dawg242

I have a Cen. .30 engine in my Cen. C1 Matrix 1/8 scale buggy. It starts right up runs like a champ until I go full throttle, then it dies. I've shortend my fuel line and my exhaust line because I noticed air bubbles in the line. That didn't help. I've richend it up to the point of it being way rich. I've also leaned it out, I even thought that my exhaust pipe might be clogged, but it's as clean as a whistle, nothing seems to work. I've had the guy at the hobby shop helping me, he says that I'm making him look bad because this is the only engine he's not been able to tune. Any ideas? I have also thought that if I can't resolve this issue I'd like to change the engine. I'd like to go to a Losi 454 with the combo pull/spin start. From all the pictures I've seen the shafts look to be the same. Would it fit in my buggy, and would all my other parts work with it, clutch bell, fly wheel, clutch shoes, bearings, ect? I sure would appreciate any help. Thanks guys.

nitroexpress

How's the compression? Maybe it's just worn out.

Ybenjulkay2x

[quote]ORIGINAL: dawg242

(I have a Cen. .30 engine in my Cen. C1 Matrix 1/8 scale buggy. It starts right up runs like a champ until I go full throttle, then it dies. I've shortend my fuel line and my exhaust line because I noticed air bubbles in the line. )
you mention you have bubbles in the line.
Did you pressure test your tank, maybe your tank got leak causing your engine to run lean and flaming out on high speed.

dawg242

nitroexpress- it's a brand new engine, has less than two hours of run time on it, including break in.It seems to have plenty of compression, it's a pull start and it feels good when I pull the cord. What would be the best way to check the compression?

Ybenjulkay2x- After I noticed the bubbles in the line I shortend them up and that took care of the bubbles in the line. As long as I don't try to go full throttle it runs really good. I would still be willing to test the tank just to be sure. What would be the best way to do that?
Thanks Guys



And would anyone have any ideas if I could replace the Cen .30 with a losi 454?

rccheech

The HSN assembly could be partially plugged, you can take it apart and clean it.

Ybenjulkay2x

I you have an extra fuel line (clean), attach one end line to the tank (tank to carb), with your finger holding the other hole (tune pipe to tank), submarge the
fuel tank to a gallon (example) of water then blow air on the hose.
you will see bubbles coming out from the tank if there's leak . if tank leak you need a new fuel tank.

dawg242

First of all I"d like to thank everyone who has tried to help me with this problem. Thank you guys! I took Ybenjulkay2x's advice and pressure tested the fuel tank, no problems there, I took the HSN completely apart and cleaned it. Still no difference. I've adjusted the HSN from factory setting to way rich to way lean, I've also done the same with the LSN, from factory setting to rich to lean and back to factory setting. No matter what I do it doesn't seem to affect it at all. It runs the same no matter what. It doesn't matter if I hammer it from a dead stop, it dies. If I give it a little gas and get it moving I can drive it around all day and it runs fine until I try to go full throttle, then it dies. I just don't know. It has me pretty much stumped

JohnP2

Does it idle okay? Have you taken any temps after it's idled, driven slowly?

rccheech

Does it die abruptly, or does it bog down then die?? Have you changed your glowplug?

dawg242

JohnP2- Yes it idles just fine, the temps are between 240 and 250 after about five minutes of run time from a dead stop to up to half throttle or better just driving it around.

Ybenjulkay2x

By the way what type of plug ur using, Hot, Medium, Cold?

dawg242

Ybenjulkay2x-I'm using a Cen.#3, on the package they are calling it a super glow-plug, platinum/irdium they give the part number as G70429. In my nitro handbook that glow-plug under that number is called a short hot plug.

JohnP2

Ifyou have the ability to post a video, that would really help.

I'm surprised the guy at your hobby shop would simply just say he could not tune it.I'd think he would at least be able to tell you WHY he could not tune it..

I'm still new myself, buthave maintained nine engines and understand it can be both frustrating, but in the end always rewarding.. Looks like you have a good attitude toward it, so I'm confident you'll get it worked out if you are tenacious enough. Don't give up on the engine yet (especially if it's new)

A few questions/comments if you DOvalidate your engine does not have a leak.

1. You noted you went from factory to 'way rich' to 'way lean'.Can weassume you did this in small (~1/16 turn) increments? In other words, even as much of half a turn the wrong way (rich or lean) will throw it off. Apologies if you are aware of that...just throwing it out there.
2. I've learned that sometimes the factory settings are incorrect (I have one engine I set back to stock per the manual, and it was off by a full turn!). If the "stock" settings are not flush for both needles, perhaps try that?
3. Check your manifold gasket
4. Ensure the bolts on your heat sink are tight.
5. Verify you are not seeing fuel anywhere. Simply clean the car, try it and if you see fuel on any parts/chassis you know that's your problem.
6. 240-250 is a little bit high for running less than 1/2 throttle for onlyfive minutes. I sometimes have to run WOT for 7+ minutes to get to that temp -but every engine is different. If it were leaning out, however, I suspect you'd hear it cut out some before stalling.
7. With fuel in the tank, turn the car upside down and see if any comes out (it should not)
8. Can you stop the engine easily by plugging the stinger....or does it just muffle the sound and take a few seconds before it stops?
9. Finally, here is a vid that will help with what CENtold you. I've never tried it, but this guy is pretty knowledgable. https://www.youtube.com/watch?v=epEGetU7NFU

This is really just all trial by error....keep us posted. As noted, however, if you can show even a short clip I'm sure one of the experts will diagnose it in nothing flat. ;-)

flatpickhippster

I had a rotary carb engine act like this on me a few years ago and IIRC it was due to the full throttle servo throw was over rotating the air hole way past wide open....actually making it smaller on the opposite side of the LSN.....and this affected full throttle in some way???.....I corrected that and my full throttle deaths cleared up. YMMV Good Luck

dawg242

JohnP2- I watched the video and tested my engine the same way Squirrel showed in his video, no leaks

JohnP2

I agree. I've never heard of this happening that soundsvery plausible.Let us know if that fixed it.

rccheech

Is the engine a rotary carb?? Or a slide carb??

dawg242

rccheech- It's a slide carb

JohnP2

Yeah, I don't think thereis any other way to fix it than taking the carb apart and setting a baseline. You canlook in theventuri and tellif it's going far.In other words you can either see, hear, or feel when it stops

Out of curiousity, have you asked CEN to send you out a new one? It's brand new, it's certainly under warranty. I'm shocked they would request you go as far as check for an air leak instead of saying 'send it to us and we'll fix it" or send you out a new one.

No matter what,. please let us know the results. This is an interesting one..

dawg242

JohnP2- I got the buggy in May of 2010, I was a newbe, (still am as far as I'm concerned) by the spring of 2011 I had ruined the engine by not knowing how to tune it. Then I became unemployed and was so poor I couldn't afford to pay attention. Rick was working at Cen at that time, I explained my situation to him and he was gracious enough to send me another engine. It took me a long time to get back on my feet, so the buggy and the engine sat around for over a year, in that time Rick has moved on and Cen went through some big changes so I don't think there is any record of me getting a new engine. I wouldn't feel right asking them to replace the engine. My son and I took the buggy out yesterday and ran it around in the yard and surprise,surprise it started running at full throttle, for about a minute then stuck in mid throttle and wouldn't idle down. Had to run it into the fence so I could get it shut down, I took the carburetor off and took it as far apart as I could and cleaned every thing. I haven't been able to get it back together yet but hoping to be able to do that today. I don't want this to sound like some kind of soap opera but my rc nitro experience has been a trip. I wouldn't trade it for anything. I'm learning something almost every day.

rccheech

If it's a slide carb it cant pull too far and start to close. What type of fuel are you running?? It is possible the front bearing is leaking when full throttle is applied and its sucking alot of air. Is the carb pushed all the way down and the clamp bolt tight?

With the engine not idling down, It sounds like you have a pretty good air leak. More than likely the front bearing.

JohnP2

Oh, you aren't alone. You just have to fight through it and continue that positive attitude like you have....you'll get it going and it will be well-worth it!

One other thought. Have you validated the LSN housing is aligned with theidle-stop screw?There is a channel on the side of the housing that should interact with the idle-stop screw. I'm unsure it that will solve the issue, but something to at least rule out as it affects the travel inward, it might also have an effect on outward travel?

Ybenjulkay2x

Try reachin it up half turn and see.
As I remember I encounter this problem on my MRX-3 with an RB S7C I beleive (engine still alive in my MRX-3),
as fuel almost reach half tank engine start to spatter then dies off, some time s when tank also full, after I reachen it up then it runs okey HSN setting too lean, I run the MRX-3 on a big parking lot at the mall when I get off from work.

flatpickhippster

Sorry for delay....my carb was a rotary and I was able to see the over-rotation when I removed airfilter and looked at air inlet hole on rotary carb. Put vehicle on stand, WOT, and fixed it by adjusting the servo horn linkage and using the adjustable throws on my TX.

If your carb is a slide then the above issue does not apply.

Good Luck.

Am I correct? An air leak like this does not affect the low end because at lower RPMs the engine is not creating enough vacuum to suck thru the bearing, but when at WOT the higher vacuum created sucks thru the bearing; hence, not creating enough suction to pull fuel from the tank/lines and starves engine of fuel. Thx

rccheech

Not necessarily, if you have an air leak the engine will ilde higer because of it starving for fuel, it will sound different too at idle and be unstable, unless the idle stop is not adjusted properly, it would just be a consistent high idle. When tuning the engine, thats the last thing you want to adjust.