Yamaha TRX850 Enthusiasts Forum

I do love my TRX but it's desperately trying to annoy me at the moment, What with the brake disc bolts debacle and a couple of other niggles.

Problem now is the charging system. The story so far,

A couple of weeks ago I left the bikes ignition on which completely killed the battery. Trickle charger wouldn't touch it so charged it using a fast charger. All seemed ok, held a charge and started the bike fine a couple of days latter. Took the bike out for a run (daylight no lights on) stopped to get petrol and the battery was flat. Bumped started it and rode home.

Bugger thinks me the battery is shot, so fit a nice shiny new battery. Two days later took it on a track day at brands (christ they jump when the sidestand decks). On the third session the bike was a bit sluggish starting but thought it was just a bit hot and bothered.

On the way home (with lights on) came to a junction and the bike stalled (thought I had run onto reserve). Again battery flat, bump started it pulled away tried to put lights on and the bike started coughing and spluttering. Turn off lights and it run ok. The bike them got progressively worse on the run home.

Checked with a meter, and the battery after charging showed 12.9v turn on engine and I've got 13.8-14.2 (some fluctuation) across the battery, rev to 5000 and figure drops to 13.0-13.4. looked at rectifier and noticed one of the prongs in the connector block had overheated and melted part of the connector, Dropped spare rectifier on and got the same readings.

Checked continuity across the 3 white wires from the alternatror and got a reading of 0 (my only problem is Im not convinced i'm usoing my meter correctly as the manual says omh +1 and my meter goes from 20 to 2000K)

Checked and cleaned all connectors

Now the question!!! do you think my alternator is shot given the info above and if yes has anyone got one for sale and if not does asnyone know which alternator coils other than TRX would fit.

Cheers all Tony

battery is fecked

Its a brand spanking new battery.

Charge the battery up, leave disconnected, check voltage, leave it for about 3 days, check voltage again. That will tell you if you have a duff battery. Is it sealed, if not check the electrolite levels. If its holding the charge, check the wiring look for earthing spots and make sure that the battery terminals are clean. If all appears ok then you are onto the charging side of things. It does sound like the alternator TBH as I had the same problem on my old Triumph. Look in the yellow pages for motor rewinders, ask them if they can rewind your alternator, otherwise its a trip down the breakers.

Dave E

Been through all the battery checks and can happily say the battery is fine. I stripped the loom completely off the bike cleaned and contact lubed all connections, checked for chaffed wires etc so dont think a lose or poor connection is the issue.

I think I agree with you that the stator coil is naffed. Anyone on the site got a spare? If not and I have trouble sourcing a second hand one does anyone know od a stator coil of a different bike that would fit?

a new battery does not mean it isn't fecked

I'm not sure the alternator is the issue. the bike is charging is it not? at least it would suggest it is given the meter readings you have taken across the battery? and you are getting the correct readings (0) from the alternator wires

so how have you drawn the conclusion the alternator is shot?

simple and old check - leave the bike idling, put on headlights and now rev the engine. is the front light getting brighter?

the symptoms you are describing point to the RR - but as you have tested 2 of them I'm stumped

can you do me a favour - take readings across the battery at idle and then at 5000 rpm. then hold it at 5k for about 1 min - do the readings change / go down?

Athud,
Having recently chucked my bike down the road and put a hole in the alternator casing, I got another second-hand one which had all the 'gubbins' inside it, so if thats what you need, I've got spares.
Dunno much about electrics on bikes, so not sure if this is what you want: inside the alternator casing there is a big coily thing with a magnetic thing with wires close by, and then a big toothed sprocket thing too, all screwed into the casing.
Dave

trixynut wrote:Athud,
Having recently chucked my bike down the road and put a hole in the alternator casing, I got another second-hand one which had all the 'gubbins' inside it, so if thats what you need, I've got spares.
Dunno much about electrics on bikes, so not sure if this is what you want: inside the alternator casing there is a big coily thing with a magnetic thing with wires close by, and then a big toothed sprocket thing too, all screwed into the casing.
Dave

yes Dave - tthe big coily thing is what he wants

phuk72 wrote:a new battery does not mean it isn't fecked

I'm not sure the alternator is the issue. the bike is charging is it not? at least it would suggest it is given the meter readings you have taken across the battery? and you are getting the correct readings (0) from the alternator wires

so how have you drawn the conclusion the alternator is shot?

simple and old check - leave the bike idling, put on headlights and now rev the engine. is the front light getting brighter?

the symptoms you are describing point to the RR - but as you have tested 2 of them I'm stumped

can you do me a favour - take readings across the battery at idle and then at 5000 rpm. then hold it at 5k for about 1 min - do the readings change / go down?

I'm pretty happy that the battery is ok (held full charge for 4 days with no drain-off). According to the workshop manual there should be a resistance of 0.22-0.32 across the stator contacts not 0.00.

I will have a check as you suggested above tonight and post back the outcome. What should I get?

trixynut wrote:Athud,
Having recently chucked my bike down the road and put a hole in the alternator casing, I got another second-hand one which had all the 'gubbins' inside it, so if thats what you need, I've got spares.
Dunno much about electrics on bikes, so not sure if this is what you want: inside the alternator casing there is a big coily thing with a magnetic thing with wires close by, and then a big toothed sprocket thing too, all screwed into the casing.
Dave

You have PM Dave

AHTHUD wrote:

phuk72 wrote:a new battery does not mean it isn't fecked

I'm not sure the alternator is the issue. the bike is charging is it not? at least it would suggest it is given the meter readings you have taken across the battery? and you are getting the correct readings (0) from the alternator wires

so how have you drawn the conclusion the alternator is shot?

simple and old check - leave the bike idling, put on headlights and now rev the engine. is the front light getting brighter?

the symptoms you are describing point to the RR - but as you have tested 2 of them I'm stumped

can you do me a favour - take readings across the battery at idle and then at 5000 rpm. then hold it at 5k for about 1 min - do the readings change / go down?

I'm pretty happy that the battery is ok (held full charge for 4 days with no drain-off). According to the workshop manual there should be a resistance of 0.22-0.32 across the stator contacts not 0.00.

I will have a check as you suggested above tonight and post back the outcome. What should I get?

ok - I'd have expected a reading of 0 across the 3 wires going into the RR (but if the manual says 0.22 to 0.32 I guess that must be right)

the reason I suggest holding the revs open is because the RR may break down under load which would explain why a perfectly good battery isn 't giving you enough juice after you've been riding for a bit. if the RR is fecked, the reading will gradually drop to under 13

phuk72 wrote:

AHTHUD wrote:

phuk72 wrote:a new battery does not mean it isn't fecked

I'm not sure the alternator is the issue. the bike is charging is it not? at least it would suggest it is given the meter readings you have taken across the battery? and you are getting the correct readings (0) from the alternator wires

so how have you drawn the conclusion the alternator is shot?

simple and old check - leave the bike idling, put on headlights and now rev the engine. is the front light getting brighter?

the symptoms you are describing point to the RR - but as you have tested 2 of them I'm stumped

can you do me a favour - take readings across the battery at idle and then at 5000 rpm. then hold it at 5k for about 1 min - do the readings change / go down?

I'm pretty happy that the battery is ok (held full charge for 4 days with no drain-off). According to the workshop manual there should be a resistance of 0.22-0.32 across the stator contacts not 0.00.

I will have a check as you suggested above tonight and post back the outcome. What should I get?

ok - I'd have expected a reading of 0 across the 3 wires going into the RR (but if the manual says 0.22 to 0.32 I guess that must be right)

the reason I suggest holding the revs open is because the RR may break down under load which would explain why a perfectly good battery isn 't giving you enough juice after you've been riding for a bit. if the RR is fecked, the reading will gradually drop to under 13

Had a check last night.

Turned on lights with the engine at tick over, revved it and the lights stayed at the same intensity. held the bike at 5000 rpm (that cheered up the neighbours ) the multi meter reading held a steady 13.8v

Trixynut can sell me a alternator coil so will get that and see what happens.

strange that the alternator would be charging the battery but that the power isn't being sent to the lights?

Pete it is trying to charge the battery, unfortunately being of the Monty Python parrot sketch it isnt capable of putting enough charge through and powering ancillery components as well.

Dave E