Idling speed

82 Maxim 750 J... I have done all the carb checks and adjustments I can find on these forums but I can't get the idle speed to play nicely... On short runs say 5-6 mls its reasonably OK, The idle adjuster is wound right out so much so as the cam is not in contact with the adjuster , and ticks over at around 950, on a longer run like yesterday, (90 mls) the idle speed gets upto maybe 1300 - 1400 and doesn't want to come down in a hurry, I can assist it by letting the clutch out a bit whilst at a standstill (in gear) and it lowers it but not enough to get a smooth gearchange when I take off. I tend to think "air leak" but everything seems to be tight and sealed as it should, - what about trying a cooler sparkplug? any suggestions anyone?

 

to check for vacuum leaks, take an unlit propane torch and blow propane around your carb boots between carb and airbox as well as between carbs and intake. also do it around your throttle shafts and the four vacuum nozzles one on top of each rubber intake boot. if you have any revving while doing this it would be indicative of a vacuum leak in that area as the unburned propane makes it's way into the combustion chamber. the other reasons i've read are a way out of sync set of carbs(sync screws or pilot mix screws) and or an improperly adjusted float level. and of course valves have to be within spec.

be more specific about carb checks and adjustments you've done lately. have they been cleaned and tuned? is this a new problem to your bike or an old one you're trying to fix? hopefully some of this helps

 

When I bought the bike it was running reasonably well on the 25 mile trip home, but the PO said the carbs needed balancing as he didn't have the YICS tool, the idling problem started after I balanced the carbs (using a YICS tool), since then I stripped, cleaned, checked linkages, float levels, jets, needle valves, and all but adjusting the mixture and pilot screws, I sealed a few holes and a crack in the airbox, replaced the blanking rubbers on each intake stub/boot, I checked the valves when I got it - they where spot on. I'll try the propane test tomorrow (good idea - wish I had thought of it) - if this wind has dropped.

 

PS, But why just when the engine is really hot?

 

It should idle at 1050rpm; generally a "hanging idle" is an out of sync condition or a vacuum leak; but out-of-whack float levels can contribute as well.

 

I know, but I prefer a lower speed - it feels better to me, and I like my neighbours (loud pipes), Sync and float levels checked. Checking for leaks tomorrow.

 

Pilots too lean maybe?

Got any pops on decel?

 

Only started after balancing the carbs and didn't touch anything else, It runs smoothly with no pops or misses, good acceleration