So my new engine sits way higher than my old ZX9 so the sausage filter is going through the bonnet.

I cannot figure out a way of marking the cut-out accurately, its going through the top on the bonnet and to complicate things my bonnet has a scoop (standard MK bonnet)

I could get a rough starting point the gradually remove material until it fits but that's a lot of itchy skin worth of cutting

Any tips would be much appreciated

I had the same job for the K&N air filter (Pinto) in my MK Indy.

I guessed roughly where it would be and drilled a hole through the bonnet. I was roughly right and then opened the hole up to size. One tip...when cutting GRP it's worth putting masking tape on the outside to stop it feathering where you cut it. Once cut I fitted some rubber U trim around the hole to finish it off.

Thanks bud, yeah it looks like a very unscientific approach is needed. good point with the tape ill do that

I have never done this but if I were to I would do something like the following.

put masking tape on bonnet.

fit the filter in place

with bonnet removed use a laser level to mark one edge of the filter along its length.

remove filter place bonnet and mark out the line.

refit filter and repeat for second line

repeat the marking out

then if you wanted you could also do the center line from 90 degrees from the two lines above then measure the length of the filter and mark where the ends will come to

that way you could possible use a compass to mark out the rounded ends and do it in one cut.

I would always cut a little bit within the line for any errors though.

I asked the same thing a while ago...know easy answer

drill/cut/check and repeat until you are a) to itchy to carry on or b) you have finally got it fitted

One tip is don't be shy on the masking tape. Its cheap compared to the bonnet so cover it all around the area or you will end up marking it! As I went I took it all off and re-applied it several times as it got marked and ripped along the edges.

I would go for a cardboard (or even soft wood) duplicate of your bonnet, then follow the cutout process as described, THEN move over to the real thing.

plastincine or playdoh on the inside of the bonnet so it marks the filter location when you try to close it?

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Originally posted by Mr Whippy
plastincine or playdoh on the inside of the bonnet so it marks the filter location when you try to close it?

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quote:

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Originally posted by Mr Whippy
plastincine or playdoh on the inside of the bonnet so it marks the filter location when you try to close it?

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quote:

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Originally posted by Slimy38
I would go for a cardboard (or even soft wood) duplicate of your bonnet, then follow the cutout process as described, THEN move over to the real thing.

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Leave the bonnet off. Make a cardboard template that's a perfect fit around the carbs. Attach the template to a fixed reference point (like the nose cone) on a 'hinge' made out of masking tape or similar. Make sure the whole thing is reasonably rigid and it always lands back in the right place when you lift it away from the carbs and drop it back over. Fold it back out of the way.

Now remove the carbs from the engine and fit the bonnet. Fold the cardboard onto the bonnet. Mark the cut out. Cut the fibreglass. Refit the carbs. Remove the template.

Voila!

I would drill two holes in roughly the right area. Put the bonnet back on and mark the filter through the holes. Then make a cardboard template of the filter complete with holes where the marks are. Template on the bonnet and cut away.

I'm another one who used cardboard - bought a couple of large sheets from The Range art department (thin, bendy stuff) and taped them together. Guessed where the hole would be and cut it out over-size. Put it where the bonnet was to go, and taped it to the sides, marking the centre line and ensuring that the card took the same curve as the bonnet (no dips).

I now had a card bonnet with a hole that was too big... I stuck on bits of card around the hole, pulled them off again, trimmed them, dumped the mistakes, etc. until I had a hole that was exactly the right shape and size (albeit a bit lumpy by now). This was laid over the real bonnet, lining up the centre marks again, and the hole outline was drawn onto the bonnet. Took it away, checked the fit (I was nervous) and then re-applied it to the bonnet. Once I was happy I cut the hole...

Brilliant folks thanks very much. Love the 'hinged' template idea. Cheers

Without a doubt, cardboard. I would cut a hole far too big then make a template just to the right size with a smaller bit of card then tape it accurately in place over the large hole.

Hinged template like Russ said.