Thread: 2 stroke question
10-19-2006, 11:39 AM #1
2 stroke question
I just bought a 95 xp and I am having a bit of a starting problem with it. I bit of background on it. The engine is stock far as I know. It has had the oil injection blocked off and the choke replaced with a primer knob. The problem I am having is it's very hard to start hot or cold. The way it acted seemed like the compression wasn't quite right on it. I just pulled the plugs to check compression but first turned the motor over and gas vapor came blowing out of the plug holes. The plugs where wet when I pulled them. I know a bit about 2 strokes but apparently not as much as I though. I thought that the cylinder had to be able to make some compression to draw fuel into the block then into the cylinder. Am I wrong in this assumption? After seeing this I have come to the conclusion that the plugs are flooding when I try to start but the engine seems to run fine at top end. Turning about 7000 on the factory tach. Any ideas on why I am getting a very rich mixture at start up? My next step is going to be making sure that idle jet isn't misadjusted. After that I'm at a bit of a loss. Any help would be greatly appreciated. Karl.
10-19-2006, 11:46 AM #2
Your plugs may be fouled. Try new plugs. Are u sure the mix is not too lean? Meening too much oil (wrong ratio)? What was the compression reading on the holes? Low compression will make it hard to start. 7g on a 2 stroke seems way low. Low compression will not yield high rpms. Stuck carb floats will be hard to start. Exhaust leaks will be hard to start.
10-19-2006, 11:55 AM #3
yea what color is the fluid thats comeing out are you sure its not milky if there is any water in there it will make it hard to start or turn over
10-19-2006, 12:05 PM #4
Ok havn't checked the compression yet since I wasn't sure about the vapor coming out. that and the carbs will be next on the checklist. That 7g is on the factory tach which is a dialtype so I figure it's inaccurate from the get go. The gas and oil is being mixed at 40:1 since the oil injection is inop. since it's a heavy vapor coming out it's hard to tell but it's a dark color. No water. Plugs are brand new that was the first thing I tried. The plugs have a black color to them but no fouling. Just wet with fuel.
Last edited by Blackhardt; 10-19-2006 at 12:07 PM.
10-19-2006, 01:10 PM #5
10-19-2006, 01:11 PM #6
o and what motor does it have in it?
10-19-2006, 01:54 PM #7
You might have a stuck float valve........Meaning you could have debris in the float valve so the float does not turn off, and when it sits you end up filling up the crank case. YOu can check if it is the problem by getting the ski started, go out and run it, and when oyu are done, turn off the fuel selector switch completely. Come back in 30 minutes turn on the fuel selector and try and start it. If it starts fairly easy that is your problem most likely.
Pull the carbs off and clean them, it is not a difficult thing to pull the carbs apart and clean out all the jets and the float valve. Carb clean everything and dry off with compressed air.
10-19-2006, 09:40 PM #8
boy, you can tell this is a 4 stroke message board First, 6800-6900 is the normal rpm range, the carbs don't have floats but a spring loaded needle and seat and there are different tension springs that allow the N/S to open at different amounts of vaccuum. There could be some trash in the N/S, a bent N/S lever, a split diaphram or check valve, a worn tip on the needle (the tip is rubber), the side of the needle could be worn and hanging on the seat. The 720 shakes a little more than the 787 and dribbles fuel at idle with low pop-offs (spring tension) but yours is stock and that shouldn't be the problem. I would recommend taking the carbs apart to clean and inspect all the parts, particularly the tiny plastic high speed bleed or check valve, or valves if it's a twin carb. This check valve is a very thin piece of clear plastic, kind of wedge shaped, that is on the block that is removed to get to the jets. If it's weak it can let fuel bleed from the high speed circuit when it's not supposed to and make the fuel mixture extremely rich any time other than wide open throttle, a 10 cent part that cost $2. The carbs are simple as carbs go, so if you can rebuild a car carb, these are simple. And it gets better, here you a carb manual for free http://www.mikuni.com/pdf/sbn_manual.pdf
Hope this helps.
10-19-2006, 09:54 PM #9
I dont know much about see doo's but it sounds like it could be something like a rotory valve.If it was a yamy I'd say reed valve.Might be worth checkin
10-19-2006, 10:09 PM #10
Leaky needles and seats.
Maybe worn out needles, or smegma in them.
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