701 runs like a stabbed rat for 15-20 seconds, then sounds like it's being choked out.

holygoat

holygoat

Location
Indiana, USA
Just did a top end on my 701. Not my first rodeo with 2 strokes or PWC engines, but my first 701. ADA head, B pipe, single 44 stock 61x bottom end.

It ran great for 15-20 minutes during break in. Then I came back, took a rest, went back out and it ran as per the title. I pulled the head and this is what I saw.

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I changed the needle and seat as per recs, but when I had issues I went back to my original spec and it ran the same. I ran with the hood off to confirm I wasn't choking out the motor with exhaust fumes. Same issue. Checked compression to be sure, 185 both holes. Spark plugs do not look obviously rich.

I am going to test how well my head is sealed tonight to see whether I may be leaking water in. I was just curious what people may think this could be. Do people think that is water or unburnt fuel?

Thnak you
 

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fastgtfairlane

fastgtfairlane

Location
Charlotte, NC
I've learned the hard way to always do a leak down before disassembly and after a rebuild. Never know and it eliminates the possibility. It could have had a very small one that got a little bigger and didn't show it's face until a little later. I don't really think it's your issue but it's always worth checking. You could have something in your ignition system failing after it gets warm.
 
WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
Don't feel bad that Seadoo GTS I just finished , I water tested it a few weeks back and it ran perfect but the jet pump had serious cavitation ,I put another pump and wear ring on it , I decided to take it to the river for Labor day since it was full of gas and had just been registered , I started it before I left the house , sounded fine, I put it in the water , it went about 100 yards and died , got it started and back to the bank and completely ran the battery down messing with it , it would crank and run but not idle or come out of the hole .

I said F it and pot it back on the trailer, I pulled the carb apart this morning and found nothing, internal filter was clean everything looked good , I pulled the pilot jet out, perfectly clean , I ran a small wire bent 90 degrees through each bypass hole, then blew cleaner through the pilot circuit and reassembled it , runs like a top , the only thing I can figure is one or more of the bypass holes got stopped up and that's all it takes for it to run like poop.
 
holygoat

holygoat

Location
Indiana, USA
WFO Speedracer said:
Don't feel bad that Seadoo GTS I just finished , I water tested it a few weeks back and it ran perfect but the jet pump had serious cavitation ,I put another pump and wear ring on it , I decided to take it to the river for Labor day since it was full of gas and had just been registered , I started it before I left the house , sounded fine, I put it in the water , it went about 100 yards and died , got it started and back to the bank and completely ran the battery down messing with it , it would crank and run but not idle or come out of the hole .

I said F it and pot it back on the trailer, I pulled the carb apart this morning and found nothing, internal filter was clean everything looked good , I pulled the pilot jet out, perfectly clean , I ran a small wire bent 90 degrees through each bypass hole, then blew cleaner through the pilot circuit and reassembled it , runs like a top , the only thing I can figure is one or more of the bypass holes got stopped up and that's all it takes for it to run like poop.
Click to expand...

I hate poop like that. That's way worse than me!

I absolutely reamed that carb body with carb cleaner and compressed air. New oem mikuni build kit, new fuel filter. I was so confident I loaded it up and drove two hours, dumped it in the water and just took off hoping that I'd got it right. Happy to say that I did!
 
S

Storbeck

Location
Minnesota
I've experienced the same thing. A crusty old snowmobile carb that is very similar to an sbn. I cleaned it very thoroughly with carb clean and compressed air and even could see light through the progression holes when I shined a flashlight into it but wouldn't run right. Noticed one of the holes was dimmer than the others, more compressed air and carb cleaner wouldn't do it had to give it a poke. Strand of fine copper from an electrical wire wasn't strong enough needed a fine steel wire, that got it, nice bright light through the hole, and then it ran great.
 
holygoat

holygoat

Location
Indiana, USA
mikidymac said:
If you are doing an new engine or new top-end because the old one failed. #1 is the rebuild the carb. Lucky it didn't cost you a new engine.
Click to expand...

I lost my old top end because I lost my cooling line. Got it as a running ski and it didn't give me a single issue all year - I promise you'd have never guessed it looked like that in the carb if you rode it.

Anyway, just one of those things I guess.
 
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