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Unused MCD Racerunner - please help - engine trouble / ... - 1/23/2013 7:53 AM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Hi all,

I have an MCD RR (older version I guess) which I bought 5 - 6 years ago.

Initially ran well and used a fair few times then I started experiencing engine problems - I searched the forums and posted a couple of times to no avail.

Starts ok - runs and drives fine for about 3-4 minutes then will not rev through at all. I have tried resetting the H and L on the carbs following online advice tweaking in every imaginable combination with no joy at tiny increments as well as drastic (desperate!) increments. I have always had 2-strokes motorbikes and pretty sure the problem is else where.

Has anyone had the same issue? Has anyone got (or know of) a trouble shooting guide / check steps / dummy guide.

I gave up and it just seems a waste just sitting there for a couple of years now - didn't want to part with it because I doubt I'll ever replace it.

Thanks, Dan

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/23/2013 3:30 PM   
badboy2



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Status: offline 		try changing your gaskets..thers prolly a leak.

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/23/2013 8:26 PM   
4C8DAN


 

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Status: offline 		Thanks, gasket set ordered.

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/23/2013 11:10 PM   
Lars from Norway



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Status: offline 		As badboy2 said. I was thinking of this too while reading the first post. I also thought of using start gas to search for leaks around the gaskets. The reason for it running fine until it gets to working temperature is that the heat has not expanded anything yet, making it draw false air from somewhere around the carb when hot.

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/23/2013 11:16 PM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Thanks - for the sake of a few quid I think changing the gaskets is definitely what I should do first - if that doesn't solve it then I'll try something like you suggest. As you say, thing expand when warm so probably base gasket or inlet manifold drawing air in.

I will let you know.

Appreciate the tips guys!
Dan

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/24/2013 12:19 AM   
bentley marshall


 

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From: hamilton waikato, NEW ZEALAND
Status: offline 		make sure you have a good vent on your fuel tank if air cant get in to your tank it wont let fuel out

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/24/2013 1:45 AM   
mooman007uk



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From: parksville, BC, CANADA
Status: offline 		+1...mcd's as with many other's have gas cap venting issues...100% guarantee that is your problem...forget about gaskets, don't fiddle with the needles as carbs stay set once set...i've seen many people noobs and experienced rc'ers start messing with needles when the motor loses tune harking back to their nitro days...if it loses tune there are the usual suspects, one of which is not the needles. start with the easy first...gas tank vent, then check base gasket for wetness, leak at carb gasket check with wd40, check clutch side crank bearing seal check again with wd40...the 2 most common causes of loss of tune or rough running are tank vent especially on new rc's and on 2 bolt cy engines clutch side seal after 10-15hrs+ running...all my old 2 bolt cy's went thru crank seals...

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/24/2013 6:52 AM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Thanks - I was thinking (hoping!) it was something simple, all the basic principles are there, starts quite easily, initially runs with good power, then it all goes to nothing.

You're right I moved (sold up) from 1/8th nitro so straight away went for the needles!

I'm going to spend some time on it Saturday and will let you know.

(It has Zenoah G260 2 bolt)

Thanks again,
Dan

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/24/2013 3:38 PM   
mooman007uk



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Status: offline 		pull the gubbins out the cap and drillout the hole to take a dubro fuel fitting, screw into the cap with a piece of looped fuel line to stop it leaking while upside down.

to test the cap before fixing it... run it until it starts running crappy and then loosen the fuel cap...you'll hear a small rush of air...with a loose cap it should run normal

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/24/2013 5:13 PM   
4C8DAN


 

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Status: offline 		Thanks all, appreciated

I will take your advice....

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/26/2013 12:58 PM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Ok so fuel cap was breathing fine. Base gasket was wet and I could see it leaking while the engine was running.

Base gasket changed and now it is very hard to start - was starting easier before I changed it. I did not change or adjust anything. Once started it seems to rev ok now and is quite responsive, so that's promising!

To get it started I have to have throttle open a fair bit and several pulls on the chord - it won't idle very slowly in fact the wheels are just about spinning to keep it running. Even after keeping it running for a while still a pig to start. I have rest needles to 1.5 low and 1.25 high with no luck.

Help appreciated!

Dan

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/26/2013 6:48 PM   
bentley marshall


 

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From: hamilton waikato, NEW ZEALAND
Status: offline 		try resetting your needles to 1 1/4 low 1 1/2 high sounds like its to rich down low all so did you reset your coil gap after you have the head off

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/26/2013 6:52 PM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Thanks. No I wasn't aware of needing to set coil gap - how do you set it ? Needles reset but did not help. Losing the will to fix it again which happened last time. I am considering a new engine...

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/26/2013 7:57 PM   
mooman007uk



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Status: offline 		use a business card between the coil and flywheel...that sets the right gap...did you take the coil off the head? if so it's probably touching the flywheel...hence hard to turn over and struggling to run with it dragging on the flywheel

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/27/2013 8:12 AM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Hi thanks for to continued help. No I did not remove the coil but I will check the gap - it is not hard to pull (I meant hard to start eg won't start without half throttle)

I even tried another carb that I have in my spares with the same result. I guess it still points towards an air leak. All that's left is the crank seals and centre crank gasket.

Next step I guess is split it and change the centre gasket.

CURRRENT SYMPTOMS RECAP!:
1 pull with choke and it semi fires
Needs half throttle to start
Needs partially open throttle to keep it running

Can barely keep it running slow enough for the clutch to disengage
Runs that way for about 2 minutes the suddenly cuts (regardless of throttle position)

I can't believe such a simple engine is causing so much pain!

Cheers,
Dan

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RE: Unused MCD Racerunner - please help - engine troubl... - 1/27/2013 5:33 PM   
mooman007uk



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From: parksville, BC, CANADA
Status: offline 		did you check the small pulse port hole in the carb and manifold gasket are lined up...the pulse is what pumps the fuel in the carb...if the gasket goes in backwards it blocks the hole

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RE: Unused MCD Racerunner - please help - engine troubl... - 2/4/2013 7:10 AM   
4C8DAN


 

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From: Kent, , UNITED KINGDOM
Status: offline 		Pulse port checked and clear. I have since stripped out the fuel lines and tank - here may lye the problem. The pickup is not good with the felt tails broken and the joining pipe creased/kinked.

Yet to test as I got carried away and stripped the car down to every last bolt, cleaned and reassembled. Just have the shocks left to rebuild and install.

< Message edited by danlovett -- 2/4/2013 5:44 PM >

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