06-27-2007, 07:24 AM #1
Any problems with 120 mains on a 1200 GPR?
I am running Stock Carbs/150 lb comp/open FA's,VF2 reeds, 87mm nozzle turning 14/20 (05 pump) @ 7110 in the heat. Plugs and wash look lean with the highs out 1.5 turns. Plugs are white with a few specs - I am pretty sure there is no leaks since all 3 plugs look identical.
I am considering going to the 125 for peace of mind but everytime I research what the jetting should be I come up with the 120 mains @ 1 1/4 out. Is 1.75 to 2 turns out to many ? When is it time to switch to larger jets ?
Choke plates are in. No timing/ignition changes (yet).
Rest of the setup =
1.5 Needle & Seat
Dull Grey spring 95 grams
Accelerator pump is disabled
Last edited by mrbtd; 06-27-2007 at 07:28 AM. Reason: spelling
06-27-2007, 08:58 AM #2
That is the standard jetting setup. You may want to check your fuel pressure. I had a lot of problems jetting my ski until I found that I only had 3 psi of pressure at WOT, when it should be 6 psi.
06-27-2007, 10:50 AM #3
- Join Date
- May 2006
125 will move it about 1/4 to 1/2 half turn.
I would run the 125 I always found with the 120 I needed to be at 1 and
5/8s to 1 and 3/4. Thats fine but I like to be a little closer to 1 turn. Should be no performance difference.
BUT your plug discreption sounds dangerous I would fatten up to 1 and 3/4 or untill you lose rpm.
06-27-2007, 11:18 AM #4
Ended up with 125m to get decent wash on my 1200 simular to yours. I was over 2 turns out with the 120s and it was still on the edge. This left me with no room when the colder weather sets in.
06-27-2007, 02:10 PM #5
Every ski/engine is different, so you will have to experiment. Mine ran great, had great plug color, and good rpm's with 120's. Ran them for about a year. On a whim, I switched to 125's and picked up all around. It's worth the time and effort to find out for yourself.
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