Tuning 500 flywheel on a 650 engine modification.

[gordinir8]

I have read many times that some people putting the 500 flywheel into the 650 engine. 650 weights 7.1 kilos while the 500 flywheel weights 5.1 kg. Problem is that when I put my 500 flywheel Into the 650 engine the starter gear cannot reach the flywheel teeth. So I Wonder if there is Any other modification that I have to do in the starter in order to be able and reach the teeth of the five hundred flywheel which are Closer to the Engine block related with 650 flywheel teeth which are closer to the gearbox. Also What if the flywheel is not Marked on the TDC as per manual. Is there a problem if you put the flywheel in any position? Or is there any factory mark ?
500 flywheel at the left of the pic.

 

[the hobbler]

When I fitted the 500 flywheel onto my 650 engine I did not 'align' it in any way--I just fitted it! When I had my engine/carb set up on the local 'Dyno', the technician commented on how smooth my engine was at high revs. As I have mentioned on the previous thread, my starter occasionally 'misses', so I just let it settle and then try again--normally with no problem. Whether this is due to wear on the starter or the ring gear will have to wait until I next remove the engine!

 

[gordinir8]

Well Tom I fit the flywheel and also the starter. Starter gear can engage the flywheel by only 1mm maybe less! Without the button attached on the starter gear can travell aĺl the way in. Only option will be to convert starter leaver. I am starting to thinking to put the stock flywheel.

 

[Franko500]

you may need to change the Bendix gear


https://webshop.fiat500126.com/electronics-und-ignition/starter/starter-pinion-gear


They list a different one for 500R/126. So presumably it allows the gear to go out further?

 

[gordinir8]

My new 650 engine comes with it's starter, i am not going to use the 500 although it makes no difference.

 

[gordinir8]

My new 650 engine comes with it's starter, i am not going to use the 500 although it makes no difference.

Wait a minute My new 650 came with a starter made by a company named ELMOT (at the right of the picture) i also had a spare 650 starter made from Marelli (at the left of the picture with the worn gear) Both leavers are pushed all the way in, difference is that at the left starter when pushed bendix gear comes to the end of the starter housing. I think that this one will be able and engage the 500 flywheel. I will tomorrow switch starter heads and see what will happen, i think that with the Marelli gear housing and a new bendix i will make it work. Maybe there is a mechanical stop inside the ELMOT housing that i can also modify.
My Marelli starter has worn rotor commutator bars and i wonder if i can repair them with the help of a lathe.
Stay tuned

 

[Toshi 975]

I am in the same situation as Tom the "Hobbler". After being told that the 500 flywheel was a good way of shedding 2kg from the flywheel I have built a number of engines with that flywheel and never had any problems as yet.

 

[gordinir8]

I am in the same situation as Tom the "Hobbler". After being told that the 500 flywheel was a good way of shedding 2kg from the flywheel I have built a number of engines with that flywheel and never had any problems as yet.

Have you ever try it like, before and after so be able to see what was the actual gain?

 

[fiat500]

I think it's interesting that you have highlighted that difference and problem Thomas. It seems likely that other people who have made that modification have just been lucky either by having a starter that just fits right or a flywheel that fortunately has quite good teeth.
Your approach in trying to make sure that you build a robust system as well as getting the "gains" from a lighter flywheel (whatever they are? ) is the right way to go.
I left the 650 flywheel on because I was worried with the amount I read about balancing the engine and the difficulties that brings; a different flywheel might upset that. Also, you hear a lot about the engine being prone to vibration and anything that can overcome that (eg. a heavier flywheel) gets my vote, especially when FIAT thought it necessary in the first place.
I find the 652 with all standard fittings is very smooth and very fast compared with the 499.

 

[gordinir8]

I hope Peter that it will run smooth and also rev up faster, I am not going to put any faster cam or bigger carburator except a more sporty exhaust. So all in all pretty stock but reliable I hope.

 

[gordinir8]

Problem solved
It was the button that was limiting the travel of the bendix gear. I put a button taken from my Marelli 650 spare starter and now it can reach the flywheel. Already crank it with a battery and looks ok:slayer::slayer::slayer:
Thomas

 

[F123C]

Hi Thomas,

It sounds like you have solved the problem but if you wish you could apply some 'Engineer's Blue' (aka Prussian Blue) or even some spray paint on the starter pinion teeth and operate the starter to check if you have adequate engagement of the pinion teeth with the flywheel teeth.

In some cases, it might be possible to re-position the starter ring gear on the flywheel to get better starter pinion engagement. (might not be possible if starter ring gear fits up against a step).

Re :- changing flywheels. I always try to use the flywheel that came with the engine. I don't know for sure if swapping flywheels adversly affects engine balance. But when crankshafts etc are being balanced, afaik all the rotating parts (crank, flywheel,pulley etc) are balanced together and I have seen balance marks (drilled holes) on Fiat flywheels..

On the other hand, (back in the day) new Fiat engines came in a crate without flywheels....

On Fiat 4 cylinder engines there was usually (iirc) a small dimple on the clutch side of the flywheel to indicate tdc on cylinders 1 & 4.

Fitting a lightened flywheel is one of those things that many people feel they have to do if tuning an engine, but is it really necessary or desirable?

Sure, a case can be made that a lighter flywheel takes less power to speed up, thereby allowing a little more power to reach the wheels and the engine will speed up and slow down quicker - sounds good when 'blipping' the throttle. There's also the weight reduction - 2 kg less flywheel weight is also 2 kg less vehicle weight, so slightly less vehicle weight to accelerate/propel.

But why is there a flywheel anyway, other than a convenient place to mount a clutch and also a gear to drive with the starter motor to start the engine?
Flywheels store energy. This energy-store drives the crankshaft between power pulses and also smooths out the crank rotational speed i.e. is a crankshaft damper. A heavy flywheel helps to give a steady idle speed and also helps to prevent stalling of the engine at low engine speeds. It might also help with engine starting especially on single and twin cylinder engines.

So, how do you chose between a standard and lighter flywheel? I suppose it comes down to what you're trying to achieve - if you want an engine that speeds up a little faster then go for the lighter unit, if a steady idle speed is desired, then stay with the standard flywheel. But I don't think that a lighter flywheel, on it's own, is going to make any noticeable difference to acceleration times.

Thomas, iirc you work on Aircraft, do you have access to facilities to check the flywheel on it's own for imbalance before fitting it?

AL.

 

[gordinir8]

Hi Thomas,

It sounds like you have solved the problem but if you wish you could apply some 'Engineer's Blue' (aka Prussian Blue) or even some spray paint on the starter pinion teeth and operate the starter to check if you have adequate engagement of the pinion teeth with the flywheel teeth.

In some cases, it might be possible to re-position the starter ring gear on the flywheel to get better starter pinion engagement. (might not be possible if starter ring gear fits up against a step).

Re :- changing flywheels. I always try to use the flywheel that came with the engine. I don't know for sure if swapping flywheels adversly affects engine balance. But when crankshafts etc are being balanced, afaik all the rotating parts (crank, flywheel,pulley etc) are balanced together and I have seen balance marks (drilled holes) on Fiat flywheels..

On the other hand, (back in the day) new Fiat engines came in a crate without flywheels....

On Fiat 4 cylinder engines there was usually (iirc) a small dimple on the clutch side of the flywheel to indicate tdc on cylinders 1 & 4.

Fitting a lightened flywheel is one of those things that many people feel they have to do if tuning an engine, but is it really necessary or desirable?

Sure, a case can be made that a lighter flywheel takes less power to speed up, thereby allowing a little more power to reach the wheels and the engine will speed up and slow down quicker - sounds good when 'blipping' the throttle. There's also the weight reduction - 2 kg less flywheel weight is also 2 kg less vehicle weight, so slightly less vehicle weight to accelerate/propel.

But why is there a flywheel anyway, other than a convenient place to mount a clutch and also a gear to drive with the starter motor to start the engine?
Flywheels store energy. This energy-store drives the crankshaft between power pulses and also smooths out the crank rotational speed i.e. is a crankshaft damper. A heavy flywheel helps to give a steady idle speed and also helps to prevent stalling of the engine at low engine speeds. It might also help with engine starting especially on single and twin cylinder engines.

So, how do you chose between a standard and lighter flywheel? I suppose it comes down to what you're trying to achieve - if you want an engine that speeds up a little faster then go for the lighter unit, if a steady idle speed is desired, then stay with the standard flywheel. But I don't think that a lighter flywheel, on it's own, is going to make any noticeable difference to acceleration times.

Thomas, iirc you work on Aircraft, do you have access to facilities to check the flywheel on it's own for imbalance before fitting it?

AL.

I have checked already that the gear engages about 75-80% so i think it will be fine.
Regarding the flywheel lets see it in a different way. Have you ever seen someone that has convert his 500 to 595, 650 or more and after he has install a heavier flywheel? I think those almost 2 kilograms are enough to increase power a little up to the point that will not harm the engine. I also hope that it will keep idle to normal and also has a normal vibration levels..i hope, if not i will re install the 650 flywheel on.

Now regarding the balancing, as you said engines came without flywheels. I really doubt that Fiat was balancing those together with the flywheels on. I mostly doubt that all those years the mechanics use to mark the flywheel and then put back together, i think they probably ignore this little detail. The old mechanics never use a manual, at list here in Greece there was no manuals available in Greek language and none of the old mechanics could read English.
On the other hand If i could choose and had that extra cash and time, of course i would choose for a full balancing tune of engine.

Unfortunately we don't have balancing equipment at work. The only thing we are balancing are the aircraft propellers and jet engine fans, aircraft itself records the vibration levels, we are downloading those to a laptop and then a special program gives the''solution'' with weights that we are putting in specific holes behind the prop hub. Actually we are putting weighted washers!! Pretty interesting but definitely something i hate doing at 03:00 in the morning :bang:

Thomas

 

[the hobbler]

May I suggest the following---balance the flywheel as best you can, possibly by putting a roller/needle bearing (on a shaft) in the hole in the centre of the flywheel, and then match the piston weights and con-rod weights so that the parts that go up and down are 'balanced'. The 'factory' balance of the crank-shaft is actually quite good, so with the above work you should end up with a fairly smooth engine.

 

[gordinir8]

Now this. Since I put the 500 flywheel to the 650 engine, which clutch to use? The 500 or the 650?. 500 gearbox has a different clutch bearing than 650

 

[fiat500]

Tony Vitesse and me had this conversation a long time ago and came to the conclusion that the later style bearing and clutch fit and work on any combination.