How close should the fins be to the cowling

[Gazbo72]

How close should the fins be to the inside of the cowling ???

I have just rebuild built a engine up with a new crank and elctronic kit and after putting the cowling on loose I noticed the gap between the fins and the inside of the cowling is 5mm. The electronic kit is one with the fins machined down. Is this about the norm or should it be closer or further away.

I have never looked/ took any notice before Just wondered if there is a set measurement to get the most cooling for the topend.

Regards Gaz.

[Muppet]

1mm

[Gazbo72]

1mm

Bugger, Mine's a bit on the large size .

[Gazbo72]

is it an Indian cowling? they stand off much more than an Italian one!

I don't think so as it isn't a GP style cowling. It come with the scooter which is a s2 li150. But I don't think it is original as it does not have the loop for holding the over flow from the carb.

The fins are 25mm from the edge of the mag housing edge were you put you timing marks.

Gaz

[rosscla]

On my AF flywheel there's 19mm to the fans, the future is chopping boards....

[Minority]

is it an Indian cowling? they stand off much more than an Italian one!

I don't think so as it isn't a GP style cowling. It come with the scooter which is a s2 li150. But I don't think it is original as it does not have the loop for holding the over flow from the carb.

The fins are 25mm from the edge of the mag housing edge were you put you timing marks.

Gaz

I have an unmachined SIL flywheel and the fins are approx 29mm - 30mm which would give the correct 1mm clearance for your magneto cowling. My cowling, although I believe deeper to accomodate the long fins, is the "Series 3" style, not GP.

I remember reading an article which said that if the gap was bigger than 1mm cooling efficiency was greatly reduced, so not something you can ignore!

[coaster]

If you elongate the holes in the cowling with a needle file you should be able to close the gap.

[mickdale]

i believe ian frankland from taffspeed states for the fan to work without loss of cooling, the fins should be within 2mm of the cowling

[Gazbo72]

Here's a pic. Is this mesurement is similar to others.

Regarding fileing the the holes. From looking at it it will pull the rear end in , But the front end won't go in because of the way it is pressed.

Looks like it might be a leathering with the hammer

[Minority]

You could also firmly attach a spacer (like a huge washer) to the inside of the cowling to fill the space between the cowling and the fan to create the correct clearance. Don't know quite how you would achieve this but it might be reversable if required. (unlike the leathering with a hammer )