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Compression test

ktmjunkie

Contributing Member
when doing a compression test

when doing a compression test on my 50hp blueband 4 cyl 2 stroke (thunderbolt ign ) do i need to earth the plug cap while i do the test ?
also what is a acceptable reading ?
Regards gordon
 
"your control box should have

"your control box should have a safety switch, man over board switch, engage it. If no switch then get a remote starting switch and jump the starter solinoid leaving the ign off (grounded). You can also use a jumper wire from bl/y on the switch box to ground and then use the key. You are correct to ground the ign wire some how to avoid damage to the switch box. Compression should be with all 4 within 10 percent of each other, expect 130 or so on your engine depending on the gage. Good luck on #4, its a pain."
 
"JB Thanks for your fast reply

"JB Thanks for your fast reply, so safety switch on and ground the plug lead and 130 psi per cyl. i have to loosen some bolts to inspect the water jacket, maybe it will make it easier to get to number 4. thanks again.
regards gordon"
 
"if you pull the safety switch

"if you pull the safety switch, there is no need to ground the ign leads. Your engine might have 150psi, as long as they all read about the same, give or take. 130 is just an estimate"
 
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