hello!



I got in a engine witch had a bad overspin, the front rotor has gone in to the mid iron, and pretty much destroyed it, and the rotor itself. happy days. picture below.



now, i'm not the one who build the motor, and its a rally N/A engine, so its ported and redone a couple of times, it has fwd and aft plates from a s5, mid plate from a s4 and the housings looks like they are s5.. the ecc shaft got no place for a thermo pellet, so is it then a s4? or older?



so when i have to change the fwd rotor i have no clue what rotors that is in the engine. any tips what i can look for? i just want to install some rotors with the same compression... i tried to measure between this rotor and a known s5 na rotor, it seemed to be the same... but not sure.. im just impressed that a overspin can cause this kind of damnage!



regards,stig

what do you meen overspin do you mean over rev ?

Usually the weight will give you the year.



Can we see the gear side of this rotor? Please.



An overspeed generally just gets the corner seal holes scuffed up, as the crank takes on a "S" shape. Also usually affects both rotors. It looks as though the whole face of the rotor was draging on the iron. More typical of the gear walking out of the hole. And, Or, the land area has been reduced too far. Another adverisement for the high film strength of a synthetic sump oil. If you know you will be screaming a 13B style engine, reduce the rotor sides by .010" each side. And lighten the rotors as much as is possible. My personal best is over 13,000 RPM with a 12A.

Hosed the rotors and irons. That engine raced again the next day with the same parts.



Lynn E. Hanover

thanks for answears!



sorry, with overspin i meant over rev! how much i dont know, he was on the launch pad in a rally, and missed a gear! he was pretty high he said... he continued half the race before pulling in to the pit, i guess thats why all the danmage..



i have not a pic of the gear side here at home, i'll take one tomorrow and post. its on the top on the rotor face the damage is, around the corner seals. the bearing has gone too, pretty bad. the engine is running with a good castrol syntetic oil! the engine is supposed to be newly rebuild, it was vert clean inside, no carbon or any other signs of wear. the rear looks just fine, housing, rotors and all!



the rotors had NOT milled combustion chambers, just the cast. so i guess they are s4?



I'll measure the gear ring tomorrow, maybe it has taken a tour out a bit!



have bought a weight today to see if i got a spare rotor laying around. hope so..



how do you take of 0.10" on eatch side? and do you rebalance?



thanks again!

cast chamber + 2mm seal grooves = s4

I use my lathe, but you could use a milling machine as well.



Just remove material outboard of the outer oil scraper groove. Practice on a junk rotor.



I balance the rotors to each other when done. I do not send the assembly out for balance if the



weights came with the rotors. The primary balance is the rotors at about 10 pounds each.



The counterweights take out a rocking couple caused by the weights being displaced along the crank shaft.



A perfectly accurate scale can be made of a 8' 2 X 4 and some dry wall screws. I can make a picture if anyone needs one.



Lynn E. Hanover

Lynn: please share with us if you got some good methods to do this!



I'll add some pictures, I could'nt see anyting unusual with the gear ring, but maybe you guys do!



I have weight the rotors too, pics comming!



thanks!

more:

here are the weights!



the old rear rotor had sideseals and 2 cornerseals in it, i put those on the weight just after, and they where 22g.

and at last, the rear CW



do this look ok?



what kind of rotors are they? s4?