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Discussion Starter · #1 ·
Hi new so any help good hi everyone 馃憤馃徏I have rebuilt the engine on a Kymco t2 50cc as a hobby.It ran before but now with a 70 cc Naraku up grade.The piston markings are IN and opposite AK it鈥檚 a window piston I fitted it with the IN next to the intake which is the side with windows but don鈥檛 have any compression to draw petrol through the carb so it won鈥檛 start.Bit long winded but any help please.馃憤馃徏
 

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Have you checked for compression at the sparkplug hole ? If you really have no compression, then you need to recheck the rings and the bore. If there is compression, but it's not drawing the fuel through, then it might be leaking crank seals, The seals would have to be really buggered though not to allow any vacuum at the carby.
This kit was a new piston and barrel I presume. Sometimes used two-stroke cylinders get distorted down where the bypass ports are and then they don't draw fuel in properly. The usual test for that is to put a ring down the bore and then hold it up to the light looking for gaps between the ring and cylinder as you reposition the ring slowly down through that critical section of bore.
 

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Discussion Starter · #3 ·
Hi thanks for advice.Stripped cylinder down checked rings etc everything ok new bolts fitted.checked spark plug smallish blue spark but not wet or black.Finger on spark plug hole could feel compression.Next check to see if carburettor air/fuel screws need adjustment the carburettor as new jets etc.I have had new crankshaft bearings fitted. Carburettor only other item that was stripped and cleaned.I believe the fuel screw can be set so as not to let fuel flow.Battery being charged.馃憤馃徏
 

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Discussion Starter · #5 ·
Yep tried that didn鈥檛 draw fuel will try again later after adjusting fuel/air screw battery fully charged.Thanks 馃憤馃徏
 

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With your hand over the carby you should feel suction, and it should flood the motor whatever the mixture is set at.

Check there is suction on the carby.. Check the exhaust isn't blocked.
 

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Discussion Starter · #8 ·
Ok hand over intake of carb can feel suction no fuel put plastic bag securely over in take could see fluctuations spark plug bone dry test spark good spark.What am I missing it points to fuel blockage in the carb.Think I will remove it and check it over.I鈥檝e definitely got petrol in float bowl 馃し馃徎
 

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Discussion Starter · #9 ·
Thought I鈥檇 found problem pilot jet give it a good clean but still not starting so I sprayed so quick start in to carb at air intake filter and cover off but it seems to blow back rather than suction 馃し馃徎Is that a clue for something else maybe reeds any help appreciated as I鈥檓 in Spain temperatures are at 40 plus.Even sprayed direct in to spark plug hole but nothing 馃サdon鈥檛 want to give in and ask local mechanic so where now.
 

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When you put your hand over the carby it should suck fuel through any of the jets, and enough to flood it or get your hand wet, so, it does sound like there is no fuel in the bowl or getting through the jets.

This kit you got, it was a cylinder and piston huh ? Is it possible that the old setup had reed valves that this one doesn't ? It should still get fuel though with your hand over the carby...

If you understand how the induction system works, with the transfer ports, perhaps it might be a good idea to pull the head off and check the ports in the piston, and the transfer ports, are getting covered and uncovered correctly. Perhaps the kit is meant to use some other stroke..

A blocked exhaust will make it hard for it to draw fuel, but that's with normal starting.. a hand over the carby should suck heaps of fuel even if it doesn't start.. might pay to drop the exhaust though to be sure.
 

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Discussion Starter · #11 ·
Thanks I am wounding if the reeds need changeing as I said it did run and the new piston is exactly the same as the old one except the old one had a large part missing 馃し馃徎
Even the markings IN and AK are the same piston rings are positioned correctly.
Could it be the I鈥檓 not getting enough fuel in the carburettor bowl.I do appreciate you interest and ideas.Going to have a day at the coast tomorrow as it鈥檚 forecast 45 here.馃サ..馃憤馃徏
 

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Whew.. That's hot alright... I hope it's not humid with it.

It does seem as though there must be no fuel getting through the carby. Either that or no vacuum, but you have confirmed there is vacuum, and that your hand didn't get wet(I think). I'd definitely be stripping the carby again.
Check the flow from the tank at the hose on the carby, then, you could try draining the carby with it's drain screw, then when it's empty, turn the tap on and check the fuel is running through the carby and out the drain at a reasonable rate. That checks the flow through the float needle(some have a filter above them), and that the float needle isn't sticking closed. If there is plenty of fuel going through the carby, then it must be multiple blocked jets I think.
 

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Discussion Starter · #13 ·
Thanks I鈥檝e spoken to my friend who fitted the crank bearings he鈥檚 going to have a look Monday so I鈥檒l wait until then will let you know out come.馃サ
 

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Discussion Starter · #14 ·
Hi been busy with family so still don鈥檛 understand why the Kymco doesn鈥檛 have compression was thinking I might have fitted piston wrong way round.So which way would a windowed piston be fitted ? Window facing intake or exhaust? would fitting piston rings wrong way cause lack of compression? Any help.
 

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The window should face the inlet.

How do the rings come together at their ends ? Do they have a notch that fits against the pin in the ring groove ? That should make it impossible to get them the wrong way.
 

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If you have vacuum, which we have established you do, then the rings are working somewhat.

Did you do as I suggested and check for distortion of the bore around the transfer ports ?
 

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Discussion Starter · #17 ·
Definitely think compression I sprayed quick start into air intake and nothing happens so it seems not enough compression to create fire but how to find out what is causing it.
 

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Discussion Starter · #18 ·
Thinking it may be cylinder head is there a way to check was thinking of removing it and re fitting with strong polythene across cylinder to see if it increases compression at the moment I can crank engine with my hand no problem either with kick start or fan covers are off.Not sure if I have the experience to check for distortion but the cylinder is brand new.
 

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How do the ring ends butt together ? Did you gap the rings ?

If the head or head gasket is leaking all the compression out, you should notice that.. If you have compressed air you could try putting the piston at the top, lock the cranks so it can't turn, and put compressed air into the sparkplug hole.. Then listen at the carby and exhaust for air leaking. Make sure the crank is locked firmly or it will rotate and you may get hurt.
 

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Discussion Starter · #20 ·
Fitted the rings as per instructions the pins were off set with v pointing upwards.I don鈥檛 have a compressor but my head shows a few cracks as it did when it ran I only cleaned carbon etc.Thank Mech for you help 馃憤馃徏I will get back to you when I鈥檝e tried to isolate my cylinder head but tomorrow family day at the beach I鈥檓 not giving up just frustrating that it ran like a bag of nuts before 馃し馃徎and the piston was actually broken but it ran馃し馃徎Now new cylinder piston crank bearings n seals carburettor new jets battery spark plug and it won鈥檛 start very frustrating.I鈥檝e rebuilt a Austin mini 850 a Takbot samba cabriolet,Audi cabriolet a very old M G B and a little t2 engine is bugging me big time馃し馃徎Will keep you up dated again thanks and if anyone wants to jump in feel free馃憤馃徏
 
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