From what we're told , they got cheaper & nastyer .THIS parently's the rigonal Iron Piston ( Generally )  ITEM . With MORE Machineing , mate .



Think the Later un fully machined one is the tird , or last , like in LA 46s , later ones . 

CRANK is common to FP 35 , 40 , & LA 46 . AND theres a ' 20 throw ' 10 actually ! stroke GP 44 Magnum crank , which dosnt really fit  , rather'n the std. 18.4 .



The Magnums based on the earlier type FP , the 44 anyway . Good Grunter , more go than the 40 . Top Ends FSR 45 ish , fit . ( 40 , rod up , is near FSR 40 )
BUT seem to suffer from liner expanding , or R C Blokes , or parts swapping. Even New . So P/L fit , compression wants a look if theyre after more than ten dollars .

THE Magnum / Royal / Thunder Tiger ' the Story Is ' made O S Parts - Engines . Shadow Factory like . SO a bit of a lottery , at tuimes you find the flash ( as above )
type cranks in thier FSRs cetra . Rather than their ' basuic ' ones . Or Maybe it was the ROYAL was the ' top line ' job , and Normall hadem .

If as is said , the Royal is true ABC , you dont pass a Royal Buy . Or a Tower .

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The FSR cranks go the same way , with the 45 . Machined , earlier with fancy counterweight . FSR 45 , 40 & FP 35 , 40 & 44 rods interchange , heads , liners bar circlip Vs PAD wrist pin .

oops,.crekshun. that was ST 46 perhaps . Your Korekt . The FP40 Gardner comes with the ROD . A bit of meandering on rod to crank fit , on that.
Just unglued three Ex RC sf, LA & FSR wrist pins . Really wouldve been better with a saddle with hole , vice & gas torch . Were firmly embedded .

ANY FSR 40 / 45 & FP 35 , 40 , and LA 40 / 46 rod interchanges . Tho some maybe bushed / unbushed .
The CLONES are ditto . Inc. The 44 Magnum. You find a few bent rods . HYDRAULICING IT can weaken / snap the Wrist Pin too .



Part No: X-OS24005000
OS Engine Connecting Rod 35-40FP/LA

O.S. ENGINES CONNECTING ROD 35FP,40FP,40LA,46LA. Code No. : OS24005000.


FSR stuff for interchange . A Garner Liner'l go in a FSR .
FP in FSR has no ciclips & pads'l fall in the ports .

Head, 40 OS 10789 24904019 40FSR CYL HEAD 5.76 Y Y
Head, 45 OS 15174 24904103 45FSR HEAD-AIR 7.66 Y Y
Head, 45H OS 10820 24904207 45FSR-H CYL HEAD 13.76 Y
Head, 40 Stunt OS 17548 24904300 CYL HEAD 40 FSR-S 5.76 Y
Conrod OS 10722 24205001 40-45FSR CONROD 5.76 Y Y Y Y 5.5mm crankpin, 4.5mm wristpin
Conrod (P) OS 16411 24805408 CONROD (P) 5.76 Y Y Y Y
Wristpin OS 10760 24806000 40SR & 40FSR PISTON P 1.56 Y Y Y Y
Wristpin (5mm) OS 15744 24806301 45 ABC PISTON PIN 1.56 Y Y Y Y Tower says this is 4.99mmD.
Wristpin Retainer OS 10770 24817007 40-45SR PISTON PN RET 0.72 Y Y Y Y
Wristpin Retainer OS 15745 24817100 45ABC PIST PIN RET 0.72 Y Y Y Y
from file:///C:/Users/PublicInternet/Downloads/FSR40,45%20Parts%20Listing.pdf



Hurumph . seems theres differnt wrist pins , 4.5 AND 5 mm. in FSR speak .

think the early ' better cranks got 5 degrees earlyer closing . Tecnically better ?

Balance factors and rpm's . Re Read the Grand Prix Engine evolution info again the other night .
Like a TRIUMPH with their 72 , 85 & other percentages , it all gets tecnical .
BUT
essentially they have a VIBRATION PERIOD . around 6500 on some , which meant you kept it over 6500
which could get awkward .

SO , with a balanced ( nylon ) prop & a tach. you could descern WHERE the ' period ( rough sspot rpm ) is ,
And avoid it or take to a old crank with a disc grinder . Multis got torsional flex . IF they kept out of that
they avoided a dampner - which get big on viscious engines . Where that leaves us I dunno ;
but,
Rally Cars are tuned more midrange & more FLYWHEEL , than the snappy top end Tarmac Engines .
Therefore the heavier crank COULD be the smoothest  , & also give a better ' tourquey ' stunt run .
suckm it and see , the old ' heavy blade with the counterweight ' trick , used if youve got one . ( blade heavier ) .

as in the 3 cranks will likely have a differant rpm ' vibration period ' & a differant ( to each ) ' Best Balanced ' rpm.
Thinking the R C flat out stuff ended up a factor . The Earlier being the theoretically superior. And More Costly .

" Vibration characteristic analysis of single-cylinder two-stroke engine and mounting system optimization design "
https://journals.sagepub.com/doi/full/10.1177/0036850420930631
Theres a thing , for if theres nothing on television .

A TRIUMPH TWIN is effectively a Twin Single , with the pistons ' in phase ' You can get a enourmous tangentalto crank movement sorta like a ' 8 ' with the crank as the lower center ,
with no head steady & untensioned mountings . so a lateral rocking of the FP / LA lugs , as well as the vertical , are forces to contend with .
G 15s we went to 1/2 Sq bearers with ply doubler &  1/2 sheet outside that , Like yr Std .35 / .46 profile . as a ' engine Bed ' to DAMPEN / absorb the  v-i-b-e-s you got running em 20.000 plus .

If i recal right , around 16 / 17 000 was its ' period ' of nastyness on the 3/8 x 1/2 nose . Stable Noses were all the rage for team race rpms etc at that time. Early 70's .

Stops the nose falling off.
QWe eagerly await your report !  needed to find a wrist pin pad , didnt see Aladin but when I do i'll let him know .