Wont Start

Hi All,

I am new to the group, i know this is a common Q but still couldn`t fault find.

I have a 2016 WR250R, looks like a cold start problem but tried basiclly everything! It cranks fine but wont start, run start the bike let it idle for 5min then it starts fine afterwards. Not a battery problem (try jump starting already), tested the ignition coil, fall switch, fresh 98 high octane petrol, etc... Its got spark and fuel so..?
Could it be the fuel pump losing pressure but if so why does it run start then? When turning the key the fuel pump runs and stops at pressure, straight after switching off then on again the fuel pump runs and stops again? One would think it will still be up on pressure, i don`t know how to fault find or pressure test the pump if its working and to pay $350 for new pump only to test well...?

Please help, ive got no hair left to pull out!

Gerhard

If you're confident you have spark and fuel, the next thing to test is compression: get a cylinder compression kit and follow the directions that start on page 3-9 of the service manual.

Thanks Mate! Was hoping it wouldn`t come to that but theres not much left to check. Cheers for that!

Measuring compression is not that difficult, the difficulty begins if the compression is low: as a first check you will have to measure valve clearance, which is not so easy on the WRR due to limited space and a complicated cam chain tensioner.

How may miles/km does the bike have?

18000km only mate.

That's not a lot of miles, I wouldn't expect the valves to be off so early in its life, but you never know until you check.

Tight valves was the issue on my no start when cold. I'm guessing the lash must open up a bit when the engine is warm (perhaps too much aluminum involved, cast iron stuff gets tighter). A multi-cylinder bike would have started when cold (assuming some cylinders had clearance) but likely would have kept running the thing until a vale burnt.