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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Hi all, Im about to bore my 03 FXDX TO 95. I had ordered some 10:1 pistons I was going to pair with a .027 head gaskets. The pistons went missing before they got to me. Rather than order another set from over seas Ive ordered a set of 10.5:1 pistons.
my worry is the 10.5 with the skinny head gasket will push the compression too high and maybe cause pinging?
in the uk i think all fuel is minimum 95 now.
im running a feuling 525 cam and a mikuni 42.
currently making 91flb 74hp if its relevant.
im pretty happy with the torque( I wouldnt grumble about a little more though.) mostly Id like it to not have to work so hard on the motorway.
That combination should be OK if 10.5 static is true; CCP about 190psi. However, the only way to know true compression would be to know chamber volume, piston dome volume and deck height; you have the other numbers which are head gasket thickness and cam intake close event.
the thing to be concerned with on this, to me, would be valve to piston clearance. I know the 525 cam is not a big one, but i'd still mock it up and clay it to make sure. as long as you have an adjustable ignition system, the rest can be dealt with. not knowing how the dome is on the piston that you get.
m
the thing to be concerned with on this, to me, would be valve to piston clearance. I know the 525 cam is not a big one, but i'd still mock it up and clay it to make sure. as long as you have an adjustable ignition system, the rest can be dealt with. not knowing how the dome is on the piston that you get.
m
JMHO but I would not set up a carbed motor at the compression shown in the OPs BigBoyz results; EFI maybe if I knew the tuner was capable. I am running a 98" at a tad higher but had complete confidence with the tuner and have had no issues but, as I said, if the bike was carbed, I would keep CCP in the 190-195 range and/or corrected CR below 9.6.
As has been pointed out, a Daytona Twintec TC88 progammable ignition and manual CRs should be part of the plan per eighteight's post. I would return the pistons in exchange for one with a 6cc dome.
Don't disagree on marcodarq's post about mockup but for a different purpose. I would want to know squish which might make me decide to machine cylinders to 0.00" deck height and adjust head gasket thickness if necessary. We have been installing SE cams like with higher TDC lifts than the 525 forever so I don't believe piston to valve to be an issue but, having said that, if mocking up, why not check.
UK gas starts at 95 octane?! lucky! I wouldnt think pinging would be an issue with a higher octane fuel. Ive run 10.5 with .035 head gaskets plenty of times with no issues on California crap gas but, as mentioned above there are other potential issues with that set up and how it behaves on the street once tuned.
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95ci compression question
