John Clark
RCTalk Racer
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Since the T-maxx is my first RC, (of many, if I have my way), I'm still trying to figure all this stuff out. Well, yesterday I had a great day of tuning, then bashing, so I figured I'd share what I learned so far and hope it might help someone out.
After putting in a bunch of hop-ups last week, I couldn't get the thing to run worth a damn. I couldn't get it to idle, and if I gave it 1/2 throttle when starting, it would take off like crazy, then stall. I put the needle settings back to stock, then tried to tune from there. I finally got it to run for more than a few seconds at a time, but it was hesitating, popping and farting, and it would stall when I hit the brakes. Ok, that tells me there's a linkage problem.
After setting up the linkage so that the carb was fully closed at neutral, I noticed that there was some fuel left in the top of the head from when I had to un-flood it for the 2nd time. As I was trying to restart the engine, I saw the fuel bubbling like crazy around the glow plug. How can you have good compression when it's leaking like crazy? Ok, take the head off, clean it up to like new condition, new copper washer, and tighten glow plug up really snug. Solved THAT air leak, but that got me thinking, (I know, I know, dangerous), and sure enough, after inspecting the fuel line, I saw that I had air leaking into it from somewhere. The trail of tiny bubbles going to the carb while the engine was running was a small hint.
Cleaned and tightened up the fuel filter, new fuel line, and zap strapped all the connections just to be sure. Ok, air leaks conquered. Getting somewhere, as it will actually idle for awhile now. Time to tune.
This will be a snap. I've had 3 dirt bikes, a jet ski, and 3 snowmobiles. Who needs a book? So after 2 hours of adjusting the needles by ear, forgetting which way was lean, then going back to stock settings and starting over, I'm ready to pull what little gray hair I have left, out of my skull. Not only that, but I was changing both needles at the same time, deluding myself into thinking I knew what I was doing. That day ended with me throwing everything back into storage while I cooled down enough so that I didn't light a match to the thing.
I decided to give it another crack yesterday, to see if I could get somewhere. What a difference. After getting some advice from Imbroken and Backspur, and reading an article in RCNitro magazine, I started from the stock settings, slowly leaning out the HSN in small increments, (after making sure the engine was at normal temps), then slowly leaning the LSN until it was running well. By small increments I mean 1/32 - 1/16 turns at a time. My problem before was richenning when i thought I was leaning, then adjusting both needles at the same time instead of the HSN first, and finally adjusting them at 1/4 turn at a time. That's what you get for not taking the time to read I guess.
The final result was, this thing hauls ass. The AE pipe and FOC kit were a huge improvement in the low end. I decided to call it a day when I flew off a 12 foot drop, touched the brake a little by accident and ended up on my lid, breaking a body post. I even called in 'sick' today to get her fixed and play some more.
For those who just skimmed my mini-novel (and I don't blame you), here are the highlights from my limited experience:
-Make sure your throttle/brake linkage is set up properly, and the throttle's not closing any more when the brakes are applied. Don't just use the trim adjustment, set it at 0 before setting the linkage.
-Check for air leaks, you'll never get it tuned properly if you're leaking
-Make sure you're at normal running temp before trying to tune. ie. 3 or 4 minutes of running, not just a couple high speed passes
-Adjust the needles in small increments only, 1/32 - 1/16 of a turn, and give it a good run before adjusting them again.
I know all of this has been covered in articles before, and in the manual and stuff, but I hope that it still helps someone out. Thanks to ImBroken and Backspur for their advice.
After putting in a bunch of hop-ups last week, I couldn't get the thing to run worth a damn. I couldn't get it to idle, and if I gave it 1/2 throttle when starting, it would take off like crazy, then stall. I put the needle settings back to stock, then tried to tune from there. I finally got it to run for more than a few seconds at a time, but it was hesitating, popping and farting, and it would stall when I hit the brakes. Ok, that tells me there's a linkage problem.
After setting up the linkage so that the carb was fully closed at neutral, I noticed that there was some fuel left in the top of the head from when I had to un-flood it for the 2nd time. As I was trying to restart the engine, I saw the fuel bubbling like crazy around the glow plug. How can you have good compression when it's leaking like crazy? Ok, take the head off, clean it up to like new condition, new copper washer, and tighten glow plug up really snug. Solved THAT air leak, but that got me thinking, (I know, I know, dangerous), and sure enough, after inspecting the fuel line, I saw that I had air leaking into it from somewhere. The trail of tiny bubbles going to the carb while the engine was running was a small hint.
Cleaned and tightened up the fuel filter, new fuel line, and zap strapped all the connections just to be sure. Ok, air leaks conquered. Getting somewhere, as it will actually idle for awhile now. Time to tune.
This will be a snap. I've had 3 dirt bikes, a jet ski, and 3 snowmobiles. Who needs a book? So after 2 hours of adjusting the needles by ear, forgetting which way was lean, then going back to stock settings and starting over, I'm ready to pull what little gray hair I have left, out of my skull. Not only that, but I was changing both needles at the same time, deluding myself into thinking I knew what I was doing. That day ended with me throwing everything back into storage while I cooled down enough so that I didn't light a match to the thing.
I decided to give it another crack yesterday, to see if I could get somewhere. What a difference. After getting some advice from Imbroken and Backspur, and reading an article in RCNitro magazine, I started from the stock settings, slowly leaning out the HSN in small increments, (after making sure the engine was at normal temps), then slowly leaning the LSN until it was running well. By small increments I mean 1/32 - 1/16 turns at a time. My problem before was richenning when i thought I was leaning, then adjusting both needles at the same time instead of the HSN first, and finally adjusting them at 1/4 turn at a time. That's what you get for not taking the time to read I guess.
The final result was, this thing hauls ass. The AE pipe and FOC kit were a huge improvement in the low end. I decided to call it a day when I flew off a 12 foot drop, touched the brake a little by accident and ended up on my lid, breaking a body post. I even called in 'sick' today to get her fixed and play some more.
For those who just skimmed my mini-novel (and I don't blame you), here are the highlights from my limited experience:
-Make sure your throttle/brake linkage is set up properly, and the throttle's not closing any more when the brakes are applied. Don't just use the trim adjustment, set it at 0 before setting the linkage.
-Check for air leaks, you'll never get it tuned properly if you're leaking
-Make sure you're at normal running temp before trying to tune. ie. 3 or 4 minutes of running, not just a couple high speed passes
-Adjust the needles in small increments only, 1/32 - 1/16 of a turn, and give it a good run before adjusting them again.
I know all of this has been covered in articles before, and in the manual and stuff, but I hope that it still helps someone out. Thanks to ImBroken and Backspur for their advice.
