83 xs 400 maxim tuning issues

[Kam1287]

So I've been snooping around on here for some time and can't seem to come across too much info on an 83 400 maxim.

I have full straight pipes and pod filters.
When I have initially went to straight pipes I had the bike running good by going up to 127.5 main jets. And playing with mix screws
Now that I have added the pods and switched to 137.5 main jets
Now I can't get past 8k rpm and also have a nasty dead spot around 4500.

I see a lot of things saying to raise the needle with the clip. My carbs don't have a clip and I'm not familiar with upswing washers to raise the needle. Also hoping some one to give me a base line to start messing with the pilot jets at.

Thanks for any help
Kam

 

[NewHavenMike]

That seems to be a big jump in jets. You should go one step at a time unless you really have an idea on what youre doing.. For this very reason, I have a collection of jets from 120 to 145! You need to get the right main jet before you move on to the next step of tuning the carbs. It took me a month or so of changing jets and getting plug readings and feeling out overall performance.

Your baseline should be factory settings.. But since you have the 137.5 in, get a plug reading. Post pictures of the plugs and you should take notes every time you change jets.

BTW- the pods and straight pipes will make it quite a bit harder to tune but its not impossible...

You may not get an optimal tune, but one that will just work

 

[Kam1287]

You have stated my exact problem I get good plug readings lol. I'm in a terrible predicament. I don't know where to go except pilot jets or new cards where I can move the needle clip. I'm confident in my ability to tune carbs. Have many times. The only thing that makes my self second guess me is the dohc. That's where I'm at a lose. Have built Manny dirt bike quads and cars. Which is why I'm looking for a base line.



I'm at 137.5 because the bike wouldn't run on the 127 And it ran on them( the 137.5 is what I had in my tool box ) after a hast decision to make a custom batt box and said F it I'll deal with it

 

[Kam1287]

And yes I'll post plugs but considering it's been below 3 here for the past two weeks it's not gonna happen too soon. I'll pull my plugs and post what they have shown from running it al summer.

Once again thanks for any input

 

[NewHavenMike]

Id put the needle back to the middle position and go down to a 135 main. What plugs are you running?

I put aftermarket exhausts on my bike yet i still had to go down on jets.

My bike had 135 mains stock and now im running 132.5.. now i have K&N filters that were made for my bike so this Spring i will have to tune it again. Lickily i have all the jets i would possibly need.

One more thing, get authentic Mikini jets from Jets R Us. The real ones are machined differently from aftermarket ones and they just work better.

 

[Jeff0133]

Are the Pods directly on the carbs?..
It Will cause issues with turbulence.
Mount the pods on the intake rubbers from the item airbox, it will smoothen-out the airflow thus helping with tuning.

 

[Kam1287]

Are the Pods directly on the carbs?..
It Will cause issues with turbulence.
Mount the pods on the intake rubbers from the item airbox, it will smoothen-out the airflow thus helping with tuning.

Yea they are directly on the cards. I will have to try that out Don't know if I keep the rubbers. If not I'll have to make somthing up

 

[xschris]

Using foam uni filters will also help. What type of filters do you have? http://www.xs400.com/threads/diy-modded-stubby-h-pipe.12406/#post-132584 Good thread for DOHC bikes going to pods.