Alternator question

[tomo]

I`m going to make myself look really stupid here, but electrickery has never been my strongpoint !. If you`ve read my previous postings, you`ll know about my GS750 starting problems. Carbs are getting fuel ok, spark at plugs ok (although not what I`d call a fat blue spark). Compression is low so I think I`ll need to take the head off, but before doing so want to check all possibilities. Daft question then.....would a dodgy alternator have any effect on starting. I`ve always thought that on starting the power is drawn direct from the battery, but like I said I am not electrically minded so thought I`d ask. I know that a spark at the plug in open air does`nt mean for sure that it will happen in the cylinder. The battery is fully charged, but I did wonder whether the starter might be drawing its power from there with not enough left over for a good spark at the plugs. I guess I`m clutching at straws here, but thought I`d fire off the question anyway !.

[Dink]

First things first. All Suzuki's (including the new ones) use stators (AC current s generated, and then rectified to DC) not altenators (DC current generators)
The most important issue is the weak spark, if it doesnt look strong in the open air it will be even weaker under compression. So you need to check that the coils are receiving 12 volts AT ALL TIMES!!! i.e. with the ignition on; motor not running, during start up etc.
The regulator/ rectifier is a weak point on these bikes!!!!
If you go to the home page look for "The stator papers" and run through them, them check clean and tighten EVERY earth on the bike, add an extra one from the rec/reg directly to the negative post of the battery.

Dink

[Boondocks]

First things first. All Suzuki's (including the new ones) use stators (AC current s generated, and then rectified to DC) not altenators (DC current generators)
The most important issue is the weak spark, if it doesnt look strong in the open air it will be even weaker under compression. So you need to check that the coils are receiving 12 volts AT ALL TIMES!!! i.e. with the ignition on; motor not running, during start up etc.
The regulator/ rectifier is a weak point on these bikes!!!!
If you go to the home page look for "The stator papers" and run through them, them check clean and tighten EVERY earth on the bike, add an extra one from the rec/reg directly to the negative post of the battery.

Dink

I think this has been covered before, but there is still a misunderstanding. All Suzukis use alternators. All alternators generate AC voltage/current, not DC. AC stands for alternating current, thus alternator. All AC (alternator) and DC generators have stators and rotors as their component parts.

A DC generator uses a commutator and brushes to keep current flowing in the same direction. A starter motor is a DC generator in a reverse application. Instead of turning a generator to create DC current, DC current is applied through the brushes and commutator to turn the starter motor.

See Electrical Generator - AC or DC and Electrical Generator for more information.

[Boondocks]

I`m going to make myself look really stupid here, but electrickery has never been my strongpoint !. If you`ve read my previous postings, you`ll know about my GS750 starting problems. Carbs are getting fuel ok, spark at plugs ok (although not what I`d call a fat blue spark). Compression is low so I think I`ll need to take the head off, but before doing so want to check all possibilities. Daft question then.....would a dodgy alternator have any effect on starting. I`ve always thought that on starting the power is drawn direct from the battery, but like I said I am not electrically minded so thought I`d ask. I know that a spark at the plug in open air does`nt mean for sure that it will happen in the cylinder. The battery is fully charged, but I did wonder whether the starter might be drawing its power from there with not enough left over for a good spark at the plugs. I guess I`m clutching at straws here, but thought I`d fire off the question anyway !.

The alternator doesn't have any effect until the engine starts. If your battery is fully charged, the alternator (good or bad) would have no effect on starting.

[chef1366]

Thanks Phillip. I always learn something from reading your posts.

[Boondocks]

You're very welcome, Bill. Thanks for the kind words.

[tomo]

Thanks everyone, I suspected the alternator would`nt play a role in starting, but just needed the confirmation. Oh well, looks like I`ll have to dust off the spanners, get the wife some chocolates and vanish into the garage to start stripping the cylinder head !.

[Dink]

Thanks everyone, I suspected the alternator would`nt play a role in starting, but just needed the confirmation. Oh well, looks like I`ll have to dust off the spanners, get the wife some chocolates and vanish into the garage to start stripping the cylinder head !.

Why do you need to strip the cylinder head to check the voltage at the coils??

Dink

[sissonk]

In regards your starting problem . I once went through what you have only to find that the vacumm line to the petcock was broken . as some as i fixed it off it started . on my bike I took all the grounds around the center of the bike and connected them all by extending wires to one ground lug and used a star washer . The coils can lose alot of their performance from a bad ground.

[Steve]

Also before you strip the head, check the valve clearances on a cold engine. The specified clearance is VERY SMALL for these engines, so it does not take very much to keep them from closing completely. If the valves do not close completely, compression will be low and it will be hard to start.

The specs on my 650 and my 850 call for .001" to .003" on all valves, and I imagine that your 750 is probably the same. Setting them toward the larger side of the tolerance will assure that the valves are closing and will extend adjustment intervals. The minimal extra noise is not noticed once on the road.


.

[tomo]

Thanks for the advice. I`ll check out connections again and the valve clearances before I look at the head. Dink, I did`t mean I was taking the head off to check the alternator. Its just that I`ve checked all the electrics and fuel system and they seem ok but she still won`t fire up. I was just asking about whether the alternator might affect starting if it is dodgy. I think I need to whip off the head to check the valve seats and bores because the compression is pretty low.

[Dink]

Weak spark will have a huge effect on starting,fix that first. Then check valve clearences. What were your compression readings??

Dink

[tomo]

Compression readings if I remember right were 55, 55, 65 & 75psi. I dropped a bit of oil in each pot but it only improved the compression by a few psi. Just checked the spark plugs again, not sure about the spark produced. Can see it in daylight ok but I would`nt describe it as a fat blue spark.

[Dink]

Forget everything we said pull the motor apart and bore it out oversize, fit new pistons and rings,whilst you are ibnthere check out your gearshaft bearings.

Dink

[chef1366]

Did you check compression with throttle fully open? When warm?
If it only rose a little after adding oil then it's head troubles.