vibration problems

[JOLLY]

I have a 1986 GL 1200A, has anyone had vibration problems that range from 1900 to 2200 rpms up or down, and in neutral or in gear (all gears) going down the road. It is a hard (rumble vibration) only in this rpm range and a loss of power. It kind of feels like a hard down shift, is the best way I can explain it. in all other rpm ranges it runs good, strong NO power loss and NO vibration. this is a new problem about 5 weeks now. ANYONE?? Thanks Kevin Jolly

[jdvorchak]

Hello and sorry about your problem. I've owned 3 1200 and none vibrated. The only thing I can think of would be that you are dropping one or two cylinders at that "mid range" throttle setting. Without any history of the bike it's impossible to help you diagnose.
A couple of questions should help a little.
1. is this a new to you bike and you have no idea of any maintenance performed?
2. Is this problem something new or always been there?
3. OEM air filter or aftermarket?
4. Spark plugs new or a million miles on them?

first thing that comes to mind is a mid-range stutter that could mean that one or more of your carb slides are sticking. I would be surprised if it were ignition related. The 1200 uses electronic ignition and it's pretty fool proof and not adjustable... well until it the ignitors or the ECU gives up the ghost. But when they do that it fails 2 cylinders and would not give the symptoms you are describing.

[JOLLY]

What is the best way to check if they are sticking? Is there a lub or oil that will help them? them sticking is my thought as well. I took the carbs out and checked them. I found, one low idle jet blocked, but it did not stop the vibration. Idles much better now. I wonder should I sand the slides with a very fine sand paper? or what is the best thing to do for them?

[salukispeed]

Cleaning the slides could be ok but sanding them is likely a bad idea. The 1200's have diaphragms instead of piston operated slides and rarely fail. Once in a while a diaphragm can get a hole or the spring can be caught out of place if removed and will cause mid range issues. I have seen the rubber diaphragms out of the groove and leak but usually they are pretty rock solid on a bike that was running regularly. Keep any and all carb cleaners and solvents away from these rubber diaphragms. float levels can get disturbed. but you may want to look over the ignition parts like wires and plug boots and plugs as they can fail too and be intermittent issues to pulling and comparing the plugs may point to you to something also. start simple and then you can go to the hard stuff.

[JOLLY]

thanks for your feedback, I am going to pull the plugs and hopefully they will point me in the right direction. And put new ones in

[Lucien Harpress]

Does she seem down on power in those RPM ranges? Does the motor sort of "surge" once you get out of the problem area? Or does it pull cleanly and smoothly all the way from idle, and just vibrate while doing so?

Dropped cylinders are the only thing I can think of. An "easy" explanation is blocked low speed idle jets and/or sticky slide, but electrical is easier. Check that first, then move on to carbs later.

Has the bike always done this? Or did it run fine at some point, and start vibrating later?

[jdvorchak]

The only way to really clean the slides, that won't cause damage, is pull them out carefully and use wadded up aluminum foil on the slide sides and interior of the carb body where the slide fits. You can remove them, on the 1200, without pulling the carb rack. Just the 4 retaining screws on top. There will be a long spring in there and the thin rubber diaphragm. Carefully lift the diaphragms up and slide the slide out. You are safe using carb cleaner on the slide body and the carb body. If you get some carb cleaner on the rubber parts it may make it swell a little and difficult to get the diaphragms back into their grooves.. Don't fret. Let them dry about 10 minutes and they will regain their original shape.

[JOLLY]

ok everyone! this vibration just has to be coming from the carbs. I am going to pull them out one more time. I can have them out in about an hour. I have a GL 1200A so I must pull them to work on them. I will pull them tonight and start tomorrow fresh. I will let you all know in the morning what I find. thanks to everyone.

[JOLLY]

OK EVERYONE CARBS. OUT MUST ADD-MET BEST TIME YET. 45 MIN. FROM START AT FIRST BOLT. TALK TO EVERYONE TOMORROW.

[ericheath]

I'm down to three minutes and change. Keep working.

[mrtwowheel]

I don't know about your area in Texas, but if you were in the salt belt like I am, I would say, check your frame for rust damage, especially around the motor mount areas.

Scott

[fish]

it is only a 300 rpm range
just drive around it

[todd54219]

Have you done any kind of work to the bike before the issue started. I have found that if you have done something recently, then that is the place to start. Go back over the area and system you were working on.

Good luck and keep us informed.
Todd

[JOLLY]

OK everyone, there was a hole in one of the diaphragms. THANKS TO EVERYONE THAT POSTED THERE IDEAS. The foil really helped to. Kevin

[jdvorchak]

You can actually patch that hole. I've done it before and 2 years and still holding. I used a small piece of the Harbor Freight 5 mil rubber gloves (blue) and high temp fuel resistant RTV got from O'Reilly's. Just smeared a little RTV on the glove patch and stuck it on then let it sit overnight. The 5 MIL rubber gloves are surprisingly strong and very supple. Of course your diaphragm must be clean and dry.