symptoms of time to replace top end

[roverhybrids]

I spent a few hours yesterday trying to get the jetting dialed in on my ec200. I have been assuming that it will take richer jetting than my 300. I have not been consistent in my changes as I have not had the time to focus on it long enough to get it right. I keep getting it to what I think is close then run out of time to get it perfect, sometimes it is a couple of months before I attack it again.
So yesterday I had JDblue #3, 45 pilot and a 178 or 180 main. Bike seemed good at first but once I hit a trail/hill the bike would bog and not be able to carry 2nd gear(12/48 gearing)

Could the bogging be a sign of low compression? I don't have a good gauge to check compression and hence don't have a base line....

[(F5)]

My 200 hardly wore the piston or rings, it was incredible. Won't bog, would just get a bit gutless if worn.

Read up on 200 jetting, but my feeling is you have a float height or fuel supply issue. Obviously new plug & clean/oil filter with real filter oil.

[Fred1956]

IMO a 200 doesn't pump as much air as a 300 so it should be leaner........I'd start with a 42 PJ & 172 MJ and go from there. First obvious sign of low compression on a 2T engine is hard to start. Check the jetting sticky in the carb section, someone will have 200 specs in there as a starting point- http://www.gasgasrider.org/forum/showthread.php?t=2162

[Jakobi]

Originally Posted by Fred1956

IMO a 200 doesn't pump as much air as a 300 so it should be leaner........I'd start with a 42 PJ & 172 MJ and go from there. First obvious sign of low compression on a 2T engine is hard to start. Check the jetting sticky in the carb section, someone will have 200 specs in there as a starting point- http://www.gasgasrider.org/forum/showthread.php?t=2162

Its actually the opposite Fred. The larger capacities pull more air across the face of the jets which draws more fuel for a given size. Thus, a smaller engine needs a larger jet to get the same amount of juice.

Loss of bottom end snap, and hard starting are indicators, but they generally occur over such a period of time that you never really realise. Best advice for it is to pull the cylinder at a set amount of hours. Take a comp reading and measure the ring gap. This will let you know where you're at and you can base your next rebuild off that prior knowledge. Also peeking through the exh port when the pipe is off can show signs of blowby on the piston skirt.