tom111

Hi,

My new engine is CY 29CC with billet head, the engine starts fine & works well for 10 minutes, but after that it just burns the plug, I already burned 5 plugs, so I have no idea what can this be? I am running it with 1:25 mixture, I run it as richer as I can, the plugs are NGK (I tried different types, even iridium ones)

Thanks

Mazda ute

What oil are you useing (brand) and what ratio how many ML's to how many LTs ?. What air filter are you useing and do you oil it ifso what with?. These things will help people out abit to help you out.

dgav407

I assume the engine is the one you have installed in your MCD MT.

Did you vent the fuel tank? If not simply drill a small hole in the fuel cap, insert one end of a piece of fuel tubing in the hole and place the other end of the tubing out the back of the truck. If you don't vent the tank the engine will start to run lean and it could eventually seize!!!!!

Adjust the carb settings so that the engine mixture is slightly rich - don't ever lean the mixture out for maximum performance. Don't just take my word for it, this advice comes from one of the best engine builders (and largescale racers) in the world who also races MCDs here in the UK.

Clive

bsrman14

Spark plugs rarly go bad if ever. The problem is the oil ratio. Change it to 32:1 and clean all the old plugs real good. I hope you didn't throw them away.They are still good. []

46u

My Feedback: (3)

If you vent the tank how do you get pressure to pump the fuel to the carburetor? This is why you have two lines going to the cant one to get fuel to the carburetor and one to pressurize the tank since there are not any fuel pumps on them.

BadClownCrawler

simple fix. no need to switch oil ratios. you said you run the needles as fat as you can. that is the problem, the needles are too fat and fouling out the plugs. lean up the low needle 1/12th a turn. bascially you getting too much fuel and its fouling out the plugs is all. lean the low up a bit, and likely the high a tad, and you shouldnt foul out as often.

the fuel moves to the carb via the diaphram in the carb itself. if the tank is not vented, then you will create a vacuum in the gas tank. that small hole that is made in the gas caps is what allows the tank to vent. Gassers are NOT nitors, and DO NOT work off Tank pressure. they have 2 lines going from the tank to the carb becuz when the diaphram is full of fuel, it has to have a place to push the excess fuel to. thus the gas flows thru the 2nd line (usually the yellow one) back into the gas tank.

and fwiw, some fouled plugs may live on, but often once its fouled out, its dead.

bsrman14

I have brought alot of fould plugs back. They may not look fould but they are. Fould plugs are a result of too much oil not burning. Changing the oil ratio fixes the problem. Not leaning out the settings.

SAVAGEJIM

I agree, go with a more diluted oil ratio. The 25:1 ratio should be only for break-in purposes, and consider your plug as toast once done: the carb is set slobbering rich from the factory and when you are done breaking in the engine, the plug will be charcoal black covered in goo.

To resolve your plug issue, once your engine has properly run in, lean the carb, this is a serious must. And of course, go with the 32:1 ratio to help reduce plug fouling.

SAVAGEJIM

Something I foound out the hard way but I find rather intersting.

I tried to run my FG with the gas cap off, and I noticed that the fuel in the line from the diaphragm was not going back into the tank and the engine refuesed to start. But as soon as I screwd the cap on, a few more tugs of the pull start and pew! pew! the engine sputtered and fired up.

I will have to dwell on this a bit more and figure out why this is.

BadClownCrawler

then i would suggest you work with some motor builders who build these for a living. The GOOD ones will tell you its too rich, not too oily. FWIW, alot of the Boat guys run at 12:1 oil mix, and they dont foul out any more plugs than we should on a Nicely tuned motor. 32:1 will be fine for ratio, but if the needles are too fat, he ll still foul plugs, but it ll be in 13 minutes instead of 10... plain and simple.

thats a weird one. ive often ran my motors with a loose or removed gas cap. hmmmmm.

SAVAGEJIM

No, I dont disagree here at all. I too consider tuning to be the number 1 factor as why plugs foul. It's just that I also have noticed some play in oil ratio in plug fouling as well, given a fixed needle setting.

tom111

Some results…

dgav407 – you’re the man ! I noticed that every time after my engine dies when I open the plug I see A LOT of smoke & the plug & piston are completely dry, so my first suspicion was that the fuel is just not getting there, then every time I opened the fuel cap I heard a sound of pressure that is being released out of the fuel tank, like opening a bottle of coke, so I drilled a hole in the fuel cap & added a small pipe there & I could ran it for ONE HOUR without any issues, amazing what a small hole can do… I just don’t understand 2 things:

1. I have been running my FG MT for 2 years without any ventilation in the fuel tank, it has only 2 lines – in & out, I never had any problems with it…???
2. If this is a known issue why does these companies don’t do this extra vent? My friend own 2 Smartech MTs & both of them came with an extra third ventilation line…

So I guess it is not the oil ratio, air filter, type of plug or needle configuration, it is just a vacuum that does not let the fuel after a while get into the carb…

dimag093

FG MT gas cups have a little hole in the center for venting purposes.Are you sure your tank cup doesn't have that vent hole?Mine has

BadClownCrawler

all gasers should have a vented gas cap. most do this with a small hole in the cap, and a rubber stopper boot under it (which allows the air to flow, but by design, should stop fuel from spilling out the vent hole). BUT sometimes things get missed in QC. i suspect your current cap either didnt get the vent hole into it. the underside rubber boot in the cap wasnt allowing airflow around the cap, or was otherwise plugged up. thus causing a vacuum in the tank (hissing sound you hear as air rushed into the tank filling the vacuum made), and starving the motor for fuel and like Dimag mentioned, even causes an intermitant LEAN run untill it stalled.

np SavageJim. hope im dont come across to gruff about it. im one of those guys thats all about Full disclosure and full and solid info. how can someone be expected to make an educated decision if they only get partial bits of info. kind of like buying an item strickly due to cost. ya you may of saved some cash now, but in the long run, you ll likely end up spending more than you would have if you just purchased the better quality unit. but if your only told its a great item cuz its cheap, and not that it has durability or early wear issues, then that buyer is going to likely be miffed over the fact they only got half the info the really needed.

SAVAGEJIM

No problem at all, if fact, I agree you hit it right on the head with the rich running part. I have no earthly reason why these engine are set so rich from the factory. I can understand them being on the rich side for running in, but slobbering rich? That is nothing short of a plug eater.

I have given up on running 25:1 ratio after the engine has broken in. I have done that before, and even when running with the needles leaned in, I noticed that the plugs still fouled. That is why I suspect oil ratio to be the problem. Granted, I did run the plugs with the needle rich too before leaning to find the good tune, so, I could have really fouled the plugs when going from rich to a good tune. What else that could have fooled me is once I feel that the engine is broken in good, I automatically switch to 32:1 ratio and change the plug anyways.

tom111

dimag093 – you are so right! I just noticed that I have a small hole in the cap of my FG MT, I guess I never noticed that, I expected to find a third fuel line like in the Smartech trucks… but I verified it & I do not have anything in my MCD fuel cap, no hole in the cap or any third fuel line in the tank...

Did you get your MCDs with a hole in the cap???

dgav407

tom111, despite MCD promising they would address this issue, the latest 2009 spec models I have seen do not appear to have a vented fuel tank cap.

King Cobra Racing (the importer/distributor for MCD in the UK) produce an alloy vented fuel cap but to be honest the best option is as I suggested in my previous post.



Clive

dimag093

................Did you get your MCDs with a hole in the cap???

[/quote]
I do not own an MCD(not yet that is) [8D]

clubin

Clive are you serious, they have not adressed the most asked question regarding MCD's! It only runs for a few minutes then dies? That is real crappy.

Comon MCD VENT THE TANKS!

dgav407

dimag093, I have had to drill a small hole in the stock plastic fuel tank caps of my MCDs. I'm using a vented alloy one on one of my MCDs but it's basically a pointless 'bling' product and the modified stock one is better option.

clubin, perhaps MCD are too busy updating the manual to fix the problem.

Clive

clubin

I got it. The evo 4's will be out when the EVO III manuals are done and the manuals won't be updated again till the EVO 6 or 7 is out. It all makes perfect sense.

How hard would it be to do the mod to the tank seriously?

dgav407

clubin, drilling a small hole in the fuel cap would be a start!!! Sinan (the owner of MCD Racing) told stevo when he visited the factory late last year that a vented cap would soon be included with all the cars (Monster Truck, Rally Car, Race Runner and Baja 1000).

This is the latest 2009 spec Race Runner and the fuel cap doesn't appear to be vented -



Clive

clubin

MY RANT

MY Rampage came with a vented cap. They just started Large scale. How long has MCD been manufacturing 5th scale models? They still haven't figured it out. I have sent Sinan numerous e-mails demanding that somtning be done with the caps. He obviously doesn't give a $#!t. It'll catch up with them though. I have never gotten a reply from MCD. Are they listening to their customers?

I bought a Redcat and for what I payed for it did not expect any real custome service, well the customer support from Redcat is spectacular.

splcrazy

what i do for my 5b is i use 200mls of oil for 5litres of fuel then run the carb stock settings then adjust the carb to slightly lean but just a slightly very small turn to lean , and have never ever seized an engine again.

BadClownCrawler

thing is the MCDs dont come with motors. so they prolly never tried to run on with their stock cap. OR the stock cap is leaky enough that it actually vents the tank anyways.