Cool Head dome sizes help/ specs!

[HondaMan2012]

Iam putting a cool head on my 250r and it comes with the 20cc dome and a brand new 21cc dome... Iam pretty sure both are for pump gas buts whats the better dome to use? Quad is 86' bored 40 over ported full fmf exhaust k n N airfilter, airbox with lid.............and I assume these dont require o-ring kits like the banshee does right?

[acecarlos]

The correct CC's is hard to "guess" without checking a few things like squish clearance, true dome volume (stamped volumes are off), and UCCR. Your bore size & stroke will also influence the Dome volume needed for your application. Dpending on the type of Coolhead you have, some used 2 o-rings and will have the o-ring gland machined in place. However; most CoolHead's use a head gasket...

If your 250R has a 67MM bore with stock 72MM stroke and your Dome really does measure 20CC-21CC with a .040"-.050" Squish Clearance, you are outside of what I call the "Safe Zone" for Pump Gas and closer to requiering 100% 110 Race Fuel or at least 50%/50% Race Fuel...you really need to perform a full UCCR.

Link: UCCR

Carlos.

[HondaMan2012]

hmmm.. dang thought I could just bolt and go...so Iam really just looking to run 93 pump gas and have this head keep my motor cool ( pro design head) . Ill figure it out or take it to a shop. dang it! =)

[acecarlos]

Or error on the safe side if you do not want to measure CC's and perform a UCCR. Go with a 22CC-23CC Dome and .060"-.070" Squish clearance...safe zone for Pump Gas.

[HondaMan2012]

alright, Iam having trouble following this UCCR test, SO I got a GOOD compression tester why cant I just keep track by compression? Under 175compression is pump gas zone?

[HondaMan2012]

Also all I located was an older but NEW atc head gasket...I read on another site that might be .010 less then the trx gasket?

do you think these are v-force 2 reeds?

[acecarlos]

They look like VForce2's...hard to tell from that picture. You can use compression "only" as a baseline, it is not 100% certain compression alone will dictate Pump or race Fuel, however; if you saty around 165-185lbs, you should be fine, still performing a full UCCR is the correct way to determine.

OEM Metal thin gaskets are .25MM or .009"-.010", OEM three piece metal is around 1.6MM thick or .060"-.064", BDTM Copper gasket is .64MM or .025". Don't use any of the Fiber Gaskets as they tend to develop leaks...

Carlos.