Scooterotica

soullad wrote:

Darrell Taylor wrote:

sean brady scooters wrote:love the suggestion about drimmeling out the fins on the near side as it can only help matters cooling wise and air flow around the head overall .

it works very well

Don't suppose you've any before and after dynos to show what difference this makes have you Darrell?

no dyno graphs i cut the blanks to specific comp ratio,s ,band widths etc to suit the engine and do 2 mods to the head to improve cooling further 1 being cutting out between fins

Darrell Taylor wrote:.... and do 2 mods to the head to improve cooling further 1 being cutting out between fins

Both sides or just the fan side Darrell? I have an idea for doing it with minimal use of the dremel

angle grinder perhaps

sean brady scooters wrote:angle grinder perhaps

Aw, well you gone and guessed it straight away Actually I have seen some reproduction clamp on legshield flashers that were made from billet using an angle grinder, rasps, emery paper and a polishing wheel so not a mad as it sounds. Just wondering what type of cutting wheel?

lol,not mad at all ,sounds like the perfect tool for the job in fact ...discs come in varying widths ,so one a bit less than the fin gap is the way to go

coaster wrote:

Darrell Taylor wrote:.... and do 2 mods to the head to improve cooling further 1 being cutting out between fins

Both sides or just the fan side Darrell? I have an idea for doing it with minimal use of the dremel

I'd do both Col, the reasons for doing the near side hold true for the other surely, and would help pass more air around the far / underside of the barrel whilst increasing the surface heat dissipation area of the head overall.

Is the fitment of the Avanti head and cowling now considered the norm for the bigger motors then? Is this just a sensible upgrade and are there any downsides to it?

i just did the fan side
sketched an outline of the cylinder top fin onto the head
drilled (6mm holes from memory) on the line at the centre of the fins
cut by hacksaw down to join the holes or slitting discs for your angle grinder "alloy and plastic" type buy from screwfix or toolstation cant remember as mine are next door to each other
cleaned up with die grinder and added a radius

just spotted your other post coaster ref timings,
i reckon youll have 183 exhaust and 127 transfers as youve raised them a bit from the standard 123/124 (providing your cylinder is standard )

Darrell Taylor wrote:just spotted your other post coaster ref timings,
i reckon youll have 183 exhaust and 127 transfers as youve raised them a bit from the standard 123/124 (providing your cylinder is standard )

I checked it a few times using a piece of paper in the port to check when just opening and got 180 exhaust and 130 transfers. My timing disc is only the size of the flywheel so maybe not that accurate? What do think those timing will have done to the performance, to peaky? would I be better off using a thick head gasket instead of the base packer?

cheers

colin

id be interested in you checking the squish again using 2 blobs of plasticine along the gudgeon pin line coated in oil as think it will be nearer 1mm/1.1mm

then measure down from top of cylinder to top edge of transfer and ex port with a digital vernier depth gauge,look very carefully and u get a really accurate measure

ex 33 / 33.2 transfers 45.9 is what i normally see ,there very consistent very old kits and the latest batch are well cast but the odd rogue one exists

i reckon how u have it is ok and as you say its easy to juggle around ,poss lose 1 base and add a std head gasket of same size will be better still