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Got a chance to do the compression check today after warming it up.
Front 112
Rear 110
Pressure stayed steady for a couple minutes.
After doing the compression test, I did hook the air hose to each of the cylinders at a pressure of 60 psi. The front cylinder initially bled down fast and then slowed and then stopped at 30psi. The rear cylinder bled down fast and then slowed and stopped around 20 psi.
Listening to the engine running with a stethoscope there is a touch more noise in the rear cylinder at the exhaust side of the head, but not much more...definitely not what I'm hearing at the pipe.
Also, here's the plugs after a 170 mile ride through the Georgia mountains yesterday...a nice tan on the insulator and ground strap.
Tony, you want to put pressure into each cylinder when the valves are closed and listen at the intake and exhaust on each and see if you can hear the air leaking out. With the stethoscope it should be easy but you might need a second set of hands to keep the air pressure in the plug hole
Hey Tony, Those plugs are super lean. Your compression seemed a lot low. Do you have compression releases or something and did you have the throttle plate wide open. when you pull the plugs pull the wires off also and make sure your battery is at full charge and crank it over at least 6 to 8 full revolutions after the engine has been warmed up a little. (not real hot, it's not good to mess with plugs in a hot motor with aluminum heads) your initial crank should get you to 130 psi even on a stock motor and 175-180 after crankin for 5 or 6 full revolutions. After that checks out then do your leak test on the valves but you need to make sure that the pistons are at top dead center on the compression stroke you can feel the piston coming up with a straw, or something a little flexible like that so you won't harm anything in the cylinder or the piston. once that is all the way up then slowly put air to the cylinder and listen. If a valve is leaking by you definitely will hear it and make sure you do both cylinders so you can hear the difference if one is bad.
Hey Tony, Those plugs are super lean. Your compression seemed a lot low. Do you have compression releases or something and did you have the throttle plate wide open. when you pull the plugs pull the wires off also and make sure your battery is at full charge and crank it over at least 6 to 8 full revolutions after the engine has been warmed up a little. (not real hot, it's not good to mess with plugs in a hot motor with aluminum heads) your initial crank should get you to 130 psi even on a stock motor and 175-180 after crankin for 5 or 6 full revolutions. After that checks out then do your leak test on the valves but you need to make sure that the pistons are at top dead center on the compression stroke you can feel the piston coming up with a straw, or something a little flexible like that so you won't harm anything in the cylinder or the piston. once that is all the way up then slowly put air to the cylinder and listen. If a valve is leaking by you definitely will hear it and make sure you do both cylinders so you can hear the difference if one is bad.
Gotta disagree.... The plugs are about as dark as you want to see them with our gas these days. It just runs a bunch cleaner. Tan is the new rich. And 110, while low is within spec. Definitely do your compression test on a warm motor with the throttle open. And make sure the valves are closed for your leakdown.
Well I got a chance to run air to the rear cylinder. With the bike on the jack and plugs pulled I brought the rear piston to the top...held the rear brake and applied air to the rear cylinder. I did have air coming out the exhaust. I'll be talking to my indy about a rebuild since the case will need to be split too to stop a minor case leak.
Well I got a chance to run air to the rear cylinder. With the bike on the jack and plugs pulled I brought the rear piston to the top...held the rear brake and applied air to the rear cylinder. I did have air coming out the exhaust. I'll be talking to my indy about a rebuild since the case will need to be split too to stop a minor case leak.
Dang it, sorry.
I don't know what kind of riding you do but I would ride it until winter. Then tear it down, wouldn't want to take any long trip, but you are probably going to need a new valve and seat anyway.
Johnjzjz would have better advice in this, so would your indi, but I would not miss riding season for this.
Is your indi any good?
Last edited by Harleycruiser; May 5, 2015 at 08:34 PM.
Dang it, sorry.
I don't know what kind of riding you do but I would ride it until winter. Then tear it down, wouldn't want to take any long trip, but you are probably going to need a new valve and seat anyway.
Johnjzjz would have better advice in this, so would your indi, but I would not miss riding season for this.
Is your indi any good?
Thanks Hc! I already talked to my indy Kevin Baxter @ Pro Twin Performance and will have him double check it next week. If I can hold off on doing the rebuild, I will try to make it to the winter. Most of my riding is just cruising and I do actually have a 500 mile ride planned with a couple friends in about 4 weeks as long as Kevin thinks the bike will be ok. Bike still runs good...just that annoying tick.
Kevin does a lot of engines and has a machine shop for doing the heads and cylinders.
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And 110, while low is within spec. Definitely do your compression test on a warm motor with the throttle open. And make sure the valves are closed for your leakdown.
