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Vintage Classic Ariel Square Four 4G MkII 1953-1959 Piston kit

Also fits MKI version engine

Pistons (4) Ring Sets (4) Piston Pins (4) Circlips (8)

STD BORE : 65mm , Please check size before ordering.

Replacement Piston kit designed by IMD Piston Co. and manufactured for IMD Piston Co. England

IMD Ref. P11024


The pistons are within a 5 gramme range of the original piston,

The correct offset on the thrust side of the piston has been engineered into our pistons; not all manufacturers follow this design as laid down in the original specifications.

The ring sets utilise the 3 piece oil control type offering excellent sealing to the cylinder wall.

The piston pins are internally tapered, and are constructed using SCM415 material acheiving virtually the same weight as the original pin.



Bruce Longman, who advises that pistons with NO offset were originally specified by Ariel for the MKI engine, but offset pistons are a good idea to fit as they make the engine run quieter. He also informs me that the MKII pistons that you have had made, will fit as they are, in a MKI cast iron engine. I could machine them down flat if I wished but don't have to. (D Colville with Bruce Longman, Ariel Owners Club in a recent Email Dec 2013.

As approved by The Ariel Owners Club England, Dec 2013


Super FAST!!!!! Very, VERY Highly Recommend!!!!!! AAAAAA++++++++++++!!!!! Buyer: 09-Nov-13 16:51
VINTAGE ARIEL SQUARE FOUR 4G MkII 1000cc PISTON KITS NEW +0.40" O/SIZE (#151028689509) £249.99 View Item


Evidently quality pistons, & 22g less than my old +30 Hepolites.Excellent! Buyer: 
16601720 286Teal star icon for Feedback score between 100 to 499) 
13-Jan-14 14:23
  VINTAGE ARIEL SQUARE FOUR 4G MkII 1000cc PISTON KITS NEW STD SIZE (#151028689835) £249.99 View Item


All IMD pistons are made from the latest specification silicon aluminium alloy material.



This conforms to the required percentages of specialist metals, the most important of which is silicon. Silicon has been proved conclusively over a prolonged period, to give the best ring groove wear rates coupled with a low coefficient of low expansion rates. Strength has been achieved using a modern construction technique which has allowed the weight to be reduced in the piston. The weight of the piston is the most important factor in engine design, since the effect of reciprocating weight is transferred directly in terms bearing loads, engine balance and maximum permissible speed. The lighter the pistons are, then the lower are the loads on the crankshaft main bearings.



IMD have achieved piston weights comparable with the original parts, and will in the future improve upon this through innovative design.

This reduction of weight is now common place in automotive piston manufacturing worldwide, our pistons conform to this industry practice without any compromise, and are kept to the lowest level concomitant with adequate strength.


Please note: All motorcycle & automotive components supplied from this site/listing must be fitted by a qualified Engineer using the correct appropiate equipment and using the neccessary technical information. No liability can be accepted for components incorrectly fitted, and any such failure ater installion.




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