Posts
44
Joined
10/3/2013
Location
NL
Edited Date/Time
10/29/2019 6:51pm
So my crankshaft rod seized up today. I am trying to understand why it happened and what can cause this. Just some info so maybe someone has a tip for the future.
-bought the bike 4 years ago and have put 70hrs on it.
Piston was changed 35hrs ago. But I don't ride that hard.
-Mix ratio is 40:1. I use 100% Synthetic Castrol Power RS 2t premix.
-changed the tranny oil every 6hrs. Had just changed the oil 1 ridding weekend ago. I use Motul transoil Expert 10w40. I drained and checked the amount of oil that came out and it was 700ml. It did seem a bit more brownish then usual.
-I clean my air filter after every ride.
I attached some pictures.
Anybody has a clue? Or just old crank that maybe never was replaced and the needle bearing just failed? It's going to the shop to get it fixed but still curious what others think.
-bought the bike 4 years ago and have put 70hrs on it.
Piston was changed 35hrs ago. But I don't ride that hard.
-Mix ratio is 40:1. I use 100% Synthetic Castrol Power RS 2t premix.
-changed the tranny oil every 6hrs. Had just changed the oil 1 ridding weekend ago. I use Motul transoil Expert 10w40. I drained and checked the amount of oil that came out and it was 700ml. It did seem a bit more brownish then usual.
-I clean my air filter after every ride.
I attached some pictures.
Anybody has a clue? Or just old crank that maybe never was replaced and the needle bearing just failed? It's going to the shop to get it fixed but still curious what others think.
1) time. Two stroke connecting rods ride on needle bearings that are directly lubricated from the fuel/oil mixture. Wear will happen no matter what, but you can slow this down by running more oil in your fuel, but that will have other consequences. Lean carb jetting can also lead to a lack of oil to the rod bearing. Oil in your transmission has nothing to do with this, and it is totally seperated from your connecting rod (on a 2 stroke. its different on a 4 stroke). FWIW, I haven't seen many two stroke rods last much past 100 hours. If you have put 70 hours on it yourself, and it already had 70 or more, it was due for a new crank or rod.
2) Dirt/debris. From the looks of the scratches on your piston and a few on the cylinder, this bike has been sucking dirt or debris. Buy a new air filter. Make sure you thoroughly clean it after every ride. Soap and water sometimes does not get out all of the dirt that is stuck inside your filter, and its most obvious when after you have cleaned it, it still has a 'dirty' look to it. If you ride in dry sand a lot, I would buy one of those pre-filters for two strokes that are like an extra layer of filter before it gets to your main air-filter.
3) Excess stress. Big bore kits will tend to put more of a load on the needle bearings, so if you put a big bore kit in it, be prepared to replace the connecting rod at sooner intervals.
Paw Paw
But what i tell people is 80 hrs on a 2 stroke crank then rebuild it. So once you hit close to 80 hrs the next time you hit your off season or a extended periode of time off the bike get it done. So right now in october if the crank had 65+ hrs on it. I would be doing a crank this winter.
Can you get 100+ hrs out of a crank yeah but why risk dealing with everything you Now have to pay to replace or have rebuilt like the jug and head when you could have used that money for head mods and a port n polish.
The Shop
I am just a bit surprised by the number of sand marks because I do change my filter every ride and buy new filters every year. I have always about 3 to 4 filters that are maximum a few months old. I use special cleaning filter (bio) powder, then wash with normal dish soap and oil them with Putoline air filter oil. When washing they are always completely clear of any dirt.
Air filter cleaning powder: https://www.wpmmotors.nl/winkel/shop/oliebanden/putoline-bio-filter-cle…
Air filter oil: https://www.resa-racing.nl/putoline-action-fluid-1l
When taking out the reed valve there were also 2 sand grains in there. For sure I am doing something wrong. Or maybe there is some crack somewhere in my filter box. Going to check it firmly.
Disassemble the entire thing, take the boot out of the box and clean everything. Make sure it's sealed up properly.
I think a lot of people who use spray on filter-oil tend to under-oil their filters.
My preference is the gallon jug of Bel-Ray foam filter oil for that reason.
Oil your filters in a gallon freezer bag... Squeeze the extra oil back out of the filter after it's been soaked.
A filter shouldn't drip oil down into the airbox, that's too much oil.
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