Jetting help on 78 cb400t w/2>1

[illking]

I have a 78 cb400t, ive been riding it around on pod filters with stock jetting and it runs pretty much the same. I just put on a mac 2>1 pipe and obviously It needs a re-jet. If there are any guys on here running the same set up or gurus that have good insight please share it with me.


Ive only jetted my moped and thats a pretty easy one as I can make all adjustments without pulling the carb off the bike. Hopefully with your help I can get it jetted right the first time around Thanks for the advice.


1978 CB400tII
pod filters
mac 2>1 pipe
Altitude & weather: Los angeles, CA

 

[hurley209]

Sweet bike dude, I'm really diggin it!
What I would do is first see how it's running, rich or lean, then after you determine which way you have to go (up or down in size of jets), order a few jets sized up or down and try them out going up or down in size, and adjusting your mixture screw. I'm guessing that with the better flow and reduced backpressure of the exhaust system you will have to go a tiny bit higher in size if your mixture screw doesn't solve it.
I wish I could tell you a specific size but it's
Mostly trial and error, but hopefully someone out there has the same bike and set up and can be more specific.

 

[illking]

Thanks hurley, Its defiantly running lean. I ran it very shortly and lots of popping and backfiring. Actually my carb boot wasn't 100% tightened down and it blew one carb outta the boot. This was at a stoplight in front of traffic, kinda embarrassing haha. Hopefully some cb400 guys with similar setups can give me a ballpark of where I should be at otherwise on to the guessing game : )

 

[Stuart Hagerman]

let me know where you end up on the jetting please... I am going to run a 2 into 1 mac pipe, and pod filters on my 1978 cb400TII too! I have found some info on this site. I will post what I have found

 

[hurley209]

Thanks hurley, Its defiantly running lean. I ran it very shortly and lots of popping and backfiring. Actually my carb boot wasn't 100% tightened down and it blew one carb outta the boot. This was at a stoplight in front of traffic, kinda embarrassing haha. Hopefully some cb400 guys with similar setups can give me a ballpark of where I should be at otherwise on to the guessing game : )

haha, that sucks man, but hey could happen to anyone, lol.

what size main jets are you running now ? did you pull the plug and take a look at it?

 

[Stuart Hagerman]

pods are working well... Im pretty sure I running 88/135 for my jets.

I think my float got stuck this weekend. It wasn't running that well and then when I got home I was leaking gas out of the over flow tubes. It was also 108 in the Valley here in So Cal.

One question for someone: My exhaust wrap on the right side is turning white from being so hot. My guess is that the plug isn't gaped right. either that or the timing needs to be adjusted. Anything else I could try?

 

[longhorn717]

You ever get this solved am looking at running pods and a x-pipe under my bike. would love to know where you got on this.

 

[crazypj]

same as 360, jet for top end and it runs rich mid range, jet for mid range it's lean top end. you can compromise both settings but won't get it right with jet changes