Suzuki king quad 300 idles great but Boggs when you apply throttle

[97kingquad]

8 minutes ago, Mech said:

Are you aure you sparkplug and coil are good ?

It's not good enough just looking at the sparkpklug when it's out and sparking, they can fail under load.

You also need a good battery and it's very likely here that you more than one fault.

Do you have a timing light ? Put it on and watch it while the bike starts to faulter. If the spark get intermittent then the spark is breaking down.. But that doesn't test the spark plug.

 

I have replaced the spark plug with a new one twice to be sure. It fires up pretty easy. First pull or two or with estart

[97kingquad]

9 minutes ago, Mech said:

Are you aure you sparkplug and coil are good ?

It's not good enough just looking at the sparkpklug when it's out and sparking, they can fail under load.

You also need a good battery and it's very likely here that you more than one fault.

Do you have a timing light ? Put it on and watch it while the bike starts to faulter. If the spark get intermittent then the spark is breaking down.. But that doesn't test the spark plug.

 

Can I test the lead to the spark plug?

[JustRandy]

2 hours ago, 97kingquad said:

Ok so I tired switching the headlights on but it makes no difference from what I can tell. 

 

I have removed the carb at least 20 times now adjusting the needle and set screw but none of it has had any impact on my issue. The only thing that has made the bike run better and hit any higher rpm is actually removing the cover from the air intake. It runs almost well. 

I know it is not supposed to be like that but I really can't figure it out. There's no debris in the intake and the carb is pretty clean. The Jets and vacuum lines all seem clear. 

Why does it need more air? Even when I max out the set screw it starves for more

It's odd that it ran better with a dead battery but maybe that was a coincidence.  Is there any way you can try another dead battery and see if it runs better again?

Assuming it's not electrical then the first thing to do is set the valve lash before tinkering with the carb.  Another common issue with these suzuki engines is worn intake valves.  Verify the intake valve lash is close to 0.001 - 0.003.  If there is no lash then that would be your problem.

Worn intake valves usually present as hard starting, so it's possible someone may have tried to compensate by richening the carb.  Unfortunately the valve will keep wearing until it won't run at all.

[JustRandy]

On 7/20/2023 at 10:24 AM, 97kingquad said:

I bought it for 800 bucks and got it running that night and it ran great for a few days 

But I parked it the other night and went to start it again and it was really hard to fire up and when I did it was bogging and idling high then low again.

Ran great for a few days then was hard to start when cold is perfectly consistent with worn intake valve.

Hard starting when hot is electrical.  Hard starting when cold is intake valve.

Do you know how to check the intake valve lash?

[97kingquad]

13 minutes ago, JustRandy said:

It's odd that it ran better with a dead battery but maybe that was a coincidence.  Is there any way you can try another dead battery and see if it runs better again?

Assuming it's not electrical then the first thing to do is set the valve lash before tinkering with the carb.  Another common issue with these suzuki engines is worn intake valves.  Verify the intake valve lash is close to 0.001 - 0.003.  If there is no lash then that would be your problem.

Worn intake valves usually present as hard starting, so it's possible someone may have tried to compensate by richening the carb.  Unfortunately the valve will keep wearing until it won't run at all.

No I haven't messed with the valves yet, I am pretty good at figuring stuff out but engines have always been hard for me because I can't see the actually process happening. 

I just recently got into figuring it all out with a small motor and now I'm trying with the quad. 

If any of you have some experience checking/setting valves can you give me a briefing? I intend on doing everything I possibly can myself before I take it to someone else. 

You don't learn what you don't try eh. 

 

I'm pretty sure I have to replace my stator as well but can't find any videos on a sazuki king quad 300 stator replacement (although many people say they've had to)

I'm trying to check as many of the things I come across as I can, I have a lt-f4wd and three parts bikes for it as well as my king quad and almost a full parts bike for it. And I know many parts are interchangeable but any part that is not working if I don't have it I will buy. I'd like to make this quad a fairly reliable fun trail bike if I can. Because the thing was awesome when I got it running the first time. I fell in love I think

[Mech]

Fair enough Mod...  I'd already stopped.

[JustRandy]

1 hour ago, 97kingquad said:

No I haven't messed with the valves yet, I am pretty good at figuring stuff out but engines have always been hard for me because I can't see the actually process happening. 

Setting the valves is the first step because how the carb is set depends on how the valves are set.

1 hour ago, 97kingquad said:

I just recently got into figuring it all out with a small motor and now I'm trying with the quad. 

If any of you have some experience checking/setting valves can you give me a briefing? I intend on doing everything I possibly can myself before I take it to someone else. 

You don't learn what you don't try eh. 

It's pretty easy.  You have to get the piston to the top of the cylinder and the hardest part is being sure it's on the compression stroke and not the exhaust stroke.  There is a timing mark on the left side of the engine under a plug but I always use a screwdriver in the spark plug hole to feel when the piston is at the top. 

First remove the spark plug and the intake valve inspection cap.  I think it's a 17mm wrench.  Then slowly pull the pull starter cord until you see the rocker arm move.  The rocker arm moving means it's the intake stroke and the piston is moving down.  The next stroke is the compression stroke so keep pulling the cord until the piston is at the top.  You can feel it with a screwdriver through the spark plug hole or you can use the timing mark on the left side on the engine.  It doesn't have to be perfectly at the top, but close is fine.

Then wiggle the rocker arm and see if there is any gap.  If it's tight and no gap can be felt, then that is your problem.

If so, then grab a small socket (5/16 I think) and loosen the nut on the screw on the rocker arm.  Use a small flat screwdriver to back the screw out some and tighten the nut.  It doesn't need to be any set value because we're just diagnosing the problem now.  Just make it so there is a gap and be sure the nut is tight or else it will come off and fall in the engine.

Then put your carb back to stock and it should run great.  Until the valve continues to wear.

1 hour ago, 97kingquad said:

I'm pretty sure I have to replace my stator as well but can't find any videos on a sazuki king quad 300 stator replacement (although many people say they've had to)

I'd be surprised if your stator is bad.  It doesn't seem likely.

1 hour ago, 97kingquad said:

I'm trying to check as many of the things I come across as I can, I have a lt-f4wd and three parts bikes for it as well as my king quad and almost a full parts bike for it. And I know many parts are interchangeable but any part that is not working if I don't have it I will buy. I'd like to make this quad a fairly reliable fun trail bike if I can. Because the thing was awesome when I got it running the first time. I fell in love I think

Good you have parts bikes because you may need to swap heads.

[Mech]

It might pay to check the fuel pump and for fuel in the vacuum hose to the tap.

[Gwbarm]

 Yes you can test the coil secondary for correct resistance at the coil , but if you checked to make sure the plug was firing consistantly you should be OK, does the spark look good and bright or weak, and does it get weak when you spin it faster, that seems to be where your problem is.

[97kingquad]

1 hour ago, JustRandy said:

Setting the valves is the first step because how the carb is set depends on how the valves are set.

It's pretty easy.  You have to get the piston to the top of the cylinder and the hardest part is being sure it's on the compression stroke and not the exhaust stroke.  There is a timing mark on the left side of the engine under a plug but I always use a screwdriver in the spark plug hole to feel when the piston is at the top. 

First remove the spark plug and the intake valve inspection cap.  I think it's a 17mm wrench.  Then slowly pull the pull starter cord until you see the rocker arm move.  The rocker arm moving means it's the intake stroke and the piston is moving down.  The next stroke is the compression stroke so keep pulling the cord until the piston is at the top.  You can feel it with a screwdriver through the spark plug hole or you can use the timing mark on the left side on the engine.  It doesn't have to be perfectly at the top, but close is fine.

Then wiggle the rocker arm and see if there is any gap.  If it's tight and no gap can be felt, then that is your problem.

If so, then grab a small socket (5/16 I think) and loosen the nut on the screw on the rocker arm.  Use a small flat screwdriver to back the screw out some and tighten the nut.  It doesn't need to be any set value because we're just diagnosing the problem now.  Just make it so there is a gap and be sure the nut is tight or else it will come off and fall in the engine.

Then put your carb back to stock and it should run great.  Until the valve continues to wear.

I'd be surprised if your stator is bad.  It doesn't seem likely.

Good you have parts bikes because you may need to swap heads.

Well lol I took the coil off and the rectifier from the parts bike thinking maybe. Because I tested with a voltmeter and it was low and would drop below 5 at times then back up around 12v 

But it made no difference so I guess next is this lol

 

1 hour ago, Mech said:

It might pay to check the fuel pump and for fuel in the vacuum hose to the tap.

Maybe I'll see if I can snag the one off of my parts bike and see if that helps 

[Mech]

Just suck on the two vacuum hoses carefully to see if you can suck fuel through them.. It would mean a hole in a diaphragm if you can.

And the intermittent readings from the gauge is probably because your gauge only takes a reading a few times a second, so you are sometimes getting it at the top of the sine wave and sometimes not.

[JustRandy]

14 minutes ago, 97kingquad said:

Well lol I took the coil off and the rectifier from the parts bike thinking maybe. Because I tested with a voltmeter and it was low and would drop below 5 at times then back up around 12v 

But it made no difference so I guess next is this lol

 

Maybe I'll see if I can snag the one off of my parts bike and see if that helps 

I'm pretty sure it's the valve man.  I suspect the guy knew it when he sold it.

Anyway the first step is to be sure you have good compression by being sure the valves are set right before tinkering with the fuel system.

I wouldn't bother with exhaust valves.  You can if you want but I've never seen a bad one.

 

[Mech]

If you have a timing light put it on and check the spark isn't dying or getting intermittent.. Then you know to concentrate on the fuel.

[JustRandy]

If it were lacking fuel then why would it run better with the airbox lid off?

[Mech]

If it has a hole in a diaphragm and it's sucking fuel in it won't be running lean

And it might have more than one problem..  Best illuminate one possible thing at a time and be methodical about it.  Start with the simplest.

Ha.. eliminate

[JustRandy]

Oh you think it's sucking fuel directly into the intake through the vacuum hose?

It's possible but I doubt it would pump to the carb with a torn diaphragm and it probably wouldn't run at all.

[Mech]

97..  If you don't have a timing light try getting another sparkplug and fitting it to the lead then resting it on the fitted sparkplug so the spark will go through the first plug and then down through the fitted one. The one on the lead can't touch the engine, only the end of fitted plug. You might have to hold it there by the lead. If you have a good spark it will go through two plugs inline. Then watch the one you can see and make sure the spark isn't dying before the crank stops turning. That will eliminate electrical problems.

Then concentrate on the fuel..

And yet they do Randy.

They can.

[Gwbarm]

Im still a little concerned you are not getting voltage out of your stator, you dont need the charging part to run but you do need  correct voltage to your pickup coil .

[Mech]

I  agree Gw, but if it has good spark then that's just an anomaly to be addressed next.

[DayBreakJim]

My king quad had this exact same issue and it ended up being tight intake valves and my carb leaking gas into the throat. 

[JustRandy]

1 hour ago, Mech said:

And yet they do Randy.

They can.

I suppose anything is possible but the fuel pump isn't very strong to begin with.  I sometimes have to blow in the hose from the gas cap to pressurize the tank to get fuel flowing.  Seems like a hole sufficient to consistently deliver fuel to the intake would shut the pump down completely.  Seems like it would also foul plugs.

Also the symptoms would vary with the amount of fuel in the tank since more fuel means more pressure.

If that turns out to be the problem I will have definitely learned something.

[Mech]

Mmm well, sucking on a pipe is easier than adjusting the valves or swapping heads.

[JustRandy]

4 minutes ago, Mech said:

Mmm well, sucking on a pipe is easier than adjusting the valves or swapping heads.

Yep, sure is.

But I could check the valve in less than a minute.  Just spin the cap off with a 17mm wrench and wiggle the rocker while pulling the rope looking for any gap anywhere.  Super quick.

[Gwbarm]

This has turned into a very interesting thread curious to see whats really wrong.

You guys are doing great!

[JustRandy]

12 minutes ago, Gwbarm said:

This has turned into a very interesting thread curious to see whats really wrong.

You guys are doing great!

Yeah I'm curious too.  Wish I could do something to speed it up lol

[JustRandy]

The symptoms seem perfectly consistent with worn intake valve.  Other owner said it was bogging and he parked it until selling it to 97 who tinkered and got it running for a few days.  Then he parked it and it wouldn't start when cold which is exactly what a worn intake valve would do.  Now the valve is open so much that no amount of tinkering will work.

The only part I can't envision is the the CV carb because I threw mine in the trash the minute I got the quad and replaced with a 28mm roundslide from some suzuki bike.  So I'm not sure how the valve being open all the time interacts with the cv carb.  But with mine the valve did produce a mild rich condition and usually when I see bad valves I also see a lot of carbon.  So removing the airbox lid could help.

[Mech]

Have you ever noticed that anything that buggers up the vacuum, like air leaks or tight valves, seems to effect them more at idle than when they are revved up ?

[JustRandy]

Yep it's like a speaker box with a big hole in it is just as loud as a sealed one at high frequencies because the air doesn't have time to get out before the speaker cone changes direction.

When the piston is moving fast the air doesn't have time to leak so even though the valve is open it doesn't change the cylinder pressure so much.  But in this case the cv carb depends on engine vacuum to open the throttle so I'm not sure how that would work out if the intake valve is open during the power stroke.  At idle the butterfly valve is closed and blocks the impulses, but when the butterfly valve is open the slide feels the pressure from combustion.  That may explain why no carb adjustment makes a difference.

I hate cv carbs so I'm no expert on them.

I have a 250 that's bored close to a 300 and it stretches the head studs and blows the head gasket out.  When it happens it whistles, but increase the rpms and the whistling stops.  The king also whistles sometimes when I'm lugging but increase the rpms and it stops.  Max cylinder pressure is usually somewhere in the lower midrange depending on cam duration.

You're not making real power if you're not stretching head bolts lol

[Mech]

My sons always say "Oh I'm not sure about that dad", and I always tell them, "yes, but I am".

Edited July 25, 2023 by Mech

[JustRandy]

6 minutes ago, Mech said:

My sons always say "Oh I'm not sure about that dad", and I always tell them, "yes, but I am".

Reminds me of Ben Franklin's speech at the constitutional convention.

"I confess that I do not entirely approve of this Constitution at present, but Sir, I am not sure I shall never approve it: For having lived long, I have experienced many Instances of being oblig’d, by better Information or fuller Consideration, to change Opinions even on important Subjects, which I once thought right, but found to be otherwise. It is therefore that the older I grow the more apt I am to doubt my own Judgment and to pay more Respect to the Judgment of others."

https://constitutioncenter.org/the-constitution/historic-document-library/detail/benjamin-franklin-closing-speech-at-the-constitutional-convention

The only sure impediment to truth is the conviction that you already have it.