Top end rebuild - full (all three cylinders vs one)

[rks60@rocketmail.com]

I melted a piston last weekend. Need to re-nik the cylinder and then new piston, rings etc... Anyone out there have an opinion on whether it's better to rebuild all three cylinders or is it OK to just repair the obvious? Looks like an OEM piston. Compression is ~OK~ on #2 and #3.

All my 2-stroke experience is on single cylinder dirt-bikes so this triple is new to me. Obviously I'd like to save $'s but don't want to hurt the bottom end or cause other issues...

Thanks for your time

 

[A couple of bucks]

If it was me I'd get..
1. 1 piston and wrist pin.
2. And 3 sets of rings.

 

[shaggyzr2]

If it was me I'd get..
1. 1 piston and wrist pin.
2. And 3 sets of rings.

That's what I would do too, unless you want to spend the extra $ for 2 more pistons.

 

[Srx007]

Why do you think you need to re-nikasil the cylinder

 

[rks60@rocketmail.com]

the cylinder wall is "wavy" on the exhaust side - not gouged but still very obviously bad..

 

[Srx007]

Measure the cylinders with an "inside micrometer" to make sure they are not oval, doubt they will be but never-the-less check them all and in different places and 90 degrees to each measurement. if they are not oval hone the cylinders to brake glaze, re-ring and you should be fine...

 

[OldIron]

If it was me I'd get..
1. 1 piston and wrist pin.
2. And 3 sets of rings.

I would do this or do the whole top end.

 

[sxviper-s]

I concur. Just do the one if cash is a concern.
I burnt one cylinder and piston some time ago. I just repaired the one. It's been just fine since. You should be ok.

 

[rks60@rocketmail.com]

Replace cylinder #3, all three pistons,rings, wrist, pin bearings. Compression is OK on all three (a little low on Cyl #1 but maybe will improve with some time on the rings...

Fired up great BUT cylinder #3 seems to be running rich. This is the cylinder that failed - also the coil on this cylinder tested bad (replaced) AND the previous owner had a BR8es in #3 (BR9's in #1 & #2) plugs on 1 & 2 look great!

The carbs / jets "look" clean - I guess I need to check #3's jetting!

What else am I missing???

#3 running rich shouldn't cause issue except power and possible fouling right?

 

[roudyroy1]

did you figure out why you melted the piston in the first place?

 

[Srx007]

What are the Comp numbers?? Plugs should be an NGK BR9ecs. BR 8 is a hotter running plug which is why it will be jetted richer. I have no idea why the previous owner would have done this other than he blew a plug away from home and had to just get back. Hoter running plug would most likely be the culprit in this matter. What year is your SRX

 

[Srx007]

I FOUND THIS ON THE FORUM ABOUT THE SPARK PLUGS.......I just had a long talk with one of the engineers (Jeff) at NGK about the BR9ECS vs BR9ES plugs. He told me that the difference is that the BR9ECS plug has a low angle ground electrode. (that's it...that's all...no special metals, no different depth, not hotter, not colder etc etc)
That being said, that causes a difference in the flame front in the combustion chamber. The ECS plug with the low angle ground electrode causes a more controlled and equal flame extension into the chamber where the ES plug causes a 3/4 circle front (blocked by the electrode).
In some engines this makes a difference in detonation control at higher speeds and loads. He concluded that the engine manufactor must have experienced some problems under testing and recommended the ECS plug to provide the best performance and reliability.
He would not recommend using the ES plug instead of the ECS plug due to the likelihood of detonation problems under high loads &/or rpm, but said that the ES plug might work just fine in some engines until conditions in the combustion chamber got hotter and more likely to start detonation.