Did ring replacement, but compression still low
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Did ring replacement, but compression still low
Had low compression and bike wouldnt start so I replaced the rings and gaskets so why am I only getting 70psi compression? I did the compression test right and I carefully honed the cylinder and cleaned off the gasket surfaces and torqued everything down to spec. I dont understand what could have happened.
- Trafficjamz
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Re: Did ring replacement, but compression still low
put a little bit of oil in the spark plug hole and test again.
new best 1/8th mile time 9.647 seconds @67.155 mph 310lbs total weight
Re: Did ring replacement, but compression still low
The cylinder could be out of round or beyond wear specs, did you mic it before honing? how much material did you remove? A ring could have snagged a port and broke, or a ring could be sticking in the groove if not cleaned properly.
Put a little oil in the cyl and see if the numbers come up. Are you doing the compression test with the carb attached? if so open the throttle completely. A fresh engine will not have perfect compression until the rings seat. 70 psi should at least start, try some ether.
Did you ever have the bike running before replacing the rings? Could be another issue altogether.
Put a little oil in the cyl and see if the numbers come up. Are you doing the compression test with the carb attached? if so open the throttle completely. A fresh engine will not have perfect compression until the rings seat. 70 psi should at least start, try some ether.
Did you ever have the bike running before replacing the rings? Could be another issue altogether.
Re: Did ring replacement, but compression still low
Make sure the tiny marks found on the rings by the gap are facing up. Sometimes a flashlight makes seeing the marks easier.
2001 Honda Elite
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
Re: Did ring replacement, but compression still low
Did you hone the cylinder before you installed the new rings? Did you oil the cylinder walls, piston and rings with 2 stroke oil BEFORE you installed the piston in the cylinder?
Bear 45/70
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Re: Did ring replacement, but compression still low
Yes he did bear.tricolour wrote:I carefully honed the cylinder
2001 Honda Elite
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
Re: Did ring replacement, but compression still low
I don't thing I ever heard the term "I carefully honed the cylinder" before. Honing is a semi haphazard process. Did he break a ring while doing the install?
Bear 45/70
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
Re: Did ring replacement, but compression still low
Bear45-70 wrote:I don't thing I ever heard the term "I carefully honed the cylinder" before.
it doesn't seem like he's going to reply
2001 Honda Elite
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
1995 Yamaha Jog
1994 Yamaha Axis
I can't believe
that cop put me
in the backseat
when I clearly
called shotgun.
Re: Did ring replacement, but compression still low
I took the head and cylinder off again and rings are not broken and they are installed the right way up. Yes, everything was oiled up before assembly. The only thing I can think of is that the cylinder is worn out. I don't have a micrometer to test with. I may end up putting the bike up for sale. Surprising thing is it ran great until I put it away for winter 2009 and never started up since.
Re: Did ring replacement, but compression still low
just curious did you ever try to start it up after you put the rings in... as long as it runs right and making sufficient power who cares what some gauge says
1985 aero 50
ported
custom exhaust
ruckus vario
1K polini clutch springs
hopefully nh80 powered soon!
ported
custom exhaust
ruckus vario
1K polini clutch springs
hopefully nh80 powered soon!
Re: Did ring replacement, but compression still low
bc117 maybe on to something here. With a fresh hone and new rings (AKA unseated rings) the compression could be low but as long as the engine starts then the seating process begins and the rings will seal better. Question, when you did the compression test, did you have the throttle at WOT?
Bear 45/70
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
Re: Did ring replacement, but compression still low
The initial compression test was around 70psi. When I added some oil to the cylinder, compression jumped up to around 120+ with WOT. It still won't start and run though. It just barely runs with the starter engaged but quits when the starter stops. Throttle position doesn't matter. Still can't figure it out.
Re: Did ring replacement, but compression still low
For start up with a cold engine the throttle must be closed. Change the plug.
Bear 45/70
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
'83 Aero 80 X 3
'84 Aero 80 X 3
'85 Aero 80
'84 Aero 125 X 2
'84 Aero 125
'84 Aero 125 X 2
'85 Aero 50
'85 Spree
- Wheelman-111
- Moderator
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Re: Did ring replacement, but compression still low
Greetings:
The next thing to check is the crankcase itself. A leaky seal at either end will be obvious as oil misting or leaking from the crank end. If that looks OK, sometimes a cracked reed valve will give low compression and hard starting. Finally the crankcase halves may be leaking from a gasket issue (SE/05) or failed HondaBond. (SA/16)
The next thing to check is the crankcase itself. A leaky seal at either end will be obvious as oil misting or leaking from the crank end. If that looks OK, sometimes a cracked reed valve will give low compression and hard starting. Finally the crankcase halves may be leaking from a gasket issue (SE/05) or failed HondaBond. (SA/16)
Wheelman-111
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH
Most of my money is spent on scooterparts. The rest is just wasted.
"ISO": '03 Vespa ET4 Malossi187 74MPH
Flash 9: 2001 Elite SR Contesta 72 ZX Tran, 9:1 Gears, Stock Airbox/Carb/Pipe 58.8 MPH
Punkin: 2010 Vespa/Malossi S78, 61MPH