R90S - starter motor, intermittent engagement

[tiktok]

Whilst I have the tank off and am going through my newly acquired R90S (1976/80k miles), I wanted to ask for an opinion on the starter motor.

There is an issue, in that the starter motor does not always engage (maybe 1/3 of the time). For clarity - the motor spins, but the engine does not turn.

Obviously this will need addressing, but I wanted to ask: is it better to repair or replace the starter motor?

There is a place in SE London who can rebuild the starter, but unless original items are particularly valuable, I'm not sure it isn't easier to buy a replacement, once you factor in shipping and repair costs.

Thoughts?

 

[Bubb]

Nissan denso starter …… lighter than the original, and better made.

 

[tiktok]

Nissan denso starter …… lighter than the original, and better made.

Cheers - I'm sure they are good, but at nearly £400 they are a bit punchy.

 

[Wapping]

is it better to repair or replace the starter motor?

You say the starter motor spins, but fails to engage one time in three.

On the one in three times, does the starter motor spin, but simply fail to turn the motor over? If yes, then why replace the starter motor, as the problem maybe lies elsewhere.

BMW 1600’s had a similar problem, which was caused by the sprag clutch. The starter motor was fine.

 

[tiktok]

You say the starter motor spins, but fails to engage one time in three.

On the one in three times, does the starter motor spin, but simply fail to turn the motor over? If yes, then why replace the starter motor, as the problem maybe lies elsewhere.

BMW 1600’s had a similar problem, which was caused by the sprag clutch. The starter motor was fine.

I suspect any issues will likely lie within the starter motor assembly, given what I understand of the design and the use of a Bendix gear. Happy to be corrected.


I could strip down the starter, replace the brushes, Bendix gear, overhaul etc - but is it worth it?

 

[Wapping]

Forgive me, different mechanism.

 

[DrFarkoff]

@tiktok just remove the starter and get it serviced


Or just Buy a later Valeo type get the pinion changed to 8 tooth if required usually the starters come with 9 tooth but earlier Heavy flywheel Airheads usually had an 8 tooth

 

[theoneandonly]

i'll do you a favour ,
to save what little hair you have ,
i'll come down next week with the trailer ,
and take it away , £ 1000 enough ?

 

[tiktok]

i'll do you a favour ,
to save what little hair you have ,
i'll come down next week with the trailer ,
and take it away , £ 1000 enough ?

I think you meant to type a larger number in there...

Why don't you come down and help me get it running instead...

 

[mikeyboy]

if the starter is spinning,that would suggest the solenoid is moving and enabling the high current contacts to connect.
This would also suggest that the drive gear is moving to engage on the ring gear.
So I think the ring gear needs to be checked first.
If the ring gear is ok ,the starter clutch and actuator fork need looking at.
Hopefully the ring gear is ok as early flywheels can be hard to come by.

 

[theoneandonly]

I think you meant to type a larger number in there...

Why don't you come down and help me get it running instead...

nope that was a big enough number .
if you really are up shit creek , i'm going to Ramsgate on , i think the 12/13th Sept.
( i'll bring cash !)

 

[tiktok]

nope that was a big enough number .
if you really are up shit creek , i'm going to Ramsgate on , i think the 12/13th Sept.
( i'll bring cash !)

I’ll keep you posted. All the best.

 

[Gelandestrasse]

As Mikeyboy says, have a look at the starter motor. Take it off and judge how corroded the components are that engage with the flywheel. And check the flywheel teeth for excessive wear. A photo posted here (if you can) can let others help you judge the flywheel teeth.

 

[tiktok]

if the starter is spinning,that would suggest the solenoid is moving and enabling the high current contacts to connect.
This would also suggest that the drive gear is moving to engage on the ring gear.
So I think the ring gear needs to be checked first.
If the ring gear is ok ,the starter clutch and actuator fork need looking at.
Hopefully the ring gear is ok as early flywheels can be hard to come by.

Much appreciated.

 

[tiktok]

if the starter is spinning,that would suggest the solenoid is moving and enabling the high current contacts to connect.
This would also suggest that the drive gear is moving to engage on the ring gear.
So I think the ring gear needs to be checked first.
If the ring gear is ok ,the starter clutch and actuator fork need looking at.
Hopefully the ring gear is ok as early flywheels can be hard to come by.

I was able to capture some footage of the ring gear and the drive gear. I would appreciate a second opinion on what an "acceptable" level of wear looks like and if either must be replaced. Thanks.

 

[tiktok]

Sanity check please - this is what I hear when the starter does not engage. I have removed and lubed the shaft. it's an old Bosch unit.

Voltage drops from 12v to just under 10v.

 

[tiktok]

Bumping this thread as I havent resolved the issue.
Fitted a new battery - no difference, the issue persists.
I removed the starter motor, loosened the casing and blew out the interior with an air line, I did not do a full strip down.
The brushes looked fine, the solenoid engages, but the motor wasn't spinning.

Apart from fitting a new +ve cable, I'm unsure what else I can do, before replacing the item.

 

[Stirlingmoz]

I think that starter motor is actually engaging on the first press. It’s just not firing up instantly. You can peek at the flywheel to confirm via the rubber ignition timing bung.

My /5 bikes (with Bosch starters and CV Bings) rarely fire on the first press, especially if I haven’t used them for a while.

They seem to treat that initial spin over as a ‘prime’ and fire up readily (no throttle but full enrichener) on the second spin over.

As you have Dellortos, from cold, I think you set full choke, twist the throttle fully a couple of times with the engine off to squirt some fuel (they’re not called pumper carbs for nothing) and then press the starter.

Bosch starters make a very different sound if they are spinning without the solonoid throwing out the gear and engaging.

Are you still running points ignition ?
Nothing wrong with it - I like points - but condition, gap and timing are key to a good fire up.

I didn’t see or hear anything concerning in that video

 

[tiktok]

I think that starter motor is actually engaging on the first press. It’s just not firing up instantly. You can peek at the flywheel to confirm via the rubber ignition timing bung.

My /5 bikes (with Bosch starters and CV Bings) rarely fire on the first press, especially if I haven’t used them for a while.

They seem to treat that initial spin over as a ‘prime’ and fire up readily (no throttle but full enrichener) on the second spin over.

As you have Dellortos, from cold, I think you set full choke, twist the throttle fully a couple of times with the engine off to squirt some fuel (they’re not called pumper carbs for nothing) and then press the starter.

Bosch starters make a very different sound if they are spinning without the solonoid throwing out the gear and engaging.

Are you still running points ignition ?
Nothing wrong with it - I like points - but condition, gap and timing are key to a good fire up.

I didn’t see or hear anything concerning in that video

The whirring sound is now happening almost continually, and often the motor won’t crank at all. Timing’s likely a factor, but I’m having issues in that regard, which I will document separately.

 

[Gelandestrasse]

Just judging on the video and photos, the starter is turning the engine over each time and the level of wear is 'normal' and should not be of too much concern (I've seen worse). I think the first go at starting, where the starter disengages and 'whirrs' is not that usual (it seems the engine might fire, spin fast and chuck out the starter pinion, but then fail to start. Look at your timing.

On a different point, I tried to count your starter pinion teeth - counted 8. For your vintage it should be 9. I could have counted wrong. Also you may have a flywheel suited to an 8-tooth starter (unusual). If your starter and flywheel are mismatched then that could be an issue (I don't know the symptoms of this as have never come across it before.

And finally, does your starter have the front triangular steady bracket?