400 conversion to 440

Garrettporter wrote: I am running lean. That's because the carbs have aftermarket needles and the floats need readjustment for them to fine tune them.

I'm not sure what you're saying here. Did you make carb mods since you've had the bike?

Because having the open exhaust is enough to make the engine run too lean. If you did any carb mods to make the jetting even leaner I'd recommend you undo those changes immediately. Also put the muffler back on: the bike will run more like it should so you'll actually have more power, and your headers will be supported by more than just the collars.

Ill have to look into the valve twist on them. So thank you for that.

Huh? :blink:

First of all get some mufflers on that thing before someone shoots you and/or you cook the engine from the jacked up carb mixture. I'm not sure what's offered in the way of carb jet kits for the 400 but I'd start there (Dynojet/Sigma/factory pro/?). A jet kit will move you forward much faster than trial and error jetting. You gotta get it right too because the engines life is at stake.

. It has stock jets. The needle valves that let fuel into the carb bowls are aftermarked. The floats have an adjustment fin that holds the clip of the valve. The factory nominal float hight is 22mm +2, -1 tolerance. With aftermarket valves the fit is correct but the height is a few thousandths off making for a sob of fine tuning.

Sorry for confusion. Valve twist - slang for adjusting the valves by twisting the adusters at the head

Garrettporter wrote: Hey riders. Ive got a build on my hands. I bought a bone stock 79 ltd. im gearing it lower to have speed with less rpm. Im wondering if i can put a 440 top end (pistons cylinders and valvetrain) onto my 400. Will it simply bolt up together

The late 400s had the same power rating as the later 440s.
What are you looking for? More torque to pull a taller gear?


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Garrettporter wrote: I am running lean. That's because the carbs have aftermarket needles and the floats need readjustment for them to fine tune them. Ill have to look into the valve twist on them. So thank you for that. And ive included a pick of the bone stock before i made changes. The pipes are stock. The baffle pipe was completely removed and left cyl header moved to rest with the right. Its geting full exhaust this winter, raked and a springer. Any more advice is always helpful. Thanks

That pipe is an aftermarket 2 into 1 made buy Mac.


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Garrettporter wrote: The pipes do need to be longer. Do you think that would cause part of the heat problem at the headers? And it does have the air box. I hate that thing lol.

Bluing of the pipes is caused by high heat. Either fuel is still burning after the exhaust valve opens
or the valve is not sealing. Run a compression test. Check valve lash and a complete tune up.
As for the air box, does it still have the snorkel that mounts to the back of the
unit. It has the air filter. Keep the air box for now.


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Garrettporter wrote: . It has stock jets. The needle valves that let fuel into the carb bowls are aftermarked. The floats have an adjustment fin that holds the clip of the valve. The factory nominal float hight is 22mm +2, -1 tolerance. With aftermarket valves the fit is correct but the height is a few thousandths off making for a sob of fine tuning.

Sorry for confusion. Valve twist - slang for adjusting the valves by twisting the adusters at the head

Interesting. I started working with screw-type valve adjusters 30+ years ago and have never heard that phrase. Maybe it's regional.

And having the floats set "a few thousandths" off is not going to cause the lean condition you have; we have covered the reasons for that already. And the fact that the float height has an acceptable range of 3mm should tell you that this is not a fine-tuning adjustment.

To be kind of blunt, I'm not sure you understand what happens inside the carbs but would encourage you to spend some time reading the forums. There is a search function at the top to help you find what you need.

Garrettporter wrote: . It has stock jets. The needle valves that let fuel into the carb bowls are aftermarked. The floats have an adjustment fin that holds the clip of the valve. The factory nominal float hight is 22mm +2, -1 tolerance. With aftermarket valves the fit is correct but the height is a few thousandths off making for a sob of fine tuning.

Sorry for confusion. Valve twist - slang for adjusting the valves by twisting the adusters at the head

You need to rejet. I would not ride the bike any further without installing the muffler back on and checking the valves.