Thread: T-handle tuning on carbs
01-16-2008, 09:18 PM #1
- Join Date
- Nov 2007
- Tyler, TX
T-handle tuning on carbs
I love the site, but I can't quite find some information on carb tuning when carbs have T-handles.
I have a perfectly good low hour '02 GP1200r that I couldn't help but to pull apart in a quest for "more". I'm sure at least a couple of guys can relate...
Anyways, I'm trying to keep it reliable (maybe too late now) and on 93 octane. I just want to make sure with my mods I won't run lean (or hot) and damage a piston, block, or what-not.
So, here's what we've got:
-37cc Speedwerx domes and girdled billet head (~170 psi, untested)
-OEM carbs rebuilt by Island Racing with High/low T-handles, acc. pump removed, primer kit, choke plate removed
-K&N flame arrestors with prefilters
-Oil pump block off , 40:1 premix
-R&D reed stuffers
-Cat bypass/ temp sensor chip
-Riva trim tabs and ride plate
-Island racing prop pitch/balance/finish to 13/19 (Solas)
I think that's about it, but I'm strongly considering adding the M-16 reeds/boost bottle while I'm in here.
Back to my original question:
Where do I even start with an initial high/low carb setting with this set-up? Do I have to read plugs initially to tell if I'm "on" (I hear this is incredibly unreliable.)? Do I have to port the engine to ensure adequate breathing?
Sorry for so many questions, but I would love to do this right, since I'm sure getting access to the T-handles with the Stinger in place will be impossible or just be plain miserable.
Thank for any advice on the matter!
01-16-2008, 09:26 PM #2
Welcome to the Hulk.
Here is a thread about jetting. http://www.greenhulk.net/forums/showthread.php?t=30369
I like to start the screws at 1 1/2 and do lots of plug chops.
Another good read.
Tuning Tips for Girls
Start with the screws set at 1 turn out, and tune with the tachometer for peak Rpm, then stop there and count the number of turns on the high speed screws. Write this down on a piece of paper.. Then turn the high speed screws in all the way and open them to 1/4 turn open. (Now you will be testing starts only, so no more big high rpm trips around the course). You are only turning in the high speeds to allow you to easily tune the low speeds.
Now check the low speed screws and set them at 1 turn and do a practice start; To test the low speed setting pretend that you just jumped the start and you have to start with no holder. Hold the ski by yourself and hold as many Rpm as you can (don't blow it out first for testing) and then nail the throttle hard.... NO FARTHER THAN 50 FEET, as you are only testing the start response
If it blubbers like a schoolgirl trying to guzzle a quart of beer, then it's too rich on the low speed screws..
If it falls flat on the line (like someone punched you in the stomach).. It's too lean on the low speed screws.
When you like the acceleration off the line, stop there and count the number of turns on the low speed screws. Write this down on a piece of paper.. Then re-set your high speed screw where they show the best peak Rpm earlier and try both a start and a peak Rpm run...
It will probably "blubber" a little off the line... DO NOT turn in the low speed screws... Instead, go back out on the course and fine tune for peak Rpm again.. The blubbering off the line is caused by having too much fuel in the high speed circuit... Write down your new high speed setting on the piece of paper along with the best low speed setting that you found earlier, this will be your base-line carburetor settings.
If the high or low speed screws are open more than 11/4 turns, then you need to swap to the next bigger jet.
If the high or low speed screws are closed all the way, then you need to change to the next size smaller jet.
01-17-2008, 12:14 AM #3
That compression (170) is to high for pump gas you are going to need some higher octane, you will not jet your way around that. Boost bottle will gain you nothing it is for racing to help when you are constantly on and off the throttle.
01-17-2008, 11:32 AM #4
- Join Date
- Nov 2007
- Tyler, TX
Thanks for the feedback, Beerdart. That's the kind of information I'm looking for!
In regards to the compression and pump gas:
I spoke directly with Speedwerx about the matter, and they assured me that the YLTD.. domes are safely compatible with 93 octane premix. I'd be very disappointed if they weren't familiar enough with their own product to give correct information.
01-17-2008, 01:17 PM #5
01-17-2008, 03:11 PM #6
Man, 170 psi is really high for a rec ski. There may be some guys running that, but they've got the tuning, prop, and gas to go with it. Please check into that before something happens.
01-17-2008, 03:17 PM #7
01-17-2008, 05:31 PM #8
- Join Date
- Nov 2007
- Tyler, TX
Now I'm worried...
All of the negative talk about the compression has me concerned. I'm not excited about a high-maintenance ski with serious issues.
My dome selection was based on Speedwerx advice and assurance that it would run on high-grade consistent pump fuel.
Do I need to worry about detonation or pre-ignition with the stock ignition and these heads? I'm really not looking to modify or change ignition timing curves, etc.
Also, everyone acts like changing jet settings is as simple as intermittently tweaking the t-handles, but with a stinger in place, in would appear to require breaking down the battery box (and poss. the stinger) to gain good access for turning the handles (and then your next run). This could clearly become a colossal pain as you tweak low/high in the prescribed manner.
I don't want to seem lazy (maybe I'm in denial), but I keep thinking someone knows a better way that doesn't involve breaking the ski down during the tuneup.
How do you tweak individual cylinders (carb-wise) once you like your settings across-the-board? Is that even possible, or should they stay uniform?
I really appreciate everyone's experience and willingness to advise!
01-17-2008, 06:25 PM #9
Set the lows and you shouldn't have to touch them again. The highs can be turned with a long screwdriver with a notch in the end. You can make adjustments out on the water. There's really no need to tune individual cylinders. Set them all the same, or perhaps the #3 an eighth of a turn further out than the other two.
As far as the compression- what's there to say? Speedwerks says it's ok, experience from a lot of folks on here says no. Not sure what to tell you.
01-17-2008, 06:34 PM #10
thanks for the screwdriver tip dave, untill that i was wishing i had made my jump boat e.f.i rather than getting carbs rebuilt ect..
i also thought 170 p.s.i was only safe if you mixed a bit of race gas
Users Browsing this Thread
There are currently 1 users browsing this thread. (0 members and 1 guests)
By fabmaster911 in forum Polaris Open DiscussionReplies: 1Last Post: 07-08-2008, 04:59 PM
By ZOMGVTEK in forum Polaris Open DiscussionReplies: 3Last Post: 06-10-2008, 07:36 PM
By ultra150nc in forum 2-Stroke PerformanceReplies: 11Last Post: 04-25-2008, 08:24 PM
By carbuff91 in forum 2-Stroke PerformanceReplies: 3Last Post: 04-11-2007, 07:07 PM
By joeyjunio in forum Polaris Open DiscussionReplies: 31Last Post: 03-20-2007, 11:59 AM