1983 400 Maxim

[TheNinjaJeff]

I have a project Maxim 400 i am working on and have lots of questions. I should also probably say that this is my first bike ever.
With the help of my dad (master fixer of all things) we had it running a couple of days ago but there are some issues.
First off im missing the original air filter and was thinking of going to pods. the OD measurement on the air box side of the carbs is about 54mm. what are a good value pod filter to get?
Second, only the right cylinder (looking at it from the back) is really running unless the engine is revved up around 5k rpm, then the left one will kick in a bit. is that because of the uneven jet sizes in the carbs? (127.5 left and 120 right)
also the mufflers are pretty much crap so im thinking about going 2 to 1 and just getting 1 new can. what does the pod filters and new exhaust mean in terms of new jets and carb adjusments?
if anyone has ANY insight i would love to hear it.

Edit: also is there anyway to get the air box out without removing the engine?

 

[TheNinjaJeff]

 

[kindest]

I have a project Maxim 400 i am working on and have lots of questions. I should also probably say that this is my first bike ever.
With the help of my dad (master fixer of all things) we had it running a couple of days ago but there are some issues.
First off im missing the original air filter and was thinking of going to pods. the OD measurement on the air box side of the carbs is about 54mm. what are a good value pod filter to get?
Second, only the right cylinder (looking at it from the back) is really running unless the engine is revved up around 5k rpm, then the left one will kick in a bit. is that because of the uneven jet sizes in the carbs? (127.5 left and 120 right)
also the mufflers are pretty much crap so im thinking about going 2 to 1 and just getting 1 new can. what does the pod filters and new exhaust mean in terms of new jets and carb adjusments?
if anyone has ANY insight i would love to hear it.

Edit: also is there anyway to get the air box out without removing the engine?

air boxes should come right out like a puzzle. Any pods that are 54mm will work.
the " conversion would be the 2 1/8 to 2 1/4 ones.. Don't get them longer then 3" or there will no room. You will have to rejet the carberateur to bigger jets .. There is 2 jets a main jet and a pilot jet. I think I went up one size on both and I went pods and different exhaust. It involves literally unscrewing the jet and screwing a new one in. 2 second job really.

and i don't know why you would have 2 different jet sizes for each cylinder... there probably is a reason somewhere but beats me

 

[TheNinjaJeff]

the mono shock on the 83 sort of makes it impossible to just pull the air box out as far as i know.
ive read somewhere that the different size jets were due to the shape of the airbox and the second carb getting less air because of where the battery sits.

 

[16VGTIDave]

Welcome neighbour! Nice score with the Maxim!

It has been said here a couple time each week, since 2010, "Clean your carbs!". I won't bother repeating what has been well documented here, other than to say "Your carbs are still dirty, clean them again. Don't argue, just do it. You will see..." Okay?

If you want a stock air filter, you are welcome to the brand new one that came out when I switched to pods. Much easier than switching to pods...

To get the airbox out, you will have to drop the swingarm and shock out. Or take the airbox apart with a sawz-all. Either way, the battery and the rear brake switch will have to be mounted elsewhere. With that in mind, are you absolutely certain you want to start modifying a bike? It is difficult to undo most modifications. But, if you have the budget, the time, and another ride...

 

[TheNinjaJeff]

ya ive cleaned the carbs quite a bit already, ive been reading up enough to know that thats the first step.
do you have any hints about the jet sizes or why the left cylinder isnt firing?
i have no other bike, but i also dont have my license so right now i have all the time in the world.
i might be interested in the filter if thats all thats wrong.
however mufflers are rusted on the inside and need replacing anyways.

 

[16VGTIDave]

Unless the carbs have spent time in an ultrasonic cleaner or pot of boiling vinegar, you have only begun cleaning them.

I have an assortment of jets as I've been changing mine as the bike gets more modifications. But jetting will come after you have the carbs properly clean. It sounds like the pilot circuit is plugged on the one carb and that is why it isn't firing until you get the revs up.

 

[Lou Ranger]

Welcome to the Forum. If that's original mileage you should have a long lived bike once you get it running right.
Nice colour choice by the way!

... also is there anyway to get the air box out without removing the engine?

I am not sure if this technique would work enough for you to get at the air box, but it does get the engine away from the frame somewhat so might be worth a try before you start any wholesale wrecking:
With the bike on the centre stand and a jack placed under the engine, one can remove all but one of the engine mount bolts. Then the jack can be lowered and the engine will pivot around the one bolt and away from the frame.

Before you do any irreversible changes though, consider the advice repeated in numerous places in the Forum. Get it running properly the way it is first (perhaps with new exhaust if they truly are toast) before you start doing multiple modifications. If you do more than one thing at a time and then the bike won't run properly it is way harder to pinpoint the problem and fix it with mutiple inter-connected variables to consider.
Dave's Maxim does run really great on his pods and mine runs really great on the standard air box and filter. Take Dave up on his filter offer initially, to get it running perfect without any extraneous grief. Then decide what and how much (and maybe if) you want to tear anything apart.