Stumped starting issue

[Guest]

So I'm going to start from the beginning. I hope someone out there can help me. I have an 81 GS650G. It was in the garage for 10 years. Needed a motor. Replaced it. Cleaned carbs and replaced jets, seals, etc. motor was getting fuel but no spark. Bought Dyna S unit and now have spark and fuel but still hard to start. It's 5C/40F here and I have to pull choke out all the way to get it just to sputter. After doing this for mang attempts it'll eventually idle for a few seconds. Then on and on we go. Eventually she's run and runs well. But when I turn it off and try yo start it again the battery is dead. Thoughts? Suggestions?

[azr]

Well it could be a multitude of many things really. I'll take a stab in the 'hay stack' and guess there's something wrong with the engine....... all kidding aside, did you pull the engine apart or just install? did you check the valve clearances? did you check to make sure the cam timing is correct? are you positive the timing is correct?

[awilchiwsky]

I just put the engine in. It was running. But I had to install my carbs and electronics. I suppose I could check valve clearances. I'll verify timing too latwr this week. The other issue is a non-functional tachometer cable. Waiting for the replacement to arrive.

[azr]

Well if you personally know it was running fine before then there shouldn't be any issue's with the cam timing. It would be good prudence to check the valve clearances though and you can verify the cam timing while you're in there to make sure. Make sure you post back the results. The fact that you can eventually get it to run kind of make me think that either your valve clearances are wayyy off or your carbs are way out of synch. Did you do a good bench synch on the carbs when you finished putting them together?

[chuck hahn]

At 40 it should take choke to start and some choke for a while so it will warm up and run off choke..so I would say thats about par for the course. May stil need a little fuel adjustment with the screws at the top rear of the carbs..try anither 1/4 turn out to richen it a tad more.

As for the electrical. Is the battery new or old..and if old..how old? Is it a regular one that you can add water to or sealed? if regular, is it full to between the lines? If not, refill it with some battery acid from the parts store and fully charge it.

Now that a battery is fully charged, get your multimeter out and set it to DC volts and start the bike. put eh probes on the posts and see what it reads when revved to around 4,000. Should be around 13.8 to 14.2 volts. If not..what is it? May be a regulator or it could be the stator is failed.

[awilchiwsky]

I'll have to look at the Carb sync I guess. Battery is under a year old. Once the new tach cable arrives I'll check voltages. That's everyone for the advice. I'll get back with results.

[Sandy]

Also make sure you're not opening the throttle when using the choke as then the choke doesn't function as it should.

[tom203]

If you had to install your first set of carbs, how did you know this replacement engine was/is a runner? That aside, sounds like your "choke" circuits are clogged- if you got spark,a little extra fuel, it should fire up even if it then idles poorly. Yes, check valve clearances- and might as well check cam to crank timing while you have camcover off.
Make sure your fuel tank is reasonably clean after 10 years of idleness.

put your location in your signature, might be member close by

[robertbarr]

In a case like this, I'd use ether as a diagnostic. If it lights up OK with a good shot of ether into the intake snorkel, you've pretty much found your culprit.

[Nessism]

Is the airbox w/air filter installed snuggly so there are no air leaks anywhere?

Did you fully break down the carbs and clean them properly, or did you just spritz them out and install aftermarket "carb kits"?

[trippivot]

electrical section - slap on a dyna and get spark - great -- now here is a simple question = is it happening at the correct time? I doubt it ... simple test put a spark plug in one wire and turn the engine with a socket- you want it to snap a spark at the "F" mark. 1/4 and test 2/3 very prudent to check both ignition events are "in time" at the F for fire

carbs are simple - anyone can tear them apart and reassemble perfectly. not.

- after replacing the bad battery and spark verified - your problem will be isolated to the other 2 categories
#1 compression 60 or more will run
#2 fuel and air mixture
#3 timed ignition (electrical)

[awilchiwsky]

Timing is spot on. I've verified with my timing gun after setting up with a simple light bulb. Even the advance is working. Now could it have something to do with the stator only generating 7V at 5000rpm and the rectifier having open circuits when it should have voltage during the diode test? Please understand that the motor runs strong and well once started. It just dies out once the battery dies and is difficult to start.

thanks,
tony
81 gs650g

[tom203]

"....or runs strong and well once started. It just dies out once the battery dies and is difficult to start. "

Well, yeah! With fully charged battery, should run about 3/4 hour with headlight on and no charging output- way shorter if you have to do lots of cranking.
sounds like your AC stator test says stator is no good- make sure you test your meter setting on AC house outlet to avoid meter reading errors.
testing r/r rectifying diodes is easy on shunt versions- is this what you have?

[awilchiwsky]

Tested stator on AC volts. Definitely going. Not sure what you mean by shunt version.

[Steve]

"Shunt version" is the stock R/R (rectifier/regulator). Many of us have upgraded to a "series-style" R/R, such as the ones offered by Polaris or Compufire.

I have not tested one yet, but I would think that the diodes in a series R/R should also be capable of being tested.

.