650sx...need help please

[Bobert540]

Well to make a long story short I bought my ski about 2 weeks ago. It was sitting for awhile but the guy got it started and sounded good when I picked it up. Took it to the lake the next 2 days and it ran great no problems at all. I took it out this afternoon and it wouldn't start. checked the plugs and made sure it has spark which it does. So we poured a small amount of gas in the carb got the ski started finally I took it out let it idle to warm up and finally got it to plane after trying to get it to take off for 5 mins.

I was riding it for about 5 min WOT to make sure it was running good and everything finally seemed fine. Made a turn but fell off, ski turned like it should but when I grabbed it and hit the gas it shut off. Now the ski feels like it wants to start but the motor won't stay running? Any ideas, hints?? I am clueless as to why it won't stay running now.

 

[extreemthrottle]

start with the simple stuff. fuel filter, make sure the choke is'nt sticking, water in the fuel.

 

[Bobert540]

Choke isn't sticking. How can I check the fuel filter? Mine is clear and the screen looks clean to me....

 

[spence]

could it be anything with adjusting the carbs?

 

[Vumad]

I heard theres a foaming carb cleaner that works exceptionally well. I eas told you don't need to take the carb apart, just spray it in and it does the rest (I think he said engine running but not sure). Anyway, I don't know what it's called but it does work so that might be a help.

Only so many things it could be. No spark, bad gas, dirty carb (or some other cariation of fuel blockage/problem)... I mean... it's 2-stroke... if it has gas/air, compression and spark, it runs. It's $3 for plugs, it wont hurt you to replace them. Spark and good spark aren't the same.

 

[Vumad]

could it be anything with adjusting the carbs?

Carb adjustment could explain it running crappy, but if it was running, it should keep running (unless it blew up or flodded itself). It not starting wouldn't be from an adjustment. It was running and they didn't touch the carb so that's not the problem. Not to say the carb doesn't need adjusting, but most likely, that didn't cause the change.

Why was the ski not getting on plane? It was running and had no power? It's not a very good description of what's happening. "it's not working" is a broad question so the answer will be broad.

 

[Crab]

Water probably in the fuel tank got sucked up, or the low jet is plugged. The small 28mm carbs were bad about that, I always run a small prefilter just before the carb and change it yearly. The stock water seperator will fill and dump water into the tank.

 

[Bobert540]

Once we got it started I let it idle and then I slowly got on it but it didn't want to go at first and then it did. It got on plane no problem and I was running full speed. It didn't want to go at first, I had to blip the throttle a few times for it to really take off. After that it ran fan, I fell off the ski did it's normal loop. I grabbed the ski and it stalled and wouldn't start again. It sounded like it wanted to but it wouldn't stay idling.

 

[slag]

Water probably in the fuel tank got sucked up, or the low jet is plugged. The small 28mm carbs were bad about that, I always run a small prefilter just before the carb and change it yearly. The stock water seperator will fill and dump water into the tank.

How? On my 650sx's, there is a 1 way check valve that will allow air into the tank, but unless its on its side for several minutes, very little water if any will get into the tank.

 

[standupwannabe]

Years ago I had a 650SX and had similar problems (the ski started to bog and hard starting. I also started experiencing power loss at wide open throttle). I took it to the shop and they opened the black plug on the front timing cover; it should be dry in there, but I had a slight white oily residue in there. In short, my main front engine seal was failing and causing the ski to run leaner and leaner (sucking in air). Unfortunately this involves a complete breakdown of the engine to fix. Not to say this is the case with yours, but something to look at.

 

[noah45]

Compression check?

 

[Bobert540]

Well I just went out to start it today and I got it going by giving it some throttle and it would rev up and idle...I am going to go back out in a couple mins to try again. I did not change a thing from yesterday.

 

[Vumad]

My 650sx usually does not start w/o throttle. I have a 44mm carb. From cold it starts right up because I have a primer, but if I fall off and it dies, then I start it differently. Hit the start button to make sure not to flood it. Then lightly hold the trottle and hit the button. Sometimes it starts right up, others it had too much gas so takes a second, and other it didn't have enough gas and needed some throttle.

Play with it, it's 20 years old. You shouldn't hold high expectations. Mine came with a 44mm carb, but as I understand it, if you have the stock 28mm carb, you shouldn't be expecting a lot of power.

 

[Bobert540]

UPDATE:

I took the ski to the lake today and here is how I figured out how I need to start it. If I start it with the choke off it will start and idle but when I hit the gas it wants to go but shuts off. So what I do is put the choke fully on start it and blip the gas and then it takes off. As I take off I take the choke off and it runs fine. IF I fall off it goes around like it should but when I go to hit the gas, again it wants to go but shuts off so I just kept starting it with the choke and so on.

Another thing I noticed is sometimes if I am just cruising around and slow down below half throttle and gas it it seems to only go as fast as half throttle. The boat will plane but won't go faster. So I just blip the throttle 2-3 times and then it will take off.

So I am not sure what it is that is causing these things but the ski does run fine once it's started.

 

[Vumad]

Rebuild/clean the carb, and convert that choke over to a primer.