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Tuesday, September 07, 2010

Author:	Topic: Rejetting carbs on 97 GTX for F/A what ones??
hhiibel1	posted: 7/28/2010 3:49:44 AM Here's my method. It's based upon the assumption you really can't safely get any more rpm's than stock when all you do is put on F/A's and don't change the head, compression, squish or pipe. Anyway, the OEM rev limit is 7200. And stock max rpm's are in the 6900's at best. You only need to go up one size on the lows to 72.5. Leave everything else OEM. But do go through your carbs. Check pop-off, dribbling seats, deteriorating fuel lines, etc. And replace the choke with a primer kit. Verify throttle plates are sync'ed and can acheive full open. On the water, start with the 72.5's at 1 1/4 turns. Adjust accordingly to remove dead spot when gradually climbing to on plane, and when doing WOT of idle. Set your idle screw for 1500 rpms. If in doubt about what a dead spot feels like, adjust them leaner and leaner till you get a stumble when climbing thru off idle. That's what a dead spot is. Keep in mind you haven't set the highs. So, don't try for max rpms. Once satisfied with off idle performance, start adjusting the highs. Begin at 1 1/2 and start going down by 1/8's. You're aiming for stable low 6900's or high 6800's that don't keep edging upwards. While doing this, I'm not talking long wot's. You're just shooting for it looks like it's hanging at 6850-6950. Next you start tuning for wash. You want to see healthy thumb nail size washes on you crowns at each charge port. Richening increases wash. You see wash by looking down your raves. Familiarize yourself with increasing and decreasing wash. Do only 1/8 changes at a time. This leads up to trying to go beyond 6900 by tuning for pencil eraser size washes. But you'll see your max rpms heat soak down to 7000's, and you'll be running a deto risk should atmospheric conditions change or a glitch in fuel supply occur. So, really just aim for thumbnail wash and consequently the max rpms will be 6850-6950. A good final check is to see that any further richening does in fact decrease rpms. Or be brave and keep a pencil eraser washes. Tune each carb as an individual. Your aiming for wash. I bet your highs will come in at 7/8's to 1 3/8's. I've done two 96XP's. One liked 6850 and the other liked 6950. Both with only changing to 72.5's and changing nothing else except a leaking seat and the fuel lines.
Buddah	posted: 7/27/2010 5:03:42 PM thanks guys. all u need to make it right.
PPG	posted: 7/27/2010 3:35:11 PM It's about $70.00, and it includes N/S's, low-speed jets, and high-speed jets. ALL Mikuni, no aftermarket junk!!
Surferd15	posted: 7/27/2010 3:06:27 PM Rob, how much is the kit and what does it include?
Buddah	posted: 7/27/2010 10:39:32 AM PPG jet kit. tried and true.
Surferd15	posted: 7/27/2010 10:26:46 AM I have a 97 GTX that I am rejetting for Flame arrestors. What combo should I go with? It was suggested that I go with 2.0 N/S, 75 pilots and 142.5 main, then LS- 1-1/2 and HS- 1/2 and adjust from there. What are you guys running and what do you suggest?

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Topic:	Rejetting carbs on 97 GTX for F/A what ones??
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