes on the battery terminals and record the voltage readings at each setting. Let us know what they read. However, like Jsandidge said, you've likely burned up a few electrical components now that you used the running battery - primarily the Regulator/Rectifier and stator. Let's get the readings before giving you any suggestions as to what to do next

 

[posplayr]

Without a running bike, the charging tests will be limited(only can check the battery). Check for spark and fuel.

 

[Ray916MN]

When was the last time the valves were adjusted?

Hard starting is sometimes caused by the loss of valve lash clearance. Valves get held open slightly making starting hard.

 

[ktaylorm13]

I bought the bike back in March and I'm not sure when the previous owner may have done it last. I have some service records I'll go through to see.

 

[Steve]

I bought the bike back in March and I'm not sure when the previous owner may have done it last. I have some service records I'll go through to see.

If you don't know when it was done, it has been too long, so it's time to do it NOW.

When you "cleaned" the carbs, did you do anything besides spritz some carb spray around?
Did you COMPLETELY disassemble the carbs and replace the o-rings? If not, it's time to do that, too.

Once you get the bike running, you can do all the electrical checks.
You might need a new battery, but do the checks first.

.

 

[Ray916MN]

As so often with these threads a lack of clarity on the problem makes me wonder whether suggestions help or hinder.

The bike has a problem starting, but will start with a jump. Does this mean, the problem is the bike cranks until the till the battery is drained and then needs a jump to start, or does this mean the bike barely cranks and needs a jump to start?. The former situation indicates that the battery is likely not the problem. The OP has not indicated how long he typically rides in between trying to start it, so it is possible that the difficulties starting the bike is gradually draining the battery because, the bike isn't ridden long enough to recharge the battery from all the cranking to get the bike to start. The latter characterization, indicates the battery and/or charging system is likely part of or the entire problem.

Good diagnostic technique relies on making sure you have a complete characterization of the problem. Reading into the characterization that the bike is becoming increasingly difficult to start, leads me to believe the OP is basically saying it takes more and more cranking to get the bike to start. Too tight valves generally show up as a hot or warm start problem since heat expansion makes the valves even tighter.

 

[Steve]

Too tight valves generally show up as a hot or warm start problem since heat expansion makes the valves even tighter.

Except in the case of the Suzuki GS series. :-k

Tight valves will make the bike VERY hard to start when cold. After the bike is warmed up, it will be easier and will continue to be easier, as long as the bike is warm. Let it sit for the 8 hours you are at work, it will be hard to start to make the trip home.

And it's not the the GS series, either. My Kaw 1300 did the same thing, as did my son's Yamaha Venture.

.

 

[posplayr]

As so often with these threads a lack of clarity on the problem makes me wonder whether suggestions help or hinder.

Random motion is better than no motion. Any efficiency in diagnosis is largely a function of the OP's abilities.

 

[Steve]

Random motion is better than no motion.

On the other hand, let's not confuse "motion" with "progress". :-\\\

.

 

[posplayr]

On the other hand, let's not confuse "motion" with "progress". :-\\\

.

You are familiar with "random walk"?

https://en.wikipedia.org/wiki/Random_walk

In the "mean", there is progress although there can be instantaneous exceptions to forward progress.

 

[eil]

Your description of the issues sounds like either a bad battery, bad charging system, or both.

You said you bought the bike in March. Did you by any chance mean April? Did you buy it in Michigan? (From me?)