Tach trouble

[Rider2898]

I'm a new rider and my 1981 GS750 is my first bike. I've had a few days to ride it and I really enjoyed it, but it is having issues. First off I was riding to school and the tachometer quit. I don't know how the tach hooks up to the engine so I don't know if this is anything serious or not. i do have the maintenace manual but I could not find out how to repair the tach. The charging system also isn't working. I believe the alternator is working because I road for a good 90 miles and the bike never quit. It bogged down more and more each time I started it. How ever when I jumped it with the car it started right up. So a couple of days later I tried to do some trouble shooting, cleaned some wires ect. Then took it out on the road to see if my efforts made a difference. However the bike got about 2 mile down the road then it just quit and I haven't been able to get it started again. The bike hadn't been riden in 5or6 months and it did have gas in it the whole time. Anyhow, any advice would be greatly appreciated. Thanks.

[mriddle]

Welcome to the forum ..

Some of the other (wiser) members will jump in and help with your issues, but they are common in these old bikes. On the bright side, the bikes are very reliable once the charging system is repaired.

I think the 1981 GS750 is a beautiful bike.

Can you post up some pictures for us ?


Mike

[tkent02]

If it just stopped suddenly, the tach cable probably broke.
Charging problems and troubleshooting are explained well in The Stator Papers on this site.
Use the search function, ask questions, You can get it working right. These are simple bikes, all these problems are simple by themselves.

[nert]

Cables may break, only if there are other tach problems. Like bent, smashed cable, or seized meterhead. Look for the easy stuff first, tach cable may have just come un-done from the back of the RPM meter, or at the engine.

As far as haven't gotten it started?? It won't crank? It cranks, but won't fire? Did you run out of gas?

[Steve]

First of all, let me throw out a quick welcome before BassCliff finds you and give you the "official" welcome. \\/

Tach problem:
Follow the tach cable from the back of the tach, you will find that it goes to the front of the engine, near cylinder #3 (they are numbered from clutch hand side to throttle hand side). See if either end came loose. Unscrew the cable from the back of the tach. Start the engine, see if the cable is turning. If not, remove the other end from the engine, see if the cable is broken. If the cable is good, it's likely the gears in the head that drive the cable, but that's not very common.

Charging problem:
Use a volt/ohm meter to check the system. There is a good troubleshooting procedure found in the garage section of the forum. You can find it by clicking on this link. First, measure the battery voltage with the bike not running. Start the bike, measure the voltage again. If it's not higher, you have problems, but the troubleshooting guide in the Stator Papers will help you find them. Basically, there are three wires (likely yellow) coming from the left side of the engine, they emerge near the starter. They go to a rectifier/regulator assembly which rectifies the AC produced by the stator to DC, then regulates it to about 14 volts to charge the battery. Make sure all the connections are clean and tight. There are tests given in the Stator Papers to determine the condition of the rectifier, but the only test for the regulator is to run the bike. It is also very beneficial to have a dedicated ground wire that goes from the r/r straight to the negative terminal of the battery. This wire alone has fixed many charging problems.

Oh, if you have to jump start the bike, make sure the 'donor' vehicle is NOT running. The way the bike is wired, it will try to regulate the output of the car's alternator, usually unsuccessfully. It also helps to put the bike battery on a charger to bring it up to full capacity, rather than quick charge connected to a car. Good chargers worth getting are about $30 or less, but look for one that says "charger/maintainer". These can be plugged in and left on for months, if necessary.

Other possible problems:
Even though you say there was gas while it was stored, the carbs can likely stand a good cleaning. If the gas was not treated or drained from the carbs before storage, some of the gas might have evaporated from the float bowls, leaving a nice sludge that tends to gum up the little passages in the jets. A few hours of detailed cleaning spread out over several days will do wonders for how the bike runs. As luck would have it, there is also a good carb-cleaning guide in the Garage section. 8-[ Follow by doing a bench sync to get the carbs close to each other, then do a dynamic sync when the carbs are back on the bike. Ask questions, we will help when you are ready.


.

[spyug]

Welcome to the forum, now start reading!

All the information you will need is here. You will need to read up on the charging system ( stator papers) and carb cleaning (carb cleaning tutorial) first

BassCliff has some good info on his site as well and I'll ask him to give you the link when he greets you officially.

If there has been old gas in the bike you should drain that out and replace it with fresh and I'd recommend adding some Seafoam which will help stabalize the gas and flush out the crap that will likely be in the carbs. This won't fully clean the carbs but might keep you running a little smoother until you can pull them. Also The tank will likely be rusty and that will need to be delt with in time but for now you should put on an inline fuel filter to keep crap out of the carbs.

As far as the electrical system, you may not have a bad stator and the charging system maybe ok so don't panic until you get into it. A lot of bike problems can stem from a) bad or corroded grounds and connections b) bad battery.

You need to do a few simple tests and you will need a digital multimeter and voltage probe and it would help if you have a 1 or 2 amp capable trickle charger.

First, clean your battery terminals and the negative and positive cables from the battery (each end). Corrosion will stop proper electrical connectivity so if you see any corroded connections clean and fix them.

Now check the battery. First ensure that the fluid in the cells are at or close to the full mark. If not top up with some distilled water. Using the multimeter on the DC scale check the voltage across the terminals. If the battery is good the resting charge should be better than 12.5 volts more like 12.7 or abit higher. Put it on the trickle charger and check it again after a few hours. it should go up abit more. If not leave it a full 12 hours and check again. If it doesn't go up then it may be suspect. If it is good the charge should stay in the high 12s for at least a few weeks. If the battery takes a charge and drops off quickly in a few hours or less it is likely on its way out and should be changed.

For a quick check of the charging system you will need to get the bike running and able to idle. Once it is warm have a helper rev it to between 3000 and 3500 rpm and using your multimeter again check the voltage at the battery terminals. Voltage should be showing between 13.5 and about 14.5 volts. This is correct charging. If less than 13 and or more than 14.5v you have an issue to delve into and a full read of the stator papers.

This is just some quick and dirty testing but it will give you an idea of where you're headed.

Working on bikers is not hard but can be a bit frustrating so take one thing at a time and work through it. Read and ask questions. We're here to help.

Enjoy the bike and good luck with it.

Cheers,
Spyug

[jbs80106]

Lube your cables annually

atleast.

Maint manual lists cable lubing as part of the annual spring maintainence. maybe more often if you live in a dusty area. Cables to lube are Tacho, Speedo, manual says to lube clutch and front brake cables too in order to avoid brakeage.

Dealer can sell you a new tacho cable for like $12.00 or so.