Maxim Hard Start

1982 Maxim. Carbs sonic cleaned and kits installed but I did not replace the idle screws (they are still under the factory seal). 4 into 1 header with stock airbox but UNI filter. I did bump stock main jets up 2 to 122's. Idle jets still at stock 40. Issue is it is hard to start. It will chuff and chug but not come up to idle. I do have better luck when I use full choke and roll on about 1/8 of the throttle. Even then I have to hand throttle it until it is warm before it will stay on idle.

Once warm, it will light right up even after sitting an hour. Runs super on the road with no hesitation or flat spots at any RPM. I am thinking that I need to replace the original idle screws and maybe adjust another turn or so out? I welcome any input. Thanks.

 

had the same hard to start when been standing and cold.i went thru all the electrical connectors and cleaned with electrical cleaner and worked in and out a few times and i mean ALL connectors(tci,coils,and all those in the headlamp) and now starts on the button cold.

 

Hmmm...that is an interesting approach. I do get some light flicker when revved so it wouldn't hurt.

 

first let it warm up on choke as it is an enrichment circuit and not a true choke. its function is to warm up bike.
anything but stock paper filter can cause problems . you did rejet for that.
do clean connectors proper voltage to coils is key. do a voltage drop test on battery when pushing starter button see how low voltage drops.
if you did not remove the mixture screws youcould still have crud in the pilot jet circuit this is what the bike runs onwhen started and idles.
you could have vacuum leaks at throttle shaft seals. which would make it hard to start bike as well. they are 30+years old

 

Good comments. After I get it started doesn't seem like I can keep it on choke for very long. Maybe 20 seconds before I have to start pushing it towards off and make it run with the throttle. Is that pointing to the idle circuits? That and the shaft seals are the only things untouched. I did do a drop test last summer and it seemed OK but will check again. Thanks for the feedback!

 

with choke on the rpms will start to climb as you close the choke the pilot jets are there to take over to keep bike running .
the uni filter is often a problem because of the increased air flow. several members had them and when they installed oem paper filters the issues went away

 

Uni foam filter on my XJ700 was a problem. When I bought the bike it was bone stock except for the foam filter. The foam filter flows a lot more air, so it has a tendency to lean out the bike, which is especially a problem starting cold. My advice is to get the correct paper filter, reinstall the correct jets an tune with a colortune plug. I think you will like the results. I got easy starts, good idle, smooth running and a substantial increase in mpg.

 

Well now I have a problem with this statement. Nothing to do with the wider airbox Vs pods argument, but think about this.
Agreed the std filter will generally be more restrictive (but this is by no means guaranteed) than a k&n panel or pods.
However, if you know anything about air restrictors vs airflow vs consequent pressure drop, you will know that at little (relative I know) flow there will be little or no restriction. Hence little or no pressure drop. So, to get to my point, at start-up, the filter has little or no effect.
As rpm and load increases this will change, increasing as they rise.
There may however, be a flaw in my argument, which I have yet to test, and that is the enrichment method on these bikes is not a choke as such, so the enrichment may need this added pressure drop. However, the enrichment circuit feeds in downstream (low pressure side) of the butterfly, so provided this isn't opened, there should still be plenty to make it work!
Phew, sorry to make that so long winded.

 

no air restriction means more air affecting air/fuel ratio resulting in very lean mixture flowing into cylinders.


with mixture screw never being removed or readjusted that may be the issue pull the caps and add a 1/8 to1/4 turn this will give you more fuel on start up ,you should not have to use throttle at all to start bike.

if this does not resolve the issue you could try a oem filter or restrict the air flow into the air box .
if there is not enough vacuum created inside the throats of the carbs fuel will not be drawn up the enrichment tube from carb bowls.

 

How so? With the throttles closed, assuming the mixture is set correctly, and the throttles are where they should be, there will be one hell of a suck on each intake stroke. As I said, think about it.

 

it is a combanation of vacuum and venturi effect. the butterflies are closed but not completely as there is a gap from diameter and offset from syncing.

air filters set the restriction by the surface area and density of material used.

think of it this way get a gallon of water put a 1 foot hose 3/4 id in it and suck on it how much water do you get in your mouth , use a straw and repeat the process.
you will notice that with the straw you got more water with less effort .
even better test put hose into water and blow across the hose did water rise if you do the same thing with a straw you will see the water rise into the straw with less effort.
now with the carb you are sucking air across a tube that feeds gas into your motor the bigger the air flow from the filter the harder you have to pull air to get the same fuel flow.

the draw of air from the cylinder pulls in the air through a filter and over jets,, less restriction(more air) from filter less gas is drawn up jet making a lean mixture. this is due to less negitive pressure in the carb pulling fuel .

 

I think the posters problem lies between not removing his mixture screws when cleaning his carbs and his less restrictive air filter. which is why he has to use his throttle to keep/get bike running when first starting .
possible he has little or no fuel flow from his pilot(s)


opening his throttle allows more of that inital pull from the cylinder to react with diaphram getting him fuel from mains.
think of how a syringe works with and without a needle on it . the butterfly would be the needle

there aer 2 types of lean one where the fuel does not burn properly giving you sooty plugs the other is where fuel burns so hot it melts your piston.
I do not want to jack this thread any more than this . you could start a new thread on how and why.
it is time to help poster solve his problems

 

Good thinking.
Retromoto, remove mixture screw covers and adjust mixture screws to correct mixture. I expect this will mean you will have to close down your idle screw ( and rebalance carbs probably, worth checking anyway). Once you do this any change of air filter will not matter two hoots, the vacuum pulled on the closed throttles will pull sufficient fuel from the enrichment circuit.

 

Partially correct. Anything other than a paper filter will cause the machine to run too lean (she was jetted lean to begin with, even the idle jetting). Airflow affects slide rise, which afects fueling just as much as jetting does. We've gone through this dance since long before I became a member here.

 

Just for grins, place a piece of cardboard over about 1/2 or a little more of the foam filter and see if that helps.

 

Sorry I have been out of touch for awhile but the debate is good. Some of the same thoughts I have been trying to rectify in my head. So I have removed the idle screws after noting the turns-in (2 5/8, 2 2/3, 2 7/8, 2/34). The turns-in had to have been factory set as the seals were intact. Idle circuits have been cleaned and blown down. All are free. My plan at this point is: #1 - turn out idle screws 1/4 to 1/2 turn past factory settings and try again. #2 - try the cardboard over the filter trick. If #1 works I will adjust further using the Rising RPM method. If #2 works replace the filter (BTW - mine is a stock filter can with the paper removed and replaced with UNI foam-see pic). If neither work then it has to be the butterfly seals. Additional thoughts?

 

I would go with #1, see what the mixture screws settings need to be for correct idle, and what that does to idle speed screw setting. Obviously needs doing hot.
Then you will need to let it cool until you can try starting using the enrichment circuit.
You have checked and set float levels?

 

So last night I tried starting with idle screws out another 1/2 turn, 3/4 choke, no throttle (see pic, does 2 1/2-ish out seem about right for factory idle screw settings?). Huffed and chuffed but would not start, exacerbated by a starter clutch that is starting to go. Came back 20 minutes later, 1/2 choke, no throttle and it starts! But needs a little help from the throttle until warm. I am full of WTH thoughts and then notice the lights are flickering. So I pull off the $100 Rick's reg/rec, pull out the original, clean the connections and install it. Of course, it starts at the touch of the button because it is warm but no light flicker. We will see if it starts cold tonight but what are the chances the reg/rec issue was interfering with cold starts!?!

 

So, much progress last night. After removing the Rick's reg/rec and installing the original it now starts after a few turns. I do have to jack around with the throttle to keep it running but I did not have the air box connected (got tired of putting on the box-to-carb boots). What a fricking wild goose chase. The Rick's reg/rec was new last fall. Thanks to all for sticky with the thread.

 

that's the same setup i have only two layers of uni foam, 4/1 pipe
did you put new o-rings on the mixture screws? your butterfly seals are probably shot, just because their old.
as soon as you give it throttle it pretty much defeats the enrichment circuit at starting rpm.
never did get it perfect with the mac's megaphone muffler, put a supertrapp muffler on it and adjusted with that
i start at 2 3/4 out and am happy before i get to 3