Honda dirt bike AMAZING transformation! Honda XR400 rebuild

[@bonafidepirate]

On this carb, there's a "air cutoff valve", a rubber diaphragm under a plate with two screws on the side of the carb. They rot with age and allow the bike to start breathing through the holes in the rubber part. You can replace it, or block it off. With it blocked off the run fine but can pop on deceleration, but they're also quite cheap to replace. Worth checking for sure! Also check for air leaks in the intake manifold between the carb and head.

[@Builditathome-Restoration]

Tanks alot for your help i have not checked that diaphram so i will have alook 🙌

[@Builditathome-Restoration]

You was right it was broken, i blocked it and i put bigger jets in and now it runs way better even without choke so thanks

[@bonafidepirate]

@@Builditathome-Restoration That's awesome! Glad I could help!

[@paulbidwell6713]

looking good 👌

[@Builditathome-Restoration]

Thanks man🙌

[@samaeldamassa2963]

Is lean on lower jet, change for a bigger one

[@Builditathome-Restoration]

Yes your right!

[@kjve9009]

What tool do you use to take out the spark plug? All my plug removers are too beefy

[@ivoman7]

Make it leaner lower the needle raise the clip on the needle one notch If the sparkplug is black, she needs more air (less fuel) Make it leaner Run it with stock (user manual) jetting, unless you put on a new exhaust system Nice video series. But try to avoid paint on plastics. Instead sand and buff plastics.

[@Builditathome-Restoration]

Thanks for your help! I didnt paint the plastics they are brand new.

[@maze7_7]

I think it's too lean. When you turned off the choke, there was more air coming in, and it wanted to stall, so i would say it needs more fuel. Since you seem to be in a colder country, the air density is greater in cold weather, so even more air molecules per volume. Because you had a 158, try a 162 main jet and 62 pilot jet (96-97 default). I know it doesn't make sense for a >=98, but those bikes came setup very lean from factory and if the snorkel in the airbox was removed, there will be more air, and the previous owners may have done even more modifications. Also, read the service manual, it explains it all. Don't try to tune it a cold engine. On my 97, i couldn't touch the throttle (even with the choke on) until the bike was warmed up, or else it would stall.

[@bijandaniali5100]

I agree it seems it would be lean since it would only run with full choke. My xr400 has the same horrible bog when you snap the throttle open wide and fast. Also when you roll onto the gas into around wide open it will accelerate but there is a slight hesitation where it takes a second for all the power to kick in. My bike has a slip on muffler and air box opened up so I am going to try a bigger main jet . I also have another issue where when I stall the bike it will be a pain to start back up. But it is only if it is stalled. If I use the kill switch it fires right back up.

[@Builditathome-Restoration]

Thanks alot for your help i will try it all 🙌

[@maze7_7]

​@@bijandaniali5100Turning up the idle helps with the off-idle bog. You can also try a bigger pilot jet. The problem is that at idle, when you open the throttle, there isn't enough air speed/vacuum to pull more gas, so it gets too much air suddenly because you opened the carburetor slide, but it didn't pull the necessary amount of gas. Some bikes are more sensitive than others. A friend of mine has a 96 XR400 and he doesn't have a big issue with off-idle bog. If you can't tune out the bog, it may indicate you have other issues, like cam chain timing, leaky valves, valve clearance, decompressor cable slack, weak compression, leaks in air boots. I fixed mine by using a 140USD chinese copy of a Keihin FCR 39 Carburetor (not MX). It was a lot of work to get it working, but now it's a dream.

[@Builditathome-Restoration]

I put a 62 and 162 jet in it and now its way better runs without choke and drives good. It has a little bog so i will order 65 and 165 and than it wil be perfect i think. Should i only do a bigger pilot jet or also main jet to fix the bog? It has a aftermarket exhaust btw.

[@maze7_7]

@@Builditathome-Restoration you can try first adjusting the idle jet screw according to the manual at 1300rpm with the bike hot

[@Дэн.Ас]

Жиклеры побольше, винт качества отрегулировать, флейту с глушака удалить если есть, шноркель удалить. Ок