When to Rebuild a Motor

[prunty]

Just a quick question, I've a 2003 EC300 which I've had for about 2 years now, although it hasn't been out that much in that time. She running fine although I've noticed the last time I was out she is rather smokey with a lot of blue smoke etc, etc... more so than some of the other guys bikes.

Anyway I've no idea what her history is and I was wondering when should she have some engine work done?? Do I wait until a failure of some sort or is it advisable to do a rebuild before she stops???

I was going to have a look at the clutch basket some of these day as the clutch drags quite a bit, so such so that it's very difficult to start in gear and I was wondering if I should be going further with my investigations??

 

[bowhunter007]

I'd open it up, and have a look, prior to any failures. The cost goes up dramatically after engine failure. Better be safe, than sorry(and maybe broke). I made that mistake...once.

 

[prunty]

I'd open it up, and have a look, prior to any failures. The cost goes up dramatically after engine failure. Better be safe, than sorry(and maybe broke). I made that mistake...once.

Just the top end I take it you talking about??

Is it just wear and tear I should look for, or is there anything in particular??

 

[Jakobi]

Ideally you will have an hour meter and service your bike at set intervals. Depending on what you find at those intervals you'll either extend them or reduce them.

Its not hard to take the drain the coolant and pop he cylinder off. Look for signs of blow by on the piston, any wear, fracturing or cracking on the skirts. Pull the rings and measure the end gaps. While you have the top off you can then gauge side to side play on the rod, and feel for any up and down movement. Remove the flywheel cover and feel for any play in the mains by grabbing the flywheel and moving it up and down. Check the reeds for chipped or damaged petals.

If the bike is burning transmission oil you will smell it and it will smoke alot. It'll also have less oil come out than you put in.

I usually pull the bike down this far every 75-100hrs. While its apart I spend the coin and replace the little end bearing, piston and rings, along with all gaskets (base & head). My bikes got 7200kms on it currently and nearly 250 engine hours.

 

[prunty]

Ideally you will have an hour meter and service your bike at set intervals. Depending on what you find at those intervals you'll either extend them or reduce them.

Its not hard to take the drain the coolant and pop he cylinder off. Look for signs of blow by on the piston, any wear, fracturing or cracking on the skirts. Pull the rings and measure the end gaps. While you have the top off you can then gauge side to side play on the rod, and feel for any up and down movement. Remove the flywheel cover and feel for any play in the mains by grabbing the flywheel and moving it up and down. Check the reeds for chipped or damaged petals.

If the bike is burning transmission oil you will smell it and it will smoke alot. It'll also have less oil come out than you put in.

I usually pull the bike down this far every 75-100hrs. While its apart I spend the coin and replace the little end bearing, piston and rings, along with all gaskets (base & head). My bikes got 7200kms on it currently and nearly 250 engine hours.

Thanks for your post, that all sounds straight forward enough. However I'm not sure about your comments on the rings. What do you mean by measuring the end gap??

 

[Jim Cook]

Thanks for your post, that all sounds straight forward enough. However I'm not sure about your comments on the rings. What do you mean by measuring the end gap??

Remove the top end.
Remove the rings from the piston, and using a piston, push the rings (one ring test at a time) down into the bore.
Take a blade type feeler gauge and measure the gap between the ends of the ring.

This lets you monitor ring wear.

While you have it apart, check the end gap on a new set of rings for comparison.

Make sure any replacement rings are the same brand/manufacture as the piston.

 

[Jim Cook]

Just a quick question, I've a 2003 EC300 which I've had for about 2 years now, although it hasn't been out that much in that time. She running fine although I've noticed the last time I was out she is rather smokey with a lot of blue smoke etc, etc... more so than some of the other guys bikes.

Anyway I've no idea what her history is and I was wondering when should she have some engine work done?? Do I wait until a failure of some sort or is it advisable to do a rebuild before she stops???

I was going to have a look at the clutch basket some of these day as the clutch drags quite a bit, so such so that it's very difficult to start in gear and I was wondering if I should be going further with my investigations??

Re: the clutch drag.

First: Make sure that your clutch is bled properly. (I do a small bleed check for air every month or so.)
Change the dot4 brake fluid at least once per year. Do not attempt to stop clutch dragging by adjusting the plunger pin in the master cylinder too far in. This will cover up the bleed hole in the reservoir, and will keep the clutch from bleeding air from the lines by itself. (You will start accumulating air in the hose.)
On the pre-2006 Gassers I use a top rated "600" dot 4 brake fluid in both the brakes and the clutch. (I personally use Motul RBF600.) My 2006 clutch came with mineral oil from the factory, so I used KTM supplied "Magura Blood" in it's clutch m/c, but still used the RBF600 in the brakes.)

Second: The oil you use in the transmission will make a huge difference in clutch drag. GasGas clutch has tighter tolerances than other manufacturers, with 8 friction plates, instead of 7.
I have tried many oils, and until I tried Amsoil 0w40 4-stroke synthetic motorcycle engine oil, I had settled on Rotella 5w40 synthetic. Once I tried that particular Amsoil oil, I never run anything else in the transmission of my primary GasGas bikes. It is fantastic, in terms of clutch drag, and clutch and transmission wear. (Thanks again, Eric Kangas!)

 

[prunty]

Remove the top end.
Remove the rings from the piston, and using a piston, push the rings (one ring test at a time) down into the bore.
Take a blade type feeler gauge and measure the gap between the ends of the ring.

This lets you monitor ring wear.

While you have it apart, check the end gap on a new set of rings for comparison.

Make sure any replacement rings are the same brand/manufacture as the piston.

Would you consider putting new rings on an old piston?? I would of thought piston and rings had to be replaced together??

 

[singletracker]

Some people just change the rings to freshen it up.

 

[Jakobi]

There's nothing wrong with just doing rings. It'll get your compression back up. But depending on the wear and hours on the piston it may or may not be a wise move. Generally you'll find racers will re ring around 50hrs to bring it back good, but will then do the full kit at 100hrs. I personally just stretch them both out. Sure you could run a piston 200hrs but really the skirt wears and the piston will rock/slap more than it once did. You run the risk of cracking or breaking a skirt at worste. At best you'll see premature wear on the cylinder. Of course, if the skirt snaps off and runs through the bottom end.... well yeah!

 

[Jim Cook]

Would you consider putting new rings on an old piston?? I would of thought piston and rings had to be replaced together??

I normally get two or three sets of rings per piston (two ring changes), depending on visible piston wear.

 

[prunty]

As I don't know the history of my bike I'll probably change both. So can I order the piston and rings in advance or do I need to get the old one out first to ensure I get the right size, i.e. do people mess about with the bores on these things??

 

[Jim Cook]

If your bore is in good shape (no streaks or gouges in the nikasil), then I'd do a light hone and put in a "C" piston kit.

If you find that you require a re-coat/recondiiton of the bore, then I'd put in an "A" piston.

Each piston size is 1/100th of a mm larger in diameter than the next (B vs A, or C vs B), so it is a very small difference.
A, B, C, & D pistons all use the same identically sized rings, as long as you keep the same brand rings and piston.

My favorite piston is the "coated" Athena, made by Wossner in Germany. The uncoated Wossner came stock in my 2006 DE300.

 

[prunty]

Thanks everybody for the comments, very useful. I've just one final question, does the new piston need to be broken in or is it good to go from the get go??

 

[Jim Cook]

Thanks everybody for the comments, very useful. I've just one final question, does the new piston need to be broken in or is it good to go from the get go??

The key is to properly warm the engine before putting a big load on it. This lets the cylinder catch up quicker to the temperature that the piston will achieve first.
I like to putt the bike around just above idle till it warms up.
The piston is fine. You need to seat the rings.
Warm the engine until you can't hold a bare hand on the cylinder, and then run it hard for fifteen to twenty minutes. (This raises the pressure that pushes the rings out into the bore. and seats them better and quicker.)

Make sure to oil the new wrist pin bearing when you install it. (not sold with the piston kit.)

Good Riding!

 

[wence]

If the clutch is still not right after using fresh oil etc it may pay to whip the cover off and check for gouges in the basket.
I had to clean up the clutch basket on my 07 at one stage.
Cheers Mark

 

[prunty]

Thanks guys, great info. By the 'wrist pin bearing' I take it you mean the wee end bearing that connects the piston to con rod...

The clutch was the same when I changed the oil earlier this year so I intend to have a look at the basket when I at it. I got some good advice on the clutch issue on another thread I started earlier.

Thanks again;-)