12-07-2011, 07:16 PM #1
Gp1200 'popping' maybe misfire? Lil help!
Hey guys, just a quick question.. I heard my ski 'pop' twice yesterday and once the other day.. All times was under pretty much full load hi rpms. It's maybe the 4th time it's been out (about 4 or 5hrs) since re-build (pistons, crank, shaved head,light port, new check valves) I also switched to premix 40:1 and have choke plates out. New br7hs plugs. Also got a few extra earth straps from battery to motor and also to electrical box just for good measure.
Would u assume it's possibly a tad lean maybe to cause the pop? What do u think about me coming half a turn out on my low and hi-speed's?
12-07-2011, 08:38 PM #2
Pop.. As in like a misfire or back fire.. And came from under the seat..
12-07-2011, 09:44 PM #3
Check the rear seal is still seated
You might have had it in ass backwards.
12-08-2011, 01:09 AM #4
is the BR7HS a typo or is that the plug you are running? The BR8HS is what is recommended stock. The popping could be lean from not enough fuel, or air leak. either of these will definitely cause a backfire.
12-09-2011, 09:37 AM #5
12-12-2011, 04:07 AM #6
12-12-2011, 04:17 AM #7
WOW!!!! thanks sooo much john!! iv learnt ALOT by reading about piston wash.. lots more to read now!! im goin g to suss it out to morrow and also going to look at my old pistons too...
i came out (was worryed for a bit trying to figure out which way richens it) half a turn on my hi-speed screws on the weekend and i think it made it feel better.. i may do another half turn our this weekend comming. i tryed to come out half a turn on my low speed screws but number two feels REAL LOOSE and feels like it would fall/vibrate out when i come out half a turn.. so couldnt do the lows and had to put lows back to how i had them previously...
12-15-2011, 11:13 PM #8
Well... Just did a comp test because i was board at work.... 145 psi, 145 psi, 000 psi. Sooo angry!!!!!! Only a few hours in on my fresh engine and i have no compression in cyl 3 at all.. Pulling the head off tonight
12-16-2011, 11:58 AM #9
Did you ever check that rear seal like I asked ?
If it popped out you would have a massive air leak.
What piston has 0 comp #3 ?
12-16-2011, 06:29 PM #10
Maybe that welded lower crankcase(if I remember correctly) is leaking. Did you pressure test the engine after you reassembled it?
Rule number 1: pressure test after reassembly. The thing has to be really air tight.
Rule number 2: Tune/make carb jetting and adjuster adjustments for your mods.
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