Dennisg

1989 Quadrunner LT4WD Starting

14 posts in this topic

I bought an old ATV and would like to get it going again. When I purchased it we bump started it as the rope starter and the electric starter was broken. The machine had a lot of other issues. One by one I have been addressing them. I fixed the rope starter,the electric starter, the choke lever and cable and choke plunger in the carb. I also changed the oil, filter and the air filter. I also bought a new battery and redid the wiring.I have been working on this machine all summer to try to get it going for hunting season. The electric starter turns the machine over like it should,the choke works like it should,but it does not start. I believe that the fuel pump is the culprit. Is there any way to test a fuel pump,and is there any way to repair it. The manual says to replace it. I checked spark and it is bright blue. I also thought that the plug was wet. Now I am confused. I need help.

Thanks guys

Dennisg

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i would not say it is a fuel pump because if my memory serves me correctly that thing is carbuerated and sould not have a fuel pump. if your plug is wet with fuel i would clean your fuel tank and your carb and most likely rebuild it. the problem is most likely that your carb is flooding.

your friendly neighbourhood mechanic

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There is a fuel pump, it believe it is vacuum operated. First thing I would do is drain the tank of any old fuel, make sure the tank and fuel petcock are clean, and start with fresh fuel. Make sure that fuel flows through the petcock to the pump by taking the incoming fuel line off the pump and turn the fuel vavle on. If that works, take the fuel hose off the carb and turn the motor over, fuel should come will come out of the line if the pump is working. I don't know how much pressure it should make though. If no fuel comes out or very little, then I would check the vacuum line that operates the pump first. You may be able to get away with taking the pump apart and cleaning it, as long as the rubber diaphragms inside are not torn or worn out. If it is working properly, then I would be inclined to agree with Gearhead, if it sat for too long, the carb likely needs a good cleaning. That means, take it off, take it completely apart, and clean every passage and hole in the carb. Use something (torch tip cleaner) to poke through the holes and jets, spray cleaner and compressed air through any holes that you can't get to with a tool. You might try spraying some starting fluid in the spark plug hole and try starting it. If it starts up with the fluid, then you know that lack of fuel is the problem. Try it a few times, you may just need to get everything primed. If you can't get it started with the starting fluid, then I would check the compression and the flywheel timing key.

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I have cleaned the carb and checked the fuel flow before the fuel pump(good) and after the fuel pump just as you described and nothing. I tried to take the fuel pump apart and the diaphragms look good, but it is hard to tell. As far as the vacuum line I have not checked that yet, but I will trace it down to where it is connected to the engine. I checked the compression and it is 125psi. I know that this is on the low side but it should at least start with that as the repair spec says lower than 104psi. As for the flywheel timing key? I assume that you mean if the timing key is broken or missing. No I have not checked that but I will. I will also try the starting fluid trick,just to see if it will fire. Thanks a bunch for your help all of you, as I appreciate it. I am determined to get this machine running and running eight.

Thanks

dennisg

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when a diaphram fuel pump sits for to long without moving the checkvalves becom hard and will not pump the fuel. the trick i use is to pull the pump apart and soak the diaphrams in automotive transmission oil for a day. this will soften them up and they should start to work. you can use a vaccum pump to pull on the fuel pump. to see if the pump works. if it does work then you need to chase the vaccum system on the engine. i hope this helps you.

your friendly neighbourhood mechanic

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Wow Gearhead01 that was the information that I was looking for. I should be able to get this thing running now and we will see what else it needs thanks a bunch

Dennisg

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125 psi isn't too shabby for a machine that old, and doesn't run that high of a compression ratio, I think you will be fine for a little while. Just check the valves and make sure they are properly adjusted.

If you can't get the pump working, I ran across a Mikuni universal vacuum operated fuel pump that should suit the needs of your machine well. It even has rebuild kits available for it. Best of all, it's only $17, alot cheaper than the $70 OEM part.

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Update

I have a running Quad. It runs good and starts right up. I have to keep the choke on all the time or it will quit. I have never seen an engine run so well with the choke on,whats up with that? It also smokes real bad and shoots black oil out the tail pipe, never seen that before either. What causes that and are the two problems related? I have a manual and I have looked up the valve adjustment as I believe that this may be the next move as DirtDemon suggested.

I got to drive it around the yard for about 10 minutes and it sure is fun and now I know why everyone is hooked on them as I will be too.

Thanks

dennisg

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if your quad runs well with the choke on that means that the carb is mixed to lean. i would say that your carb needs rebuilt or you have a vaccum leak. are you sure it is oil squirting out the tail pipe or is it sooty water or moisture build up. you said it has valves so it would be a 4 stroke. there is no way possible with compression like that to have oil going past the rings. the oil burning is most likely because the engine oil is contaminated. do an oil change with clean oil and leave the old oil filter on it. run it for 5 - 10 minutes and then do a complete oil change oil and filter. i would do that and rebuild your carb and check for intake leaks.

your friendly neighbourhood mechanic.

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Running better with the choke on is usually an idication of a lean condition as Gearhead pointed out. A vacuum leak is certainly a possibility, or there could still be some kind of obstruction in the carb. Are you sure you got it cleaned out COMPLETELY? You may have a choke problem too. The first thing I would do is check for an intake vacuum leak by spraying carb cleaner around the intake area, the outside of the carb or anywhere there is a vacuum line. You will know you have found a leak if you hear a change in the engine's idle. If you find no air leaks in the intake, and the valves are set properly, but you still have the problem, then maybe it would be eaisiest to just take the carb apart and get a rebuild kit. Here is a link to an ebay page with a few kits for your machine. I also think that Gearheads suggestion to change the oil is a good idea.

89 Quadrunner LT-4wd items - Get great deals on ATV Parts items on eBay Motors!

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Update I got it running right. I started it and let it run for a few minutes and set the choke to half as the manual said and ran it some more and then moved the choke lever to off,and it ran great with a lot of power. It is still a mosquito fogger however. I thought that oil contamination was the original problem, so i changed the oil and filter. It blows out a thick white smoke layer that you have to be moving forward or you can not breath and you will die,it is awful. I am sure that the previous owner did not clean the exhaust out and i was wondering how long to would take to burn off the residue. Gearhead it may be a sooty water that is sitting in the exhaust and burning when it is warm. Is there a fix for that? I am reading up on the valve adjustment, looks like a lot of work and special tools. Dirtdemon thanks for the link, but I think i have that problem solved. I am thinking of taking off the exhaust and see if it still smokes so bad, what do you think of that idea?

Thanks

dennisg

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Not being able to get the engine to quit smoking, I have taken the head off and inspected it visually and nothing appeared to be bad. I took the head to the local shop and he is cleaning it up and re seating the valves and reconditioning the head. I took the cylinder off of the piston and have inspected that and the cylinder is smooth and scratch free, and the piston looks ok too. Could someone have put in a new piston and rings and lined up the ring gaps to cause this condition? I cannot see any reason for the amount of oil leaking past the rings other than the ring gaps were lined up and they are not supposed to be. What else can i check to get this motor running?

Thanks

dennisg

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they possibly could have but it doesn't show anything because piston rings slowly rotate in the bore when the engine is running. it is a way of letting oil through for lubrication. most mechanics call bull on that but we proved it in college by assembling the engine and running it then pulling it apart. if your cylinder is smooth to the touch and your rings move freely. then i would have to say the cylinder bore is glazed and needs to be honed to put your cross hatch back in the cylinder bore. check the sides of the piston for scaring. if there is any on the side and on the land (which is the shoulder of the piston) replace it. i would replace the rings as well.

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First off, I appologize that your last post went un-answered, I did not catch your post, or I would have responded sooner.

Check the cylinder bore for excessive wear, if the bore is too worn or is out of round, you may need a bigger piston. Standard bore size is 66mm, you can get pistons in .5mm increments, if needed bore up to the next size. I know Wiseco makes pistons up to 68mm, hopefully, you aren't worn past that, or you may need to re-sleeve or replace the cylinder.

Edited by DirtDemon

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