ESE's works engine tuner

[wobbly]

Short stroke , very light reciprocating parts , and a rebuild every hour if you are lucky.

[yatasaki]

Hi What is it about a 100 cc direct drive reed or rotary kart engines design that allows it to rev to 20,000 quite happily all day .
cheers

All day is actually few sec per lap.

[41juergen]

So I would like to get your thoughts on these piston...
It's a TZ250 4DP setup on a street bike with TZ cylinders, heads, pistons and pipes. The engine has the street airbox on it with TMX38 Mikunis. The comp is approx 7.2 with 50% squish and 0,8mm distance. The engine had only 20 km before (incl. a lite acceleration up to 9500 rpm) when seized at approx 6.500 rpm with maybe 1/3 throttle. The engine is on oil pump, the other cylinder is still fine. Exhaust temp at that point was approx 420°C.. The piston has a coating with a piston clearance of 5/100 mm on 100 Octan pump gas. As the engine was running rich on the needle the guy dropped the needle for about 1 notch...
And its not my bike, so don't know more details yet.

[jonny quest]

What brand pistons.

What's different about this engine than a previously reliable engine?

[41juergen]

What brand pistons.

What's different about this engine than a previously reliable engine?

Stock Yamaha TZ pistons, the only change was the drop of the needle for 1 notch (and the engine was running rich before)...

[yatasaki]

Stock Yamaha TZ pistons, the only change was the drop of the needle for 1 notch (and the engine was running rich before)...

That carbon deposit tells me that squish gap is too tight

[F5 Dave]

I'd be checking oil feed to that cylinder. That's ugly.

[wobbly]

Has it got an Ignitech with 28* advance flat line out to about 8000, things seize when run at part throttle for any time doing this.
And due to the big differences in case volume and intake length the 3XV/3YL/4DP always lock up one side well before the other.
Running the Ignitech on a 4DP I ended up with 2* advance split on the LH cylinder - this gave almost dead equal jetting and equal egt.

[philou]

the needle profile is not good.
often the case on Mikuni carburetors.
use a needle jet calculator which gives you the distribution curve.

[41juergen]

So it looks like that the coating was done not proberly, the piston what seizured was too large, the piston clearance was only 0.035 mm... the onyl question remains for me why the engine didn't seizured already during the first 20 km..

[philou]

the condition of the piston crown is not due to lack of clearance

[jbiplane]

I use manual decompression valves to facilate start of 2-stroke engine with electrical starter.
But pilots of paramotors want start-stop engine in a flight. Stop when flying in thermic and launch if dont sucseed.
I saw on husqvarna chainsaws automatic decompression valves which actuated by pressure variation in crancase.

Claimed non-reliable and in my case useless cause 534gramm LiPo battery cannot make even first turn.
Manual actuation a bit pervert. For me decompressor which always open after 10 seconds of engine stops could be a solution.
To actuate manual valve enough 600gramm pressure and 5mm movement.
Any suggestion-solutions? Preferable simple addon to chainsaw decompression valve.
Thinked even of solenoidal electrical actuator...
But better automatic mechanical simple. Actuated after engine stops.

[diesel pig]

I use manual decompression valves to facilate start of 2-stroke engine with electrical starter.
But pilots of paramotors want start-stop engine in a flight. Stop when flying in thermic and launch if dont sucseed.
I saw on husqvarna chainsaws automatic decompression valves which actuated by pressure variation in crancase.

Claimed non-reliable and in my case useless cause 534gramm LiPo battery cannot make even first turn.
Manual actuation a bit pervert. For me decompressor which always open after 10 seconds of engine stops could be a solution.
To actuate manual valve enough 600gramm pressure and 5mm movement.
Any suggestion-solutions? Preferable simple addon to chainsaw decompression valve.
Thinked even of solenoidal electrical actuator...
But better automatic mechanical simple. Actuated after engine stops.

You need a victer automatic lawnmower 2-stroke decompressior. works great on my Husqvarna motorcycle engine.

[teriks]

Hi, trying something different than those 6.6cc glow plug engines..

Does someone by chance have ENGMOD model of a AS3/TA125/RD125 twin to share or even sell?
Very old stuff so I strongly doubt that, but unless you ask...

Got myself an AS3, first intention was to keep stock and just enjoy, but.. well that failed.
First thing fitted is an Ignitech, what a luxury to have direct control over ignition timing!
I'm fortunate enough to have two spare sets of cylinders + heads so some work on those and pipes are in the (very long term) plan.

Not that it will ever be a super powerful racer being air-cooled with super crappy transfers due to cylinder spacing, but that may be a good thing.
-Those drum brakes are not very impressive either, not to mention the handling, but I get to enjoy the lovely sound of a two stroke twin.

[pete376403]

You need a victer automatic lawnmower 2-stroke decompressior. works great on my Husqvarna motorcycle engine.

https://sesdirect.co.nz/collections/...e-short-body-1