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Discussion Starter #1
Bike was running fine just the other day, no weird noises or lack of power. Went to go for a morning ride and wouldn't start.
Battery good and charged
Brand new spark plugs today
Plugs are sparking (visually checked)
Air filter cleaned recently
Carb rebuilt about a month ago
Starter fluid didn't do anything (not fuel)

After a while I got bored and just did a compression check. 60psi on right cylinder and 20-30psi on the left. It ran fine the other day. Now I'll admit I've been putting off doing my valve check but did I really destroy some valves just like that?
Everything in my gut says 2 valves wouldn't fail at the exact same time.

So again ran fine, parked overnight, wouldn't start and random low compression in both cylinders.
What the heck stumped
 

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Possible your compression tester does not fit the spark plug hole. Look at spark plug hole with flashlight; notice notch that allows water to drain away. Unless your compression tester has very narrow surface, it does not get past the notch, so you're not measuring compression. Probably need an extension. I'll take a picture of mine to post later. Cheers!
 

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Current mileage and miles since last valve check? We've historically seen valves near 0 clearance corrected and bikes returned to reliable service. Tight clearances absolutely DO effect starting. This element of service is SO important, should not be disregarded.

PS discontinue the use of destructive starting fluid...(it dilutes and washes oil off cylinder walls).
 

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Discussion Starter #4
The tester looked good but I'll check to see if maybe that's the cause of the compression reading.
Current miles are 32,xxx. Last valve check was around 26,xxx.
The bike was always reliable before this. What should I try first? At a loss for direction at this point
 

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check valve clearances
check petcock function (fuel actually reaching carb bowls under vacuum, but petcock not flowing without vacuum)
check spark wires intact and plug cap innards tight and clean

If no positive results, revisit the state of carbs
 

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Comp Tester Extension for recessed 12mm spark plug holes:

51908


Made from gutted end of 12mm spark plug and thick 12mm nut, some fancy welding, voila!
 

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Gen1 or Gen2 bike? If Gen1 (came with bad tensioners), the cam chain may have jumped time.
 

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Discussion Starter #8
check valve clearances
check petcock function (fuel actually reaching carb bowls under vacuum, but petcock not flowing without vacuum)
check spark wires intact and plug cap innards tight and clean

If no positive results, revisit the state of carbs
Valve check went good. Started up first time this morning. As soon as I start the bike it shoots right up to like 7000rpm. It runs and starts without choke. Got any ideas? Breaking back down now
 

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Discussion Starter #10
It was the cable or my idle screw one or the other. Adjusted everything, running like a champ now. Let her warm up and made sure the coolant was on point.

Thank you everyone. These bikes are awesome.
 

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"Bike was running fine just the other day, no weird noises or lack of power. Went to go for a morning ride and wouldn't start."
"It was the cable or my idle screw one or the other. Adjusted everything, running like a champ now."

deked
 
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