Motorcycles BS Thread 2.0

Why? That's what I put on originally

 

That's some serious scoring. I'd second a new bearing for the big end. When the cylinder and piston look like that, there had to have been some metal roaming around in the lower end.

 

Ive been doing this kind of stuff for a long time.
I just did a complete rebuild on my wr due to a bad big end bearing.
It felt fine upon inspection- rotated smoothly with no up and down free play but once i got it apart the rod was visibly worn.
If you have an engine seize up like that it puts tremendous strain on the big end bearing. You wont be able to replicate the rpm just spinning it by hand so even if the bearing stayed intact theres still a high probability that it was damaged.
If its just a dirtbike id flush the cases after inspecting everything short of splitting them. On a street driven bike id definantly go through the motor. Having an engine lock up on the street can really suck.

 

I bought a supposedly "matched" piston and barrel from rmatv. The rings were nowhere close to being setup for the right gap.
On top of that there was a huge burr where the dowel pin/ coolant passage goes through the cylinder.
After finding all of this i googled cw problems and found alot of quality control issues ranging from the issues ive had to cylinder base not being machined right.
Their quality control sucks, you might get a good one- you might not-
If you decide to purchase another make sure you check your ring end gaps and gasket surfaces with a straight edge,

 

I really don't want to pull the bottom end apart.

That's where the first one locked up already.

 

How many miles/ hours did you have on that cw setup?
Did you check the end gap? .
What caused the piston to do that?
Forgive me if it was already stated but i just saw the post you made with the pic of the piston/cylinder and didnt read back any further.

 

About 100 miles. But the oil filter housing bolt fell out so lost oil. It ran smooth for those miles though.

Yes I checked ring gap, it was good

 

Did the motor seize? Id think it almost had to by the looks of that cyl/piston. If it didnt lock up the rear tire you might get away with another top end rebuild- id be skeptical seeing as it lost all the oil.

 

It locked the rear tire up for a second, I immediately pulled in the clutch. but still turned over after new oil (just trying to see if it would do anything)

 

You still got a good month or so before the really nice weather gets here-
If you are mechanically inclined enough to do a top end then id say split the cases and at the very least have a new pin and big end bearing put in the lower end.
Not sure where your at but i know a guy here in ohio that could rebuild the crank for next to nothing.
He charged me $30 to install a carillo rod,press in a new pin, replace the bearing and true it up. I supplied the parts of course.
Just remember to tighten the oil filter housing this time around

 

Im guessing this is a drz?
Have you done the loctite fixes on it yet?

Heres a couple shots of my motard.
07 wr450
Venom head, hotcams, bored carb to 44mm,
Hi c piston, slipper clutch, brembo radial master cyl, braking sm caliper, steel lines. .
Other stuff im sure im forgetting

 

By pin you mean the one holding the gears on right?

Yea drz and yes I did those after the initial ride home from the dealer

 

Im talking about the pin that connects the two crank halves together and the big end of the rod rides on.
#5 in the pic

 

I know some of these words

Matt

 

Ah OK. First motorcycle engine rebuild actually. I don't know of any motorcycle shops around the area that would do that kind of work. It'd be easier just to order a hot cams crank setup albeit more expensive.

Having a tough time deciding if I need to though. Worst case it knocks when I put it back together which at that point I know it needs done?

 

It could wear out another top end before you notice it. Then you're into your third round of doing this.

 

That would be better than worst case..
Worst case your pulling out in front of traffic or leaning into a corner and it locks up on you..
Your better off with oem than anything hotrods or wiseco has to offer as far as cranks go.
Id say a new pin and bearing would be about $100 oem - if you used the shop i suggested he would probably charge you $30-50 to install the pin, bearing, rod and true it up.
A new hotrods crank would be $220-250
For that kind of money you could rebuild your crank with oem parts (better quality) and either use a carillo rod (substantually stronger than stock) or put new main bearings in the cases ( probably a good idea since the motor was starved for oil)..

 

Ohhh yeah. That's toasty.

If there's no up and down play in the rod it's probably OK, when you spin the crank while holding the rod do you feel ANY grittiness in the big-end?

 

Another way to look at it is the oil starvation didn't help, if you tore it down this far splitting the cases might not be a bad idea to get a the big end. You could inspect the oil pump too; if metal went through it you might have to replace it due to wear (and thus lower oil pressure output from it if not replaced).

That being said you might be ok with not doing the bottom end; it's just hard to say without actually looking at it.