Topics

1

Tech Talk / Wiseco Ring End Gap

« on: April 07, 2025, 02:47:15 pm »

Wiseco recommended ring end gap for my WR500/YZ490 is .35mm (.0137 inch).

I am about to install new rings and the gap is .485mm (.019 inch).

The bore is 1st oversize (87.5mm), as are the new rings, and a measurement of the bore shows it bang on 87.5mm.

Can anyone suggest why the gap would be so big and also if this ring gap is acceptable?

2

Wanted / Wanted: Bearing Cover Plate

« on: March 20, 2025, 03:17:49 pm »

For Yamahas:

YZ 250 - '85, '88-'94
WR250 - '89-'93
YZ490 - '85-'90
WR500 - '92-'93

Part # 3SP-15381-00-00

3

Tech Talk / Spluttering When Rich - What's Actually Happening in There?

« on: January 09, 2025, 05:55:20 pm »

Hi all,

Wondering what is actually happening inside the motor (2 stroke) when spluttering under load at higher RPM from too rich jetting?

Is it capable of causing any damage other than fouled plugs?

4

Tech Talk / PVL Timing

« on: December 24, 2024, 06:07:15 pm »

Hi all,

I am about to replace my OEM ignition system with an analogue PVL system on an air-cooled 500cc motocrosser (Yamaha WR500).

PVL recommend timing start at 2.2-2.4mm BTDC for open class machines, however standard OEM setting for my bike is 1.7mm BTDC.

Should I set to OEM or PVL measurements?