XR400R big bore kits and starting

[paddy70]

Is anyone aware of any effect big bore kits have on the xr400r starting nature - positive or negative.

[Trailryder42]

The starting nature didn't change on my 440. I used the same procedure as I always had. It was just a big bore. Same stock cam, same stock carb. If the carb was jetted well before the big bore, don't change jetting before seeing how it's going to run with the big bore, as it won't require as big a change as you may think.

It's more switching to an aftermarket cam or carb that will create different starting nature.

[bajatrailrider]

Have many big bore 440s with all different mods. Lucky the most easy kick start bike in the fleet.We run large pilot jets in pumper carb.

[paddy70]

I put a pumper 36-68 on mine and it improved cold starts. The thing is hot starts and spills are a bear to get it started.

[paddy70]

I'm not going to a big bore I'm just trying ti make mine easier to start.

[bajatrailrider]

We chuck the auto decompresser  leave the manual easy start when you fall down.

[paddy70]

Could you explain further for me how that affects hot starting

[bajatrailrider]

On full manual 5 kicks lever held down,throttle wide open. To clear fuel . With auto makes it harder to start,what p jet you run.

[Trailryder42]

3 hours ago, paddy70 said:

I'm not going to a big bore I'm just trying ti make mine easier to start.

Do a valve clearances inspection. When they get tight, ease of starting suffers.

Always start your kick from TDC. Be sure you're not running too low an idle speed and don't touch the throttle on a cold engine. Use full choke.

[Schwartz2M5]

With my bbk, has always been a one kicker. lucky me

[paddy70]

I'm running Mikuni TM36-68.  Cold starts I can do , just the hot and spill starts. Can't believe they've made a bike so hard to start

[paddy70]

all jets are stock on mikuni

[paddy70]

that's what I wondered if more compression or greater ccs made a difference

[Trailryder42]

1 hour ago, paddy70 said:

I'm running Mikuni TM36-68.  Cold starts I can do , just the hot and spill starts. Can't believe they've made a bike so hard to start

For the Mikuni, on hot and spill starts, hold the manual decomp and kick the engine over several times. When you give it a starting kick, always start from TDC. On the Mikuni, wick the throttle open at the bottom of the kick.

Edited May 7, 2017 by Trailryder42

[paddy70]

That's something I willl try

[paddy70]

1. I saw something about eliminating auto decomp. It looked as though the guy was starting his bike relativly
2.  

[bajatrailrider]

Anytime I do work upstairs on our Xr4s  I press off decomp from cam and weld up oil hole. Works for me.

[paddy70]

This is something I think I will try

[bajatrailrider]

With me having to start a fleet of Xr4s first start cold in the morning. They all need to start in few kicks or Im worn out before the ride. If you have the correct pilot jet bike is running correct. Still start problems its 99.9 the rider. On the bad fuel in Baja and Calif,I find.That bike sits as little as one week,I drain Fuel carb bowel. That helps fast start up.

[Off-Road Adventures]

On ‎5‎/‎7‎/‎2017 at 2:13 PM, Trailryder42 said:

Do a valve clearances inspection. When they get tight, ease of starting suffers.

Always start your kick from TDC. Be sure you're not running too low an idle speed and don't touch the throttle on a cold engine. Use full choke.

Agree! If the valves are out of adjustment it makes starting a real chore.