Is the new engine I just bought dead?

[Street Ryderz]

no sarcasm for real it will work just take your time one problem at a time.

 

[gary55]

He's right you know. If you don't put it back together it won't work. Sarcasm, mmmm 50/50.

 

[Nahom]

no sarcasm for real it will work just take your time one problem at a time.

Do you know how I can check whether there's a problem with exhaust? like clogging e.g
Also I think a piston ring broke off into pieces and fell down into the crankcase- I really really dont want to have to uninstall the motor and try and get it out- surely it can't matter that much?

 

[Street Ryderz]

if you can blow thru the exhaust full force with ease or only slight restriction its fine. if there is a piece or pieces of ring in the case then yes they have to be removed as they will destroy the engine in no time! also need to replace the ring .

 

[KTOKTO]

Do you know how I can check whether there's a problem with exhaust? like clogging e.g

Also I think a piston ring broke off into pieces and fell down into the crankcase- I really really dont want to have to uninstall the motor and try and get it out- surely it can't matter that much?

sarcasm?

 

[Nahom]

sarcasm?

nope- the pieces were all tiny and I thought it wouldn't affect the crankshaft motion that much- clearly by everyone's reaction this was a very stupid assumption. Apologies.

 

[Nahom]

What the...


The exhaust is supposed to have a gasket? Where was mine in the kit?
Also if the exhaust has a hole in the end why does it even need a gasket- it's aleady exposed to outside air which can flow in and out...

Do these gaskets really make that big a difference to preventing excess air getting in? And the head bolts being tightened real good before every ride too? I thought these were all things it would be great to do for slightly better efficiency but I had no idea they actually can stop an engine starting completely...

Edit: Oh... I think the gasket for the exhaust is to stop exhaust gases seeping OUT through the crack between the engine and the exhaust..

I assume the rest of the gaskets e.g right side cover, left side covers are to stop extra air seeping IN.

I should really stop assuming any part is surplus- they all seem to serve a purpose which makes a big difference when removed -even the smallest- how bloody efficient!

 

[Nahom]

So, back to post#9
You have spark, timing is good because you didn't have the rotor off.
You have compression because it will drag the tire if you push the bike but goes THUP-THUP when you try to start.
And you have checked for fuel flow to the carb. When you pulled the plug, it didn't smell of fuel.

This tells not enough fuel getting to the cylinder.
Are you using the choke?
Is the carb and intake tube seated tightly so there are no air leaks?
Are the headbolts tight and the base gasket in place for no air leaks?

Steve

Can we safely say that if there is a problem then it will lie here?
I will take the the broken piston ring pieces out make sure everything is as airtight as possible put the choke up, get fuel line from the motorcycle garage and try again tomorrow. Also I will remove one of old piston rings from the old engine and transfer them to new one because it look fine. There's at least a litre of fuel mix in there so that cannot be a problem I don't think. Also if I turn the bike upside down the fuel leaks out of the can so there can't be a venting issue with the tank. I am also hoping and praying that the gasket of the old exhaust is still there on it. If so I will replace that on new exhaust.
If it's not there where can I get a new gasket for the exhaust?
Hmm I'm starting to think that the first time when the engine started and then died there was a pop and the head bolts were loose already and that initial explosion loosened it even more and it died there and then. A few days ago I shook not the head but the cylinder fins and it shook but I didn't think much of it because I'm a moron.

 

[crassius]

whenever one suspects a clogged muffler, it is easy to loosen it just 1/8 inch or so and see if it runs better (don't leave it loose long though, as cold air can sometimes damage a hot piston)

 

[Steve Best]

So the silencer pipe has to be tight because it is part of the resonant tuning of 2 cycle engine. If it is loose air will get drawn in and lean out the mixture causing it to burn over hot and burn the piston.

A litre of fuel mix in??? The base of the engine? That would be bad. Tank? that is OK.
If the base of the engine is flooded with fuel you have a problem with the carb overflowing.
Drain the engine case (flip upside down) and see if and why the carb is overflowing.

The guys lead you straight on your cylinders. If you can feel the scratches with your fingernail it will affect performance but may still be usable with some loss of performance. This cylinder was damaged by me riding in sandy conditions with the original (poor) air filter. Sand getting past it damaged the cylinder but engine ran well for hundreds of miles like this.

So no worries about the minor dimples in the piston, or faint scratches.

The oil in the fuel mix falls out of air suspension and coats everything. The aluminum piston glides through the chromed cylinder with a faint skim of oil separating them. The oil also helps to seal the rings and glides under them too, building a hydrodynamic pressure wedge to prevent serious metal to metal contact. The bearings are rolling elements, there the oil acts to cool the metal to metal contact and absorb shock to prevent brinelling.

You picked a good engine to learn on. Even a moped is much more complicated and expensive. Others are watching and thinking the same questions you are asking I am sure.

So, you learned that the iron rings are very brittle and break easily if stretched!

Steve