2001 Srx compression

auji700triple

auji700triple

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What is the normal compression for the 01 Srx. Roughly 8,000 km on the motor and I don't think it was ever rebuilt. For my checks I got 110 psi across the board, I hope to hear thats normal.
 
Probably not bad, different peoples readings range depending on the guage used. Should be good as long as they are all within a few psi of eachother.
 
If it runs good I wouldnt stress about the 110 number. Alot of factors, Altitude being one alot of guys dont think about. Leak down test more accurate towards good bill of health. i had a 700 SXR (red head) that still had 114psi on a burnt down cylinder, other 2 were @ 120psi.
 
U will only see those numbers if its real healthy and ur using a short hose guage. If ur guage is short then a few new rings would pep things up a little.
 
One other factor that many people fail to recognize during a compression check is the position of the powervalves. An open powervalve will show less compression than a closed powervalve. Just as the throttle being open or closed will affect the numbers. Because the ecm controls the opening and closing of the valves, we don't really know their position without looking at the servo position. We can't assume that the ecm/servo will leave the valves in the same position (open/closed or anywhere in between) on every sled. This can certainly skew the results when comparing numbers from sled to sled. I can say on my machine with my gauge on the day I checked was in the low 130's psi. ;)!
 
Macheater said:
One other factor that many people fail to recognize during a compression check is the position of the powervalves. An open powervalve will show less compression than a closed powervalve. Just as the throttle being open or closed will affect the numbers. Because the ecm controls the opening and closing of the valves, we don't really know their position without looking at the servo position. We can't assume that the ecm/servo will leave the valves in the same position (open/closed or anywhere in between) on every sled. This can certainly skew the results when comparing numbers from sled to sled. I can say on my machine with my gauge on the day I checked was in the low 130's psi. ;)!
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Actually the powervalve set up is spring loaded so that the valve does return to fully closed, the only time the valves are open is below 900rpm for a self clean feature and above 6000rpm. Thats why if you pull a cable thru the valve it returns the valve to the closed position, and you have low peak rpm (8000rpm)from the engine because the exh port is effectively lower with the valve closed.

The valves not being closed is not a factor in checking cranking compression, yamaha has thought this set up thru and it works perfectly without glitches. the varying numbers are from the hose length on the compression guage and the thread adptors length. Ambient temp will also have some effect on your readings, colder out the thicker the oil is, the less rpm you pull it over at.
 
just do a leakdown test with a differential gauge and make sure the numbers are below 5% = keep beating on it and recheck when your buddy wastes you in a race or 1 year, whichever comes first.

Compression numbers are not real important but will show if you have a dead hole.
 
Aircraftman said:
just do a leakdown test with a differential gauge and make sure the numbers are below 5% = keep beating on it and recheck when your buddy wastes you in a race or 1 year, whichever comes first.

Compression numbers are not real important but will show if you have a dead hole.
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awesome, I like it, if you get beat or 1 yr whatever comes first...lol.... ;)! :2strokes:
 
A shade tree wade of checking ring/cylinder wear is to test all 3, give each a snort of WD-40 or similar oil, re-test. If PSI's significantly jump its an indication of excessive wear, the oil "fills the gaps" = higher comp numbers.
 
mrviper700 said:
Actually the powervalve set up is spring loaded so that the valve does return to fully closed, the only time the valves are open is below 900rpm for a self clean feature and above 6000rpm. Thats why if you pull a cable thru the valve it returns the valve to the closed position, and you have low peak rpm (8000rpm)from the engine because the exh port is effectively lower with the valve closed.

The valves not being closed is not a factor in checking cranking compression, yamaha has thought this set up thru and it works perfectly without glitches. the varying numbers are from the hose length on the compression guage and the thread adptors length. Ambient temp will also have some effect on your readings, colder out the thicker the oil is, the less rpm you pull it over at.
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Yes ur quite right on every account. However, a broken or misadjusted cable are 2 things that can effect the position of the valve. In "my experience" the postion of the valve will effect cranking compression. So I stand by my statement.
 
Macheater said:
Yes ur quite right on every account. However, a broken or misadjusted cable are 2 things that can effect the position of the valve. In "my experience" the postion of the valve will effect cranking compression. So I stand by my statement.[/QUOTE


True, on a four stroke when camshaft lift and duration come into play along with intake/exh valve overlap.
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Macheater said:
Yes ur quite right on every account. However, a broken or misadjusted cable are 2 things that can effect the position of the valve. In "my experience" the postion of the valve will effect cranking compression. So I stand by my statement.
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if the cable is broken.... the valve is kept closed by the spring.
if the cable is misadjusted... the valve is kept closed by the spring.
I dont see how your going to have a valve open for checking compression unless you adjust the cables all the way out(shortest spot) which it wouldnt run too good after you get it started ,so its not just a accident setting by adjusting the cable adjuster clear out to pull the valve from the closed spot.

go out and take the 4 bolts loose on your srx youll see what i am saying, its spring loaded, that spring keeps the valve closed. The only way it comes open is when the servo pulls the cable which compresses the spring inside the housing.
 
Which reminds me, I am going to change the 6 gaskets on the power valves. Seems like I have a small bit of oil leaking onto the manifold. I'll do that swap sometime this weekend. As for a leakdown test, no issues. 110-112 on all 3 cylinders, she will be fine for this season

Seeing how I'm going to have the powevalves out of the sled I'll be letting them soak in some cleaner over night... Back to brand new!! :letitsnow
 
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auji700triple said:
Which reminds me, I am going to change the 6 gaskets on the power valves. Seems like I have a small bit of oil leaking onto the manifold. I'll do that swap sometime this weekend. As for a leakdown test, no issues. 110-112 on all 3 cylinders, she will be fine for this season

Seeing how I'm going to have the powevalves out of the sled I'll be letting them soak in some cleaner over night... Back to brand new!! :letitsnow
Click to expand...


You should think about replacing the PV shaft seals if the oil is leaking through the weep hole in the PV housing or the cable o-rings if its coming from the top of the housing where the cable enters.
 
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