03 yamaha sx viper 700

D

David Mcfadzen

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New Brunswick
03 yamaha sx viper 700.
Hello, i was hoping someone could help me with an issue i have been having with my new to me sled. Her symptoms are whenever she gets warm it wont go over 60mph and bogs, when cold( or for the first 5 min or so) it works flawless. I have taken the power valves apart gave them a light cleaning and do not apear to be sticking also not getting any error codes on dash. It feels like its just starving for gas but cant find any issues there either. she does have high mileage (7000 miles) but truly in mint condition, would it be possible that the powervalve survo motor itself stops working when warm? One more symptom is that even when warm it never likes to start first pull usually 3rd or 4th. Sorry for the drawn out issue but i dont trust my local dealer especially at 90$ hr :( best regards, David
 

Anyway to test this? It doesn't have the other symptoms of bad staror like trip reset? Lights dimming and such just lack of power after warm, going to do a compression test today and watch to see what my power valve survo does just before bog. All 3 plugs are the same dry light brown so not thinking carb issues
 
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Update, out on it now and its working much better then yesterday. Took it out on the pond and first trip across it did 164km/h second trip 140, before she started a slight bog put the choke to full and never made a difference, back on the trails now and it workin great so its a mystery to me :(
 
still likely your stator starting to fail - you might try to line up a spare one in case it goes.
 
Something simple to try is removing the foam when it starts to bog, my thought is as the engine warms up it needs a leaner mixture. If the foam on the air box is choking it you will get a rich mixture, especially at WOT when the demand for air is at it's peak. Worth a try anyways.

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If you can do so safely, you can ease your starter flipper (some call it a choke) open to see if it improves the power or makes it worse. If opening increases the power you are dealing with a lean condition, if it makes it worse you have at least one of a number of possible issues.
 
What lol? You lost me on the last one hahaha. This is were its at now. After 80 km yesterday it was working mint providing i kept it under 100mph all i did was a little gas line anti freeze and fresh gas. When I was 5 min from home it started acting up again and wouldn't do more then 1/4 throttle and then bog and engine sounded different, i made it home and parked it in the garage. This morning i checked the plugs and the clutch side was wet and dark while tbe other 2 were nicely dry brown. I checked fire and all had fire but i replaced with new plugs anyways and took it around the block and worked flawlessly. Curious if the coil on that plug has a bad ground? Or starting to fail? Wish it would just make up its mind lol. Thsnks for all your help, Dave
 
It could be something with the clutching. Tired springs or worn bushings. I had similar problem last year except I couldn't get it past 60 while on a trip. The inconsistent feel of it made me think clutching and all I had was a new secondary spring and a different helix. I wasn't sure if it was the spring or bushings but I changed both the spring and helix just to see what it would do and the problem was gone. Also could be a wire rubbed through somewhere. It could be as simple as spark plug caps. Try giving the wires a slight twist on the plug caps. Sometimes that works and sometimes they need replaced. I doubt its the tors but how much slack is in the throttle cable at the carbs? Should be plenty of slack.
 
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Well figured out that the reason she was working bad at the end last night was that she went down to 2 cylinders. The clutch side is not working. It seems to have fire and wet plug?? I switched the coil to the middle cylinder but did not change anything. I took off the exhaust manifold and pistons all look good couple light scratches but nothing severe. Im lost and not sure what to do next ��
 
for sure a compression check as stated, then..... if it has compression like 90-100lbs or so then I would next remove the carbs and then the reed block as its either a plugged up carb or a bad reed petal.

by the way you cant switch the wires on a viper as it has a 3d ign system and each plug fires on it own cylinder, the old engines you could mix the wires up and it didn't matter. Also the viper has staggered compression meaning the pto cylinder will be LOWER compression then the center and mag side will be, so don't get alarmed if you notice that. will be a good 10-15lbs less depending on your guage used.
 
Could this be a reed problem? I also drained the fuel from that carb today through the screw on tge bottom just to see if there was any dirt, could a carb air lock?
 
David Mcfadzen said:
120 120 110 and 110 is the clutch side were my trouble is coming from
Click to expand...

well good, its likely not blown up or hurt then in that cylinder! Next stop is to the carbs, pull the rack off and remove the pilot jet, and spray carb clean thru the carb hole and see if it comes out in the front throat of the carb. you should be able to hold the pilot jet up to the sky and see light thru it. You may need to refer to the carb cleaning 101 post here on this site for pictures and show you how to do it.

after you do that, remove the reed block assembly for that cylinder and inspect if the reed petals are broken off or burned back and exposing a hole in reed block.
 
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