New mcd cy motor tuning trouble(gas tank)!
 

I just purchased a race runner buggy. For the last 3 days I've been trying to get it to run at full throttle without sputtering. I have had the H speed needle from 1 turn to so far open that it would foul plugs. I found that drilling a hole in the gas cap and installing a small coiled piece of fuel tubing helped quite a bit, but it still sputters sparatically at WOT going arond the track. I didn't notice it when the tank was full but it does it from 3/4 full and down. I think it is sucking air as the buggy bounces around. Has anyone else expirenced this, and what would the easiest fix? I was going to try a smaller tank comming off the main tank with the supply tube in it to reduce the movement of fuel away from the pick up tube. Other than that I would recommend 1/5 scale mcd to anyone.

RE: New mcd cy motor tuning trouble(gas tank)!
 

try;
put high speed needle to stock setting and leaning it out a touch (with exhuast off if its stock can)

check for airleaks in fuel lines

spray water around carb gasket and linkages (everywhere but down the carb) and listen for engine noises changing or use soapy water and look for air bubbles

check your fuel filter in the tank

all i can come up with for the moment

Ryan

RE: New mcd cy motor tuning trouble(gas tank)!
 

rebuild the carb.

RE: New mcd cy motor tuning trouble(gas tank)!
 

i was thinking of an air leak too. what i would do would be as 'da mad" said, set it back to the stock settings and check for air leaks.. make sure you clean the plug up and check it to see if its running lean.. also check the exhoust. it can run lean if its got an air leak at the manifold..

RE: New mcd cy motor tuning trouble(gas tank)!
 

i think he said its brand new..

RE: New mcd cy motor tuning trouble(gas tank)!
 

he said he just purchased it... dunno if its new?

hey chipracer! is it new?

im thinking if hes drilling holes in the tankcap already, it cant be new lol

:)

RE: New mcd cy motor tuning trouble(gas tank)!
 

if the fuel tank level has anything to do with how it runs, about the ONLY thing it can be is a bad fuel line to the clunk. these carbs have fuel pumps, they are capable of pumping fuel from a good 4 feet below the level of the carb

I say rebuild the carb and get some new fuel line, for the carb, go to a small engine shop and get a D10WAT rebuild kit, their fuel line is probably going to be expensive though (I was quoted $5 or so a foot, but I had no money back when I asked then...), so might want to go to a hobby shop for that

RE: New mcd cy motor tuning trouble(gas tank)!
 

I noticed this when I first got my RR too, there is a fair bit of washing around going on in the tank and I was seeing bubbles in the fuel line even at about 1/2 tank to 2/3 tank level after venting the tank as well as before and even replaced all tubing incase there was a hairline split in it that I couldn't see. I tried weighing down the clunk in the tank with additional weights (it was pretty lame the factory installed clunk) and then ended up fitting an HPI baja clunk/filter and it has been okay ever since.

RE: New mcd cy motor tuning trouble(gas tank)!
 

Yes, this is a brand new race runner. I drilled the cap because when I unscrewed it I could hear it was vapor locked. I would hope I don't have to rebuild the carb already, only have 1/2 a tank through it. It may be the fuel line, I installed a filter between the tank and carb on the suction line, so maybe I have a split line and didn't see it. Monaroman sounds like the same problem, I think I will order a hpi baja clunk. Thanks for all the responses I will check a few things out and get back.

RE: New mcd cy motor tuning trouble(gas tank)!
 

my thunder bolt has the same problem, it likes to cut in and out at wot....its only after the gas tank is 1/2 empty that it begins.....I'm thinking the clunk or gas lines

RE: New mcd cy motor tuning trouble(gas tank)!
 

a filter clunk would probably help that, if you can't find what you're looking for locally, go to a mower shop and get a clunk for any chainsaw...

RE: New mcd cy motor tuning trouble(gas tank)!
 

I got it to run great just by adjusting the fuel clunk in the tank so it just touches the bottom, guess I had it in too far before. I ran a whole tank through it and it didn't bother till it was almost empty and I was turning some high speed donuts. Awsome machine I am very happy with this buggy, I highly recommend anyone thinking about it to just get one. Your friends wont talk to you anymore but they will get over it. Race runner,cy29,jet pro unsilenced,K&N filter,114 oct w/32:1 amsoil syn(just because it smells sooooo good!) Thanks to all for the help!

RE: New mcd cy motor tuning trouble(gas tank)!
 

post some pics of your race runner.

RE: New mcd cy motor tuning trouble(gas tank)!
 

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Having trouble uploading a pic.

RE: New mcd cy motor tuning trouble(gas tank)!
 

[img][/img] Here are my latest mods

RE: New mcd cy motor tuning trouble(gas tank)!
 

Guess I have the pic thing figured out, sorry for all the dirt in the pics. I fitted fg stadium tires and chrome wheels to it last night, I will take some pics today. Just a warning to others wanting to put fg wheels on your RR, they don't fit. Fortunately I just happen to have a $4,000 lathe/mill and it was no big deal. The centers are to thick and need to be milled down so the axle nut will thread on to the axle. The plastic mesh gear cover works well. I have ruined two sets of gears already, but none since I built the gear cover to keep out the bigger rocks and debris.:D

RE: New mcd cy motor tuning trouble(gas tank)!
 

That unsilenced JetPro must be real loud, I pulled the packing out of my Silenced Jet... and it was loud TOO LOUD. I think I am gonna get a set of those tires and rims for my Baja, the ones on there spin too easy, those look like they would do the trick. Nice Race Runner.

RE: New mcd cy motor tuning trouble(gas tank)!
 

to stop bubbles in the fuel line get a felt covered clunk. they are used in chainsaws

RE: New mcd cy motor tuning trouble(gas tank)!
 

The felt covered clunk sounds like a good idea, I will have to get one. Yes your right clubin, those skinny stock tires don't give you enough traction. These stadium tires are much wider and seem to hook up better. The only problem is I need to get a wider door for my shop just to get it in and out.:D

RE: New mcd cy motor tuning trouble(gas tank)!
 

Chipracer what car is that in your last 4 pictures,looks really good for some reason?I suppose the tires...

RE: New mcd cy motor tuning trouble(gas tank)!
 

^^ I can help with that, it is a MCD Race Runner with FG Stadium truck Tires/Rims.

RE: New mcd cy motor tuning trouble(gas tank)!
 

The buggy looks nice.

A few tips for you though - replace the 24 & 25 teeth plastic gears with the 23 & 26 teeth steel ones and cut out most of the front side windows on the bodyshell. If you race or use the buggy for long periods I would recommend cutting out all of the four side windows and drilling holes in the front window as well - your engine will run alot cooler as a result of this.

Clive

RE: New mcd cy motor tuning trouble(gas tank)!
 

Thanks clubin, ya it's a Race Runner. Thanks for the compliment and the tips Clive. I think I will take your advice on the steel gears, the plastic 24/25 setup doesn't seem to hold up to well. Is it the heat that weekens and strips these gears or is it rocks getting caught inbetween them? Is there a problem with these engines overheating? Hate to cut holes in the shell and let in all that dirt but if it helps with the gears and the cooling I could give it a try.

RE: New mcd cy motor tuning trouble(gas tank)!
 

chipracer, the engines will run slightly hotter in the 4WD off and on-road cars - the engines work harder due to the extra weight and the inefficient drivetrain (compared to 2WD). For example my Baja 1000 Evo 2 ready to go weighs 27 pounds and my all-alloy Harm Bx1 buggy significantly less at 23 pounds!!

The plastics gears (24 and 25 teeth) can suffer from the heat generated by the engine - although in 16 months of racing/bashing two MCD cars I have not melted any of the black plastics gears - the only damage is from small stones/rocks. One tip I can suggest with the plastic gears is from new and when alternative or replacement gears are installed is to bed them in by driving the car slowly for the first few minutes.

I installed the KCR alloy gear plates in my cars and this helps with cooling but to be honest the steel gears are the only option part that is needed. The cars being raced off-road successfully here in the UK are just using the steel gears - no expensive alloy gear plates. These cars are being raced with expensive full-race engines (oddified, Alro etc) and I don't think the owners would risk them if there was the slightest chance of the engines overheating and seizing....

As for cutting out the windows - I initially only cut out one side window for access to the kill switch and pull start plus a small hole for the standard CY can exhaust. I could not understand why the engine ran so hot and continually needed the carb to be adjusted. There was always a noticable drop in performance towards the end of 15/20 minute final at race meetings as the engine slowly cooked!! Only as a result of cutting out the side windows (and drilling holes in the front window) and changing to a Castor based oil have I seen a drop in engine temperature and consistent engine performance.

At the very least you should have access to the kill switch and pull start without the need to remove the bodyshell.

Clive

RE: New mcd cy motor tuning trouble(gas tank)!
 

Dgav407, thanks for taking the time to respond in your last post with all the details. Your Bx1 must be pretty quick at 23lbs. I am amazed that you haven't stripped any plastic gears yet in 16 months time. I stripped a set in the first tank. I think there might be something to your sugestion of bedding in the new gears, will deffinateley try it. I bought a few extra plastic gears so if (when) I go through them I will get the steel gears. I have also noticed a drop in performance after only 10 min. I am giong to cut my windows out today, I really like the idea of being able to get to the pull starter and kill switch. I guess it makes sense whe you think about it, these engines get their cooling by pulling air in one side and out the other, so with no holes in the body it is just re-using the same air that is continually getting hotter. Thanks again for your input. It's guys like you that make this hobby more enjoyable for the rest of us.