Hey guys! I wanted to get your thoughts on how many hours you run your 2 strokes before you rebuild the top end? Please post your hours.
Still original at 150 hours. It's lost a tiny bit of power, but that's not so bad in my view. I will redo at 200 unless something specifically moves up my schedule.
A quick compression test is usually a good indicator. I don't have a berg 2t, but on my husky 144 @200 hours it was due for a piston and rings.
Joined Sep 2013
322 Posts | 55+
Nova Scotia Canada, Granite Hills enduro park
For TE-250-300 owners manual says every 80 hours if not raced every 40 if raced ..whats everyones option on that ? My TE250 has 49 hours on it now
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
Is it hard starting? Does it foul spark plugs? Is there excessive smoke out the silencer and oil dripping from the pipe at the cylinder? Does it have low power? Is the compression weak? Can you hear any rattle from the cylinder?
If any of these it is time.
The user manual has a hour reference point, but that is all it is. Some riders are harder than others, climate and temperature are also a facture. Are in you a super hot climate? The list can go on. I would recommend the rebuild when you find a issue unless you have deep pockets, then once a season. I have heard of some machines with 200 hours and still running strong, then some with 10 and done in. If you are mechanical and don't mind pulling the top end, take a look check clearance etc.
If any of these it is time.
The user manual has a hour reference point, but that is all it is. Some riders are harder than others, climate and temperature are also a facture. Are in you a super hot climate? The list can go on. I would recommend the rebuild when you find a issue unless you have deep pockets, then once a season. I have heard of some machines with 200 hours and still running strong, then some with 10 and done in. If you are mechanical and don't mind pulling the top end, take a look check clearance etc.
Joined Jul 2012
223 Posts | 84+
South Africa
It will all depend on how its ridden and maintained. I agree, a compression test will be the best indicator. A friend of mine has a KTM 250 exc, 2011 model, has 380 hrs on, he bought it new and it still starts dead easy, touch that button and the motor jumps to life, hot or cold. His wife has a KTM 200, did the topend at about 200 hrs. My sister has a 125 Berg, sitting at 130 hr, no issues so far.
Maybe do an inspection like FE350 said, and decide based on that.
Maybe do an inspection like FE350 said, and decide based on that.
My 2013 TE300 was done at 62 hours. It showed slight wear but was good overall. I am going to wait until it has 75 hours this time around. That is about as far as I will push it. It will go longer because there isn't much to the two strokes but a $110 piston is cheaper than catastrophic engine failure. Plus I want to keep it tight.
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
This is all and fine to throw a piston into the cylinder, But to redo the top end correctly you will need a cylinder, piston and rings as well the gaskets. When the piston rings wear, the coating on the cylinder wears as well. So to hone or bore and re cote is a cost as well if you chose this route. I like the idea of the kits so everything is new
Nikasil survives better than the pistons with rings, so no need to change out the cylinder until it's really worn which will not happen that quickly.
Hi best way is to get front pipe off (two springs two bolts) and with a light you can inspect condition of piston through exhaust port checking for signs ov where as it's the piston it's self it what you need to worry about
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
IMHO
Yes this is true, but again it depends on how the machine is rode. Sometime rings are just required without a piston. My kids KX had thirty hours on it raced and I just did top end and the cylinder was worn.
It is kind of like throwing brake pads in without machining rotors. It works but is it a correct fix or quick fix? Piston, rings, and cylinder should all be fitted within correct specs for maximum reliability, compression etc.. No matter what surface the cylinder is plated with, there is always some wear.
True. But it's expensive to do that and probably cost more than what it's worth for most of us. I don't think you loose much, if anything, if you put in a new piston with rings in a slightly worn nikasil cylinder.
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
That is the best idea if pockets are not deep
I did my sons and he is still paying his bill back lol, Maybe I should have just fired a piston in it and not tell him haha.This is all good information guys, thank you so much! I will run a compression test and see where I stand. What SHOULD the compression be at?
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
What I do
1 set up gauge
2 remove the air filter
3 hold throlle fully open
4 kick 10 good kicks
5 read gauge
Make sure to use a quality gauge such as Snap-On as cheap gauge can read 20psi out
There is the formula to use to get your compression LOL its pretty much a pain in the a$$ unless your a math professor
EG:
Bore x Stroke = 72x72
Head volume = 24
72/2 = 36
((pi*36^2)*72) / 1000 = 293.15cc (Cylinder volume)
72-40 = 32
((pi*36^2)*40) / 1000 = 162.86cc (Cylinder trapped volume)
162.86 + 24 = 186.86cc (Cylinder + head trapped volume)
162.86 / 24 = 6.79:1 (not including squish)
186.86 / 24 = 7.79:1 (including squish) (so pretty much 7.81)
So I would say the best idea is to check with a service manual
The KTM 300 is what I will quote you and should be the same, Please correct if wrong.
A KTM 300 should get around 200 - 210 psi on a fresh top end. Minimum acceptable compression is generally about 150 psi anything below will be a major performance change.
1 set up gauge
2 remove the air filter
3 hold throlle fully open
4 kick 10 good kicks
5 read gauge
Make sure to use a quality gauge such as Snap-On as cheap gauge can read 20psi out
There is the formula to use to get your compression LOL its pretty much a pain in the a$$ unless your a math professor
EG:
Bore x Stroke = 72x72
Head volume = 24
72/2 = 36
((pi*36^2)*72) / 1000 = 293.15cc (Cylinder volume)
72-40 = 32
((pi*36^2)*40) / 1000 = 162.86cc (Cylinder trapped volume)
162.86 + 24 = 186.86cc (Cylinder + head trapped volume)
162.86 / 24 = 6.79:1 (not including squish)
186.86 / 24 = 7.79:1 (including squish) (so pretty much 7.81)
So I would say the best idea is to check with a service manual
The KTM 300 is what I will quote you and should be the same, Please correct if wrong.
A KTM 300 should get around 200 - 210 psi on a fresh top end. Minimum acceptable compression is generally about 150 psi anything below will be a major performance change.
You are right...you do need to be a mathematician to figure this stuff out! I appreciate the good info. I will see what I am reading for a compression test. Come on 200psi!
You absolutely do not need to replace the cylinder with every piston. This would be complete ridiculous. If you are the guy who pushes the envelope on the hours your piston will start to wear the cylinder drastically faster. Which is why I replace the piston often. It is far cheaper than piston and cylinder. The cylinder can easily last for 10 Pistons if done without stretching the hours between too far. The nikasil is drastically harder than the piston and therefore is hard to wear unless things are way out of spec. You can also measure specs of the cylinder. But for the most part inspect the cycling for wear grooves and marks. If you cylinder is still showing smooth and even criss cross patterns from the original hone you should be fine. But you can re hone a cylinder several times before it needs to be replaced.
Joined Apr 2014
689 Posts | 252+
Chilliwack, BC, Canada
Nikasil can not be honed, Nikasil is a very thin coating and should it be honed, will reduce life of rings. However Nikasil can be deglazed and this would be a procedure to use prior replacing the piston and rings.
Nikasil is a hard coating but under heat and friction does wear, It might not wear as fast, but does wear.
Most times you will be fine changing out the piston, but if any wear is on cylinder wall, you will need to rectify as it will prematurely wear rings.
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