1992 Suzuki DT 40 Carbeurator

[DrewR]

My engine runs fine sometimes, and fails others??? My mechanic has pulled the carb, adjusted it to correct settings, reinstalled, and is still having the exact same issues. He seems "certain" that the carb is causing the engine to spuratically run improperly as he has verified the fuel is being delivered to the carb. He is reccomending that I buy a whole new carbeurator as he is "stumped on this one". Is there something that he could be overlooking? Any advice is greatly appreciated. Also, where will I be able to find the best deal on a new/reconditioned carb should I choose to go that route?

 

[DrewR]

Re: 1992 Suzuki DT 40 Carbeurator

Anyone out there have an idea?

 

[jim dozier]

Re: 1992 Suzuki DT 40 Carbeurator

No magic bullets. He could be right or he could be just grasping for a solution. Has he tested everything else? What about the ignition system? Has he ruled out everything else? Maybe its fuel related but not in the carbs. If it was a faulty carb it's likely that it would run crappy all of the time, they don't usually fix themselves. Check your fuel system from the tank to the carb for leaks, dirt, water, clogged filter, stuck anti-syphon valve, etc.<br /><br />These carbs are pretty simple. They usually fail when they get dirty, which is why we clean them. Unless somthing broke inside which can't be replaced I am betting the problem won't be solved by a new carb. Just because fuel is getting to the carb doesn't mean the carb is the problem. What is the condition of the fuel when it gets there? Is it full of water or dirt or air bubbles?<br /><br />When you say it runs OK some times but not others, be more specific. Does it suddenly start to run poorly like it lost a cylinder or does it just start to run rough? At all rpms or just low medium or high rpms? The devil is in the details. You will get more responses if you give more information. (That applies to the mechanic too).

 

[DrewR]

Re: 1992 Suzuki DT 40 Carbeurator

jjmd, good tip...sorry about the vagueness. So far as I know, he feels that the fuel delivery is working properly b/c after the engine dies, he has pulled the carb and there is still fuel in the float bowl. Also, he has pulled the plugs after the engine dies and states that they are dry. He did dump out some sediment from the fuel filter but does not seem believe that there is any sediment in the line after the filter. A little history here. First the engine was VERY difficult to start/idle. We replaced the manual choke lever (b/c it was broken and not working at all) and presto....the engine starts much easier and will stay cranked at idle (even in water which it would not do before????) However, once that small repair was made, the top end (higher RPM) running ability of the engine which functioned flawlessly before was now gone. So basically, if you gunned it or went to high RPM it would just die? He is absolutely certain that he has the adjustments set correctly. Next, If he has tested the ignition, he hasn't informed me of it....so I'd venture to say that he has not. When I say "runs poorly", I mean that it doesn't run at all at times...and other it runs like there are no problems at all? After the engine does die....it is extremely difficult to get cranked again. Personally, I am at a total loss on this one?

 

[flatsfisher57]

Re: 1992 Suzuki DT 40 Carbeurator

did this motor sit for any length of time how many hrs on it,as the motor starts to die did you pull the choke to see if it comes back to life,did the mechanic decarbon motor

 

[DrewR]

Re: 1992 Suzuki DT 40 Carbeurator

I believe that the motor sat for a while, but the mechanic went through it pretty thouroughly. I am unsure if he decarboned the motor....I'd venture to say that he did not. Number of hours....your guess is as good as mine but my guess is that it has quite a few. When I tested the engine....when it would start to die, if I even touched the choke it would kill the engine faster. That's what I know....what do you think it could be?

 

[flatsfisher57]

Re: 1992 Suzuki DT 40 Carbeurator

if you pulled the choke in it gives it more fuel so it doesnt sound like a fuel problem but make sure float is adjusted,fuel pump is good and try a different gas tank also bypass the plastic filter housing after time they crack and air will get in,then I would do some test on the electronics on motor like spark check and stator check,what do the plugs look like

 

[DrewR]

Re: 1992 Suzuki DT 40 Carbeurator

The plugs are in good condition. The mechanic states that the plugs are "dry" when the motor dies on it's own. He says that he has the float adjusted properly. The spark on the engine is fine. As far as the stator, I have not asked if he has tested this yet....but I will. He seems very certain that fuel delivery is not the issue, but the fuel is randomly not being delivered from the carb? I'll ask about the stator and see if he will just humor me and try another gas can. thanks. I'll post when I have an update.

 

[clanton]

Re: 1992 Suzuki DT 40 Carbeurator

Not sure about this engine, but some had plastic tube in center of carb(forgot Correct name of part) if this broke,loose, installed incorrectly may be problem, look at parts book for this tube. Sets on top of main jet.

 

[DrewR]

Re: 1992 Suzuki DT 40 Carbeurator

thanks clanton, I'll see what I can find out.

 

[jafa]

Re: 1992 Suzuki DT 40 Carbeurator

On top of the carb is a brass air jet , you can remove it fairly easily , its the high speed air jet. Check its not blocked with grease or crud. Note you cannot see all the way through it but you should be able to put a fine piece of nylon line through it. On the oil tank side of the carb at the top on the side is the air vent for the carb bowl. If it gets blocked it will vacume the fuel and die.<br /><br />There are two idle jets under the pressed on cap , look for a tiny hole before the butterfly valve and a small one on the other side. They are the idle and fast idle jets. You've got to look hard !! There are some other air vent drillings , one on the gasket facing the block and a couple inside the top of the carb assy.