new battery, still slow cranking

[beachbum3478]

i just replaced the battery in my 82 gs1100L today thinking that would solve my slow crank problem, but it only helped a tiny bit. the old battery was def bad, it never held a charge past 12.3, the new one stays at 12.55 to 12.6. i replaced the starter brushes recently too, so i know its not inside the starter. when im at school im going to hook a vat-40 to it and do a starter current draw test and few others. but im curious how many amps the starter is supposed to draw. and what the allowable resistance is for the positive cable to the starter. when i go the crank the bike when its cold it starts right up no prob. but its when its hot is when the bike has trouble starting. like it will start to crank then stop and then slowly go past a compression stroke then it starts spinning the engine enough to get it to fire. all of the connections look good. thats all iv checked so far. so any ideas what else to check. thanks.

 

[paco13]

Does it run hot?
hows the timing?

 

[SPARKSS]

i just replaced the battery in my 82 gs1100L today thinking that would solve my slow crank problem, but it only helped a tiny bit. the old battery was def bad, it never held a charge past 12.3, the new one stays at 12.55 to 12.6. i replaced the starter brushes recently too, so i know its not inside the starter. when im at school im going to hook a vat-40 to it and do a starter current draw test and few others. but im curious how many amps the starter is supposed to draw. and what the allowable resistance is for the positive cable to the starter. when i go the crank the bike when its cold it starts right up no prob. but its when its hot is when the bike has trouble starting. like it will start to crank then stop and then slowly go past a compression stroke then it starts spinning the engine enough to get it to fire. all of the connections look good. thats all iv checked so far. so any ideas what else to check. thanks.

A couple of possibilities come to mind here. First, assuming that the engine doesn't have any mechanical, timing or continuous fueling problems, then you might have a starter with poor bearings, which, when hot and expanded can allow the armature to deflect, dumping torque and maybe even contacting the pole pieces - Did you check the bearings when replacing those brushes?
Secondly, would be that the engine has mechanical issues.....which might even be clutch related, causing high torque requirements when hot (more than the starter is capable of providing). What's the history of this problem occurring and does it coincide with any other recent work done on the engine?

 

[beachbum3478]

iv never checked the timing. im not sure if runs hot. whats the normal operating temp? it runs great, so i dont think theres a fuel problem. i put my finger in the roller pin bearing and turned my finger, and it felt fine. i dont think its the clutch because i always start it in neutral. and since iv had the bike iv dont no engine work besides valve adjustment. bike only has 7000 miles on it.

 

[hampshirehog]

Classic symptoms of worn brushes. However, as you've replaced these I'd check that the brushes are free to move on their springs (no grit in there) and that the armature is nice and clean - polishing with a bit of Brasso does wonders.

 

[SPARKSS]

iv never checked the timing. im not sure if runs hot. whats the normal operating temp? it runs great, so i dont think theres a fuel problem. i put my finger in the roller pin bearing and turned my finger, and it felt fine. i dont think its the clutch because i always start it in neutral. and since iv had the bike iv dont no engine work besides valve adjustment. bike only has 7000 miles on it.

Ok....good info. Only 7000 miles on it (where'd you find THAT!). When it has cranked slowly, has it started? If not, did you boost it (and did it then start right up)? With low miles but quite a few years for a history, it's possible that it's hydrolocking due to the petcock leaking when the engine is shut down but you didn't mention any starting problems once hot, except the slow cranking.
It could also be that you're looking at a heavy current connection or 2 with a little corrosion under it OR even loose, resulting in the slight resistance needed to cause a large power loss to the starter (more noticeable when hot with a tight engine). Note that many (and especially electronic) ignitions fail to produce enough spark when system voltage gets much below 9 volts so if this occurs during cranking you're into double trouble.

Because you mentioned the VAT-40 specifically, I'll guess that you have some auto electrical knowledge, so I'll say that if it were mine, I'd want to monitor battery voltage while cranking and if no problem found then monitor cranking current (clamp type ammeter), cold and hot, AND then check the following voltage drops in the related heavy current circuit - Battery neg to starter housing - Battery pos to solenoid switch - Between solenoid heavy current terminals - Solenoid switch to starter. EACH MEASUREMENT while cranking of course.

Apply a little ohms law for power based on what you found and you will easily see how much power is being dissipated in wiring and connections (and more importantly - WHERE) and will probably find your problem (P=i^2*R).

 

[beachbum3478]

yes the bike starts when it cranks slowly when its hot. i just have to keep hitting the starter button so it gets over the so called hump of the compression stroke. once the starter motor gets some enertia it gets easier to spin the engine to get it to fire. im pretty sure the fuel petcock isnt leaking. i mean when the tank is always off, fuel never comes out of the petcock when i move the tank around in all positions. iv cleaned all the connections. iv only done voltage drop tests with the bike just on, not running. never when the bike was cranking. so i will try that. i have checked the voltage while cranking and it checks out ok. it doesnt go below 11 volts with the new battery. two more questions. what is the normal current draw on a gs1100 starter. and what wire is the battery neg to starter housing? isnt the starter grounded through the case? thanks for the help.

 

[SPARKSS]

yes the bike starts when it cranks slowly when its hot. i just have to keep hitting the starter button so it gets over the so called hump of the compression stroke. once the starter motor gets some enertia it gets easier to spin the engine to get it to fire. im pretty sure the fuel petcock isnt leaking. i mean when the tank is always off, fuel never comes out of the petcock when i move the tank around in all positions. iv cleaned all the connections. iv only done voltage drop tests with the bike just on, not running. never when the bike was cranking. so i will try that. i have checked the voltage while cranking and it checks out ok. it doesnt go below 11 volts with the new battery. two more questions. what is the normal current draw on a gs1100 starter. and what wire is the battery neg to starter housing? isnt the starter grounded through the case? thanks for the help.

I don't know what the "normal" starter current will be for your engine, but suspect that 50-80 amperes wouldn't be out of line. This data is often unpublished. Use terminal voltage vs cranking rpm (acceptable performace) as your main guide. As a guide, many engines start best when cranked at least 150 rpm or so.

Sounds like you're progressing logically - You could start your voltage testing as you did with noting the battery terminal voltage (I assumed this is where you tested).....and then noting what it is between the starter terminal and case. This brings up your last question on info I should have clarified. Yes the battery neg cable goes to the engine/trans case but when you look at this drop, put your meter neg lead right on the starter case - reason here (lots of experience) is that many times I've seen the starter mounting corroded (not necessarily on bikes)....and sometimes even the through bolts or between case sections corroded. Remember that the negative circuit actually runs right to the brush holder....often this relies on good current transfer though the starter case sections which includes any though-bolts.

Quite a few times over the years I've found a significant voltage drop between one end of a starter case and the other or to the block etc - I think you'll understand this. Quite often this is overlooked as the appearance of good continuity can be deceiving due to corrosion or looseness.

 

[DanTheMan]

One thing that has not been mentioned here, is, on many of these bikes (and small cars as well), if the clutch is NOT disengaged while starting, and it's a bit chilly the clutch friction will drag the starter down and cause excessive current draw. Try starting it with the clutch handle pulled all the way to the handlebar, I think it'll crank more easily there.

 

[82Shafty]

i just replaced the battery in my 82 gs1100L today thinking that would solve my slow crank problem, but it only helped a tiny bit. the old battery was def bad, it never held a charge past 12.3, the new one stays at 12.55 to 12.6. i replaced the starter brushes recently too, so i know its not inside the starter. when im at school im going to hook a vat-40 to it and do a starter current draw test and few others. but im curious how many amps the starter is supposed to draw. and what the allowable resistance is for the positive cable to the starter. when i go the crank the bike when its cold it starts right up no prob. but its when its hot is when the bike has trouble starting. like it will start to crank then stop and then slowly go past a compression stroke then it starts spinning the engine enough to get it to fire. all of the connections look good. thats all iv checked so far. so any ideas what else to check. thanks.

Maybe heat has weakened the magnets... My dad's 82 Gs1100GL was the same way and his bike only had 10G miles on the clock. We through in a reman and no more problems.

Check starter case to battery ground for a voltage drop when cranking as was stated earlier.

Check voltage drops on the wires both neg and pos, starter solenoid, and again starter case to battery ground.

I don't have an inductive clamp to measure the amps on my bike otherwise I would perform starter amp draw test for you.

 

[beachbum3478]

ok thanks guys. if it does happen to be the heat hurting the starter until it cools down. i was thinking it wouldnt hurt to make some kind of mini air scoop and have a tub run into small hole in the starter cover with a breather inbetween. maybe that will keep the starter cool enough for now till i have the money to get a new starter. assuming there is no voltage drop or resistance issues.

 

[twistedwankel]

ok thanks guys. if it does happen to be the heat hurting the starter until it cools down. i was thinking it wouldnt hurt to make some kind of mini air scoop and have a tub run into small hole in the starter cover with a breather inbetween. maybe that will keep the starter cool enough for now till i have the money to get a new starter. assuming there is no voltage drop or resistance issues.

It is a simple matter to remove the starter and clean out all the carbon left in there. Clean off the armature too with rubbing alcohol while you/re at it.

Then replace the bullet connectors from the alternator with spades. Recharge the battery.

You will not have any more problems with the starter There will always be a sluggish spot in the stater when really hot but if you hit the button a second time it will go away

If were perfect it wouldn't be 27 years old. Would it?

 

[beachbum3478]

yea iv cleaned the starter out pretty good when i replaced the brushes. ill def get on changing the bullet connectors with spades this week sometime. thanks.