Hi guys

I've been looking all over for help with a suzuki atv.

It's really hard to imagine but there are very few technical forums out there, most are "Hey look how shiny my rims are!" and this is not what I need.

I've been on this forum for a number of years and I know there are guys here who will know the answer to this, I need one of those guys to help me out

I have a 93 Suzuki King Quad 300CC engine, air cooled of course, the model number is LT-4WDX. I bought this thing over a year ago and it has a problem I can't seem to fix (as emberassing as it is to admit). In any case, this is what happens.


The quad fires up when cold like a champ, on the first cycle of it's 4 stroke engine, it never gave me a problem even with the pull start. It will also run like a champ while warming up. Once it warms up, it's a different story. I usually fiddle with it and take it for a spin. I'm on it for maybe 10-15 minutes going at some speed above 20kmph. NO problems at all. Once I'm on it for the 10-15 minutes, I bring it to a stop and let it idle for a few moments. As soon as I do this it starts missing. The longer it idles the worse the missing gets until the motor stalls and will be impossible to restart until it cools down, and then the entire process repeats like clock work.

The thing is, as long as I'm moving, and I guess the air moves through the cooling fins and keeps everything relatively cool, it will not show this behaviour, but as soon as I slow down and heat builds up (please note the heat building up theory is just a theory) it will start missing.

I know it's not fuel cause I bought a spark tester and the spark simply vanishes. I pulled the plug and it looks fine to me, a bit dark but no damage, or anything suspicious on it. I tried many different plugs. I replaced the ignition coil, I replaced the stator and pick up coil. I tested all wiring, did many crazy things to solve this, but nothing. The only part I have not replaced is the CDI computer since it's very pricey and it's a solid state electronic component, nowhere near the engine so it's not exposed to heat, and with these things it either works or it does not, as far as I know, but if I'm desperate enough I'll replace it too, I'm hoping there is another way to fix this.

So, what more can I try? I took the cylinder apart, the compression, although I have not measured it is very good, the motor has plenty of power, and without the decompression lever it's impossible to start it by recoil starter.

I even tried swapping plugs while the engine was hot, it helped for a minute or two then right back to the same problem with a completely different plug.
The plug is gapped at 0.6mm, this is what the manual says to gap it at.

The piston, cylinder and everything else looks to be in good shape. The machine has 5000km on it, I put another 600km on it in the past year, all with the problem, except I was driving in spring time when it was still cool, so it took longer for the problem to surface.

I'm kind of desperate here cause I put a lot of time and effort to get this machine and I can't even enjoy it, so if anyone knows what might be the cause of such a strange problem, please help out.

Thanking you in advance

xp

__________________
1985 190E 2.3L - a constant project.

have you checked the spark timing? if its retarded it will heat up.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Sure have, I took the engine apart, timing is set just like in the book, unless the book or the marks on the engine are wrong.... but how would i test that?

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1985 190E 2.3L - a constant project.

I have had the exact same experience with a early 90's Mazda MPV. It was one of my favorite vehicles in regards to the way the interior would change out.
Anyway, I changed out the "ignitor" and it fixed it. I would loke at the electronic portion of the ignition system. Hope this helps.

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Jim

The ignition system on these is rather simple.

You have the pick up coil which picks up the tdc mark on the flywheel, you have a CDI box which controls the timing, you have the ignition coild which generates the spark, and you have the spark plug which fires the spark.

All of these parts have been replaced except for the CDI box.

No idea where I could find an ignitor on there, but I'll check for it

__________________
1985 190E 2.3L - a constant project.

Try a different cdi box.

__________________
Jim

If you have ruled out the possibility of it being a fuel issue than I agree to get another CDI. When they get hot they can act up. Also a new CDI is reasonably priced so its worth a shot.

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'86 300E 5 speed
'71 Triumph TR6
'46 Cushman Scooter
'41 Ford 9N tractor

This is a typical problem with some lawn mowers too. If there is not enough airflow around the exhaust valve area, the engine tends to heat up around that area, the valve seat expands more than it needs to and the exahust valve doesn't seal well. Results in a hot/wamed up engine sputtering and dying when idling and is a pain to restart. Let the engine cool down, everything shrinks down to what it needs to be and your engine starts and runs fine.

The simplest thing for you to do is to clean the area around your exhaust valve(s) so that it cools well in that area. If it doesn't fix the problem, you will have to replace your exahust valve and seat and it will cure the problem.

BTW, on lawn mowers, the cooling fins get clogged with grass clippings thereby reducing the cooling capacity leading to the exact same problems you are experiencing with your quad engine.

Hope this helps & let us know how it goes.

__________________
1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

Thanx for all the suggestions guys, keep them coming, at least this is giving me some ideas as to what to try next because honestly it really is bothering me.

I did some reaserch, and I found an electrical component which is rather heat sensitive, as well, I was at the dealer today to check pricing on it, and I found out it was discontinued and superceded by an upgraded part most likely due to problems.

I'm not going to say that I know what the problem is because I don't know, but this part kind of fits the bill at the moment. The part is the recitifier, which is mounted on the front for maximum air flow since it has a big heat sink on it. It's responsible for voltage regulation, and is directly hooked up to the ignition coil. It makes sense that it would warm up instanly when idling, electrical parts do that, and the heat sink can't keep up with it, hence the part starts either giving too much voltage or too little upsetting the coil.

I devised a simple test, I'll warm the machine up and let it start missing and when it does I'll blow compressed air on the recitifier and see if it makes any difference, if it does, I'll have to get a new one. If it makes no difference I will look into the CDI box.

I'll get back to you with the results, I'm going up north tomorrow morning and I'll be back sunday night.

cheers and thank you all

xp190

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1985 190E 2.3L - a constant project.

Well it's not the recitifier, I pulled the part out and disconencted it, the quad ran off the bettery and the same thing happened.

So I guess if it's not the CDI box, which also checks out, it's something else, but what could it be?

The exhaust valve like hs_300e said? I cleaned up the engine quite well when I had it apart just a couple of weeks ago, maybe I'll order that new CDI box after all.

xp190

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1985 190E 2.3L - a constant project.

There is a product called "freeze mist" (R-134) which you can spray on electronic components when you suspect a heat related failure. It cools them rapidly and makes it easier to diagnose the problem. It's even safe to spray on circuit boards and individual components.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

I got a chance to do some more testing, andunfortunately it's none of the electronics parts, since I replaced them all.

It looks like the engine is overheating, I just need to figure out why. I pulled the spark plug out and it was blueish in color, which indicates overheating, with some carbon deposits on it. I don't want to, but I might have to try adjusting the mixture, it might be running to lean, if memroy servers, that would cause overheating along other problems.

Second idea is that the oil cooler is plugged up, but it warms up along with the engine, I'll try bleeding it just to make sure that's not the case.

I bought a set of colder plugs, I will try to see if they make any difference.

Lastly, if all else fails, I will do a leakdown and compression test, it might be the cylider is worn although I hope that's not the case, it still has plenty of power to me.

Other then that I'm stumped

xp

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1985 190E 2.3L - a constant project.

Wild stab at it. Carburetors can get really hot if there is no thermal break in the intake runner. Is this engine completely stock?

In the old days, people would leave out the thick intake gasket in an attempt to get more airflow, only to have heat from the engine conducted back up to the carburetor, boiling the gasoline out of the float bowl and causing all sorts of problems.

Maybe a blast of cold water on the carburetor float bowl to cool it off will tell you something.

What the heck, it doesn't require replacing any parts to diagnose.

Too rich will make it hard to start a hot engine.

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

This would be my next move.