Compression test

[WatchingGhost]

Hello!

I was wondering if I want to do a compression test on my bike, the exhaust has to be installed for a legit result? The exhaust is on the cylinder. Two stroke 50cc water cooling bike.

[jaffa90]

Both ports should be able to breathe.

[jeffyjeff]

Why would it? You are testing compression, not flow. Whether or not the exhaust system is installed is immaterial to your test results.
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History shows again and again how nature points out the folly of men - BOC

[Nobby the Bastard]

On a 2T, the compression only starts once both ports are covered so unless both ports are actually blocked so no air can get in or out of them then it makes no difference if the exhaust is on or not.

I know that reed valves will prevent escape out of the inlet but it can still escape out of the exhaust. To test the compression you don't strip half the engine apart, you just screw the compression tester into the spark plug hole.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[WatchingGhost]

I just want to know because I have just finished replace the top end but also got for my exhaust a new paint so at the moment it is not installed.

[jaffa90]

[Nobby the Bastard]

[MCN]

[WatchingGhost]

Thanks everyone

[WatchingGhost]

By the way I have a problem one of my cylinder stud(there are 4 overall on the cylinder)When I have tried to tighten bolt on the cylinder head with the proper force(what is in the manual) the stud broke.I have already changed that stud and still happened the same. I have tried tighten with less force and the other three work great but this one not. What could be the problem?I guess this could cause lower compression and leak from the cooling water :S

[jeffyjeff]

[MCN]

[jeffyjeff]

[WatchingGhost]

Could be the problem that I haven't used any kind of compound? I just screw the stud in place.

The torque come from the service manual and the unit was checked. Plus the other three stud was totally fine with the torque.

[jeffyjeff]

[WatchingGhost]

Thanks I going to give it a try!

[Robby]

If the stud is breaking - presumably snapping in half - I would assume you have bought very cheap pattern studs.

Cylinder head torque settings tend to be around 30 lb-ft on an M8 or M10 stud. It should take more than twice that to snap a mild steel stud, but you could easily snap cheap stainless at that torque.

As a matter of course whenever you do cylinder heads, make sure all the bolts holes are clean and dry. I tend to poke a small screwdriver into the hole and wiggle it around to loosen any crud, then hoover it out. Then don't use any oil, grease or threadlock unless the instructions ask for it.

[WatchingGhost]

Honestly in my service manual the torque is 50Nm which is around 37lb-ft, and this is an M7 stud(minarelli am6). I definitely going to try with half of it because I believe my replacement stud is not as durable as the original.

[A100man]

[Nobby the Bastard]

The pinch bolt for the chain adjustment hub on my sprint is only 55 Nm and that's got a 17mm head....
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[A100man]

[Riejufixing]

[WatchingGhost]

It is a Generic trigger Sm 50.I have just downloaded the service manual for the ksr version of this bike(which has liquid cooling as well) and it says 18-22Nm.But there was no problem with the other studs when I tightened them. But this aftermarket studs not strong enough so I going to try with 20Nm.

[Riejufixing]

[MCN]