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The 2-Stroke Garage => Turning Wrenches => Topic started by: SDDaytona on June 23, 2025, 09:11:38 AM

Title: Low cylinder compression
Post by: SDDaytona on June 23, 2025, 09:11:38 AM
Measured the compression on my new to me Daytona (16k miles) and got a measly 65lbs per cylinder. Bike is still running well and making plenty of power.. any reason not to wait a few more months before a rebore?
Title: Re: Low cylinder compression
Post by: m in sc on June 23, 2025, 10:56:01 AM
you absolutely sure the gauge is accurate? 65 is pathetic, I rebuild at 90 ish. I got bit by a low reading gauge once, I'd verify it's accuracy 1st
Title: Re: Low cylinder compression
Post by: teazer on June 24, 2025, 03:56:43 PM
Quote from: m in sc on June 23, 2025, 10:56:01 AMyou absolutely sure the gauge is accurate? 65 is pathetic, I rebuild at 90 ish. I got bit by a low reading gauge once, I'd verify it's accuracy 1st

I found that a lot of good looking economy priced pressure gauges read low. I have several good gauges that I use, but you also have to pay attention to the throttles which must be wide oen and did you kick it once or keep kicking until it peaked - typically 5 or 6 kicks?
Title: Re: Low cylinder compression
Post by: 1976RD400C on June 26, 2025, 05:54:25 PM
Make sure your gauge has a schrader valve right in the piece you screw in the spark plug hole.
Title: Re: Low cylinder compression
Post by: danketchpel on June 26, 2025, 10:02:05 PM
Quote from: m in sc on June 23, 2025, 10:56:01 AMyou absolutely sure the gauge is accurate? 65 is pathetic, I rebuild at 90 ish. I got bit by a low reading gauge once, I'd verify it's accuracy 1st

Do you test hot (running temp) or cold?
Title: Re: Low cylinder compression
Post by: SoCal250 on June 26, 2025, 11:18:05 PM
Quote from: danketchpel on June 26, 2025, 10:02:05 PMDo you test hot (running temp) or cold?
cold
Title: Re: Low cylinder compression
Post by: Pravin on June 27, 2025, 06:48:33 AM
65 is very low , if the bike is running well then surely the gauge is not accurate , 120 125 is the start on stock and 90 is the bottom line I guess..

Get the readings with some other gauge and check !

Cheers,
Pravin