I've got a 87 , 18000 miles, runs great when the motors cold, but about 15 miles into my 20 mile trip to work the rpms start hanging out when i pull the clutch in, actually sometimes they will increase as soon as i pull the clutch in and hang there for a second or two and then slowly drop, most the time they drop within a second or two, but theres times that they will hang at a certain rpm for as much as 5 seconds. I know for sure that its not in the throttle cable as it snaps back nice, and with the tank up i can rev it up, and physically push the throttle block on the carbs all the way down and it will still hang up or slowly come down if the bike is warm. The warmer the motor gets, the worst it is, I was thinking that maybe the previous owner has car oil in it and it was something to do with the clutch, but it will do it in neutral as well. Any insight on what to check would be great. I've only had the bike for a month or two and probably put less than 500 miles on it and its been doing the same thing pretty much the whole time i've had it. Not sure on previous service records, but i plan on doing an oil change, air filter, fuel filter and plugs here soon.

 

Gas Tank Air vent hose kinked or pinched ?

Lift the tank and check

Of course those 87's had electric fuel pumps too ......... hmmm forgot that
I'd start there

 

Sounds like
1 Stuck choke cable
2 Carbs are sticking

 

Sounds like the carbs to me too. Lift the tank and take the tops off the carbs for a look before the hassle of taking the carbs off. Those '87 rubbers would be pretty stiff to get the carbs on and off.

 

I'm just going to roll with it as is for the rest of the work week, too nice outside and diesels too expensive to drive the truck right now, dumped a bottle of seafoam in the tank today hopin that might do something, would much rather not tear into the carbs this weekend, but if it comes down to it i guess thats what'll happen, thanks for the replies and any more help would be great

 

Sounds like a vacuum leak. When you are checking around the carbs, look to see if the all the vacuum ports have the screws in them. Check to see if the rubber boots between the carbs and engine are tight.

It could also be that one or more carb slides are not returning.

 

Also check the throttle cables for free play and the correct route the cables take from bar to carbie.
This happened to mine as well and it was the cable free play

Aussie Johnno

 

No offence Sprock, but the fuel pump will only supply fuel if one of the carbs asks for some.

 

Well I seafoamed it and it seemed to help, still not perfect, but alot better, I ended up building a pulling garden tractor this weekend and drinking way too much beer so the carbs didnt make it off the bike , In the next couple weekends im going to do plugs, oil and a fuel filter, and if its still hanging up at all after that the carbs will be coming off