Hi!

Mine is very hard to start when the engine is cold (first start of the day). sometimes i have to use ether to get it running.
it starts easy afterwards

I run the bike on 98 octan fuel and have unrestricted airbox and cherrybomb

any ideas to make it start easier?

Usually a such issue is linked with valves

starting cold, and in sweden.... do you mean at -20°C???? ;-)
as HM said, valves and cam chain could need a check...
ciao

Hi =)

Actually when i was winter driving it was easier to start (-15), man its scary to drive on snow, never now if it will bear or not.

will check the valve clearance and chain tension when i come home

i had this trouble and i found that i had to turn the black choke/ idle knob on the carb a few clicks clocwise or anti clock wise, (you usually pull it out to start when cold but it also turns to adjust idle). mine also runs better below 0 degrees.

4 Strokes tend to be hard to start in general. As people mentioned that valves are typically the most common issue as it pertains to starting problems. The timing chain (as someone mentioned, once again) can also cause problems. If you feel capable, pop off the valve cover and see if the timing chain is still tense. If not, that's could be a problem.

Also, carb problems can also be a problem. If the temperature varies a lot from winter to summer, then you made need to adjust your fuel screw a little. My assumption is it's a little rich (if it's hard to start), the fuel screw should be located on the bottom of the carb, on the side closest of the head, in the middle. Tighten it a 1/4 turn, if it doesn't help, set it back to what it was.

Is the RMX 450 not EFI ??

Col 84, on 15 August 2012 - 01:03 AM, said:

The RMX450Z has EFI.

try switching down to a lesser octane fuel, 92-93 max. Higher octane fuel burns cooler. Had this exact problem with an crf100, changed back to pump gas 92, and it fired easy