Thread: fresh rebuild / random shut off
07-24-2010, 05:28 PM #1
fresh rebuild / random shut off
Just got done with the rebuild on my ski. I had a neighbor do it who used to race skis (he has a TP gpr and a ported GP). 3 new pistons, new first cylinder, new (used) head, rebuilt carbs, removed accel pump, and changed some jettings in the carbs. Instead of a 95 low he went to a 100 (I think thats what its called) basically he said he fattened up the low end. We switched to premix, we put 10 gallons in at 32:1 with premium gas and amsoil intercepter oil. I did about two and a half heat cycles on the hose (let it idle on the hose for 15 minutes, let it cool down, idle again) last night. Tonight my dad and I took it to the lake to do some more break in. First 15 minutes I was trying to stay under ~4300 RPMs and I did 2 QUICK bursts to WOT. Took it home let it sit with the cover off for about 45 minutes, and took it back to the lake. This time I was trying to stay around 5000-5500 RPMs and did a couple more bursts at WOT and did one WOT run which was like 10-15 seconds. I was going at about 5500 RPMs and suddenly it bogged and then shut off but it turned right back on. I turned it back on and got plained out and then it shut off again, this time the first time I tried to start it it just beeped, then the second time I tried to start it it fired up and I took it right back to the trailer. Did I overheat the engine? Anything I should check?
07-24-2010, 06:31 PM #2
07-24-2010, 07:36 PM #3
I might shoot someone if I have to rebuild this again...I just asked the guy who rebuilt it and my jetting is 120 main, 100 pilot, 1.5 needle and seat and 95 gram spring. Not sure if makes a difference or not but I have a stock head now, not 150 psi. My dad said he also heard a "popping" sound throughout all the RPM range.
07-24-2010, 07:55 PM #4
ok, just got off the phone with the guy who rebuilt my ski. He says there is no way that it lean seized because from the settings BEFORE the rebuild all he did was fatten up the bottom end.
old settings: 120 mains, 95 pilots, 1.5 needle and seat, 115 gram spring. Accel pump was not removed on these settings
new: 120 mains, 100 pilots, 1.5 needle and seat, 95 gram spring with the accel pump disabled and choke still installed. He also fattened it up because the airbox does not have the front chamber installed so its sucking in more air
07-24-2010, 08:12 PM #5
What is the popoff set to??? What are the mixture screws on the bottom end set to? The lows are too small, by the way. You need 110's.
You had a shutoff in the worst part of the rpm range - more than likely a lean seizure. Better fix it or you just might be doing another rebuild.
07-24-2010, 08:22 PM #6
before I read a response to this, we took it out again. This time I took it easy for about 5 minutes, then bumped it up to 5500-6000 for a few minutes and it ran fine. Then did a WOT run and it shut off, didnt bog really as much, but did shut off. I idled it in, shut it off to tell my dad what happened and he told me to go out for another 6 minutes (to finish the heat cycle) but to take it easy until he waved his hands (this was at the 6 minute mark) and I did 4 WOT passes no problem and took it in. I think he said the pop off was like 43.5 pounds down from what he guessed was like 55? I think? I will let him know that the lows are too small and I will not use it tomorrow. Do I need to pull the head again to make sure I didn't do any damage?
07-24-2010, 09:34 PM #7
Do a comp test before pulling the head...you also should not be pulling that high of rpm on a new motor like that...gotta take it easy...or you will blow it up..
07-24-2010, 10:20 PM #8
I did take it easy. I did what I read and was told. The guy who rebuilt it told me to run it on the hose - 15 minutes on, 15 off for 4 cycles, and I read on here to go out for 15 minutes, vary the throttle and come back in and let it cool, so I guess I kinda did a mix of both
07-24-2010, 11:53 PM #9
You ran it 15 minutes on the hose then 15 minutes off the hose on the trailer? Am i reading this right.
07-25-2010, 08:15 AM #10
no no no no no sorry. 15 minutes on the hose, then let it cool down sorry hahaha.
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