mr. ilikehelp

whats that moter size

j.m.

1.08 Ci. Read the first post.

mjderstine

yup. 1.08 its a great motor, has the power of a 1.20, without the weight, and uses the same muffles as a .91

j.m.

now you need to knife edge the con rod and port the sleeve. Also, thin your prop out. It'll increase the rpm's because there will be less resistance, and it will get there faster because of the lower weight.

Also see if you can't find a bigger card for that engine.

mjderstine

come again?

i get the prop stuff i think. you mean sand it down? or just get a different prop?

bigger card? you mean carb? right?

what does knife edging the con rod mean? thanks for the help !

j.m.

yeah just thin it down with sand paper and make sure it is balanced.

I did mean carb.

Knife edge con rod:

Stock (yours):
http://www3.towerhobbies.com/cgi-bin...?&I=LXUP79&P=7
Looks something like that.

Knife edge:
http://www3.towerhobbies.com/cgi-bin...?&I=LXLBU5&P=7
http://www3.towerhobbies.com/cgi-bin...?&I=LXLBV8&P=7
http://www3.towerhobbies.com/cgi-bin...?&I=LXLDG8&P=7

It reduces the rotational resistance inside the engine and can significantly increase engine rpm's.

Att you have to do is sharped each edge and maybe thin it out a little.

mjderstine

i see. so i would need to disassemble the engine, and could i use a dremel wheel or a file to take some material off it that way?

i do have a bit of work to get done adjusting the needle valve too. right now i just have it turned out the stock 1.5 times. it needs to be leaned out quite a bit. i am hoping tomorrow i will be able to get some real time on the motor. i would like to get a fish scale hooked up to see how much its pulling as well.

j.m.

okay, cool. I thought it didn't seem like it was making that muchpower for such a big engine, and it was taking an AWFUL long time to spool up.

mjderstine

i agree, it might be the prop too, its on the larger size of the effective props, its a 15 x 8 and could probably run better with a 14 x 8 or a 15 x 6. heck it could even be the linkage because the puchrod is pretty tight. gotta get some Teflon in there.

j.m.

you could also try something like a 12X10 for more speed.

mjderstine

ill keep that in mind. i tihnk the smallest i want to try is a 13x8 0r 13x9 to start. there will be losts of testing with this thing

vamp131

I was going to turn my engine upside down but was told they are harder to start for your glow plug you can get a clip that go,s onto the glow plug and you put the glow clip on it at the side

mjderstine

i can try to show you whats going on down there. i use one of these.
http://www3.towerhobbies.com/cgi-bin...0&I=LXD695&P=K
and that gives enough room. but i am going to get one of these to use instead.
http://www3.towerhobbies.com/cgi-bin...0&I=LXBC35&P=K
so i can mount the glow plug right side up.

the motor starts fine upside down. its just tricky to prime the carb. gotta be quick about it...

planebasher

Try using Sullivan Gold N Cable #508 for the Throttle pushrod. You can bend it down to about a 2 inch radius, but it won't handle a
big load.

mjderstine

thanks, ill keep that in mind

mjderstine

motor testing vids.
at half throttle it cuts off. i have to check the linkage to make sure there isnt too much throw. or its adjusting the low end on the carb.

also, i can adjust the needle valve though. but it doesnt seem to do much.

http://s63.photobucket.com/albums/h1...t=MVI_3118.flv

DJLaPalme

Mjderstine, to get your throttle working the best with minimum effort, you will need that Sullivan "Gold n Rod" or any cable type throttle hookup. The stuff you are using is good for straight or close to straight like your rudder linkage, but it binds too much when bent like that. You will have to look at the carb barrel to see if it is moving from full open to full close, and please make sure you can shut the engine off with the throttle. That boat with that engine should really move and if it ever gets away from you its nice to be able to shut it down. Remember, you have to set the high side, then the low. Your engine reving that slowly is either the linkage( very likely the problem) or the low needle is set too lean. Good luck with it! Dennis

mjderstine

DJ,

thanks for that reply. it will help a lot. i have since put some silicon lube in the pushrod tube, and that has cleared all the binding. i also have a pretty high torque digital servo on the throttle. its the hitec HS-5645MG.

i also had to adjust the linkage because the entire thing was not long enough. i just unscrewed the clip a couple turns and it moved it to the inner hole on the servo arm and it cleared up that part.

my main question, i can adjust the high end while the motor is on, but the low end. is that adjusted while the motor is on or off?
because of the way the motor is mounted i cant really get to the screw unless the prop is stopped.

also, is tightening making it more lean? and vice-versa?

thanks for all the help

planebasher

Tower Hobbies sells a twisted wire flexible pushrod that comes in three different diameters the smallest can be mounted down to a
1.5" radius and is perfect for throttle hookups; I recentlyl ordered some of all three but the .063 was backordered; it would probably be sufficient for an average air rudder hookup.

That is a nice looking boat.

I built the Dumas BSB and put a .52 Four Stroke on it but its not quite enough; have it now fitted with the OS .46 AX; and have an
OS .61FX on the way, maybe one of these will get it up.

It is porpoising quite a bit right now with the .52, since this is my first airboat I am sort of at a loss as to what is causing it; my bass boat will porpoise at midrange but I have enough power to drive thru it;; so I am guessing I dont have enough thrust on the BSB to get it out of the wat er sufficiently.

DJLaPalme

Mjderstine, you adjust the low end with the engine NOT running. On the majority of engines turning the needle clockwise leans it out. CCW richens it up. When changing the low end make very small adjustments then test it. If you make too big of an adjustment you will be hunting back and forth for a while. I consider a small adjustment to be less than 1/8th of a full turn. Good Luck! Nice looking boat by the way. Dennis

mjderstine

thanks for the help guys, I'll be testing some more this weekend. ill be sure to make the adjustments very small.

planebasher, i got the linkage stuff all figured out now, but thanks for the advice!

DJLaPalme

Mjderstine, if you can make Ocala on 9/28/08 around 9:00a.m. there will be some people there who should be able to help you tune it. When tuning remember to never run the engine too long while it is lean. It can ruin an engine real quick. When setting the high end, lean it out till the engine peaks out, then turn it back to the rich side till the engine just drops off a little bit. The engine will unload(lean out) a little bit when you turn it loose on the water. Go to Lester Burch's thread on the NFMABA and the Ocala site to find out where it is at. Dennis

mjderstine

sorry i missed the invite. i was at Salt Springs all weekend at Lake Delancy, its near Ocala. so i was pretty close anyway. I am sure there are more weekends in the future where we may get together.

mjderstine

i took some weight measurements last night.
the boat with everything but fuel was a shade over 12 pounds.

the boat with not motor, fuel tank, battery, RX, and hatch weighed about 7.0-7.2 pounds.

I am already thinking about re-making the hatches out of balsa wood, and switching to a smaller battery, but that might cut .75 pounds if I'm lucky.

I would like to get around 9.5-10lbs when its all done.

any other ideas from the guys out there?

j.m.

Skin it in 1/32" ply.

Not 1/8", unless you really do like floating tanks.