OK 48cc w good compression, fuel+spark. Doesent Run though

[WhizBangAndy]

OK this is giving me fits.

I got a low hour broken in 48cc Grubee that will either run like a bear (briefly) or just wont start. I have checked/cleaned replaced everything i have came across in the forums. I took apart the carburetor and cleaned/blew it out with compressed air even though it looked clean inside.Verified fuel flow through carb Checked for spark and have a strong blue spark. Changed the sparkplug. Cleaned out the bottom end of the engine with a blow gun as specified in another thread. Got fresh gas and mixed it 30:1(synthetic) and put it in the tank after cleaning it out too. I originally thought it was low compression since it only had 60psi so I milled the head down so now its got 90psi. I did notice while I was cranking the engine with a power drill off of the magneto side(got tired of pedaling up and down the street for 2 hours) I have some airflow from the bottom of the jug when cranking. Would a bad block to head gasket foul up the works? I didnt notice any other leaks while cranking it with the drill (I know this isnt an ideal way to crank the engine but was out of people power and wanted to check everything while standing still) Thanks for any input!!:-/

 

[WhizBangAndy]

And FYI I tried to start it with the exhaust removed after everything above (and yes that was checked too..lol) with no improvement.

 

[Mountainman]

got a feeling fuel is not getting in there

remove plug -- pour in 1 table spoon -- any pop pop ??

yes a bad gasket could do that -- but with 60 psi -- would think you would get someTHING

MM

 

[Egor]

The air leaking is a (BIG) big deal. All the air that is supposed to be pushed up to the combustion chamber is going out the side of the engine. You will need to remove the barrel and replace the gasket. Hope this helps. Have fun, Dave

PS:Check the carb manifold gasket also, they are a culprit too. Mountains Idea will tell you if it will run when you get the gasket done.

 

[Al.Fisherman]

got a feeling fuel is not getting in there

remove plug -- pour in 1 table spoon -- any pop pop ??

yes a bad gasket could do that -- but with 60 psi -- would think you would get someTHING

MM

By what you are saying I'm making it out as remove plug, pour the fuel into the cylinder, replace plug and attempt to start. If this is correct wouldn't it be either easier or even better to remove the air cleaner and squirt fuel directly in the carb throat? This way you won't remove plug, install plug, try to start only to have to repeat the process again if necessary. Also what are the "normal" perimeters for compression on both the 49 and 80?

 

[Mountainman]

if your engine is under 90 psi -- slightly worn and torn
" " " " " 60 " -- gone baby gone

if you are 90 psi or above -- not the problem


that above is just one quote I found in search engine regarding compression
(( one of many many ))
it appeared to be a post by Mountainman

 

[WhizBangAndy]

Yup Yup..

Tried the gas in the cylinder and no fire or pops at all which surprised me. Im going to take Egor's advice and order up a top and bottom head gasket. I will install the 80cc while I await the bits..Thanks to everybody and Ill update as soon as I get the gaskets.

 

[Egor]

Hmmmm - You should have gotten at least a pop out of it with the petrol in the plug hole. you will need the gaskets, but look to see if the router for the ignition has slipped, see if the key in in place. I have a new engine that has a bad case gasket, I was looking for the leak at the intake gasket and every time I sprayed fuel on the place it would speed up. I kept checking the intake and then I noticed that the fuel that dripped on the case was disappearing so I put the fuel on that spot and "what do you know" bad gasket from new. But this one will take a complete tear down. I also had a new one that had a bad seal on the right side drive on the crank, another potential no go. Just something to think about. I never sent any of the engines back under warranty, I guess I expect these kind of flaws. Have fun, Dave

 

[WhizBangAndy]

Thanks Again Dave for your insights..I too am surprised that with gas in the top end it didnt fire. The magneto hasnt slipped and the key way is intact so who knows? Ill tear it down and check all the seals while I have it apart. Been curious to see the insides of this anyway..lol I think I will try my other CDI too just in case something weird is happening with it but I doubt it since the one on there gives a nice spark now. I think its upset since I wanted to sell it so its giving me some problems now

 

[Egor]

All the engines that I had that had problems still would at least run. I have had Ignition that would fire out of the head and not under compression, and sometimes the plug is bad under compression, keep up the good work you will find it. Have fun, Dave

PS: Mark the outside of the router if it is installed upside down it will not run.