Suzuki Central Forum banner
1 - 18 of 18 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
Ok so I’ll start from the top. I picked up a 2007 ltz400 last week and it started really easy. Guy said it would start cutting out after riding all day. I brought it home and was riding it for maybe 10 minutes and it’s started cutting out and died. I was thinking fuel issue. Started back up and I limped it back home while it was cutting in and out and then it stopped and was running fine. Then I tried to ride it hard for a second and it kept dying and then starting back up. I checked the oil it was a bit low so I added some. Took the carb off and checked it out and everything was clean. Pulled the plug and did a compression test it was 120(quad was semi warm) and has good spark. Air filter was filthy so I recharged it. Cleaned the petcock out and put it all back together. Now it won’t start. Not with starting fluid or pulling it. Checked the compression again and it was 60. Put a new petcock on and completely rebuilt the carb. Still nothing. Checked timing and valve clearance and they were both good. Any suggestions
 

·
Registered
Joined
·
464 Posts
Does it start when you try to pop start it? I would start to look at a valve issue, You could have a stator/cdi/coil issue that acts up when hot. Usually a valve issue would give cold start issues not hot but with compression issue it is worth a shot and you should check it any way as normal maintenance. Start ruling out one thing at a time.
 

·
Registered
Joined
·
464 Posts
Yes that is in spec, I would check compression again, You checked compression with good battery and throttle wide open?
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #7 ·
I have checked the compression a few times and it’s 60 every time(cold) since that first time I checked it when it was semi warm. I haven’t been able to get it to start since. I guess it’s possible when I checked it the first time some dirt or dust fell down the spark plug hole and made it lose compression? Because it was running before that
 

·
Administrator
Joined
·
3,961 Posts
It may be unrelated to the previous issue, but 60 lbs of compression wont cut it..I would try another gauge to verify, then pull it apart. First i would put a bit of oil in the spark plug hole, see if it makes a difference in compression.
 

·
Registered
Joined
·
464 Posts
If compression was good then dropped I'd try another gauge, if it really is 60 that won't allow it to start, It's possible that you have a decompression set up on the cam which is broke.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #10 ·
I tried the oil test and it didn’t change from 60. Used the gauge in my 400ex and it was reading 128 which is what it was running so I know the gauge is good. If it has the decompression on the cam shouldn’t it be lower? Because it was only 120 after I had been running it then checked the compression after about 30 minutes. Now that I can’t start it the compression is 60 every time
 

·
Registered
Joined
·
464 Posts
If it was your rings the oil should have raised it unless one broke or something, I would pull the valve cover and have a look. I am going to guess one of your valves are hung up maybe bent. Check exhaust cam.
 
  • Like
Reactions: amcf18

·
Administrator
Joined
·
3,961 Posts
Compression should be 142 with de compressor.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #13 ·
Ok so I pulled the top end. Both compression rings were completely stuck in the piston and there were dirt all over the top of the piston. Cleaned everything up and got it back together (cylinder looked fine). Tomorrow morning I’m going to pick up some oil and a filter from Suzuki and I will keep everyone posted. Thanks guys
 

·
Registered
Joined
·
464 Posts
Were you running it with out a air filter? if you have a filter on it I would replace it should be no dirt and that is a sure way to kill motor. While it was a part I would check the ring gap and throw fresh rings in it ( doing that currenlty to my sons friends Z400) Doing a top end and his ring gap was way to big. Whats your compression now?
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #15 ·
I checked gap and the rings/cylinder look good. Compression is 140 now and she’s running smooth. When I get my web cams I’m going to go back in and put a fresh top end in her. I’m gonna take it easy for a couple days then change the oil again and go ride it hard and see if it still is cutting out after it gets hot. Thanks everyone
 

·
Registered
Joined
·
464 Posts
K&N Filters are known to allow dirt into cylinder, I do run them on some of my quads but I keep them clean and oiled and if I am going to be riding somewhere really dusty i'll swap on a uni.
 
1 - 18 of 18 Posts
Top