Originally Posted by
Sonora
I am big on changing the plug so I doubt this is it. As for the top end, I get good smoke out of the corners and have temps in the 210 to 230 range so I doubt the top end is lean. The problem arises when I try to lean the bottom end, I sometime get a bog when I try to give it throttle.
If I lean at full operating temp of 200 + I have better luck but find it difficult to keep it in this range while I'm trying to adjust it and end up putting it back on the track in the 170 range.
Since I always preheat to about 150 shouldn't I be able to get it close at this time, or do I have some small leaks that are causing this. I have ordered new seals for the carburetor and am planning on pulling the needles and carb and reinstalling all with grease.
The engine now has 4 gallons through it and still has very good pinch. The tunning issues I am mentioning started during break in after about 1 quart of fuel. I did add booster to the first 1/2 gallon of fuel se there was a lottt of oil present during the first 1/2 gallon.
For what its worth, I started with a # 6 plug and switched to a # 5 after about one quart as I couldn't keep it lit with the # 6.
Thanks for all the help.
Engines should always be fully warmed before tuning, ALWAYS! If you tune too soon then 5-10 minutes into a race you will see the engine begin to fall on it's face due to lean bog, if you tune to performance at initial start up.. And once it begins to lean bog, richening it up it futile, until you kill engine and let it cool off completely..
All that said I prefer to run as close to a half tank of fuel as I can before tuning. When you decide to tune try to tune the engine around the 1/2 tank mark. If you tune with a full tank you may be too lean at end of tank and if you tune at empty tank then you may be too rich at full..
For plugs I run O'Donnell, but only because it is hard for me to get Orion in my area, and I have a ton of O'Donnell plugs.. Orion plugs are very nice and Orion engines work best with Orion Plugs. With the warmer months of racing coming a slightly cooler plug might be in order.
After rereading everything posted between the 2 of us, I don't think we are going to be able to diagnos this over the net. I'm going to suggest finding the best engine tuner at your local track or LHS, and asking them for help..
Essentially my suggestion is to reset needles and retune from scratch with .8-1mm idle gap, and go from there.. Good luck and keep us informed on what you find out.