Troubleshooting the 81 suzuki twin gs 400; Potential troulbe – JustAnswer

23 May 2015 | Author: | Comments Off on Troubleshooting the 81 suzuki twin gs 400; Potential troulbe – JustAnswer

Customer Question

Expert: Spencer replied 5 years ago.


You are dealing with not one problem but more like 5 problems simultaneously. I am going to try to attempt to break each one of them down in order to properly advise repairs on them individually.

#1 thing to do. Please, collect all of you tape, glue, and epoxy and immediately throw it all away. None of these repairs can be done with those materials and they are likely causing you additional problems.

Lets start at the top and go from there. Top/Gas tank:

-It is very likely that you have some debris in you tank. If you open you gas cap and see any rust (or any color other than shiny metal) then you cannot go any further before taking proper steps to rid of it. Rust will go right through a fuel filter. The rust particles are too small for a filter to block without blocking the fuel flow itself.

Even worse, rust has a tendency to coagulate in the float bowl of the carburetor causing a multitude of problems including sticking floats to pilot jets that clog quickly no matter how many times you clean them. There are a couple of ways to get rid of the rust. The best way to deal with the problem is to replace the tank with a new tank or a used tank that is clean inside and shows no signs of ever having rust in it.

Though this is the most effective way to deal with rust or debris in a tank it is usually somewhat expensive. The alternative is to coat the tank with a product called Kreem Coat. It is a three step treatment sold in most motorcycle shops (both dealer and independent).

It only cost about $45. The treatment is advertised as a permanent solution to rust and related debris in a tank but the reality is that the coating typically lasts about 2 years before it begins to flake off. How closely the directions are followed and how carefully the product is applied makes a big difference on how long it actually lasts. If you choose this procedure be aware that you will need to dedicate an entire day to deal with your tank.

The coating process requires constant attention every 10 to 15 minutes for hours on end. You will also need to remove your fuel tap, fuel level sensor (if you bike has one), fuel cap, and any other accessory installed on the tank for that matter. Use other methods to plug the holes during the coating process.

Problem #2. Fuel tap (petcock): If your fuel tap is leaking you will need a complete rebuild kit or a replacement fuel tap (new only). This repair is pretty point blank. If the fuel tap leaks not only can it cause the risk of fire and fuel flow issues but it will also cause vacume problems. (No Permitex Allowed!)

Problem #3 The fuel lines and the vacuum line from the fuel tap to the intake manifolds should also be replaced. Do not use automotive fuel line. It is not the same.

Motion Pro makes an excellent non-braided fuel and vacuum line selection specifically meant for motorcycles (available through most motorcycle shops). Use it! This is a cheap and effective way to eliminate fuel leaks and pesky vacuum leaks.

Problem 4# XXXXX: Your carburetors are still dirty. The fuel leaking out of the overflow is the dead give-away. Debris and rust in the tank can cause your carburetors to dirty up almost immediately.

Sometime so fast that you don’t even make it out of your driveway. Regardless of and debris the reason your carburetors are leaking from the overflow is because the float valves are stuck open or leaking and causing the carburetors to overflow. Outside of the leak, some of your running problems are directly related to the pilot jet circuit in the carburetor being dirty.

Remember, when cleaning carburetors it is not just the jets that need to be cleaned but all of the small passageways, fuel related adjustment components, and fuel valves. When the carburetors are cleaned the float levels will need to be set and the fuel/air screws set (2 turns out will work better as a starting point).

-Floats need to be adjusted without compressing the spring portion of the needle valve. This can be accomplished by adjusting the floats while the carbs are on their side instead of turned up side down. This will give you a far more accurate adjustment.

If the spring portions of the needle valves are not working then the valves need to be replaced.

-Fuel/air screws are adjustable on your carburetors. The EPA requires that all carburetors have this adjustment blocked to the public because when not adjusted properly it adversely effects emissions at idle. When the carburetors get dirty this restriction has to be removed so the fuel/air screws can be removed to be properly cleaned and serviced.

The fuel/air screws are blocked by small press fit aluminum or brass caps that must be carefully drilled and pried free of their sockets.

-You will need to inspect the rubber diaphragms on the top of your slides for any rips, tears, or holes. If there are any they will need to be replaced with a good used component or new. Upon installation of the diaphragms special attention will need to be paid in order to make sure that they seat properly.

It is extremely easy to pinch or fold the edges of these diaphragms which will cause running problems and will sometimes ruin the diaphragm by pinching small holes in it.

-Float bowl gaskets should be replaced. not Permitex’ed (Remember! Permitex is a BAD WORD in motorcycle land)

Problem #5 Intake rubber: The intake rubber needs to be replaced before you can even attempt to get the machine to run properly. Any leak, even a small one, will cause the engine to stall at idle and race above idle. It is not just the intake rubber between the carburetor and the engine that needs to be replaced but, the rubber between the carburetor and the air-box too. The air filter will also need to be in very good condition or new.

An old, or dirty air filter will throw the whole thing off.

Problem #6 Carburetor synchronization: The reason you are getting such wild readings has nothing to do with a malfunction of the machine or your gauge. The vacuum lines to the gauges must have restrictors in them to smooth out the pulse of the engine vacuum and provide you with an accurate reading. You will find that if you slowly pinch the lines that go tot the gauges that they will stop swinging wildly and there will be a sweet spot when they will also respond to changes in vacuum when the engine is revved, stalls, or the carburetors are adjusted and balanced (ideally).

Concern: Slack on your cam chain is NOT usually a good thing. Make sure that the adjustment is done precisely as the manual suggests. 4-mm of slack seems extremely excessive to me.

There are so many problems happening at once with this machine that you may want to take the bike to a shop and let them take care of the basics. From there you will be able to tackle the problems as they arise with much greater ease. The most important thing you can do if you do decide to tackle this entire project is to divide and conquer.

Do not try to handle all of the problems at once or even a couple at a time. Taking on one at a time and especially taking your time as you go through the steps will give you the best success. Motorcycles are built like a swiss watch in comparison to common machinery such as cars and need to be handled as such if you want to get then to run smoothly and reliably.

I imagine that few people have been avoiding this question due the multiple problem and multiple question nature of the repair(s) you are seeking. There are also MANY variables, some of which are outside of the processes described above. You may need to break this project down into smaller projects and questions in order for us to provide you with more specific and detailed instructions, information, and helpful advise.

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