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DDM 30.5cc kit question

Old 12-08-2006, 07:55 PM
  #1  
DarkZZ
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Default DDM 30.5cc kit question

Hi Guys,

Was just bored and tried to install the 30.5cc kit for my ST Hummer, just got some questions since the engine wont start no matter what I tried, spark plugs are dry and there are sparks, engine inside is clean, no leaks or any sign of damage..... my concern is the piston position, as you can see in the picture, there are no forward sign on the top of piston, but there is one little circle sign, is that it? and there is one hole on each side of piston, what does that one do? someone please educate me since im out of clues what else is wrong with the engine.... thanks guys!

ps. could it be the sparking problem under compression? I noticed the engine is harder to pull once i screw the spark plugs in....






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Old 12-08-2006, 09:12 PM
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Default RE: DDM 30.5cc kit question

i think the small circle that you see on the top of the piston is suppose to face the exaust port on the engine.maybe some one else can shine some light on the subject.i will be doing the same thing to my baja when i get home have the 29cc coming.
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Old 12-08-2006, 09:44 PM
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Default RE: DDM 30.5cc kit question

thats the way i did it, and it just dont want to start....something to do with the magnet brush??
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Old 12-08-2006, 10:10 PM
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Default RE: DDM 30.5cc kit question

On a stock piston there is an arrow that indicates its meant to be facing the exhaust side. If that arrow is no longer there then the other way of making sure you have it facing the correct way is on the side where the piston ring comes together on small circle rod that side has to face the carb. Also another thing to check for as to why your motor is not starting is the gap for the coil to the flywheel magnets that may be incorrect and does not allow the engine to start. Make sure when you gap it that you are doing it on the side that has the magnets not the side that doesnt.
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Old 12-08-2006, 10:36 PM
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Default RE: DDM 30.5cc kit question

yup, piston mark points to exhaust, ring gap towards carby. now, did you use the stock 28mm crank? or did you put a stroker crank in, either the 1mm or 2mm?
also did you put in a NEW plug, or the old one from the original top end. hook up your gas lines correctly, pick up in tank goes to bottom, overflow goes to primer bulb.
is your kill switch shorted out? or is it stuck in, Getting any spark?
use a regular ( OLD STYLE ) business card to measure your gap, i actually folded my DDM card in half and used that for gap setting, worked well.

Timmahh
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Old 12-08-2006, 10:41 PM
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Default RE: DDM 30.5cc kit question

The gap setting is 0.3mm using a thickness gauge.
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Old 12-08-2006, 10:49 PM
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Default RE: DDM 30.5cc kit question

thanks for the response guys, i did get sparks from it, but does it still matter how close the gap is between the coil? i thought as long as you get sparks, the gap should be ok?

Timmahh:
the kit comes with everything crankshaft, pistons. it was coverted on my stock G260RC engine.
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Old 12-08-2006, 10:50 PM
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Default RE: DDM 30.5cc kit question

The gap is crucial. It must be correct or the engine wont run. 0.3mm is standard and upto a max of 0.4mm.
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Old 12-08-2006, 10:56 PM
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Default RE: DDM 30.5cc kit question

Thanks Caad5, I will give it a try later tonite, my right arm muscle has been damaged after 2 days of pulling this sucker.., need a rest. lol
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Old 12-08-2006, 11:07 PM
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Default RE: DDM 30.5cc kit question

man that just dont sound right.lol just messing with ya.dont worry you will be up and running in no time.
ORIGINAL: mic300zx

Thanks Caad5, I will give it a try later tonite, my right arm muscle has been damaged after 2 days of pulling this sucker.., need a rest. lol
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Old 12-09-2006, 12:21 PM
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Default RE: DDM 30.5cc kit question

Sometimes it just takes some time. My fore arms and triceps hurt a bit after all my pulling as well. Keep playing around with the needles. Mine was flooding, if yours is pull off and start it up to urn off the excess gas inside first. Also make sure the piston is not hitting the spark plug. I had to use both gaskets to raise the head on my kit.
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Old 12-09-2006, 10:40 PM
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Default RE: DDM 30.5cc kit question

ok guys, got some updates today, corrected the gap with a business card, tried many times to start it, it wont, so i full throttle it, still wont start, then i used a few drop of 2 cycle oil into the cylinder, it starts after a few pulls, but then it dies again, i thought it was something to do with the fuel line, but cant find anything wrong... unless there is something to do with the carbulator? because every time i try to start with full throttle, its just worse compare to start without any throttle. just seems like theres no fuels pulled into the engine...but it still gets wet spark plug though....
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Old 12-09-2006, 11:15 PM
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Default RE: DDM 30.5cc kit question

Did you install a new carb gasket ? make sure the vaccum holes arent plugged up with any sealant or anything . you resest the needles you said ?might need to turn up your idle as well that wontr hurt anything till you get it running because once you richen out your needles the idle drops right down and might be closed ..?..
Good luck
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Old 12-09-2006, 11:36 PM
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Default RE: DDM 30.5cc kit question

the carb gasket is still good, so i didnt change it, anyway i can check if the carb is not working?
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Old 12-10-2006, 03:25 AM
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Default RE: DDM 30.5cc kit question

another question guys, for the L H adjustment, do you just turn the screw all the way in and then start to count the turns out? I have 1.5H and 1.75L.
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Old 12-10-2006, 04:52 AM
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Default RE: DDM 30.5cc kit question

business card ????
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Old 12-10-2006, 05:54 AM
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Default RE: DDM 30.5cc kit question

Too rich on the L needle - setting on the L needle shoud be at 1.25 turns out to start with and then tune from there
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Old 12-10-2006, 10:38 AM
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Default RE: DDM 30.5cc kit question

yes turn the screws all the way IN, then count out 1.25 - 1.5 on l, and i ll start at 2 out on the H with the bigger ccs. be carefull NOT to seat the needles to tightly or you will damage the needle end.

now whats got me miffed is the when you add oil into the cylinder it started. to me thats when i know its time for new rings. basically the oil causes the ring to seal to the cylinder, temporily stopping the BLOWBYE of compression past the ring allowing the motor to start as its got "GOOD" compression. once the oil burns away, the blowbye returns, you loose head compression, and the motor stalls/wont start. but this is a new kit, so maybe the ring is/was bad or became damaged in the assembly process. i would check the cylinder gaskets and make sure the cylinder is sealing and the head gasket is sealing ( i htink you stated you have a HEAD KIT, and not just the cylinder with head attatched). if all that proves ok, i d yank it apart and recheck everything.


JD, 10 years ago, when you had to go to a printer to get business cards made, the thickness was almost perfect for setting gaps on plugs and coils. nowadays with the DYI printers, the business cards are alot thinner now. i have always used a Cover on a Book of Matches as its the same thickness and EVERYONE has a book of matches handy, not eveyone has feeler gauges available.


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Old 12-10-2006, 04:36 PM
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Default RE: DDM 30.5cc kit question

Thanx guys, I will open the engine one more time, if it doesnt work, i think i will send them to the scrap yard soon.
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Old 12-11-2006, 12:21 AM
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Default RE: DDM 30.5cc kit question

ill be glad to take it off of your hands
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Old 12-11-2006, 09:50 PM
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Default RE: DDM 30.5cc kit question

Updates guys!

Basically i think it was my carb, but im not too sure, since i got 2 engines beside me, and also 2 carbs, so I kept swtiching them around in the past few days, I had one engine that is 4hp+ (bought from DDM), and one 30.5cc kit (built on my stock G260), i tried to started my 4hp+ engine today, and everything worked, but I had to set my idle screw all the way in, plus L 1.2 H 1.5 just to keep the engine running, however, that one didnt went well, and i cant even full throttle it, it just dies. so i took that sucker apart and loaded on my 30.5cc engine with another carb, started, idle screw about 10% in, L 1.2, H 2.0, then she runs like a dream, well i cant consider she is running because the wheel is off, and theres no gears attached. idled it for 10mins in my kitchen since is 7pm here, then i came here
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Old 12-11-2006, 10:01 PM
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Default RE: DDM 30.5cc kit question

u ran an engine in your kitchen ???
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Old 12-11-2006, 11:06 PM
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Default RE: DDM 30.5cc kit question

is that something you cant do when you are married?
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Old 12-12-2006, 12:06 AM
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Default RE: DDM 30.5cc kit question

yes
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Old 12-12-2006, 12:37 AM
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Default RE: DDM 30.5cc kit question

guess im still free then
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