Bike wont start
 

The last few weeks the battery has hardly had the power to turn the engine over fast enough to start it.

I assumed (probably wrongly) that the battery was past it's best so I bought a new one, followed the instructions regarding filling with the dilute acid and put on a slow 12 hour charge.

Using the multimeter I just bought the old battery was putting out the same volts as the new battery so not surprisingly the new charged battery wont start the bike either, it seems fully charged but can hardly manbage to turn the engine over.

It used to start straight away.
Lights are not on and I don't have anything on permanently like an alarm that could drain the power.

Any suggestions?

Dodgy brushes in the starter motor or dirty commutator can cause these symptoms. You could get an Auto Sparkie to take a look at the starter.

I am new to this area and a bit isolated so don't know any mechanics in the area.

In the parts catalogue is the starter motor listed as "Generator"?

Under the electrical section in the catalogue, ignitor unit assembly, ignition coil assembly, rectifier and regulator assembly are listed but not starter motor or commutator.

Start with the easy things.

So you know the battery is working. Good.

It should be easy enough to check the spark plugs are working too. Pull out one spark plug. Check that it is clean. Now with the spark plug out of the engine but connected to the distribution cable, turn over the engine. Keep an eye on the spark plug to see if you get a spark. If not then clean it with a wire brush or sand paper and try again.

After the spark plugs check the starter motor. This can be tricky especially if you don't know what to look for, try a continuity check first then second take off the starter and investigate.

Next would be a solenoid problem or possibly Carb??? I'm getting out of my depth. Check general health of the electrics for any obvious corrosion or burnt out components.

Good luck.

Yes the battery is good but even on full charge the engine turns over very slow.

The spark plug is clean and sparking well.

I have followed the leads and connectors leading from the battery and all are clean dry and corrosion free.

I don't know where the starter motor is, is is where the black negatice battery lead goes to? If so it's a bit awkward to get to.
What am I looking for if and when I get inside the starter motor?

the battery was always a bit weak for the engine in XTs, could do with a decompressor!

My enigne turned over for several minutes when my starter relay got stuck, so i beg to differ =)

How many volts does you're battery hold, after it has stood overnight without a charger? (both of 'em) They should be well over 12v.

does it drop the battery volts right down (like 8v) when you are turning it over? either use a bulb to check it (sidelight?) or a multimeter. If so, then it has something restricting the starter motor turning.
If the volts on the battery stay high whilst the motor is struggling, then something is restricting the current flow, like a bad joint on the earth cable (most common) or a corroded cable, muck on the brushes, etc

Jens, the new one was disconnected last night and the old one is in a box.
Both batteries are holding 14 volts according to my multimeter.

Joe, I turned the engine over and the volts drop to around 6 or 7 while the starter button is depressed , then back upto 14 when I let go of the button.

All joints look clean and corrosion free, the thick plastic covering of the leads are perfect so I assume from the test that something is restricting the starter motor turning.

As you can tell I am inexperienced with working on bikes, I can change tyres, sprockets, exhausts but have not worked on the engine before except to fit a spark plug, oil change etc.

I assume the starter motor is where the black negative battery lead goes to?
See Pic, looking from right side of bike in betweeen headers and rear brake reservoir.

Reading through the workshop manual electrical starting system there is a set of procedures for if the starter motor does not operate.

Checking continuity on the fuse

Check the battery condition (I know this is good)

connect starter motor cable and battery positive terminal using jumper lead

Disconnect starter relay coupler, connect battery and frame to starter relay coupler with jumper leads

Test main, engine, sidestand, neutral, start and clutch switch

Not sure how much of that I will be able to do with my limited knowledge.

There is also an exploded diagram of the starter, instructions on how to dismantle and reapir.
Thing is I don't really know what I am looking for with regards to the Commutator, Mica and armature coil not ever having inspected one before to compare with.

I would buy a new starter motor but would hate to find out that is not the problem like I did with the battery.

By process of illimination you should be able to get to the source of the problem by crossing things of your list (above) as you go.

Have you checked the fuses? Visual inspection is usually enough but if you're unsure you can set your multimeter to Resistance (infinity symbol) and put +ve & -ve on each end of the fuse. If there is no resistance ( high read ) then the fuse is ok. Just test is on a piece of wire first. BUT don't put the Multimeter on anything with voltage in this setting, it might blow the internal fuse (if it has one!) or worse.

If you get to illminating everything but the starter then follow the instructions in the manual for the starter motor re cleaning and repair. If you don't feel confident then try to get your hands on a second hand one or refurbished one that you know is working and swap them over (this could be a friends bike if he lets you :smartass:).

The test procedure in the manual uses a process of elimination to find the faulty component. The fact that the starter actually turns means that it can only be the starter, the starter relay, the battery or the cables between them. Forget about all the other switches, they're clearly OK.
If you try step 1 and the starter cranks properly then it's clearly OK. If you try step 2 and it all works OK then it's the relay. You could possibly use one of those small cheap sets of jump leads for these tests. They're rubbish for starting cars but will have no problem with a bike. If you use leads that are smaller than the ones on the bike, then you'll just confuse things.
One thing that bothers me is the voltage you say you're getting from the battery. A resting, well charged, disconnected battery will give a maximum of 12.8-12.9 volts. On cranking, the voltage should drop by 2.0-2.25 volts. I've just checked my bike and these are the figures: resting 12.6v, cranking 10.4v. You've either got a miracle battery :innocent: or a strange volt meter.
The problem when trying to diagnose this fault is that you could have a starter that's become very resistive, which will take a heavy current draw and result in a low battery voltage on cranking, or a starter that's shorted out across its windings and will therefore take less current and result in a higher than normal cranking voltage. As suggested by my test, a healthy starter will produce a voltage difference of just over 2v.
So here's my suggestion. Check and clean all cables between the battery and the starter, ESPECIALLY the earth side. Make sure the starter securing bolts are tight. Run the first two tests described in the manual. Oh yeah, use a decent meter.
Good luck!

Geoff

Thanks both for the replies, I appreciate it.
I have to visit family over the weekend but will have a go Monday and report back.

It is a new multimeter and it is the first time I have ever had the need to use one. It was not very expensive and it's hard to get an accurate reading on the 10-50V scale. But it is certainly dropping by way more that 2 volts on cranking.

So I will check all cables between battery and starter again, make sure starter securing bolts are tight, run the first 2 tests.

If no luck I will take the starter motor off and try to take apart and clean.

I did ring Fowlers and a new starter motor is £334 + VAT
Brush set is £59 +VAT Armature Assembly £326 +VAT

I can't afford a new starter motor or armature assembly so if I can't get it going I will have to think about scrapping the bike.

I checked and cleaned all cables between battery and starter.
The starter securing bolts were tight.

I had a go at the 2 tests but failed miserably, I am sure I was doing it wrong due to misunderstanding.

So I took the starter motor out, there is lots of fine black dust everywhere inside.
I plan to clean it with acetone, is it safe to sand inside the yoke with number 600 grit sandpaper?

Following instructions in the manual regarding inspection and repair.
I need to buy some 600 grit sandpaper to clean the commutator.
I measured the commutator at 28.5mm, the wear limit is 27mm so it has some life left.

The mica is supposed to have an undercut to ensure proper operation of the commutator, it has not, it is flush.
So I need to undercut the mica to 0.7mm, it seems quite a hard material, what is the best way to trim/shave the mica off?

Just those 2 questions for now.

Why use the sandpaper, acetone or even brake cleaner should get all the dust off and leave the surface free of residue. If there is rust and you want a nice shiny contact then yes probably it's ok.

A dremel tool? Can you post pictures?