Re: Yamaha RX 135 - post rebore- running rough beyond 40 kmph

Topic Approved.

I'm not too aware about 2 strokes, but even during run in this shouldn't happen.

@psr sir, could you help the member please?

Re: Yamaha RX 135 - post rebore- running rough beyond 40 kmph

Yam RX 135 Being a 2 stroke engine, is sensitive to the bore to piston clearance , afr ,and the lubrication level. From what you have said I could only guess as to probable causes.

1. If the Bore to Piston Clearance is less then the roughness is possible , since at higher RPMs the heat generated is more and the bore slowly becomes tighter..This can be resolved after a few thousand Kms depending on the way the engine is run on load. If you had run the engine for 3,000 Kms already it should have solved by now. You have to check the bore for even re-boring. If it is not done, then engine will heat up and run rough .

2. The 2T oil Pump output should be increased to give more oil into engine, since the cc increase and resultant heat is depending on the lube is more.

3. The Air to Fuel Ratio should be also enriched..ie., more fuel than before to feed increased CC capacity and also to cool the engine. Please remember the 2 stroke engine is Air Cooled and is dependent on correct AFR , since a little of the fuel sprayed inside the engine is also used for heat quenching.

4. Always check and maintain proper Tire pressure for optimum performance..

My suggestion would be to do point no 3 first, along with 2, and see if any improvement is there.
Good luck.

Re: Yamaha RX 135 - post rebore- running rough beyond 40 kmph

Do the run in as advised. rather than depend on the oil pump, i would say be safer and use premix in the tank directly. during run-in add 35ml per liter of fuel. use good quality 2t oil like from castrol or motul.
the other points psr has touched upon. usually too tight a clearance might be the cause, or another thing that comes to my mind is bad clutch plates.