Everything2Stroke Forum banner

21 - 34 of 34 Posts

·
Registered
Joined
·
104 Posts
Piston wash is for sure on the rich side. Thats keeping any deto at bay. But you boiled coolant.
My guess is your bore is not true all the way thru the stroke. Sometimes they recess the exhaust bridge a bit, that way when it's hot it wont push (heat expand) into the piston. That said, the piston ring can float out just a bit as it passes the exhaust port area. The piston can then "lean" over on the exhaust side on pass over the port, then straighten up as it gets near the head.

Any one ring piston has a tough life, even less life you your getting coolant that hot. Not sure it will help if you make this motor tight and true. I'd be happy re-ring it / piston as needed
 

·
Registered
Joined
·
854 Posts
Let me back up a few posts here - the original poster said he replaced the crankshaft, was it an OEM replacement or did any of your variables (stroke, rod length,) change? It seems odd to me that there is that much ring wear on the exhaust side so relatively quickly. The bore is either very out of round, the hole (exhaust port) is much too big, or there is way too much angle and leverage on it from the crank.

Perhaps I'm over simplifying things :)
 

·
Registered
Joined
·
167 Posts
I thought I was over-simplifying, but he is wearing out his ring so fast, seemed like dirt or honing grit or something similar was likely. Unless you are racing, and I mean racing where the engine spends nearly all its time at very high rpm, I like a 2-ring piston, but with his problem appearing so soon, an extra ring would just wear out as well, seems like.

Possibly if it is a pre-mix bike rather than an oil-injected bike . . . a common problem for owners of chainsaws, weedeaters, and similar pre-mix machines that sit unused for a while is that the oil settles out of the fuel. If they don't know to shake up whatever gas is still the machine, and this includes pre-mix motorcycles (and outboard motors), on start-up the engine is drawing a very oil-rich brew from the bottom of the tank, and smokes a lot. Movement will tend to re-mix some of the oil, but in some cases the engine burns off the oil-rich stuff in the bottom of the tank and progresses to drawing an oil-lean mixture. I doubt this is causing dANbOT's problem, but . . . .???
 

·
Registered
Joined
·
17 Posts
How are you torquing the jug back to the case? Are you torquing it in sequence? I'm curious if maybe the jug is smushing the base gasket in an odd way.
 

·
Registered
Joined
·
35 Posts
Discussion Starter #26
Torquing as per my Honda service manual, with a good wrench.
Not racing, I'm a cross county freak... spend my time in first and second gear on tight technical trails.
Someone asked about my crank, it is a Hotrods that has been spinning in there for a few seasons problem free.... same specs as the OEM aside from the Chinese rod bearing.
I have to suspect the cylinder as the cause, previous to its installation I always changed piston / rings @ about 40-50 hours and they always looked mint. Since the new cylinder was introduced last spring, I have worn several rings this way.

Anyways, I had big plans to send the cylinder out for inspection / repair / plating before spring, but I have since purchased a new bike so, for now.... it will just get a fresh top end and settle into semi-retirement as a backup / buddy bike. Unfortunately this means there will likely never be a solution or root cause to share. Here's a pic of the new bike as compensation lol:

2014 Gasgas XC300RE
 

·
Vendor
Joined
·
1,500 Posts
Maybe the cylinder isn’t square; it can be chucked by the bore & have a gasket thickness cut off of the base gasket surface. This squares it right up.



This file is unlocked for any of you who are interested what a machine shop does, click on the picture.
JT
:Cheers:
 

·
2 stroke thinker
Joined
·
2,062 Posts
I agree that it is a possibility that the bore is not perfectly round or the exhaust port might be too large due to porting.
Also, If it was bored...were the port edges chamfered afterwards so they aren't like a "razor blade finish" basically trimming the piston ring?
 

·
Registered
Joined
·
35 Posts
Discussion Starter #29
I agree that it is a possibility that the bore is not perfectly round or the exhaust port might be too large due to porting.
Also, If it was bored...were the port edges chamfered afterwards so they aren't like a "razor blade finish" basically trimming the piston ring?
It was a brand new oem Honda cylinder as I installed it last spring. The first ring only lasted 20 hours. I can't see anything anomalous by looking / feeling in the cylinder.
 

·
2 stroke thinker
Joined
·
2,062 Posts
Maybe it might be a bad crank or rod bearing causing the piston to "cock meaning angle against the bore".
What brand of oil are you using?
What oil/gas ratio are you using?
Just wondering, If it's lean, it may wear the ring sooner.
If it's lean, just thinking...how about a bad crank seal...Just thinking here.
Of course, a single ring piston is gonna wear much quicker than a 2 ring piston.

Also, I've seen KLOTZ Benol mixed with race gas...Separate meaning the fuel and oil don't stay mixed.
 

·
Vendor
Joined
·
1,500 Posts
The cylinder may still be crooked from the factory. Back a page or so a dial bore gauge was suggested & the comment was that they are too expensive. Not So; An acceptable model is available on eBay for about $60.00. I purchase around 1 per year since they are easily damaged.



The digital units are too sensitive & very tricky to work with. Sometimes drilling larger or another oil hole in the piston at the exhaust bridge area is very helpful in lubricating.
JT
:Cheers:
 

·
2 stroke thinker
Joined
·
2,062 Posts
True point John.

The Cylinder might have Not been decked properly on the base side...Even tho it is a factory cyl. They can send you one that is not trued properly.

It could have been completed on a Friday at 4:45 p.m. When the person wanted to leave for the weekend or on a Monday when the guy doing the cylinder was hung-over after a hard partying weekend!

I guess the best bet would be to chuck it up on a lathe with a dial indicator and check the run-out.
 
21 - 34 of 34 Posts
Top