tjc
Expert
So I have a turbo nytro and I am afraid I may have damaged the engine. I tested the compression on the stock motor today to end the season. I warmed it up to about 140 to 150 degrees on the digital temp gauge and shut it down then tested it. I have about 2200 miles on the engine with about 600 boosted (hard miles and a little lean a couple times about 13:1 on AFR so I would not be surprised although I didn't really run it long at those levels).
I got around 145 PSI plus or minus a couple on all three cylinders. Then we added a little oil to the cylinders and it jumped to about 230 PSI across the board. Does this sound like rings?
It is weird to me that all three are low and all are the same. Maybe this is not out of the ordinary but with my experiences on two strokes it would be one cylinder or the other.
Im going to try another compression gauge to be sure its not my gauge. Any other thoughts? I dont get smoke or anything when it is running.
I got around 145 PSI plus or minus a couple on all three cylinders. Then we added a little oil to the cylinders and it jumped to about 230 PSI across the board. Does this sound like rings?
It is weird to me that all three are low and all are the same. Maybe this is not out of the ordinary but with my experiences on two strokes it would be one cylinder or the other.
Im going to try another compression gauge to be sure its not my gauge. Any other thoughts? I dont get smoke or anything when it is running.
Do a leakdown test. Compression tests don't always tell the story. Compression should be a little higher but normally when they're hurt cylinders don't have equal compression across the board.
Adding oil changes the air compress's thus the higher readings (be careful doing that).
Adding oil changes the air compress's thus the higher readings (be careful doing that).
yukon yamaha
TY 4 Stroke Master
- Joined
- Jan 30, 2008
- Messages
- 1,092
- Reaction score
- 83
- Points
- 688
- Location
- WHITEHORSE, YUKON CANADA
- Country
- Canada
- Snowmobile
- 2008 nytro custom! 2014 viper custom
Also boosted your compression number will change if you have a head shim
Riceburner
Lifetime Member
- Joined
- Apr 14, 2003
- Messages
- 1,760
- Reaction score
- 123
- Points
- 1,158
- Location
- N.B. Canada eh
- Country
- Canada
- Snowmobile
- SideWinder LTX 50th
13.1 should not bother it cruising. 13.1 on a long hard pull, not so good.
My 2011 MCX Turbo Apex runs high 13's at around 6,500 rpm and has well over 1,000 miles like that. It runs like a top.
Head shim in the engine?
My 2011 MCX Turbo Apex runs high 13's at around 6,500 rpm and has well over 1,000 miles like that. It runs like a top.
Head shim in the engine?
tjc
Expert
No headshim. It's all stock. I tried the compression test since that is how the nytro manual said to do it. I have seen a lot of people do a leakdown test on here though.
juwalantz
Extreme
Your good
Good numbers
Good numbers
juwalantz
Extreme
Your good
Those are great numbers from my experience. And since they are all the same I would guess that it is normal wear. Leak down test won't hurt but I would say you are just fine with those numbers my friend. In fact I'm looking at a service manual. Says 213 psi at sea level. If your engine fires right up and it Does not stall or bog i would say Let her rip buddy. Motors will run crappy with bad compression.
Those are great numbers from my experience. And since they are all the same I would guess that it is normal wear. Leak down test won't hurt but I would say you are just fine with those numbers my friend. In fact I'm looking at a service manual. Says 213 psi at sea level. If your engine fires right up and it Does not stall or bog i would say Let her rip buddy. Motors will run crappy with bad compression.
givemeaboost
TY 4 Stroke Junkie
- Joined
- Dec 5, 2003
- Messages
- 689
- Reaction score
- 24
- Points
- 1,028
- Location
- Great Falls, MT.
- Country
- USA
- Snowmobile
- 03 Rx1 Turbo
- LOCATION
- Great Falls,MT
Did you test with the throttle wide open?
Ken......
Ken......
tjc
Expert
Wide open
tjc
Expert
Well for those who were curious, my gauge was bad. 205 across the board on a good gauge. Thanks to those who provided input.
rxrider
Jan-Ove Pedersen
- Joined
- Apr 25, 2003
- Messages
- 7,355
- Reaction score
- 64
- Points
- 1,753
- Location
- Lakselv - 70N & 25E
- Country
- Norway
- Snowmobile
- 2014 Phazer XTX, 2013 Phazer RTX, 2008 Apex RTX, 2007 Warrior, 2006 Attak
That's what it should be 
glad you got that verified.
My friend used my Equipment testing his old RX-1 With 10000 miles on it turboed. It showed from 66 lbs to 102 lbs With 10:1 pistons and 2 head gaskets. The rings were shot. But I started to question my gauge, had it verified to be 100% accurate. He changed to Stock pistons and rings, added a head shim, all is good.
At 145 lbs I would assume you had massive compression leaks running Stock compression.
Glad to hear all is well
glad you got that verified. My friend used my Equipment testing his old RX-1 With 10000 miles on it turboed. It showed from 66 lbs to 102 lbs With 10:1 pistons and 2 head gaskets. The rings were shot. But I started to question my gauge, had it verified to be 100% accurate. He changed to Stock pistons and rings, added a head shim, all is good.
At 145 lbs I would assume you had massive compression leaks running Stock compression.
Glad to hear all is well
smokingcrater
Expert
tjc said:
Thats why the difference between the readings is far more important than the reading! Even a crappy gauge that is wrong will still give consistent readings between holes, and will also show if one cylinder has a problem. If an engine is low on compression on all holes, it will start hard and run badly and less than full throttle, no need for a gauge to tell you that.
tjc
Expert
good info, thanks guys. It seemed weird but I dont have a lot of 4 stroke experience.
