Carburetor Question.

[robtangie]

Self proclaimed new to nitro guy here... Got a used Maxx 2.5 converted back around xmas and spent a few weeks doing a tear down, clean and rebuild. Been ready to fire it up for weeks now but the deep snow and cold temps here in Iowa have kept me looking at it sit in a corner.
Yesterday being the day I decided to give it some fuel and see if I could at least get it to start in the garage. It took two sessions of rope pulling, plug swapping, and head scratching for me to realize that the longer I was out there in the cold the less likely it was to start. Three being the magic number as I got it started and warmed up. Even managed some slow passes on the street.
Anyway,,, I'm making a short story long... Found I couldn't get my idle down far enough for it to stay out of gear. Partly because the air filter was hitting the linkage. Easy fix... But I also notice the slide in the carb doesn't seat down far enough to shut completely off. I can give it a little help by hand but then it sticks slightly when it goes to open again.
Fortunate to have a spare carb on hand that dose seem to slide nicely I went to cleaning it up before installing it and as I was tightening the the HSN housing back down I went that little bit too far and stripped the carb threads out... I know,,, rookie mistake... So my next option is to take the good slide and put it in my original carb. But as easy as that sounds I can't figure out how to get the slide out. So that's my main question, how dose it come loose.
I'm also wondering what little tricks you guys might use to keep a plug in the plug wrench when changing it,,, as well as how to keep the little washer on the plug as both seem to be a pain.
Regards and Thanks,
Rob.

 

[olds97_lss]

On my dynamite plug wrench, I CA glued a piece of fuel tubing up in it. The hole in the tubing is just big enough to hold on nice to the plug post.

For the carb, are you sure your original wasn't just at a bad angle? TRX carbs are all composite and have a tendency to bind up on you if your alignment of linkage isn't just right. The more parallel you can make the linkage with the slide of the carb, the better.

To get the slide out, take out the idle set screw completely as it holds it in via a slot on the side of the slide. Also, the blue boot should come off once you take the throttle arm off. Underneath, you will find a soft return spring that should come off as well.

The washer on the plug... about the only way to consistently keep it on the plug when removing the plug is to stand the truck up on it's end so the engine head is parallel with the ground or even better, the top of the head is pointing at the ground a bit. Then gravity keeps the washer on the plug as you remove it.

 

[2revo1maxx]

Sounds like you just need adjust your throttle return spring. First make sure the angle is good like olds said. Then with the throttle closed adjust the little collar on the linkage so the spring has just a little bit of tension. It should always have some tension on it or it will hang open a bit. Once you get it outside don't forget to richen up the high speed needle as much as one full turn, depending on how cold it is out there.

 

[robtangie]

Thanks for the input guys... Yes I can be sure it's not just the angle because it still dose it when I have the carb in my hand, so kinda rules out the angle... But being able to compare it side by side with the spare I have it's more than obvious that the spare slides smoother, doesn't stick at the bottom of the throat, and shows less rotational play. I just hope that it is indeed the slider that is bad and not the carb body...
I will admit though I have had a tough time getting any kind of angle on my linkage that will work right. I tried as per the Traxxas recommended configuration but when I install the air filter it hits the linkage bell and stops the throttle from closing. A bit more angle would send the carb arm and linkage into the spur gear or nut at full throttle. So I ended up moving the arm up a bit and lessened the angle of the carb some which seems to be working so far.

2revo1maxx,
I did get out in the street just a bit today... It was about 30 today. I started with the factory recommended setting (4 turns out) and I thought it to be running a bit rich. Do you think it would need to be richer than the factory setting?
I have to confess,,, after all I've heard and read while waiting for some decent weather I thought I'd be on top of this tuning thing... But to my surprise I'm way too busy trying to keep it on the road, out of the snow piled on the sides of the road, away from the busy highway at the nearest Tee intersection, out of any water and puddles, braking (because the brakes on this suck), turning, and running so I don't have to walk to restart it, that I completely space off the whole tuning part. But I did keep enough mind about myself to notice I was getting the blue smoke, and it seemed to be loading up at lower speed and idle.
But I can tell it's going to be loads of fun and I'm looking forward to the warmer weather.
Thanks,
Rob.

 

[olds97_lss]

I usually don't have to tune that rich in the winter to compensate, but I do wrap the head to keep air from going through it, so it doesn't cool off as quick. You might want to try that as well. Just wrap the head with a couple thickness's of tinfoil and put a couple rubber bands around it. May help with the erratic tuning some.

 

[2revo1maxx]

You can also screw the ball cup in or out to adjust the linkage and keep it clear of the air filter. 4 turns out is never enough for my 3.3 at 30 degrees. I do partially wrap the head, but I want to make sure it's getting enough fuel. I ran in 20 degree weather one time, I had the needle out 7 full turns and it was barely enough to run decent. I think 5-6 turns is about the most fuel you'll ever get through the needle. Anything beyond that just doesn't seem to make a difference. I would start at 5 and turn it in til it runs good. Also 3.3's like a medium plug in the cool weather.

 

[robtangie]

Yes wrapping the head... I knew I needed to do that and happened to spot a small sock that I hacked the top off of. Doubled it the first day i fired it up as it was only in the 20s, but cut it back to a single layer yesterday as it was in the 30s, (looks like a little stocking cap). Easy on and easy off and although I don't have a temp gun/gauge yet it's seems to be coming up to a good operating temp.
Ball link... Good call... I did notice the ball link when I was hitting the spur gear nut. Of course it wouldn't make a difference there,,, but could change the throw of the bell crank enough to get it off my air filter....
I'll give the 5 turns a try today and see how it works for me, Also going to look into the carb slide today as well... I'll be sure and check back in later with what I find.
Thanks Again Gents,
Rob.

P.S. 2revo1maxx, you mentioned a 3.3 liking a medium plug... When I stated I had a "2.5 converted", I can see where that might read a bit confusing,,, I should have said "converted to 2.5" as it was originally a .15.

 

[2revo1maxx]

Ok, I thought you went 2.5 to 3.3. But a 2.5 would like a medium plug too. It's cold out, you'll want to back off the timing a bit, with a medium. It might run ok with a hot plug, but you should notice a difference going to a medium.

 

[robtangie]

Ok, I thought you went 2.5 to 3.3. But a 2.5 would like a medium plug too. It's cold out, you'll want to back off the timing a bit, with a medium. It might run ok with a hot plug, but you should notice a difference going to a medium.

Ya, that was my bad for the way I had it worded. I have a medium hot plug in now (traxxas tra3232) as luck would have it.
I changed out the slider on the carb and the new one works much better. I put the other back in the extra carb (just to keep track of it) and dose the same thing in it. Sticks at the very bottom seated position and doesn't slide near as smooth in the carb.
I tried again to get the carb linkage and angle configured as per the factory recommendation but even adjusting the ball link would not help. But by moving the slider arm up some and the carb down a bit I still maintain a good parallel motion...
Thanks Again,
Rob.