rear brake sticks and idle fluctuates...

[thrashin88]

Hey everyone, i got 2 questions on a 1980 gs750 that i got for $100.00. the bike was chopped into a hardtail and the airbox wouldnt fit so i was stuck getting a dynojet kit and running pod filters. now the bike seems to run right having full power through all the gears but the idle fluctuates. i will start the bike and set the idle to where it sounds right and the go drive it for 10 minutes and when i stop it will be idling around 3000-4000. ive sprayed starter fluid on the intake boots and there doesnt seem to be any leaks but i never had the carbs synched, could this cause the problem?? if not any ideas?

question number 2: the rear brake sticks, and i know that it didnt before it was hardtailed. theres one thing that could potentilally be the problem. the rear brake cylinder was mounted crooked so the rod connected to the pedal pushes up into the cylinder crooked. not by much and it still goes in and out just fine so i dont know if this could be the problem, i dont know much about brakes. its possible they just reassembled the brake off a little bit. thanks for the help, these are the last 2 problems im having

[almarconi]

If the carbs are not synced, the bike more than likely will run like crap. When was the last time the carbs were cleaned? Have you checked the fuel level in the carbs. Carbs that are not set up properly and/or dirty will cause all kinds of drive ability problems.

When you say the rear brake stick, I assume you are referring to the caliper. Have you taken apart and cleaned the caliper and master cylinder? If the rod is going into the cylinder crooked eventually the the seal inside will start to leak. Did you check to see if your rotor is warped. You should be able to check the run out with a dial calipers.

[psyguy]

you need to set the idle when the engine is fully warmed.
if you then can't start it (when cold and with the choke) you have a problem with the carbs (either dirty pilot/choke circuits or wrong mixture ratio).
but carb sync is in order nontheless.

if the piston in the rear brake master cylinder moves freely in/out then most likely the caliper needs rebuilding. you can try take the caliper off, then apply the brake LIGHTLY and see if the pistons come out and then retract as much as they came out. if they dont - the caliper needs rebuilding.

[thrashin88]

alright thanks, ill look into it. one more question... being laid off and all theres no way i can afford to pay someone $80 to sync the carbs but i know how to make a homemade one fairly easy. my question is this... where do you connect the four hoses to on the carbs? ive never done it, i have no idea. and do homemade ones usually do the job or is it really worth the money to pay someone?

[psyguy]

do a search here for home made carb sync tool - it's been done many times with good results
you connect it to the openings on the intake rubber boots between the carbs and the engine

[tejasmud]

On the rear calipers, did you replace the pads?

If not.

I think I read somewhere the pads will sometimes wear uneven or become tapered, front to rear or rear to front, not putting them back the way they were before might cause some sticking/binding issues with the caliper pistons.

My rear pads were not the same thickness after removal, didn't mark them before I pulled them, but new EBC pads were only $20-$25 from Z1. Or flip the pads might work as well.

[Kitten Tooth]

I know that a 1982 GS300L and a 1980 GS750 are two different bikes all together,
but try disconnecting the rectifier when it starts to idle high.
My rectifier is malfunctioning and when I disconnect it, my bike idles way higher too.

If the idle doesn't change when you disconnect it its may be a bad rectifier.

[thrashin88]

huh. well on my bike the boots have no intakes. just a piece of rubber tube, one end clamped to the engine and one to the carbs. i see what you mean by some photos ive looked up and mine dont have that but ive heard the 1980 gs were a weired year. so either someone ghetto rigged it or this bikes just different. any ways around it or any ideas? and what screws do you adjust while doing a carb sync? thanks

[psyguy]

and what screws do you adjust while doing a carb sync? thanks

look up the Carb Cleanup Series link from the GSR homepage - there's a pictorial

[psyguy]

huh. well on my bike the boots have no intakes. just a piece of rubber tube, one end clamped to the engine and one to the carbs.

i think there should still be an intake bolt, in front of the rubbers, no?

[almarconi]

There is nothing weird about the 1980 GS750. In front of the carb boots is a screw. Remove it and screw a 5mm adapter into it. You attach your vacuum gauge sync tubes to the adapters.

Where are you located? I would suggest finding someone who has one and see if you can work something out OR just pay a shop to do it for you.