Aftermarket jets and cold mornings

[merka685]

Hey everyone, I recently purchased a RF400 with aftermarket jets :Punk: However now that the weather is cooler I am having a hard time getting the bike started in the morning. Do jets need to be tuned regularly or changed for colder temperatures? Or should I put the stock jets back in?

[Taz]

Firstly why has it had jets replaced? Has the exhaust been modded? Are you using the choke to start? Are valve clearances and compression within spec?

[merka685]

It had jets replaced for more bottom end, and has recently had valves balanced (last 3 months). Don't normally use choke as it floods but used a little this morning and it worked.

[Anarkist]

Choke, mother fucker. DO YOU USE IT?

[vifferman]

Don't normally use choke as it floods but used a little this morning and it worked.
Then presumably, it had bigger jets fitted (i.e., it's running richer). Therefore it should start more easily as it gets colder.
What octane fuel are you using? If it's 95 or 98, try using either 91 or a mix of that and what you usually use.
I found when running the VFR on 98 I had to do this as the weather got colder.

[Hoon]

Its really only the choke and idle jets that affect start up/closed/low throttle positions.

Learn to use the choke - that's what it's there for. Full choke, throttle closed, push start.