Engine Trouble Engine loss of power when hot n fourstroking alot

The rings don't meet in either of the ports thou

seen lots of arrows & other markings on these when ordered from diff places - the mark isn't important - what you need is to have the locating pins in the rings on the intake side

Doesn't appear to have them on either port

if the arrow points toward the carb then the ring ends are on the exhaust side. if they were previously on the intake side then now you lose compression because the rings wore down to match the cylinder previously on the intake side. but its not a terrible compression loss. switch it back

Just to clarify it came this way meaning arrow towards carb and I should switch it other way or I'd it too late. I appreciate the help thnks

I'd switch it back

crassius said:

seen lots of arrows & other markings on these when ordered from diff places - the mark isn't important - what you need is to have the locating pins in the rings on the intake side

Click to expand...

exactly. two lil pins in the ring grooves, should be pointing to carb or intake. ive seen pistons with the number 2 on them as well, and the two i just recieved have the mark on opposite sides. go figure. locate by the locating pins, not the marks. you dont want the rings to meet in any ports, but, you also dont want those locating pins too close to the exhaust port, as they bulge out into the port and break in a rather short time if so. thats why they face towards the intake side. the more ring in contact with cylinder wall, the less they bulge into the ex port, the longer they last.

remember, if you want it to last, you need new circlips on the wrist pin if you have removed them to switch the piston around. point the ends vertical or they buzz up and down and eventually snap. lucky its still fairly new so the rings wont have worn much, nor be too much of an issue.


the head gasket and sealing surface looked fine, with no leaking apparent. no need to sand anything, and unless you did it on a really flat piece of glass, or similar flat surface, and rotated the head rather than slide it back and forth, you wasted your time. (easier to push down on the head and rotate the paper underneath it btw )

im sort of assuming the plug pictured in the head is a new plug. possibly ran, but not for very long. the other plug, by itself, that looked fine. if you used it for, say, twenty minutes then yes, id say its too lean but...

theres enough carbon there to not suspect an overly lean condition, an air leak, or bad jetting. the heads only new, so the clean patches are fairly normal too. if it WAS lean, the carbon would be turning grey.

it also would NOT be fourstroking if it was lean, you just wouldnt be able to open the throttle COMPLETELY without it dying. you havent said anything about what happened at full throttle...

what does the bore look like, and what does the piston skirt look like? THATS the important thing, and the whole reason for popping the head off. if its been rubbing(badly, a few lil marks is fairly normal), then somethings been machined wrong, and the only fix is a new cylinder + piston.
if you take the rings off the piston, then try sliding the piston in the bore, is it tight? it shouldnt be. holding up to the light, you should see a very fine gap all the way round between the two. or, you should be able to get the piston through the bore with a strip of paper in between. there has to be some clearance.

take note on which ring went on top when you remove them.

yes, the carb can get hot enough to boil the fuel, but its very unusual on a HT engine. therefore, something is wrong, and it isnt the air/fuel ratio.

its either extremely advanced ignition or the piston is too tight in the bore. maybe, possibly, the end gap is too small on the rings. possibly. worth checking. place one in the bore. push it up with the piston, so its sitting level. is there a gap at the ends? repeat with the other. it wont hurt to file the ends a touch anyway. two to three strips of paper wide, for the gap, is ideal, you dont want to overdo it.

meh.

It revs out at full throttle just sounds like a lawnmower. Bore appears to be good and rings are where there soposed to be. Seems like it's not too tight. This advanced ignition issue could it only occur once it's warmed up?

on a side note, that #2 (according to my measurements) should mean 40micromillimeters over size - I've seen 3s & 4s too - appears to be 20mics over per number

as far as the problem goes, it may sound like 4-stroking due to richness, but looking at that plug, I doubt it - I'd be looking for a very slight leak in a seal or in the case halves when hot (tho it could be lack of fuel flow when hot)

How would I fix lack of fuel when hot