Off-Topic: Nitro RC Trucks

Hello folks,

I couldn't find a group for nitro cars or trucks so I figured I might ask the question here as the issues I'm having are with the motors themselves.

I am relatively new to the hobby but have been an auto mechanic for years and years, so familiar with all the pieces parts and what they do.

My question: I have two motors that will not start. They are getting fuel and heat from the glow plug/ ignitor (both tested on another working motor) and the carb is set to factory default. I have them bench mounted and trying to start using a drill adapter on the starter bolt. They are getting fuel and heat, but I think compression might be a problem.

How much compression should these little guys produce? My compression gauge doesn't have an adapter that small so I can't give a number. As it is now, with carb wide open and muffler off, with the head removed and my thumb over the cylinder opening, I can keep my thumb firmly over the hole while turning at 50 RPM or so. I can feel more suction than compression. There is a little bit of compression, but not much.

Shouldn't this thing blow my thumb right off the hole on the compression stroke? FWIW, Megatech M16, 1.15HP. One motor was "new", the other used of unknown hours.

Thanks in advance!

Doc

Reply to
"Doc"
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Are you using fresh fuel?

Does it have the proper nitro content? (Say 5% to 10%?)

Can you borrow some fuel from another truck driver?

I don't know the number, either.

I've never done the "thumb test" so I can't help you there.

Other desperate measures to try:

-- new glow plugs (contaminated plugs can glow but don't produce enough catalytic action)

-- borrowing a car starter, if the exist. I think you can have the wheels spun by the starter.

-- new batteries for your glow igniter.

-- Be careful about flooding the engines. Once they're flooded, you've got to take the plug out, get rid of the excess gas down in the bottom of the crankcase, and try again.

-- Remove the needle valve and flush out the drawbar. Sometimes dirt can get in there and cause all kinds of trouble.

-- You might try just a tiny, tiny squirt of fuel to act as a primer--you may have to take off an air filter to get at the venturi. (DON'T FLOOD THE ENGINE!)

-- You might try opening the main needle valve four turns. That's probably way too rich to run the engine, but it's a respectable place to start when trying to get a balky engine to run. If the engine never pops but just floods, dry it out and try again with 2.5 turns on the needle valve.

If you've got a good glow plug, good fuel, a good battery, and a method of spinning the engine quickly enough, you should be able to get some kind of "pop" out of the engine. If it starts running and bogs down, it's too rich. If it starts running, winds up quick, then quits, it's too lean.

Glow plug threads are 1-4/32 (National Extra Fine). You might be able to cobble together an adapter for your pressure gauge, but be careful--the heads are a relatively soft alloy and the threads are easy to strip. It's conceivable that the pistons and cylinders have been abused by the original owner and that both are toast. Replacement parts are available, but it's rare that they are cost effective.

Let us know how it all turns out.

Marty

Reply to
Martin X. Moleski, SJ

Yep, and fuel from the same quart runs like a sonofabitch in my other truck w/same model of motor.

See above, I'm using Trinity 20/12.

Don't have to, see above.

Tried that. I used the plug from the running motor and still nuthin'.

Using a drill adapter on the crank bolt to the same effect.

Tried that too.

Did all that!

Using a fuel filter, but tried that already.

Tried that too, no dice.

I have tried it with both mixture adjustments at all conceivable turns and combinations!

No pop at all, just turns and turns.

Agreed. I'm gunna sell em' on E-Bay cheap is someone wants to rebuild them (very popular motors for the T-Maxx) and just get me a new one. Over 24 hours invested so far and I'm tired of messing with them. The other one starts on the third pull every single time and runs great.

Thanks so much for taking the time to reply Marty! I'm thinking about getting into flying as well so I might just stick around on this ng and learn from y'all.

Doc

Reply to
"Doc"

Makes sense. You've obviously exhausted all of the tricks I can think of. ;o)

It's great to have a baseline to compare the non-working motors to.

If you're going to check compression, you can do that with the good motor.

My pleasure. I hope to get a truck some day.

Great to have you here.

Marty

Reply to
Martin X. Moleski, SJ

"Martin X. Moleski, SJ" wrote in message news: snipped-for-privacy@4ax.com...

Hello, Father Marty. Good to see you back again too. I wondered where you gotten to.

IB (wink)

Reply to
Incredible Booms

Reply to
R.A.Gareau

The sleeve has a small groove on the top ring that aligns with a pin on the top of the block, so it will only fit one way. This defies all logic!

Doc

Reply to
"Doc"

A Jesuit padre, I knew I liked this guy!

Doc

Reply to
"Doc"

I don't think I've been away. Just haven't had much to say recently, I guess. ;o)

Marty

Reply to
Martin X. Moleski, SJ

I am not catholic. Have I made an error?

IB

Reply to
Incredible Booms

No, but maybe I have? You called him Father Marty and he signs his name with SJ (Society of Jesus, aka The Jesuits). Maybe that's just his nickname and SJ stands for something else?

Doc

Reply to
"Doc"

I apologize to Marty for making this a topic of discussion. I know he likes to be known as Marty in the newsgroup.

I had always "assumed" that padre training was the first part of the Jesuit experience. But, alas, I am totally ignorant of the process.

At any rate, Marty is a great guy and a very active modeler. The latter is what counts here, I suppose.

IB

Reply to
Incredible Booms

It's no problem. Like Popeye, "I am who I am and that's all that I am." ;o)

Most of us Jesuits become priests. I was ordained in 1981, so (in Catholic terminology) I am a "father."

I expect my students to call me "Fr. Moleski" or "Dr. Moleski" (I've got a Ph.D. in systematic theology). When it comes to making RC airplanes behave, neither credential buys me any airspeed, altitude, or insight. :o(

Thanks for the kind words. I enjoy the hobby very much.

Marty

Reply to
Martin X. Moleski, SJ

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