Suzuki gt380 compression

[bazit]

Hi
My bike is difficult to start from cold so I have done a compression test on the cylinders ,these have come back at 5 bar ,is this too low?
The bike has new pistons and rings and is 1mm oversize. Perhaps a head skim might improve things
Bazit

[GT750Battleship]

Hi,what's that in PSI Just done the conversion,that's pretty low at 75psi !!
Should be around 110 to 120 psi ? I think your crank seals have failed,or a massive air leak somewhere
Cheers,
Roger

[bazit]

I was going down that route but I didn't want it to be seals (probably clutching at straws) been quoted £350.00 to have them redone .
Bazit

[Alan H]

Compression test should be mainly rings/head gasket. Squirt a teaspoon of oil down the plug hole and try again (plug in of course).
Where are you in the UK?

[Craig380]

Was the compression test done with the engine fully warmed up, throttle wide open and after 6 or 7 quick kicks in a row so the needle on the gauge won't go any higher?

If so, 5 bar means a rebore. You should see at least 7.5 bar (110psi+).

[bazit]

Hi
Warmed up engine then did another compression check and its starting to get close to 6 bar ,if it doesn't improve much more after some more running its off to the machine shop.

[old racer]

If you can ride it get a couple of hundred miles on the clock,
Let the rings bed down then try a compression test again.

[bazit]

Compression still crap @4.5 bar, failed to start this eve engine now in pieces again ,checked piston to barrel distance and it too big as I am able to get 9 thou down the side between piston and barrel manual states if you get 6 thou you need a re-bore and I have got almost 10 thou if pushed .
Any body know where to get re bore done without breaking bank.
Bazit

[Alan H]

If you let us know where you are, we might be able to suggest a local mender.
New pistons and rings you say? Who did them or who told you that had been done.
Sounds like someone has been lifting your leg a bit there.

[Suzukidave]

Hi
My bike is difficult to start from cold so I have done a compression test on the cylinders ,these have come back at 5 bar ,is this too low?
The bike has new pistons and rings and is 1mm oversize. Perhaps a head skim might improve things
Bazit

If the shop doing the bore and hone doesnt know what the final clearance should be with new pistons after honing they could have over done it and they must know to chamfer the ports so they dont eat up the rings . http://www.youtube.com/watch?v=WDKiv-nQtwA" onclick="window.open(this.href);return false;

[tz375]

It's hard to imagine how the compression could be so low with new pistons and rings and that makes me wonder if the gauge is reading low.

Can you borrow another pressure gauge to double check or try your gauge on a bike that you know is running well. Harbor Freight gauges and similar designs are prone to read about 60PSI and stick there even on a good motor with 120 or more PSI.

[Suzukidave]

Checking ring end gap would tell the tale of to much clearance machined in .