81 maxim 650 Idle problem?

I just got a 1981 Maxim 650. It starts up, however, it has problems staying running until its warm. But wait....theres more

as warming, it seems to run at 1500 rpms, then as it reaches running temp(I assume) the idle speed increases to like 3-4k automatically..(In other words, I do not touch the throttle at all.).

I thought hummm could it be the throttle cable getting stuck? I tried to pull the throttle back a little to see if it snaps back(while running) and it will just go back to the 3-4k rpms. I then turn the bike off and pull the throttle back and forth several times, start it back up and it runs at 1500rpms for about 10 seconds then moves back to 3-4k again.

What Do you think this might be? What would you suggest I try first? The bike has been maintained byt the previous owner, who started it and ran it as much as possible.


I did notice a throttle/idle adjuster behind the carberator that can be reached ... it is a single (what looks like) plastic knob that seems to increase or decrease the idle speed. That is the only adjustment I made but it does not seem to matter where I set it once its warm...the idle speed increases to 3-4k by itself.

Any insight is much appreciated!

Thanks,

Matt the newbie.

 

Check your choke to make sure it isn't on. There is a fast idle once the bike warms up a bit if the choke is on somewhat. Make sure it is released and that you have play in your choke cable. You should also check to make sure the choke is actually open all the way and not sticking. The idle adjustment is a knurled knob located between carbs 2 and 3 and you kinda need small hands to get to it when the engine is hot. Counterclockwise should turn the idle down and clockwise should increase it. The bike should idle around 1000 to 1050 RPM when warm.

 

Thanks, I will check it out.

 

I checked to make sure the choke is not getting stuck and I see that it is reseating all the way down when turned off and there seems to be play in the cable. I turned down the idle adjustment a bit to see if that does it. I will let it run and give you an update.
Thanks,

 

Well, I warmed the bike up. and adjusted the idle adjuster. It seems to seek a bit as if its not getting enough fuel sometimes.....that is when I adjust the idle around 1200rpms If I adjust it to 1050~k it will stall eventually.

I added some seafoam to the fuel to see if it helps longterm. I then took it for a ride around , after I got back it was idling at around 3k which was much higher than when I left....

The symptoms dont seem to be consistant to this novice.

Matt

 

It's possible you have a vacuum leak. Check your plugs and see what they look like. There is a chart available from NGK which should help.

 

this could be a vacum leak. make sure your intake manifolds are not cracked and that all your vacum ports have plugs on them, if your running CV carbs take the top caps off and make sure there arent any holes on the diaframs.