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Lightweight Flywheel + Lumpy Cam = Bad?

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#1 zebigfatman

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Posted 25 February 2019 - 02:45 PM

Hi all. I posted about this problem a few months ago but didn't realise what was happening at the time.

 

Basically built a high revving 1310 engine. it was very difficult to start unless you retarded the timing to start it and then re advanced it to drive it.

I tried replacing the dizzy for this one

 

http://www.minispare...|Back to search

 

Which helped on the power front but not with starting.

 

It munched 2 starter motors,

 

Then I bought this starter motor thinking it would help. It did not...

 

http://www.minispare...|Back to search

 

 

 

The engine spec is:-

 

1310

286 cam

1:5 rockers

ported head 

twin 1.5" su's 

9.5:1 compression ratio

KAD flywheel 

Pre engaged starter setup 

 

It stopped starting due to not having any ring gear left.

 

I took the engine out, checked the cam timing which is spot on 106 degrees ATDC

the static ignition timing is 5 degrees BTDC.

 

I put a standard SPI flywheel on, kept the clutch cover off so I could view the starter teeth engaging. It starts and runs well (out of the car)

 

I then bought a second hand KAD flywheel off ebay. The ring gear was immaculate.

 

I then fitted that flywheel, and again it is having big problems starting. If you look at the starter teeth while it is cranking, metal shavings are coming off the flywheel because the solenoid is pulling and pushing the starter gear through the flywheel teeth.

 

It appears that the momentum of the heavier flywheel is the only difference, possibly damping each cylinder as its firing?

 

My questions are. How many of you use lightweight flywheels with lumpy cams? Is this a known problem? and is there a way around it?

 

I imagine all of the race spec minis use similar arrangements, so how do they work?

 

I am getting quite disillusioned with the car because I spent ££££ on this engine and a few hundred trying to sort this problem out and I am not a rich person!

 

Sorry for the rant. I honestly thought the problem was sorted so this is kind of disappointing.

 

Any help or advice would be greatly appreciated!

 

Cheers

Regards

James

 



#2 Midas Mk1

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Posted 25 February 2019 - 02:49 PM

Run a lightened MED one on both of mine, totally fine on idle with a lumpy cam. Comp ratio seems low for a 286?



#3 nicklouse

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Posted 25 February 2019 - 02:50 PM

were the ring gear and the starter pinion gear compatible? you know the tooth count id different.

 

it also sounds like your dizzy needs setting up for your build.



#4 hhhh

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Posted 25 February 2019 - 02:57 PM

A lumpy cam reduces dynamic compression at low RPM and makes the engine easier to turn over, so I would think a light flywheel would not be a problem.



#5 zebigfatman

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Posted 25 February 2019 - 03:06 PM

I know the compression ratio isn't ideal, but it is my first engine build and didn't quite realise its importance until after it was finished...

 

It is still the fastest car I have ever had :) when it works..

 

The ring rear is designed for pre engaged starters. I have compared the KAD flywheel to the SPI one and an old 998 one. It is deffo the same as the SPI.

 

Define setting up the dizzy? Mapping with different weights and vacuum? How much would that cost?

 

I might try a standard starter again because the number of teeth on this new high power one is different to standard

And the solenoid extends the gear to about halfway then it has a bendix type arrangement which relies on a force pushing against it to keep it extended. (very strange thing)   

 

On a side note, I have been developing my own ignition ECU based on an Arduino. It is not ready yet. it works until you introduce a spark which interferes with the crank trigger signal and messes up the timing.



#6 nicklouse

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Posted 25 February 2019 - 03:08 PM

I might try a standard starter again because the number of teeth on this new high power one is different to standard

so they are not compatible. there is your issue.

 

How many teeth does the starter have?



#7 zebigfatman

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Posted 25 February 2019 - 03:23 PM

It has 11. I think the standard has either 9 or 10. However the axis on which the gear spins is not central relative to the bolt holes.

 

I thought they had sent me the wrong starter initially but I looked on the manufacturers site and the datasheet says 11 teeth.

 

http://www.powerlite...roducts/rac803/

 

But I'm not entirely convinced its right..



#8 Bobbins

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Posted 25 February 2019 - 03:28 PM

Is this intended as a road or competition engine?



#9 zebigfatman

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Posted 25 February 2019 - 03:34 PM

It is a fast road engine/ trackday engine. I live in North Wales so town driving isn't and issue :) 



#10 nicklouse

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Posted 25 February 2019 - 04:13 PM

It has 11. I think the standard has either 9 or 10. However the axis on which the gear spins is not central relative to the bolt holes.

 

I thought they had sent me the wrong starter initially but I looked on the manufacturers site and the datasheet says 11 teeth.

 

http://www.powerlite...roducts/rac803/

 

But I'm not entirely convinced its right..

there is no such thing as standard. there is inertia and pre- engage they are not mixable.

 

inertia has 107 teeth on the ring and 9 on the starter the Pre-Engage has 129 Teeth on the ring and 11 on the starter. 

 

so can we say your starter has 9 teeth and the ring gear has 129 teeth. no wonder you are killing the ring gear and having issues to start the thing.

 

don't think you can swap out the pinion gear.



#11 whistler

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Posted 25 February 2019 - 04:49 PM

Don't know if this is relevant or not but I remember reading that under certain circumstances it is necessary to space out the starter motor on the 2 mounting bolts. This I would assume allows the pinion to engage further onto the starter ring. Aplogies if I have it wrong.



#12 zebigfatman

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Posted 25 February 2019 - 05:05 PM

Cheers. But I don't think I conveyed the information right.

The high power pre engaged starter has 11 teeth. This is the one I am using now. However the gear appears more similar to an inertia

The standard pre engaged starter (I killed 2) I thought had 9 or 10 teeth. At any rate the gear on the new one is far bigger in diameter.

The standard inertia starter has 10. I have not even tried this because I know its wrong.

I think spacing the starter out is if you are trying to use the wrong starter for your Ring gear to stop it from being meshed constantly.

#13 Spider

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Posted 25 February 2019 - 05:57 PM

I wouldn't be concerned with the number of teeth on the Pinion, just that they are the correct form and pitch are the main things here. It may have a different tooth count due to it being a different size, being a 'high power' starter. The Pinion is where I'd start looking and in particular the point mentioned, but, it seems you ahd similar troubles with a stock starter, so while it should be checked thoroughly, I don't think this is the issue.

 

Can you post up a pic of your last flywheel ring gear teeth so we can get a better handle on it?

 

It could also be a misalignment from a twist, leaving the starter not parallel to the crankshaft.

 

It sure does sound like the distributor has a curve that's not suited to your overall engine spec. and this is actually the very next item I'd be looking at. It sounds like there's too much static advance and as it's being cranked, it's trying to run in reverse. That will chew out a ring gear in short time too.

 

Just as a side note here, the (Static) CR looks on the low side for that combination, but that's not the issue with the ring gear.



#14 Cooperman

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Posted 25 February 2019 - 06:26 PM

The 286 is far from an ideal cam for road use, especially with a light flywheel. In fact I have exactly that on my 1964 historic rally 'S' and to get it to go well I use a 3.9:2 FDR and a SC CR gearbox. Even then it is 'lumpy' and can 'bog down' easily unless the revs are kept up.

 

I also had a starting problem when starting with the engine hot. The CR on y car is 11:1 and the standard starter would not spin it over when hot. I spoke with Aldon Automotive and they re-curved an Aldon 'Red' to have an additional 4 degrees of mech advance and with the top end advance set as on the rolling road, the additional 4 degrees of available total advance means it always spins over with no problem even when very hot. Of course, the starter must match the ring gear and you need to check that.

 

Personally I would never use a 286 cam on a road car because the power/torque band is too narrow unless a very close ratio gear set is used and that, in turn, means a low final drive ratio and hence high revs at a decent cruising speed. I get just about 14 mph/1000 rpm in top gear and I often think it might be better on a 4.1:1 FDR which gives about 13 mph/1000 rpm in top gear.

 

The two Mini 'Comics' are no real help and go on about max bhp when what is needed for any sort of road use is really good mid-range torque. Unless for out-and-out competition a well-built engine with a less aggressive cam is usually much better.



#15 wile e coyote

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Posted 25 February 2019 - 07:28 PM

I think the principal problems are incompatible ring gear / starter, timing that needs sorting, although dizzy itself  seems right.....  and dare I say it an ebay purchase..., '286 cams are ok  on a CR of 9.5:1

 

The lack of sorted timing means that the starter, standard or otherwise is having to work long & hard to start it - and that's presuming a match between starter and flywheel, the lightweight item  wont be doing you any favours in starting. 

As well as a tooth count to check compatibility of components it may be worth comparing  the thickness of the ring gear on the KAD item as that may be the cause of "shavings" (unlikely but)...

 

I'm a suspicious swine... particularly of shiny components sourced off ebay - it may just be worth a quick call to KAD both to check it's a legit one of theirs, and if so whether it was a production item,  and more pertinently for any recommendations parts or otherwise.....(the KAD website has very decent write ups / specs on their current offerings)... if it's a dud or a failed development item (said I was suspicious) then ........







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