Ring Gear/Starter Motor

[CONCRETE24]

Hi,

I know there have been a few posts about starter motors in the past, but I haven't been able to get to quite the info I need, so any advice appreciated!

About every other time I start my 6 I get a horrible 'graunching' noise that sounds like the starter is not engaging the ring gear properly. This raises a few questions for me as I am due to drive to Le Mans in it in June and would like it to be as sorted as possible by then;

 

1. Is it likely that the ring gear needs replacing or that I could get away with just changing the starter? or will I need to do both?

 

2. If the ring gear is worn beyond repair, how difficult a job is it to repair/replace the flywheel? I will probably have to pay someone to do this as I have neither the facility nor the skill to do it myself and need to work out a budget, (should I upgrade to a lighter flywheel while it's in bits, should I fix the noisy clutch release bearing - where does it end?!).

 

Anyway, I would welcome anyone with the same experience' advice.

Many thanks,

Michael.

[jonlar]

Hi Michael, the flywheel can only be changed by removing the gearbox etc. - quite a lot of work - it would be worth your while, removing starter motor and having a look at the throw out gear (this revolves a lot of times faster than the ring gear and wears a lot quicker). Starters regularly come up on eBay, or go for the Hi Torque type.

[CONCRETE24]

Thanks Jon,

I'll show my ignorance here and admit to having not appreciated there was a throw out gear! (Makes sense though now I've thought about it!). I'll make that first port of call. Looks like both ends of the car will be up in the air this weekend then as I've just been told by a Sunbeam Alpine trying to catch up with me, that I have a rear wheel wobble too, (weird as not noticible in the car, maybe he was just trying to con me into slowing down so he could keep up)!?

[jonlar]

Hi Michael, old starter motors have a "Bendix" gear, which gets thrown backwards as the motor spins, to engage with the ring gear and start the engine turning, later and improved types were pre-engaged, the solenoid throws the gear back into the ring gear and doesn't start the motor revolving until the gear is engaged, which reduces the engagement wear considerably.

[Richard Crawley]

Michael

 

The TR6 uses a pre-engaged starter motor. The first thing to do is remove it & inspect the flywheel ring gear for damage with a torch while a volunteer turns the engine over slowly by hand. Look at the leading edge of the teeth; they have a chamfer on them to assist initial engagement; some wear (rounding off) is acceptable but if there are obvious missing or badly graunched bits, it’s knackered. Look at the starter bendix if its badly worn, it should be pretty obvious through inspection; if not it could simply be a case of the solenoid is sticking or the engagement mechanism is out of adjustment.

 

If the ring gear is knackered, you don’t have to replace the whole flywheel only the ring gear but it’s obviously a gearbox out job. Getting the old ring gear off is easy but you will need some serious heat to fit the new one (like access to an acetylene torch!) & some even freeze the flywheel as well. It makes sense to reface the flywheel while you’re at it but if you’re hankering after a lightened unit you might as well go for an exchange unit.

 

Before you go for a lightened flywheel, however, I would question why you think you need one? I don’t see any merit in a lightened flywheel unless you have a seriously modified engine; you will gain throttle response & the engine will rev more easily but you will loose a fair bit of torque which, in my view, is the heart of the 6. You also need to be careful as the standard cast iron flywheel can disintegrate if lightened too much or if it’s done incorrectly; a better bet is to go for a steel unit.

 

Having said all that, if you’ve got a noisy release bearing, you might as well haul the gearbox out & completely overhaul the lot, including fitting a new clutch unit!

[jonlar]

Getting the old ring gear off is easy but you will need some serious heat to fit the new one (like access to an acetylene torch!) & some even freeze the flywheel as well. It makes sense to reface the flywheel while you’re at it but if you’re hankering after a lightened unit you might as well go for an exchange unit.

 

Before you go for a lightened flywheel, however, I would question why you think you need one? I don’t see any merit in a lightened flywheel unless you have a seriously modified engine; you will gain throttle response & the engine will rev more easily but you will loose a fair bit of torque which, in my view, is the heart of the 6.

 

I've done one at home Richard, using the domestic fan oven to heat the ring, and sticking the flywheel in the freezer overnight! If the ring gear is knackered Michael (although I doubt it) once the fly wheel is off, you drill a couple of holes 180º opposite each other in the ring gear and split it off with a cold chisel. The most important thing is to make sure that when fitting the new ring gear is that you're working on a flat surface, so the ring gear drops straight onto the flywheel (having expanded with the heat differential).

 

I'd have no doubts about getting flywheel lightened and, in my opinion, you certainly won't lose any torque, you may lose a bit of the flexibility (and even have an occasional stall until you get used to the difference) when pulling away. Quite a lot of metal (several pounds) can be removed quite safely. I'm sure someone else will come in with the actual amount. I also wonder if it may help avoid crankshaft breaking as there is that much less momentum in the engine..........?

[JohnC]

Back on the original topic - I used to get a graunching noise every so often when starting, from when I bought my 6 in 1985 until a couple of years ago. I'd get the noise about 1 in 3 or 4 starts, and the engine wouldn't turn over. Sometimes a deep breath fixed the problem; once or twice I rolled the car (in gear) to re-orient the flywheel & ring gear.

 

I had the ring gear replaced during my engine rebuild five or so years ago, but the problem remained. Next time I replaced the clutch I had a chat with the machinist who balanced the clutch cover & skimmed the flywheel. After I'd shown him the starter motor & described how it was fitted, he observed that the ring gear was the wrong way round. I got him to take off the ring gear (which was a bit damaged after a couple of years' graunching) & replace it with a new one the right way round. I haven't heard the noise since. I guess my engine rebuild wallahs assumed the old ring gear was the right way round and put the new one on with the same orientation...

 

I can't remember which way round is correct, but it sounds like Richard does . Remove the starter as he suggests and be alert to the ring gear being not only damaged but the wrong way round!

 

Good luck,

John

Edited April 5, 2006 by JohnC

[Richard Crawley]

I can't remember which way round is correct, but it sounds like Richard does . Remove the starter as he suggests and be alert to the ring gear being not only damaged but the wrong way round!

 

The solenoid on the pre engaged starter pushes the bendix away from the motor whereas the older type starter rely on centrifugal force to throw the bendix towards the motor. The chamfer on the ring gear should face towards the pre engaged starter bendix & the front of the engine.

[CONCRETE24]

Thanks for all the advice, sounds like first thing is to get that starter motor off and inspect the starter iteself and then the ring gear (in situ). I have receipts going back a long way and no evidence that it is anything but the original starter, so after nearly 95,000 miles since '74 it's had a good run - lets hope it's just that! I'll check the chamfer is the correct way round as the symptoms do sound very similar to John C's. in light of the comments and with my fairly limited budget, if I need to replace the ring gear, I will probably stick with the existing flywheel but get a hi-torque starter, (which after reading various older posts seem to be favoured on balance). I will let you all know how it goes when I can get the thing apart!

Regards,

Michael.

[Tom Fremont]

As for flywheel weight - I'm not convinced that the standard 6 is so much over-endowed with flywheel mass. Triumph engineers were nobody's fools, and they didn't waste money on surplus engine weight. Shaving off just enough to achieve spot-on balance is one thing, any more than that is quite another. Sorry Jon, but I doubt that a lightened flywheel will increase longevity of 6 cranks or thrusts. It's a risk/reward analysis, and you need to be sure of what you're trying to achieve.

Thanks for this, Alec. I've been mulling this for my upcoming TR250 with projected 160-170 BHP. I realize flywheel mass dampens vibrations and stores energy for takeoff, but have been tempted by other accounts of lightening exercises.

 

Racetorations told me that early flywheels such as TR5s/250s and early TR6s have far less mass than later ones - so there was no compelling reason to lighten mine. Your comments strengthen that view.

 

Cheers,

Tom

[jean]

Strange enough the ring gear on my 70 TR6 is the wrong way around since the car came out of the factory. I think Triumph did not bother to modify it when the pre-engaded starter was introduced. I must say I never had any problems with starter engagement.

What I recently saw on a 6 was a ring gear that was pushed backwards by the starter gear. The owner complained about starting problems and asked for the starter to be replaced. As the starter worked well after removal, we checked the ring gear and noticed the it was just bound to part with the flywheel, about 2mm further and it would have gone

Jean

[PILKIE]

HI JEAN,

 

This happened to my 1970, 6 recently, it was hard to turn over, when the original starter was removed and tested, it was very hot,and it had shorted out. I inspected the ring gear and it was ok, I did not notice then it was the wrong way round. I replaced the starter with one from my local moss, I presume it was a high torque unit. as when it had been fitted,,, WOW!!!! what a difference in turn over!!! however it sounded a bit harsh!! A bit of a thump before turning over, : then, after a days playing about with other bits on the car,injection/timing etc, it just whirred?????? I checked battery,wiring etc!! all ok, removed starter and tested it, perfect!!! but I did notice that there was some damage from impact/grinding on the bendix!! then, I saw the ring gear had been pushed nearly off the flywheel!!!!!! thank god it had not come off when the car started up!!!! it would of made a real mess!!!

I then saw the rearward edge of the ring gear had a taper on it!! as ive found out in this thread,,this is to gather the bendix in on start up. so mine is on the wrong way and has been whacked so hard by the high torque starter its almost fallen off.

so its back to moss for a new gear,,, or, is it worth refitting the original back on the proper way round??

[jdbinnington]

when i builty my 2.5PI spitfire with a gt6 flywheel and a pre eng starter I noticed that the starter gear approached the flywheel from the opposite side to that which it was used to.

 

I took a angle grinder and ground a bevel on all of the ring gear teeth to help the starter gear engage

 

j

[Gary Guthrie]

Can I leave the engine in place and just remove the gearbox to take off the flywheel, it does say in the Haynes manual I have to remove the engine but I think thats if you want to remove the flywheel and the back plate which I don't need to remove just the flywheel, thanks 

[aardvark]

In short, yes.  Don’t forget to prop the back of the engine before you take the gearbox off.... 

[Yarm 783]

Michael, I think a lot of people fit hi-torques these days, I did. It is a fiddly but doable job and not (overly) expensive, that would be my start Point as it is a sensible upgrade anyway, if the issue persists you know then that a bigger (ring gear) job is required. There are plenty of threads on here about fitting the HT starters.