[Beewerks]

Hey guys, I just did a compression test of my '05 Tdub with 12,000 miles on it and got back 95 psi. Isn't this kind of low? Or is that right about where it should be? I checked the main service manual but couldn't find any info about cylinder pressures. Thanks!

 

[admiral]

I found in both the main manual and supplement manual the compression pressure listed as 128 psi. Didn't list a range, but I suspect 95 psi is a bit lower than what you're wanting.

 

[Beewerks]

Oh snap!

Maybe it's my prolonged periods of riding WOT that is messing it up.

 

[Beewerks]

Qwerty, if you see this, do you know what compression you have on your engine with the 40,000 plus miles you have?

 

[TWBARR]

double post

 

[TWBARR]

Can't remember where it is in the manual but I found it on this forum. 114 PSI min to 149 PSI max so 128 would be normal range.



http://tw200forum.com/index.php?/to...395__hl__compression__fromsearch__1#entry4395

 

[lizrdbrth]

Did you have the throttle open when you ran the compression?



Just axin'.

 

[jbfla]

Did you have the throttle open when you ran the compression?

Just axin'.

My thoughts, too.



Normally about 100 psi minimum is required to have proper detonation of the fuel.



jb

 

[qwerty]

126psi with the throttle open and a good battery. It was 130psi when I bought her. At this rate, she'll be down to 114 in another 146,000 miles and time for new rings.

 

[-Jake-]

you checked your valve lash lately?

 

[elime]

Sometime little bits of carbon break off when you remove the spark plug and get caught in the valves. Start it up and run it and then do a second test. Try another gauge too.



If it runs well don't worry about it.

 

[TWBARR]

I am having issues also. My bike will not start. Think I have bent valves, so i ordered them from Amazon for $35. Can you run a compression test by starting it since mine will not start at all? I am not getting any reading from the tester. I tried kick starting it and electric starting it and no compression.

 

[B-dub]

I am having issues also. My bike will not start. Think I have bent valves, so i ordered them from Amazon for $35. Can you run a compression test by starting it since mine will not start at all? I am not getting any reading from the tester. I tried kick starting it and electric starting it and no compression.

Procedure for doing a compression test as I understand it:



Start the bike and let it warm up. If your bike won't start, you can skip this step.



Make sure battery is fully charged.



Pull spark plug and twist in compression tester, making sure it's snug enough to seal



Open throttle all the way and press the starter button. Using the kick starter will work, too.



Watch the needle come up on the compression tester with each compression stroke.



When the needle reaches it's highest reading, usually after 2 or 3 compression strokes, stop and record the reading.



If you get a low reading and want to determine if it's ring trouble or valve trouble, squirt a little bit of oil in the cylinder and repeat.



If the compression reading comes up, then the trouble is with rings. If not, it's valve problems.



If the tester will read nothing, as in your case, it's safe to assume you have a bent valve.

 

[elime]

If the tester will read nothing, as in your case, it's safe to assume you have a bent valve.

Could be a hole in the piston.

 

[TWBARR]

Could be a hole in the piston.

Piston is good I had an issue that involved replacing gaskets and timing chain slipping off of sprocket and causing some issues. Compression test does confirm that I indeed have bent valves as they do not seat properly in cylinder head. Valves on their way. Thanks to Ayers Garage and B-Dub for their input and advice/walk through to help me figure this out.





PS take your time and triple check everything before proceeding, lesson learned(the hard way). Bright side is that I still will save myself a lot of moolla by doing the work myself. base gasket is a fairly simple job. Just take you time and label/picture everything and study parts diagram thoroughly and familiarize yourself with it before proceeding.

 

[PalmStateCrawler]

Instead of starting a new thread I figured I'd just add to this one. Still having a hard time jetting my pumper carb. Out of curiosity from playing with the carb, I did a compression test and it reads 153psi. Seems a bit high right? What adverse effects would that have and would this effect the jetting?

 

[like2wlz]

My TW has over 11,000 miles and has lived a hard life as a MSF training bike, run lean and hot with a FMF muffler installed at unknown mileage so I was wonding if rings or valves have taken a beating. Compression test with a HF compression tester read 148psi so I assume everything good in that regard.

 

[elime]

My TW has over 11,000 miles and has lived a hard life as a MSF training bike, run lean and hot with a FMF muffler installed at unknown mileage so I was wonding if rings or valves have taken a beating. Compression test with a HF compression tester read 148psi so I assume everything good in that regard.

Sounds good to me. If it is running well then don't try to fix it.