Piston query

[Fruitjuice]

Recente rebuilt an engine for a friend after he seizend his crank (SIL 200 engine).
The SIL-barrel was unharmed but the piston was scrap so I ordered him a Rapido 200 piston and a 60/116 crank. Running the engine in it seized at 3/4 throttle after 500 Miles but plug colour looks good. Are the Rapido pistons a different tolerance?

[Fruitjuice]

26 PHBH, AV266, X7 top clip, 122 main.

[drunkmunkey6969]

What was the comp ratio and ign timing?

Running top clip on X7 can be a gamble unless running AV268 atomiser, which that engine/carb size probably wouldn’t handle. AV264 with an X13 on 2nd clip might have been better.

[coaster]

Did you check the piston to bore clearance when you fitted the piston should be around 3.5 thou. Also, did you set the ring gaps?

[Fruitjuice]

What was the comp ratio and ign timing?

Running top clip on X7 can be a gamble unless running AV268 atomiser, which that engine/carb size probably wouldn’t handle. AV264 with an X13 on 2nd clip might have been better.

Will try an X13 needle next. X7 with clip on second groove was very spluttery so tried top clip.

Did you check the piston to bore clearance when you fitted the piston should be around 3.5 thou. Also, did you set the ring gaps?

Don't have tools to properly check piston to bore clearance but ring gaps were checked with feeler guages.

[Lamaddict]

Unless Rapidos have got better, the piston bore clearance used to be inconsistent and you need to check it before installing.

[HxPaul]

You can get a rough check of the piston to bore clearance by inserting the piston(without rings)into the bottom of the cylinder pushing it to the top of the cylinder,then use a feeler gauge between piston and bore.