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Mysterious rich running issue (Read 278 times)
DragBikeMike
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Re: Mysterious rich running issue
Reply #30 - 08/02/24 at 20:42:31
 
Regarding the worn slide, I have never experienced that particular problem.  I imagine it could result in grossly rich mixture under certain conditions.  If the slide is hung up the slide needle position will not match the throttle plate position.  The slide needle will be allowing way too much fuel into the air stream at small throttle plate openings.  I suspect even idle would be affected.

The needle jets come in .0002" increments so even the smallest variation can make a big difference.  Your description of the problem points to the needle jet and slide needle combo, but if the worn slide is hanging up it would create the same sort of condition since the needle would be positioned way too high in the needle jet.

Ohiomoto, was it you that had the worn-out slide problem?  What were the symptoms?
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ThumperPaul
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Re: Mysterious rich running issue
Reply #31 - 08/03/24 at 05:40:07
 
DBM has done an incredible job as usual reviewing and assessing the photos.

My hunch is a sticking slide is the main culprit.  I’ve seen similar and probably got lucky not addressing it.

You posted pics of the choke (fuel enrichment as some call it).  The actual TEV is on the right side of the carb behind the 3 screws.  See photo.  As you can see, the screws can be easily stripped.  A good JIS (Japanese Industry Standard) “screwdriver” and not a #2 Phillips screwdriver is strongly recommended.  This is a “before photo”, and a popular change is to swap out for Allen head screws (I think M4x16 - double check me).  There is a post somewhere with the size verified, but I can’t find it at the moment.  People also ditch the float bowl and carb top (dome) screws in favor of Allen head screws.

Here’s a link to all kinds of good discussion about the TEV.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1342323516
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JOG
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Re: Mysterious rich running issue
Reply #32 - 08/03/24 at 08:19:06
 
Your #2 Phillips can be a JIS . You only need to tell it it needs to learn to Identify as a JIS, then, once it's psychologically ready, after it's spent a week living as a JIS, you take it to the bench grinder and point its little pointy tip straight at that brutal spinning stone and grind it. Put a flat spot on it. Test it for proper fitment into the JIS screw. Keep going until the tip doesn't hold the X up from engaging with the head of the screw.
Aftercare is really easy, a little oil before slipping it back in the drawer is all it needs.
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lucme
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Re: Mysterious rich running issue
Reply #33 - 08/03/24 at 13:41:04
 
Those particles are fixed, just some tiny pitting. The enrichment circuit is unobstructed. And the rubber on the end of the choke plunger looks good.

The floats are not leaking, they are very light and do not make any noise when shaken.

The main jet does have its washer, always has.

If I remember correctly, the actual TEV (forgot about that) looked good when I pulled it apart the second time I had the carb out. I don't plan on modifying it until the bikes running properly if needed. I would pull it out again but I don't want to take my chances on those screws right now, even with my JIS driver.

The main air bleed also appears to be free. I sprayed carb cleaner though it and it came out the needle jet passage.
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ohiomoto
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Re: Mysterious rich running issue
Reply #34 - 08/03/24 at 16:04:59
 
DragBikeMike wrote on 08/02/24 at 20:42:31:
Ohiomoto, was it you that had the worn-out slide problem?  What were the symptoms?

---------------
Yeah, that was me.

The slide looks similar to mine.  It only caused extreme lean conditions for me.  

The first time the motor would make it to the mid-range with full throttle but could hardly pull 20 mph in any gear.  I had just rejected the carb so I assumed I didn't seat the diaphragm properly.  But it looked perfect when I assembled it and it looked the same when I pulled the carb to inspect it. I cleared the slide, put it back together and the bike ran perfectly.  

I believe the slide was moving but the vacuum couldn't fully open it.

A few weeks later I lost all throttle control while shifting from 4th to 5th...chop the throttle, shift, crack the throttle, and nothing.  The bike was still running but would only idle and I had to pull off the side of the road.  I tapped the side of the carb with a rock and it came back to life.  It ran perfectly fine the rest of the ride home.  

I'm pretty sure the slide was stuck closed in this case.

I replaced the slide and haven't had to touch that carb since.  It was about $120 from Partzilla but that must have been 5-6 years ago.  

I don't think it would cause an excessively rich condition unless it was stuck completely open with the throttle plate closed as DMB said. Pretty unlikely IMO, but I could be overlooking something.

I would try to get it running with that slide before dumping $200.  It will be interesting to see what happens with the new jetting.

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JOG
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Re: Mysterious rich running issue
Reply #35 - 08/03/24 at 16:40:30
 
I had just rejected the carb so I assumed I didn't seat the diaphragm properly

It may have just been sad.
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ohiomoto
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Re: Mysterious rich running issue
Reply #36 - 08/03/24 at 16:52:55
 
It's nice to see the ghost of JOG is with us.  Wink
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JOG
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Re: Mysterious rich running issue
Reply #37 - 08/03/24 at 18:33:29
 
With you from beyond. Some people would say Waaay beyond.. Meh,,so they don't get it.  The science really is settled..
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lucme
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Re: Mysterious rich running issue
Reply #38 - 08/13/24 at 06:58:36
 
Hey all, I'm back from vacation! Sorry for the radio silence.

I got the Jets-R-Us order in while I was gone. I checked to make sure that what they sent matched what I ordered and it's all good.

They were out of stock on the 52.5 pilot jet but I had ordered a 47.5 and 50 as well so hopefully that will work. It looks like the only next size up they have is a 60 so I'd have to find another supplier if I need larger than a 50. Unless I want to try one with the emuslsion holes.

Otherwise, I've got a 145, 147.5, and 150 main and 230/45 pilot airs in their respective styles.

The needle, needle jet, and mixture screw are still on the way from Partszilla, UPS says they should be here next Monday.

I'm going to wait till that all arrives and then throw it together with stock jetting, save for obviously the pilot which I'll try the 50 first.

Anyways, I'll probably be pretty quiet again until the Partszilla order comes in.

Thanks again everyone!
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ThumperPaul
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Re: Mysterious rich running issue
Reply #39 - 08/13/24 at 15:06:00
 
Cool.  The 50 pilot jet will be fine.  You can adjust it with the air/fuel mix screw.  It'll be fine.  You can make any pilot jet 47.5 - 52.5 work.  The 60 would be way too big.
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Dave
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Re: Mysterious rich running issue
Reply #40 - 08/14/24 at 04:10:10
 
ThumperPaul wrote on 08/13/24 at 15:06:00:
 The 60 would be way too big.


Cough/Gag/Belch/Blaaaaaaah! Undecided

It would be similar to a wet gasoline vapor sauna!!!!!!!
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ThumperPaul
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Re: Mysterious rich running issue
Reply #41 - 08/14/24 at 04:22:30
 
Great sound effects, Dave!  

I think the 128 main jet in my PWK38 carb is giving me a case of the blaaaaahs at wide open throttle.  It’s just not crisp and seems “thick”.  Acceleration seems dull compared to acceleration while finessing the throttle in the midrange.  Back to the 125 and see what happens.  I’m very good at selecting a main jet that’s too big due to a terrible fear of running too lean at WOT.
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lucme
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Re: Mysterious rich running issue
Reply #42 - 08/27/24 at 05:18:22
 
Well guys you were right! All new good jets and the OEM needle, needle jet, and mix screw makes her run like a dream!

Been out riding for a couple days and it feels great. Gonna mess with the mix screw a little more to see if I can cut down on the backfires a little but I'm not too worried about that.

I really appreciate all the advice y'all gave me!
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ThumperPaul
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Re: Mysterious rich running issue
Reply #43 - 08/27/24 at 05:33:04
 
Cool!  Good job!  Glad you didn’t have to replace the slide.  Expensive suckers!
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ohiomoto
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Re: Mysterious rich running issue
Reply #44 - 08/27/24 at 06:36:55
 
That's great news!  

Now leave that carburetor alone.   Wink
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