Please Help - Suzuki DT40 eary 80's model

[evski]

I have a Suzuki DT40 from the early 80's. Last summer I ran it regularly at it was fine. After having been stood for the winter (without prepration due to my lack of knowledge) I'm now having troubles getting it going again.<br /><br />I replaced the plugs as the previous owner had been using the incorrect ones.<br />I ran the boat and it started after about 30 pulls and worked fine for about 10-15mins then slowly stopped as if it was starving from fuel or flooding, revs dropped and eventually it stopped. After being towed in by the coastguard I tried starting the boat again in a tank to no avail.<br /><br />After a week I tried again and she started with a cloud of smoke and continued to ran if I held the throttle open slightly. However it seemed to be continually smoking and filling the tank with oil/fuel, although the oil level did'nt seem to drop, pumping the fuel made fuel appear in the tank.<br /><br />After reading various forums on this site I decided that a rebuild and clean of the carb would be a good starting point. I did this and now I'm unable to get it start at all. Can someone please help. I live in England and we get very little sun. Its running out fast and I want to take advantage of it! Please excuse my lack of knowledge!!! Any help is greatly appreciated.

 

[suzukidave]

Re: Please Help - Suzuki DT40 eary 80's model

Evski, welcome aboard. I am not even a shade tree mechanic but we have similar motives and similar problems so I'll try to help.<br /><br />I assume you left last year’s untreated gas in the carb bowls and fuel lines and filter when you started up. You didn’t by any chance also use last year’s gasoline to run did you? If so, then rebuilding the carb might have been the right thing to do but if not, it may have added to your problems if you can’t start now at all. If you used old gas I would also drain all your fuel lines and clean your fuel filter in solvent. Assuming your carbs are mikuno’s like mine they are fussy to set up. <br /><br />I have a DT55 manual start circa 1989 or 90 2 cylinder. I think we may have the same block or close. I religiously winterize mine and I have still found it tough to start at first in the spring. I use fresh gas/oil, fresh plugs and pull hard! I also had a similar problem late last season with it bogging down and dying only it happened at the end of the season and after about an hour of running. My mechanic suspected an airlock in the fuel system that took time to build up but could not find one other than a missing o-ring in the fuel filter which he doubted was the cause (but check that). In my case the problem is gone if you can wait a couple of hours. I am guinea pigging this year as I have not run it for an hour yet since the mechanic checked everything in the fuel system. One possibility checked on mine is that your fuel pump has a tiny hole in it and needs rebuilding. <br /><br />You mentioned you changed plugs, what range are you running and what did you start with? Mine is recommended for BR8HS, but my mechanic says to run one range lower at BR7HS.<br /><br />Will it start with brand new plugs or with quickstart (ether)? Latter is not recommended very often but unless you have volatile wd40 over there it is one way to find out if your problem right now (after the carb rebuild) is hard starting or no starting

 

[jim dozier]

Re: Please Help - Suzuki DT40 eary 80's model

Don't use ether, squirt some premix gas/oil into the carb throats and see if it will fire up. Check your manual, you do have a manual don't you, and see if you synchronized the carb butterflies with the ignition advance properly. If you have spark, the timing is right, and you squirt premix in the carb throats it will fire, though it might not run if the carb setup is wrong. When you rebuilt the carbs did you dismantle them thoroughly and clean the orifices and jets with carb cleaner and compressed air, install the rebuild kit a reset the idle circuits and float bowls?<br /><br />If I had to guess, from your description you don't have the floats adjusted correctly, and you are dumping too much gas in there. If you pump the fuel bulb while looking in the carb throat does gas come out?

 

[evski]

Re: Please Help - Suzuki DT40 eary 80's model

Firstly thanks for the replies.<br />With my lack of knowledge yes I did leave untreated gas in the system. And yes again I am using last years gasoline too. How do I drain the fuel system fully? Yes the carb (there’s only one) is a mikuno.<br /><br />The owner before me had been running completely wrong and odd plugs!! So I referred to Suzuki’s website (no I don’t have a manual, can’t find one in the uk) and bought BR8HS plugs. These seem fine and are not becoming oiled, I tested for a spark on both, and they are ok. I also tried changing the plugs for new again and it still won’t start.<br /><br />When I cleaned the carb I stripped it right down and soaked the small components in gasoline overnight and sprayed/cleaned the chambers with WD40 and a cloth. I don’t have access to compressed air. How do I synchronise the crab butterflies with the ignition advance? Also I did’nt have a rebuilt kit so cleaned gaskets etc (again I’m not sure where I can get a rebuild kit in the uk). Also how do I reset the idle circuits and float bowl? I’m sorry I’m not a mechanic I’ve done loads of work on cars but nothing on boats. I will check tonight and see if gas is visible in the carb throat when pumping the fuel bulb. Thanks again.<br />

 

[jim dozier]

Re: Please Help - Suzuki DT40 eary 80's model

Evski,<br />You can buy a manual here on iboats, you'll just have to wait for it. You can order parts online here in the States, I use brownspoints.com but again you'll have to wait. You're not the only mate with a Suzuki in Britain, I'm sure there must be somewhere over there. Many of our bookstores and autoparts stores and marinas carry manuals here.<br /><br />Alas, you have committed 3 cardinal sins of carb rebuilding<br />1. Get rid of the old gas. Siphon the gas out of the boat and put it with in your car with half a tank of good gas. Better yet put it in your neighbors car.<br />2. You need to remove all the parts of the carb, the bowl, the float and float valve, the jets, and soak them overnite in carb cleaner (available in buckets for immersion at the auto parts store) and then take them to a gas station that has a air hose to air up your tires and blow the orifices and jets out with compressed air. Gum and varnish deposits won't be removed with gas and WD40. The object is not to make the carb look good but to open the orifices.<br />3. You have to replace the parts that come in a carb kit, which is likely the float valve, seals, and gaskets. You should not reuse gaskets. You have to remove the idle mixture screw to clean the circuit. If you haven't boogered the adjustment up already, count the number of turns to seat it gently before you remove it, and put it back the same number of turns from gently seated. You will have to fine tune it once you get it going. If you have tinkered with it and don't think its right, this is where you need a manual for the initial setting. My Suzuki DT85 is 1.75 to 2.25 turns out. Yours could be entirely different. <br /><br />I do believe your difficultly still lies with carburetion, I think you still need a proper carb rebuild and adjustment and that requires prior knowledge or a manual. Every manufacturer is different and every model within the manufacturer is different in the adjustments and tolerances.<br /><br />P.S. Boats are like cars only different.

 

[evski]

Re: Please Help - Suzuki DT40 eary 80's model

Fair comment. Thanks for your time. I'll try you suggestions and let you know what happens.

 

[evski]

Re: Please Help - Suzuki DT40 eary 80's model

Ok here's the results. I cleaned the carb (properly using cleaner and blowing out all jets etc) replaced the gaskets and rebult. Adjusted idle as advised by local dealer. Carb kits are'nt available here. New fuel etc. Engine starts lovely, ticks over great. <br /><br />So off we go to sea. When giving the engine a bit of power it begins to cut in and out as if its starving of fuel or something, back of and its fine. We thought it was the fule connector going into the outboard leaking. So as we're going along my brother turns and wiggles it, after a while it goes fine. So we conclude this is the problem replace the connector and go to sea again.<br /><br />To my dismay the problem still exists.<br />While adjusting my (more mechanically minded) brother noticed the screw on top of the carb (I belive this is the jets?) was lose and the edges curled on the screw head. He adjusted and this effected the problem. The screw will not stay fixed though unless tightened all the way in. He did manage to adjust it and wedge it, but setting the throttle remote flatout made the engine barely rev. Please advise, I know I'm an amateur, but the local marine engineers told me it would'nt be worth them looking at it. The cost would easily ouyway what the outboard is worth.<br /><br />Thanks in advance.<br />

 

[evski]

Re: Please Help - Suzuki DT40 eary 80's model

Please help you clever boat people! Don't make me beg. I really want some fun in the sun. We don't get much here in the UK!!! I will be eternaly grateful

 

[jim dozier]

Re: Please Help - Suzuki DT40 eary 80's model

I'm trying to understand your picture. The screw that you are describing as the one of top of the carb, do you mean top of the carb as in top while looking down or, top of the front while looking at the front. The point is that there is a fixed pilot jet which is screwed into the top (top of the carb body approximately center). This is screwed in tight and is not adjustable but is removable for cleaning. When viewing the front of the carb looking into the open throat where the choke butterfly is located there is an adjustable air screw located at the top of the throat of the carb. The screw meters air and the is adjustable and held in position by a spring. If the spring is missing the screw will not hold its position. Since the screw meterd air, opening it by unscrewing (counterclockwise) will lean out the idle mixture. This will affect idle and take off from idle but not midrange and high speed which is controlled by the main (high speed) jet which is not adjustable and is located beneath the carb throat within the center of the bowl. When cleaning the carb the high speed jet, pilot jet, air mixture screw, flot valve and float, should all be removed, cleaned, blown with compressed air and correctly reinstalled with the float height adjusted as per manual. New gaskets should be installed. Hope this helps.<br /><br />In your orignial post you made a comment that the engine was "However it seemed to be continually smoking and filling the tank with oil/fuel, although the oil level did'nt seem to drop, pumping the fuel made fuel appear in the tank". What tank are you referring to? Have you tried pumping the fuel bulb once the engine is going and you are trying to accelerate? If it helps, you might have a look at your fuel pump, as they are relatively easy and inexpensive to rebuild. Also verify that all of your hose connections from the tank to the carb are not leaking air.