Posts
124
Joined
11/22/2017
Location
IL
Edited Date/Time
3/20/2019 11:04am
Hi, i have a Honda CR125R 2007 With big bore that done by known workshop in US, on the first rebuild I’ve seen that the exhaust bridge is not polished good but i am not sure if it came that way
So, before i am paying for shipping to US (i live in Israel) and getting allmost one month of downtime
So what is those marks?
Can you guys tell me what cause it?
Can i fix this myself?
I ride mostly gnarly staff, my bike haven’t seen open power valve for more than 100 hours
The bike is basically running good butl t starts to loose compression after 40 hours of each piston that kind of bothers me (normally i can run 80-100 hours on each top end)
Plus, maybe the engine can run better with this problem fixed
Thanks guys
So, before i am paying for shipping to US (i live in Israel) and getting allmost one month of downtime
So what is those marks?
Can you guys tell me what cause it?
Can i fix this myself?
I ride mostly gnarly staff, my bike haven’t seen open power valve for more than 100 hours
The bike is basically running good butl t starts to loose compression after 40 hours of each piston that kind of bothers me (normally i can run 80-100 hours on each top end)
Plus, maybe the engine can run better with this problem fixed
Thanks guys
.
Paw Paw
This piston was taken off after 68 hours as for preventative maintenance, not because of lack of performance.
The service manual says every 7.5 hours if i am not wrong but it refers to pro guy that race and taking a factor of safety/quality
I ride in tigh technical terrain, my bike never reach to the mid-top range
My KTM EXC 125 got piston every 80 hours for almost 600hrs in total and that is my reference
So consider the fact that this piston was taken off after 68 hours and according the piston condition, what you would do?
Thanks
It can’t reduce compression and piston “life”?
The Shop
I wanted my CR to be a gnarly weapon and he did very good job with it
My bike fells very good and have lot of torque from idle, too bad he have no double ring set up
It has an insignificant affect on compression and piston life.
This is exactly what i asked initially
Maybe should I sand it little with fine sand paper 1500+?
or maybe even diamond paper?
I would suggest that between 25 and 30 hours is a very long life for this set up and you have gone way beyond that.
I would also suggest a ring change at 10-15 hours max.
Paw Paw
What about the exhaust bridge?
Should I do something with it?
In the photos stock vs big bore, you can see the difference
Is this a nickasil cylinder?
.
But here’s some more photos, all these where taken long time ago, the bike is running new piston since then for about 40 hours.
It is just starting to feel like little slower and lacking compression that was one of the triggers to this thread (hard to start it cold).
uv
Heat the cylinder as hot as you possibly can (I’m talkin hot, torch right in the bore hot) then drop it in a bucket of the coldest water you can get!!
Works like a charm every time
Pit Row
Get a new one in there and go ride... I am not seeing anything wrong with that cylinder... if there was a problem, it wouldn't have gone 40 hours.
Looking at the piston and the wear on it, I'd grind it down a small amount more. You could call Eric Gorr and send him these same pictures, I'm sure he'd tell you if you need to do a little more grinding.
I'd have to agree with the rest of the comments that 50-60 hours on a 144 is a lot.
Before reassembly, I'd hone the cylinder, then make sure the new piston clearance is good, just to be sure.
It worth checking but As much as i know 2 smokers shouldn’t be honed no matter what, especially those with nikasil plating
The honing process doesn't take a bunch of surface off any plating. Even after a fresh plating, those cross hatches have to get into that surface somehow, and I've been told that a new honed surface will allow a better mating of the ring and cylinder wall to seal better. Like I said, I've been told that by a bunch of people, but that certainly doesn't make it correct.
If you call Gorr, ask him. I'd be interested in what he says.
EDIT - you got me curious so I did a quick search. Of course there are always conflicting viewpoints, but here is a Thumpertalk thread that talks about honing, but points out that with a plated cylinder, you are actually just deglazing it.
https://thumpertalk.com/forums/topic/294800-honing-nikasil/
Clean the cylinder, fit a new piston and go ride. It shouldn't be this complicated.
We have a Gore CR144 and usually go between 25-30 hours on top end. Better safe than sorry.
Honing is fine on Nikasil with correct hone. A brush hone is usually recommended for the home mechanic.......scotch brite is fine also I've never seen any real performance/longevity difference between either method.....
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