Posts
13
Joined
9/19/2014
Location
Simi Valley, CA
US
Edited Date/Time
10/26/2017 6:44pm
Hi Guys,
I'm rebuilding my sons KX85 again after only 53 hours on Bottom end. The bottom end does not seem to be getting enough oil. Right now the rod has lots of up and down vertical play. It looks like it got hot on one side of Crank.
The bearings and seals are still good.
Couple of questions:
1. Does this cylinder look okay to reuse? It has very small blemishes, but check out pictures and let me know?
2. Will increasing the fuel jet size a couple of digits help get more oil down into the crank area? Or should i use 32:1 mix. I have been using Maxima and Yamalube at 36 to 40:1. We haven't fouled a plug in a real long time.
All of our 2 stroke bikes run great. With no fouled plugs, and no rebuilds in a long time. This KX has been completely rebuilt 3x in the past couple of years. All lower and upper ends plus all new seals each time.
Thanks for your time and responses.
I'm rebuilding my sons KX85 again after only 53 hours on Bottom end. The bottom end does not seem to be getting enough oil. Right now the rod has lots of up and down vertical play. It looks like it got hot on one side of Crank.
The bearings and seals are still good.
Couple of questions:
1. Does this cylinder look okay to reuse? It has very small blemishes, but check out pictures and let me know?
2. Will increasing the fuel jet size a couple of digits help get more oil down into the crank area? Or should i use 32:1 mix. I have been using Maxima and Yamalube at 36 to 40:1. We haven't fouled a plug in a real long time.
All of our 2 stroke bikes run great. With no fouled plugs, and no rebuilds in a long time. This KX has been completely rebuilt 3x in the past couple of years. All lower and upper ends plus all new seals each time.
Thanks for your time and responses.
Jetting - Well technically yes that isn;t your issue and the bike will run like crap.
What brand crank? It seems odd to have up and down play with thrust washers that look like new? I wouldn't use anything but OEM and they have the plastic inserts. If you are usuing Hot Rods/Wiseco cranks well, there is your problem. That looks like a Hot Rods crank to me.
What year KX?
This isn't a jetting issue. I would run 32:1 in a KX85 and keep an eye on your LH crank seal as it might be sucking air in.........
The Shop
Will it run with the cylinder like that? I'm sure it will.
Will it last long or make good power? Probably not.
For the cylinder, do i take it to a car/hot rod engine shop and have them do it? Or look to my local MX shop here in town? Also, what will be the ball park costs to have it honed and re-plated?
Again thanks for the responses. I was going to put it back together and run it this weekend, now i'll wait and do it right.
You need to increase the premix, 28:1 or 32:1 depending on where you live and how hard your kid rides. This is an 85, not a 125. Note when you change the premix ratio you need to change jetting as well. More oil means you need to go richer on the jets to get the same amount of gas. No idea what jets you ought to be running though.
We are at sea level and very close to stock jetting. 32:1 Motul 800 with a 75:25 pump/race gas.
I wouldn't run anything but an OEM crank.
It sucks when I always seem to have 1 bike broken out of 3 bikes and 3 people want to ride
Thanks for all the responses/suggestions!
After rebuilding it, I would fatten that sucka up until you are seeing obvious signs of it being too rich (oil coming out of the silencer and plug fouling) and then lean it down slowly. I also would run at least 32:1 or richer.
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