[DougCentralCoast]

Have owned since new, currently with 2k miles. Has always started immediately, but lately it takes 15+ seconds to turn over and in doing so it's very slow to wind up. The engine begins to start putt- putt and then kicks in. I thought it was fuel flow - cleaned out the fuel tank, filter, replaced pump and lines, and checked fuel flow. But that was not it.

It has never idled very well, now once I do get it started it wont idle at all. Once running it goes just fine when gas is applied. It may also be generating more dark smoke at start-up than it used to.

All idea welcome - thank you in advance

 

[ajl719]

Try cleaning the carb and installing a carb rebuild kit. Most likely the idle circuit is plugged up. Is the bike hard to start cold, or both cold and hot.


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[Dacaur]

Dark smoke I means it's running rich.
You don't mention it, but I bet you are having to give it throttle to start, a classic sign of flooding.
You replaced the fuel pump so that's one possible area taken care of, but you should also look at the fuel petcock, it's also vacuum operated, and if it has a hole in the diaphragm it can allow fuel to run through the vacuum line, causing an uncontrollable rich condition.
Luckily that is extremely easy to check. Just use vise grips to clamp the vacuum line, set it to prime, and see if it solves the problem. If it does, just replace the petcock and you are good to go, if it doesn't, at least you have ruled it out.

The last possiblity is the needle and seat. I recently went through the carb in one of my quads, installed a carb kit, but the needle looked fine so I left it and didn't even pull the seat out. Well, I ended up pulling the carb twice more trying to figure out why it was flooding. Turns out that while the needle was fine and was sealing fine, the o-ring between the seat and carburetor had hardened and was no longer sealing, allowing fuel to flow AROUND the seat, flooding the carb.
I installed the needle and seat that came with the carb, adjusted the float for the new needle/seat and now it runs perfectly.

 

[DougCentralCoast]

Try cleaning the carb and installing a carb rebuild kit. Most likely the idle circuit is plugged up. Is the bike hard to start cold, or both cold and hot.


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Thank you - my 250 is slow to start when cold, but could take 30 seconds when warmed up or on hot day... ??

 

[DougCentralCoast]

Dark smoke I means it's running rich.
You don't mention it, but I bet you are having to give it throttle to start, a classic sign of flooding.
You replaced the fuel pump so that's one possible area taken care of, but you should also look at the fuel petcock, it's also vacuum operated, and if it has a hole in the diaphragm it can allow fuel to run through the vacuum line, causing an uncontrollable rich condition.
Luckily that is extremely easy to check. Just use vise grips to clamp the vacuum line, set it to prime, and see if it solves the problem. If it does, just replace the petcock and you are good to go, if it doesn't, at least you have ruled it out.

The last possiblity is the needle and seat. I recently went through the carb in one of my quads, installed a carb kit, but the needle looked fine so I left it and didn't even pull the seat out. Well, I ended up pulling the carb twice more trying to figure out why it was flooding. Turns out that while the needle was fine and was sealing fine, the o-ring between the seat and carburetor had hardened and was no longer sealing, allowing fuel to flow AROUND the seat, flooding the carb.
I installed the needle and seat that came with the carb, adjusted the float for the new needle/seat and now it runs perfectly.

Thank you - the petcock - okay - that's an easy test - I'll try that today. Otherwise, the carb looks to be the issue. I've read the rebuild kits are not all created equal - any recommendations on brand and source for this older model?? Thank you again.

 

[ajl719]

Shindy is a good carb rebuild kit.


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[DougCentralCoast]

Thank you for Shindy - unfortunately the petcock was not the problem, but I did discover that by removing the vacuum and teasing the air supply the idle was greatly altered. I wonder is the vacuum has anything to do with my 250's inability to idle. Again the start issue is awful once the unit warms up. First start cold seems fine, no throttle needed. Once warm and restarts attempted, the unit just does not want to start unless throttle and lots of cranking. And thank you for all your support on this issue so far.

 

[DougCentralCoast]

If I were to buy a replacement OEM carb, the dealers all list three assembly models - how do I determine which one is correct for my unit?? Thank you

Suzuki OEM Parts, Babbitts Suzuki Parts House

Shop our large selection of Suzuki OEM parts, original equipment manufacturer parts and more online or call at (231)737-4542

www.suzukipartshouse.com

 

[ToyFord]

This link is for the 2WD model. Not that it matters, as the 4WD is the same. I have '97 4WD QR. This site lists the same carb options for both the '97 and '98. My owners manual says my '97 has a MIKUNI BST31 carburetor on it. I suspect yours does as well.

I did a Google search on the MIKUNI model number and found a knock off version for $40. $40 Knock Off Carb

That a bit better than the $500 plus at the Babbitts site. I also saw the OEM on eBay for less than $150.

Not really sure what the Suzuki part number is, but only one of the three listed at the Babbitts site is actually available, I suspect the one that is available would be fine.

 

[DougCentralCoast]

Thank you for taking the time and passing along this information - I appreciate it.

 

[Dacaur]

First, don't buy a knock off carb. It just introduces no problems.ive never talked to anyone that was completely happy with one, plus it's tough for us to help since there are so many possible variations...

Second, don't buy a new oem carb, you would just be wasting money.

Unless your carburetor is missing or physically damaged, there is no reason to replace it, as all parts that could wear out are included in a carb kit.
I was going to recommend shindy as well.

When I was trying to diagnose mine, I also found that clamping the vacuum line to the petcock with it in the "on" position would make it run good, so don't make to much of that.

You have ruled out the fuel pump and petcock, so really the only possibilities now is the carburetor. dollars to foughby it's either the float or the needle/seat that is the issue.

 

[DougCentralCoast]

I think I'll replace the Petcock for good measure and put a rebuild kit in the carb as you (and others) recommend. Thank you all for your help.

Assuming there are three carb assemblies for the unit - is there still only one rebuild kit that you know of? or, three versions?

 

[ajl719]

As stated, do not buy a cheap knock off carb. From everyone I’ve talked to over the years they typically make things worse. Unless your carb is physically damaged, a carb rebuild kit is all that should be needed.


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[DougCentralCoast]

Thank you very much

 

[Dacaur]

Just one rebuild kit, but they will be different for different years, so make sure you get the right one.

As you are doing the rebuild, check the rubber diaphragm attached to the slide, make sure it doesn't have any holes in it, and be careful you don't put any holes in it, they aren't cheap. I had to replace mine because it was a little ripped. It's possible was a little stuck and I just yanked it... ..

If you don't have a sonic cleaner, I recommend one. Not strictly neccisary, but it makes things easier.
Also, pro tip - the little carb cleaning wire kits are cool, but the idle orifices are too small for even the smallest wire, but the smallest string on a guitar is the perfect size...

 

[DougCentralCoast]

Thank you - the problem is this is my first carb rebuild. I'm fine with replacing parts, barrings, pumps, seals, gaskets, but this is going to be all new. I appreciate the advice and pro tips - I'm certain this will be a struggle and I'll have questions - including best cleaning solution? I've read calibrating the float? The kit and replacement Petcock is on order, and I'll start pulling the unit apart today. I've had the body off this thing a dozen times, but this time I'm doing so with a lot less self-confidence in the outcome.

 

[ajl719]

If you feel like tackling the carb might be a bit challenging. You can always pull the carb from the bike then take it to a reputable shop to get it cleaned, rebuilt, and adjusted accordingly. At least this way you’ve saved yourself half the labour by removing and installing the carb yourself. Just a thought.


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[DougCentralCoast]

its a great thought, I'm looking in that option - Thank you for the kind reply.

 

[DougCentralCoast]

Just one rebuild kit, but they will be different for different years, so make sure you get the right one.

As you are doing the rebuild, check the rubber diaphragm attached to the slide, make sure it doesn't have any holes in it, and be careful you don't put any holes in it, they aren't cheap. I had to replace mine because it was a little ripped. It's possible was a little stuck and I just yanked it... ..

If you don't have a sonic cleaner, I recommend one. Not strictly neccisary, but it makes things easier.
Also, pro tip - the little carb cleaning wire kits are cool, but the idle orifices are too small for even the smallest wire, but the smallest string on a guitar is the perfect size...

Dacaur - quick question - while Im at it, im adjusting the values. Adjusted to TOP and the out or bottom value adjusted fine, but the top (intake) I can seem to find the gap. I've backed way off and still nothing - ANY THOUGHTS? thank you

 

[DougCentralCoast]

So, I've installed a new OEM petcock and rebuilt the carb. I noticed the oil level looked high, and I'm very careful not to overfill so I decided to drain a little - but discovered fuel in the oil (about an extra quart). Since I've replaced the petcock, I've changed the oil and now I'll hope for the best.

During my rebuild, I had an issue with the pilot jet that came with the Shindy kit. The one in my unit had several holes on the sides and a larger orifice. Here's what Shindy says:

We believe the Pilot Jet that was in your vehicle is Mikuni BS30/96 Type Pilot Jet.
Shindy's kit is made to meet exact O.E. specification as Mikuni N151.067 Type Pilot Jet.
1998 Suzuki Quadrunner (LT-F250) uses Mikuni N151.067 Type Pilot Jet. (mine is a LT-F4WD, but they use the same kit) So, it is safe to use Shindy's Pilot Jet for your vehicle.

So, I install their jet and again, I'll hope for the best.

@@@@ I'm stuck at the moment with a valve adjustment. The intake (top) value isn't giving me a gap no matter how far I back out the adjustment screw. The engine is aligned on Top, and the exhaust (bottom) valve adjusted just fine. Any thoughts would be helpful.