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Post by atbigbucks on Jan 9, 2012 18:05:14 GMT -5
Hi there everyone. I just did a rebuild on my 150cc. I replaced the cylinder head and piston due to it freezing up. Everything went back together just fine but for some odd reason it will not start. It cranks over great but it will not fire up. I checked the values for the proper gap , I know I have a spark coming from the plug , I have a full tank of gas , I have taken the crab off at lease 5 times so far to clean it just in case . I've even put on clear lines so ill know the gas is traveling but I get nothing. I'm stressing out cuz I have not idea what the problem could be. I even tried putting my finger over the spark plug hole to feel for comparison. I keep checking the values to make sure its right. I just don't know what else it could be. When I'm trying to start it cranks over strong but to me it sounds like its no gas getting to it to fire. I plugged the choke back up like it was before but still nothing. I also noticed when I try to start it I never see the gas suck into the carb. I think that's the issue that y I keep cleaning it but I get the same results. If I unplug the line from the tank it runs out and its the same with the petcock and filter but once Its plugged into the carb u never see the level drop.
Please help open to any advise tips or anything please be patient this is my first rebuild.
P.s. I've watched the videos from here also
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Post by Fox on Jan 9, 2012 18:41:17 GMT -5
When you installed the cam in the cam chain did you make sure that the holes in the cam sprocket were in the proper position with the T mark aligned as shown below?  |
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vvtr
Scoot Enthusiast
Posts: 243
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Post by vvtr on Jan 9, 2012 19:11:38 GMT -5
did you reuse the head gasket?  i have had the same issue on a baotian qt9 and it turned out to be the head gasket leaking, not making any vacuum to draw in fuel. take the plug out & put your finger in the hole, feel for good compression (or use a tester if you have one) - sorry, just noticed you'd done that. are you sure the spark is good & at the right time? cam timing spot on? valves not bent? there is also a fuel stop valve in the carb.... im assuming you have a cv carb on the scoot? its under a small plate on the side, with 2 screws holding it down. check the vac pipes are all in the right place and that you have vacuum to the carb when you turn it over. i tried 3 different carbs on mine and could not get it to fire, exactly the same problem (on 2 separate scoots) my bet is on head gasket though... |
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Post by atbigbucks on Jan 9, 2012 21:55:02 GMT -5
Yes Fox I did make sure the wholes are lined up
Vvtr I didn't use a old Gasket. New ones came with my cylinder. No bent values and the timing was on .003 and now I'm trying .004 to me it seems like its not getting gas. I had the same trouble with my bike and it was a fuel problem how can I find out if about the fuel stop. I've taking everything off that carb and blew air through all the holes
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Post by jmkjr72 on Jan 9, 2012 22:25:16 GMT -5
pull the vaccum line of and pull the fuel line off
pull a vacuum on the vacuum line to the petcock and if its working fuel will come out the fuel line
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Post by Fox on Jan 9, 2012 22:32:20 GMT -5
yeah what he said^^^
Suck on the vac line with the fuel line disconnected to see if you have good fuel flow. If you get good flow connect the vac line and crank the engine to see if fuel flows with engine vac.
Grab the fan and spin it by hand. If the compression is good you'll feel it. If it's weak or none at all then there's a problem.
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Post by atbigbucks on Jan 10, 2012 18:29:14 GMT -5
Ok guys I tried sealing the head Gaskets again and I also tried to suck on the vac line to see if gas comes out. When I did it the first time gas shoots right out of the petcock but when I put on clear hoses to see if the engine would pull the gas through it fills up about half way and then it just stops. I know its filling up that much just because its gravity feed system but why won't it fill up and pump through the carb. So i took the advise and checked the carb and the head gasket the carb was cleaned out again and blown with air and the head Gaskets was done over but I'm getting the same results. It just sounds like a try fire. I tried to spray some starter fuel in but I get 1 lil puff like its a back fire. I'm at a lost right now cuz I just don't know what it could be. Any ideas.
And yes I checked the valves again after the reseal
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vvtr
Scoot Enthusiast
Posts: 243
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Post by vvtr on Jan 10, 2012 18:59:23 GMT -5
after doing the gasket on mine (exactly same problem) it woul still only fire intermittently....
the only other fault i could find with it was one primary ignition coil (lt coil) was blown in the stator.
it was giving a weak spark in bare air but i dont think it was sparking under compression.
youre not the only one who has had this exact same issue.
i tried different cdi's, 3 different carbs, different plugs, head gasket, different cyl head, checked rings werent stuck, everything,.
only fault i could find was with the stator.
mine ran fine until i filled it with fuel. then it wouldnt restart. mates did exactly the same later.
tried different fuel etc - i even thought maybe i was so tired i couldve put diesel in it by mistake lol. fresh fuel, same.
test the output from the stator.
(the ignition coils not the charge coils)
a weak spark in air means nothing.
doesnt mean it is sparking under compression.
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Post by atbigbucks on Jan 10, 2012 19:15:54 GMT -5
So u saying that it could be the stator that's not giving a strong enough spark. I mean I do have a spark but it seems mal to me. Maybe that would be the issue but if I didn't have spark under compression y would I have the flame shot out the exhaust port when I spray carb cleaner in the carb.
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Post by Fox on Jan 10, 2012 21:48:44 GMT -5
I'm thinking low compression. In your first post you said it froze up and you only replaced the piston and the cylinder head. maybe the cylinder has a crack in it or something else wrong with it.
How does the compression feel if you grab the fan or the variator and spin them by hand?
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Post by Goosey on Jan 11, 2012 8:43:02 GMT -5
Test what Fox said...
And my 2 cents, a bad stator will seem the same as a fuel issue as far as the engine turns over, it just won't fire up. It can also cause stalling like a fuel issue if it has intermittent week spark.
I had a problem when first my scooter backfired and stalled due to bad compression when a hose came off of my emmissions system (now removed), after I corrected that problem on the road, the scooter continued to stall on the way home, and after that as soon as it warmed up, until it wouldn't fire/spark at all.
Turned out to be the stator was bad, soooo, the problem was not related to the first fail, but at the same time...&it happens.
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Deleted
Deleted Member
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Post by Deleted on Jan 11, 2012 17:55:37 GMT -5
a compression test should be done at this point. you can rent them from a parts house if you dont have one. popping back through the carb sounds like cam timing too.
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vvtr
Scoot Enthusiast
Posts: 243
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Post by vvtr on Jan 11, 2012 18:56:32 GMT -5
popping back through the carb sounds like cam timing too. yup - or a bent inlet valve. did you fit a high lift cam by any chance? and was the new head gasket the same thickness as the old one> and the new cylinder the same height as the original? reason i ask is because apart from the obvious risk with a thinner gasket of valves kissing the piston, with a thinner gasket, there would be more slack on the camchain so it would be very easy to set the valve timing out. afaik these engines run a 'wasted spark' so it cant be timed up on the wrong stroke??? ive seen some articles online saying the cam should be fitted with the hole pointing downwards, not up.... ive always timed them up with the hole at the top as pictured earlier... do the compression check first... if its inconclusive, as in you have good compression (120psi+) then you will have to look elsewhere. its worth checking the stator though.... its a pain getting the flywheel off as you will need to get the right extractor... once it's off, you will see 2 small encapsulated coils side by side.... they should be wired in series. on mine it goes from earth to a blue & yellow wire which is separate from the other wires in the stator connector... check you have a resistance from this wire to earth. if not, check for a resistance between earth and the solder joint between the 2 coils.... then between the (blue & yellow?) wire and the central solder joint. you may have to pick a bit of insulation off the central solder joing to check for continuity. if you dont have a resistance from the wire to earth then the coil is bushed and will need replacing. i could add some pics but my spare stator is in the garage lol.... |
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Post by Goosey on Jan 11, 2012 19:53:05 GMT -5
Feel Free to play with these pics, Update, The scooter was still inadvertently losing spark, so after eliminating again, the relay, coil, plug, & cdi, I ordered another stator. This time I looked very carefully at the pictures when I ordered, both stators shown advertised as "GY6 150cc 8 coil, 3 plug 2 wires...the left stator is the one that blew my lights out, the right stator matched my old one perfectly, notice the differences?   I was FINALY able to ride the beasty to work today  |
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Post by atbigbucks on Jan 15, 2012 19:08:10 GMT -5
hey guys i did some work on the scoot today and i found out that i have the exhaust port open from a bent valve (sad face) now im just waiton the parts store in the a.m.
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