the heatsink in silver with a lot of holes along the side, the version after the one with a handled heatsink. dont know how to tell what version it is
but i was told it used the xz-r crankshaft

XZ-R has a 16.8 stroke..... not possible when all R210x engines have a 17.2 stroke as explained earlier. And then, what is so specific to the XZ-R crankshaft. It is round 14mm with some holes etc like any other crankshaft. I will measure the R2105 but I bet it has the same timings as all previous standard R210X models and so I expect the 2106 will have too.

Hi Rody,
Just wondering what your experience has been with the 2105 & 2106 problems. Do you think is it liner surface finish that is causing this issue as some of the engines are doing it after run in and during a long run final. Or is it a piston material issue?

When pushing the engines to their maximum we more easily also pass their limits.

Even though the finish of the liner and piston of the OS engines are excellent we still can encounter some problems which also the other manufucturers are facing sometimes, so not only OS...

I do not have technical insight in the manufacturings process of OS and the materials they use but I know it is a very delicate issue. The weird thing is that this does not happen on all the engines but only a very small qty which of course always comes out in front compared to when there are no problems.

My experience is that the fuel used is very important and also the OS on-road engines are more delicate on their working temperatures and you should never push too much the engine in the first few laps.

The new main-needle with their 2 o-rings have improved the stability of the carburetor setting(included in the R2106) and the extra lubrification groove on the piston should help, now the racing season is over here in France but I am sure these improvements go in the right direction.

Fuel is probably the main cause. Over here many do use the Energy fuel also sold as Maxima within Europe. Me and some fellow drivers experienced failing rods with OS engines, After adding some extra oil there were no issues anymore and all of them also do not face the scratching pistons.

Its interesting. I have experienced marking of the piston during run in even with more oil but I know I was just pushing too hard. It wasn't in the sealing area so I cleaned it up and it runs ok, but then it started picking up in another spot. So you could be right. Do you use energy/maxima? Assuming you add extra castor?

What fuel do you recommend?

ENERGY is the one most used in high competition in Europe.

That’s what I use. I’ve heard of people adding extra castor to it aswell.

Normally it is not needed but if you want to play it safe you could add 2%

Curious as to what this marking on the piston looks like.

R/C Tech Forums - View Single Post - OS R2104 engine Thread

I was curious because I had the same thing happen to one of my Ultimate M5S engines (PS set is OS B2103 type R) last year while doing the final break-in though mine's not as extreme as the one's in the link. I was using Bones break-in fuel added 50/50 with 30/8 Bones fuel for the initial break-in so I know I was getting plenty of oil for the process. I tried measuring the piston to see if the spot was worn more than the un- affected parts of the piston but it was the same side all the way around. Also there is marking on the sleeve, both on the exhaust side. I noticed it after a tear down for inspection at the end of the day. I replaces it w/ a new P/S set and haven't had an issue like this with the new set. I've never even had this issue before w/ any of my engines. Are these just over polished spots from carbon buildup or something different? I haven't used the set but am wondering if these marks will impact performance.

Hard to say what is happening but on the 1st pic a small black spot on the left side should be related to a specific spot on the sleeve. As mentioned by me in that R2104 topic, in the past it was normal to remove all sharp edges of the ports and I think that still will help today. About the spot over the whole side, a friend who worked at a metal company said such spots look like a cold welding. A moment that the pinch and temperature was high and the lubrication too low. Still I do not rule out that the rough edges of the ports can be the cause.

Now some time ahead of the introduction I wonder if people have seen issues with damaged pistons with this model. It is a bit quiet so probably it is solved?