Clinician
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Post by skikman on Mar 31, 2011 11:43:26 GMT -6
hi folks.i have a wee suzuki 50cc katana scooter that i replaced the piston and gasket on some months ago[water in head so take it blown gasket].i put the engine back in today.it has good compression and a good spark at plug.it would'nt start.so with the carb off i tried to fire it up by spraying fuel straight into the inlet while turning it over.[it should start and rev up]but no go.so then i tried putting some fuel into the plug hole,putting plug back on and trying but still no go.i know the reed valve is ok as i had it on another bike.the plug is new and ive tried 3 others.cap and ht lead seem ok as well.anyone have any thoughts as what i should try next. the fuel is fresh.
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Scooter Doc
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Post by sprocket on Apr 1, 2011 15:08:05 GMT -6
Could taking the plug in and out have done something to the plug boot connection? I have seen this happen on chainsaws. Take the plug out... it works, put it in and it doesn't even cough...
Also check that your engine and frame are grounded together...
I spent a week with a guy that said he was getting a good spark at the plug. He put it in the engine.. nothing. Only after my hair went white, did I realize that he was grounding the plug to the FRAME. When he grounded it to the engine...NO GROUND... NO SPARK.
So simple...
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Clinician
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Post by skikman on Apr 5, 2011 16:06:12 GMT -6
Could taking the plug in and out have done something to the plug boot connection? I have seen this happen on chainsaws. Take the plug out... it works, put it in and it doesn't even cough... Also check that your engine and frame are grounded together... I spent a week with a guy that said he was getting a good spark at the plug. He put it in the engine.. nothing. Only after my hair went white, did I realize that he was grounding the plug to the FRAME. When he grounded it to the engine...NO GROUND... NO SPARK. So simple... thought you might have had it there with the ground to engine but sadly no.i just got back to looking at the wee bike today and i reconnect carb and noticed it was'nt pumping fuel into it[vacuum tap].i sucked on the pipe and still no fuel came out so took off tank and cleaned it out[lots of **** in it]put it back on and sucked the pipe,fuel came out.happy days i thought but when i connected the vacuum pipe to the carb and turned it over nothing came out the end that fills the carb.i then put my hand over the airfilter side of the carb and it was'nt sucking that much when turning it over.somthings not right there.thats the point when i threw the tools down and came home |
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Scooter Doc
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Post by Kaveman on Apr 5, 2011 16:50:51 GMT -6
Hang in there ! You will figure it out. Little scooter with big big headache (for you ) !
Bill C.
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Scooter Doc
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Post by sprocket on Apr 5, 2011 18:27:45 GMT -6
Take the plug out.
Stick your finger over the plug hole and try and start it.
The compression should push your finger away forcefully.
If it doesn't adjust your valve gaps... if it still doesn't then you probably have a major engine problem.
BUT
It could also be that your carburator is totally plugged... If you have**** in the tank you have it in the carb and it needs to be remove, taken apart and cleaned very well. Run a fine wire through the jets too.
There should be a petcock and a fuel line filter either mounted on the tank outlet or in the fuel line. You need to change the fuel filter for certain.
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Post by Alleyoop on Apr 5, 2011 19:01:41 GMT -6
Sounds more a compression issue if it was not sucking much when you put your hand over the Air Inlet of the Carb. The Carb can be dirty as heck but it should be drawing into the engine.
So do like Sprocket said, take the plug out and put your finger in the hole and hold it and crank it. It should blow your finger off the hole if it doesn't you do not have much compression and your going to need some rings.
Alleyoop
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Post by skikman on Apr 6, 2011 17:18:11 GMT -6
Sounds more a compression issue if it was not sucking much when you put your hand over the Air Inlet of the Carb. The Carb can be dirty as heck but it should be drawing into the engine. So do like Sprocket said, take the plug out and put your finger in the hole and hold it and crank it. It should blow your finger off the hole if it doesn't you do not have much compression and your going to need some rings. Alleyoop it does seem to have enouigh compression with finger but why is it not sucking.carb has been cleaned and blown out.awell looks like the head and barel has to come off again somethings not right. |
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Post by Alleyoop on Apr 6, 2011 17:49:59 GMT -6
"It does seem to have enough compressionwith finger"
My question is DID IT BLOW YOUR FINGER OFF or Not, if you felt pressure that is NOT ENOUGH compression. You can take the whole carb off and put your hand over the Intire Intake Manifold and see if it has suction. The Suction has squat to do with the CARB, you can Load it with DIRT It should still have suction going through the Carb. When the Piston Goes down and opens the INLET for the the GAS TO COME in that is when it creates Suction to DRAW the air and fuel in so that on the Next UP SWING of the Piston it Spark Plug Fires and Ignites the Fuel.
Alleyoop
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Post by royldoc on Apr 6, 2011 23:18:16 GMT -6
I had s similar problem on a different type engine one time. took me a while to figure out. It appeared to have good compression but not much vacuum through the carburetor. turned out it was the exhaust spring was to short and weak. On the intake stroke the exhaust valve would drop open slightly. On the compression stroke it would close up. This engine didn't back fire. I even tried the paper at the exhaust tip trick. Hold a piece of paper at the outlet of the exhaust and plug up the intake while trying to crank it. If the paper tries to get sucked in the exhaust valve is suspect. I'm probably wrong but never know. Good luck.
Roy
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Post by Alleyoop on Apr 6, 2011 23:48:24 GMT -6
I was under the impression it was a 2T and not a 4T, if it is a 4T then yes, check the valves and adjust, to tight and you will loose compression, to loose and they will not open enough.
Alleyoop
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Post by royldoc on Apr 7, 2011 0:43:11 GMT -6
You are right alley. I didn't catch the part about the reed valve. Its late and I had a real bad day today. Any way even if it is a 2t if it appears to have good compression but no vacuum at intake it's sucking in from some place else. Just not sure where. I could be wrong again.
Roy
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Post by royldoc on Apr 7, 2011 0:57:32 GMT -6
I have to agree with alley. bad rings will cause low vacuum and low compression.
Roy
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..BAD TO THE BONE..
