This melt down just might have me stumped..
- Thread starter Roseand
- Start date
Pilot jets are always very sensitive, going from a 120 to 125 is very noticeable. Single carb setups make the main circuit insensitive to small changes, you need to make larger moves. My last 61x cased 701 needed a 160 and 2 turns in order to get 20 rpm rich of peak.
They most certainly do if you want to save a burndown. Been there. Egt's on my sled saved a burn down three different times with three different problems. Those combined with plug reading and wash is how I tuned that motor and it flat out rips
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How do you know the proper temps? Some engines run great at 1100, others melt at 1000. These instruments are not widely used in watercraft anyway. An experienced ear and cheap tach will allow you to find best power quickly and safely. Exhaust temp and plug color are secondary to the fact that best power has been attained. No need to make the tail wag the dog.
Little bit of an update: My porter said that he'd honestly recommend switching to a 2.0 n/s since it'll change the fuel curve, different than a 1.5 would even with different springs. He said he personally would try that without even touching the jetting again, since there was just a lean spot from 1/2ish to 3/4 throttle. I still think I'm going to change up the jetting and start rich and work my way down. He said the goal is to have the largest possible pilot jet you can have without it loading up.
Does anyone have some ideas on where to start with popoff with a 2.0 n/s? I was planning on starting with a 130 pilot and 160 main and going down from there. Like I said, there were no hesitations or bogs anywhere before, but it was obviously running on the edge melting down.
Does anyone have some ideas on where to start with popoff with a 2.0 n/s? I was planning on starting with a 130 pilot and 160 main and going down from there. Like I said, there were no hesitations or bogs anywhere before, but it was obviously running on the edge melting down.
Dropping the pop off will make the pilot jet and idle screw much richer. I found a 130 to be too rich with 2.0/80g, it did allow for a peaked out WOT without hesitation. A 125-2.0/95g is probably about right but try an 80g and note the difference. Changing the pop off won't change full throttle mixture very much.
What kind of setup were you running with this?
i didn't realize, but i did reply on your other post
did you glass bead the piston skirts before reusing the pistons?
if you didn't, i think you just continued the seizing till it got really bad and finally stuck it good
you always have to remove any of the imbedded black death from piston skirts before ever reusing them
once it starts, its like cancer, you have to remove all traces of black death
Interesting!! No I just reused them. But looking back at the posts, the rear piston was fine and it was the front one that had the black mark.
This engine used a stock 61x bottom with a 61x cyl ported almost to 62t timing. The pipe was a sizzler and the pump was set for 6900 min. I never could get it to rev over 7k. It had fair response and ran 48 all day. I later exchanged this lower for a complete 760 case/carb. It made the pipe hit harder but didn't turn anymore rpm.
SpaceCowboy
breaking something
- Location
- Ypsilanti Michigan
Man...I cannot believe I just read 7 pages on a 701 blowing up...
Order some parts, change jetting, do some more testing!
Good Luck!
Order some parts, change jetting, do some more testing!
Good Luck!
You didn't have to.. Sorry that I like to know what happened before I throw parts at something?
SpaceCowboy
breaking something
- Location
- Ypsilanti Michigan
Don't be soo serious man...it's the X! I think you have the problem narrowed.
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Yeah for sure. Like I said, I was just really surprised since my porting isn't that extreme and I was running similar jetting to most ported motors and it ripped hard. But, sometimes you gotta learn the hard way. I just got lucky that all I need is a piston kit and a hone!
N/s are only needed for adjusting pop-off. 1.5 flows more than the pump can push.
Didn't yet! Think we've narrowed it down to being lean, but I'm gonna grab a small mirror so I can check the upper reeds without taking the mani off. The lowers are fine.