Hi all,

I need to do a compression test on my 2004 TE 450 but im unsure of what readings I should be expecting with a healthy engine & what readings would mean trouble down below!! ,the test would have to be done on a cold engine as bike is currently not wanting to play so I guess I will have allow for this but no idea how much???

any help apreciated.

compression test on a bike with a working Automatic DeCompressor (ADC) will tell you nothing, except that the ADC is working.

Compression test on a bike with an ADC that is not working or disabled will be very hard to do, the e-start wont be able to turn the engine over.

Thanks for the reply,the bike has a manual de comp lever on the bars so think? this should enable me to do the test,ill post any results if it gives a reading.

Porkyblader, on 06 February 2012 - 12:01 AM, said:

I guess you are saying that the bike does not have an ADC. If your bike does not have an ADC, you will need to avoid using the manual compression release to get an accurate compression test. You will have to kick the bike over with no decompression devices.

IF you can kick the bike over with no decompression, you definitely need a valve job or piston/ring job.

You do have an Auto Decompressor on the 04 models.

Yes my mistake Ricky but I guess if the engine cranks fast enough the ADC should be disabled ,have done a compression test & with the engine cranking fast & throttle wide open I was getting approx 80 psi then dropped a little oil into the bore,repeated test & got approx140 psi.

Porkyblader, on 06 February 2012 - 02:29 PM, said:

I did a compression test on mine last year, got 135 lbs, guys here told me that's all I'd get with my ADC working. And 135-140 is not what the bike's are capable of.

Basically, if you are getting 140lbs, you're OK and the bike should start, that's enough compression to run the bike.

Check your intake manifold boot.

I have 2 TE250's. Mine is a 2006 and my sons a 2007. The 2007 starts and runs flawless. The 2006 is hard to start cold. After checking several things ( valve clearance in spec, carburetor clean & jetted correctly, strong spark) I did a compresion test and found mine struggled to reach 60 psi & my sons reached 120 psi within a couple revolutions of the starter. I tried closed and open throttle and came up with same results on both bikes. I went one step further on the low compression bike and did a leak down test and could hear air hissing through the air box. I am now in the process of getting valve job done on the 2006.
Your bike is 450 so I would assume the larger bore will give you slightly higher compression.
Also the 2006 has lower miles and less hours but has valve problems. When I first bought the bike used I immediately found it had a vacum leak at rubber intake manifold. Had fixed that months ago but still remained harder than normal to start. I do not know how long previous owner rode bike like that. I assume between running lean with air leak and possibly sucking dirt in has caused my current intake valve problems.