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540 conversion - clearances, and 41mm, SX CDi etc

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Am just rebuilding the head and top end in general on my EXC (04) while doing a 450-540 conversion and I wanted to check for certain parts what the 'norm' is in terms of fitment and clearances (if there is a norm).

I'm using a bored out to 97mm 525 barrel, a wossner 11:1 piston, and a Hotcams Stage1 cam (3015-1).

I've got two base gaskets I can use (0.5mm and 0.8mm) and I've already been given useful info about checking the squish and checking valve to piston clearance in lieu of using a hotcam and a non standard piston. Don't want to be hassling the same guy with more and more questions though!

I figured I'd ask if anyone else has had the same combo of parts in their own 540 build to advise on what theirs was like, and if there were any piston/cam clearance issues with this setup?

Aside from that, I've read the 41mm SX carb is a good bolt on to go with the 540 job. Will I notice much difference with that? I use the bike on the road a lot and need nice idle behaviour etc. And also saw comments about using an SX CDI unit for more power too. Is that a straightforward swap? Any downsides or problems etc?

Cheers for any info!

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CDI box is a straightforward swap but you may not like the idle and part throttle characteristics. And you may want to change jetting/needle to get less harsh behaviour. I guess you could get the same results with disconnecting or leaving out the throttle position sensor but I hear there is a risk of detonation. Don't know if anyone has had it but still.

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Cheers for the reply mate.

I rather suspect if the idle behaviour from the SX CDi is questionable (do they just not idle, or lumpy idle or what?) then I'd probably not bother as I need it to be nice and stable.

Total guess but is the part throttle using more advanced ignition to make it snappier or something with the SX unit?

Wouldn't want to be risking det since I'm after as much longevity as I can get with this. I use 97 ron fuel so I'm not sure how that rates in terms of this kind of motor, but I know it's hardly the highest rated stuff and wouldn't want to do anything to provoke any det.

Re' the 41mm carb - are they more or less a straight swap and are there downsides to using it over the 39mm EXC one? Presume it just needs to be from the same era bike to be the right ones.

Must admit the jetting is something I haven't given any real thought to, ie which needle & jets & clip position would be most likely to run right with the 540 and hot cam (ie with my existing 39mm carb). Any suggestions on that?

Cheers!

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There is a percentage chance of cylinder wall failure on overbored 95's. I have personally had several. Roll the dice. 90% work. Notice how light the overbored cylinder feels in your hand? Thin liner left is why.

Low compression you are using will help with this issue. The hotcam and low compression will take away a lot of low and mid power. Only at full revs will it help. You won't like it I feel.

Am just rebuilding the head and top end in general on my EXC (04) while doing a 450-540 conversion and I wanted to check for certain parts what the 'norm' is in terms of fitment and clearances (if there is a norm).

I'm using a bored out to 97mm 525 barrel, a wossner 11:1 piston, and a Hotcams Stage1 cam (3015-1).

I've got two base gaskets I can use (0.5mm and 0.8mm) and I've already been given useful info about checking the squish and checking valve to piston clearance in lieu of using a hotcam and a non standard piston. Don't want to be hassling the same guy with more and more questions though!

I figured I'd ask if anyone else has had the same combo of parts in their own 540 build to advise on what theirs was like, and if there were any piston/cam clearance issues with this setup?

Aside from that, I've read the 41mm SX carb is a good bolt on to go with the 540 job. Will I notice much difference with that? I use the bike on the road a lot and need nice idle behaviour etc. And also saw comments about using an SX CDI unit for more power too. Is that a straightforward swap? Any downsides or problems etc?

Cheers for any info!

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