Engine Trouble engine sounds like its gonna start but doesnt

[Sitherus]

at least it is running now - if the cylinder you bought is taller than the one you had, then piston won't reach to the top - you'd need to measure to find out, but it may just be that the rings aren't seated yet

yet? does that mean break in? because this bike has been running "well mostly running" for 4 years across 3 different bikes

 

[Sitherus]

I dont think I still have my other cylinder. My engine is gt5 stinger or thats what ive been told. It has the stinger sticker on it. thats the cylinder i bought. Im making brakes for it soon then i can safely test top speed.

 

[crassius]

a new cylinder needs to run a bit to smooth out the walls

 

[Sitherus]

a new cylinder needs to run a bit to smooth out the walls

Do I need to take steps to break it in, like oil/gas ratio? Also would timing and non smooth walls affect compression? I don't think it should in my opinion because liking at the engine as a big air pump it is still sealed and the poison would still be pushing up air.

 

[CrazyDan]

I don't see a key in that pic. Edit: Also, yes it's advisable to do the break in oil ratio steps on new cylinders.

 

[gary55]

This is my timing.

I believe like crassius said earlier that your replacement cyl. is a little to tall. The taller cyls. were used in A type engines, and when used in a B type engine they need material removed from the top to maintain stock compression. You can mic the jug to see if this is the case. Your pic looks as though the piston is to low.View media item 60634View media item 60633View media item 60720

 

[Sitherus]

I believe like crassius said earlier that your replacement cyl. is a little to tall. The taller cyls. were used in A type engines, and when used in a B type engine they need material removed from the top to maintain stock compression. You can mic the jug to see if this is the case. Your pic looks as though the piston is to low.View media item 60634View media item 60633View media item 60720

I will measure my cylinder. You should know that my piston does in fact go to the top, I just cant time it right and stop it at the top. When I try I get close to the top. it rolls over back to the bottom. I've done it both by spinning the back wheel and by using the pedals. I now remember know its better to use a ratchet to fit over the magneto then i'd get good precision, but I didn't remember that until just now. Also I was only intending to show timing.

 

[Sitherus]

I just went and looked at it and my cylinder body doesn't have a fin on top like your does i has a little material above the last fin. I measured from top fin to bottom fin at 63.43mm

 

[Sitherus]

Forget that I said the measurement is off. I couldn't see the top fin because its dark. The measurement from the top fin to the bottom fin is 70.00mm exactly 69.99 on the other side

 

[gary55]

The measurement has to be from the mating surfaces at top and bottom, but it does not mater now that you explained the slight roll over in your pic.. Chances are your comp. issue is the gauge rather than the engine. I bought 2 from harbor freight and the both read wrong. If your comp was really 30lbs it more than likely would not run. Another thing I have noticed on the after market heads is it can be hard to get a good seal on the head to gauge connection because the rubber O ring keeps wanting to squish out. A hard rubber washer that fits the gauge tightly might help if this is happening. Take a look as you tighten the gauge to the head to seeif the O ring is staying between the fitting and the head.