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The airbox thing suggests you're still too lean. When you loosen the airbox, you're creating a vacuum leak and are allowing air to get into the engine from places other than the airbox. If your mixture is still too rich, the vacuum leak effect could be balancing that out, resulting in the correct mixture. But you definitely need to fix that because dirty air can get into the engine.

Are you going to re-name the engine? Honduki? Suzuka?
 

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I would make sure the airbox isn't blocking flow to the pilot air inlet on the carb as this can cause this issue as well. Let us know anything new! :trink39:
Ranger, something just caught my eye since you mentioned the pilot air inlet. In this picture is the air inlet the hole on the upper left where the gasket is cut out?


If so, in this picture the gasket is backwards and blocking it. Could it be that simple as the gasket got thrown on wrong maybe? Or like you said the air box is blocking it when mounted if the gasket is correct.
 

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Discussion Starter #23
Y Block, Ranger, BDM--you've all narrowed in on the problem! Snuck in 30 minutes of tinkering today and drilled a hole in the airbox & metal mounting plate for the pilot jet's inlet.

Instantly ran better, great idle, super fast throttle response and smooth top end. Has actually become a little more difficult to start (4 pulls vs. 3). So I think this is the final piece of the puzzle -- I still need to get run time on this (and snap a picture), but the jetting actually seems great, no smoke at all and it still sounds a bit like a dirt bike at idle!

Branden, good eyes. That was an early trial fit photo, before I opened my eyes at all to the pilot jet hole...and then plugged it with the airbox!

I think "Honduki" sounds good, although by percentage, Sukuka is more correct!
 

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Discussion Starter #24
Doh, forgot I can't edit the original post. Here's what I learned through trial & error...
1. The $14 carb does work on the Suzuki with stock studs & only 1 Honda gasket,
2. You'll spend less time than me on mods,
3. A Mikuni may be better, but it's not 10 times better like the price.

The summary of changes needed

1. Remove mikuni & clean up old gaskets if you’re going to reuse. All gaskets on the engine side of the carb can be reused.
2. Tape up all the places on the Honda Carb you don’t want aluminum shavings, and enlarge the mounting holes towards the center of the carb body. I couldn’t get a dremel in the holes, so I used a regular round file. Probably took 10 minutes – not a big deal.
2a. [Optional] Notch the back side of the throttle arm on the carb, may help get a lower idle. 1 of my Suzukis needed it, the other didn't.
3. Drilled the main jet to .78 mm or wire gauge 68. Duraforce folks should know this size well. Main jet can be difficult to get to drop down, carefully unscrew it through 2 stages of threads.
4. Attach the stock linkages to the Honda carb, and mount the carb to the stock studs. Here is where everyone gets to play their games for getting the carb on/off the studs. I was able to get the carb on/off with linkages attached, but it was a squuuueeze.
5. Start practice fitting the airbox, you’ll have to do 3 things:
a. Cut the gasket listed below to be very close to the carb body, or the airbox won’t fit flush, and
b. Grind away/cut away a lot of the plastic on the choke lever. Just lots of trial & error.
c. *important* Drill out a hole in the airbox & metal mounting plate for the pilot jet air inlet (to match the hole in the top left of the gasket). I used a 11/32" bit I believe, whatever fits the gasket, do not restrict this or you will run rich. Ensure the airbox, plate, gasket & carb air inlets all align!
6. [optional] Grind off the tamper proof notch on the idle screw. This lets you adjust your mixture at idle for your pleasure. I'm running 1/2 a turn out, but stock seemed OK too.
 

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Awesome, congratulations on the conversion! We'd love to see a video if you have a camera.

You say it takes 3-4 pulls to start. Does this Suzuki have a primer? From what I've seen, the primer models take 1-2 pulls and the choke-only ones need about 3 pulls. I've never studied how the primer works so I'm not sure if you could use it with the Honda carb anyways.
 

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Awesome, congratulations on the conversion! We'd love to see a video if you have a camera.
Agreed!!!!!!


I've never studied how the primer works so I'm not sure if you could use it with the Honda carb anyways.
The bowl carbs with a primer all work the same way so if there is the 'plumbing' for it on both the airbox and the carb then it would work fine. I don't see a primer air intake on the Honda carb picture though.

As for how primers work, I beleive its like this for most engines:

Bowl-carb machines - primer forces air into the bowl which lowers the float and allows a bit of fuel bast the needle and through the carb

Tank mounted diaphragm carbs (most Briggs mowers) - primer shoots a shot of fuel directly down the intake throat like a squirt gun.

Small engine diaphragm carbs (weed whips, chain saws, etc) - primer purges system with fresh fuel getting it ready to run but doesn't let fuel past the diaphragm and into the carb
 

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Discussion Starter #28
I'll try to grab a video this weekend. No primer on either of my Suzukis. I moved the Honda carb (yesterday) to my ex-commercial Toro that really needed a replacement carb-tons of slop in the throttle. Happy to say, once the carb is modded, the airbox & swap are maybe a 20 minute job.
 

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Great job there! Sorry I've been away for a few days but I'm guessing you got your questions answered. I'm kinda surprised it takes 3-4 pulls to get it started, though other factors such as compression and ign coil condition would have an effect on this as well. I'm not what you would call an "expert" on carbs but I have learned alot about how each component works and spent many hours disassembling/cleaning/rebuilding carbs. I'm glad you were able to make this conversion work and I'm sure it will benefit users in the future.

Ahh so you got your hands on a 125V eh? Great engine. I totally love mine. The carbs used for this engine and the 4 cycle versions are almost identical with jet sizes being the only major difference that I can tell. The bowl gasket was probably causing the leak on yours. They are also somewhat sensitive to how centered the bowl is when you tighten the bolt so keep that in mind whenever you have to remove the bowl.
 

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Great job here fellas. Between Mantas and his thread on the internal governor parts and Atomix on this carb swap, I think we should sticky those and the thread on the NOVA II coil fix for early suzukis in one spot as I think with those thread we have all the major issues settled on the Zuk motors.

I have done about 5 or 6 of these complete engines and they really are worth the effort to save. Its great that we can find rebuild parts cheap, carbs, bearings and ignition items. Mine run great but are slightly tempermental-it takes a good wrencher to keep these running tip top-and these threads help those up and coming to Suzukis.

Brad can we sticky those threads? Anyone have the thread on the NOVA II?

Here is Manta's on the governor.
http://www.mytractorforum.com/showthread.php?t=237483&highlight=suzuki+coil

Atomix...where did you source the Carb? I have the original part number 16100-Z0Y-013 that I was sourcing for $16.50?

Awesome job everyone !!
 

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Discussion Starter #31
GTP, glad you enjoyed the thread, hope your Zuki's can use the help!

I bought the carb from, of all places, ' boats.net ,' I had never used them before, but they had all the parts I needed and were the cheapest. I'm not sure I'd use them again, the carb took ~7 days to even ship but it did arrive just fine, and I'd rather support my local shop.

Video to follow!
 

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Discussion Starter #32
Alright, took a short video of the Mikuni & 'Honda' Carb. Not a real fair comparison since one of the mowers had BBC. Mowed a bit with both today and then the Mikuni/BBC wouldn't restart for me when hot...May have the $150 coil failure coming. The Honda ran very good, although I still think I have it set up too rich, lots of burbling and a hint of smoke (Mikuni doesn't do that.) I leaned out the idle jet more on the very adjustable idle screw, but I think the main may simply be too drilled out.

Should be available shortly at :
https://vimeo.com/50860415
 

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Just FYI if you want to remove the idle mixture cap all you have to do is heat it up with a propane torch and melt the loctite and pull the gray cap off. Obviously this should be done without any gas in or around the carb LOL. Great thread BTW :fing32:
 

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...the Mikuni/BBC wouldn't restart for me when hot...May have the $150 coil failure coming...
Great sticky on the Honda carb retrofit, and it sounds like one more may be in order for the Nova II transitorized module retrofit for the hot restart/coil failure issue (not to volunteer your services, but you did such a top notch job on this one - maybe a fall/winter project :) ) These two issues should cover 90% of any problems folks have with these wonderful engines.
 

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Just did this to my Toro 20684. Thank-you!!!! In the words of Peter Boyle, "Holy Crap!" I spent all summer messing with jets for the mikuni. First, I spent $90 on a used mikuni to replace my original one with a leaky needle seat and that just got a carb broken in a different way. Then, I spent $13 on manifold gaskets thinking I had a leak. Then I got another set of $13 gaskets because I tore the first ones up taking the carb on and off. Then, spent $50 on pilot and main jets.
2 weeks ago started to read this thread so I spent $16.50 on the carb and roughly $2 on a gasket. Had the carb on in 30 min. and the mower that I hated is now a pleasure.
By the way, I melted the stop of the pilot mix screw and set it 1/2 turn out and DID NOT change the main jet. The mower runs great and the plug is beige. So, the jet seems correct.
 

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Discussion Starter #36
Joe,
Awesome to hear this was 'the fix' for your 20684! That may be my favorite mower, so it's great to hear another one is running well!

I will probably repeat the swap on my second Suzuki this winter, so that's great info about the jets. I won't complain about buying a $6 main jet to replace the one I drilled either after all the money you spent.
 

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Had to replace the governor arm, so while I was at it I noticed that I was getting a bit of contact with the shaft between the governor and the butterfly, and the top of the heat shield plate. You might want to add a step that removes a little material off the top off the heat shield as well.
 

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OK. So, I've been toying with this some more and I feel that the carb for the 190cc honda may be a bit much. The plug is tan, so the mix looks good, but the mower wants to run at HIGH rpms. I had to do a governor adjust that left 1/8 inch gap until the wide open stop. That way the motor ran at a reasonable speed.
I think I'd try to put on a keihin for a 160cc or 120cc even. Well next time...
 

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Discussion Starter #39
OK. So, I've been toying with this some more and I feel that the carb for the 190cc honda may be a bit much. The plug is tan, so the mix looks good, but the mower wants to run at HIGH rpms. I had to do a governor adjust that left 1/8 inch gap until the wide open stop. That way the motor ran at a reasonable speed.
I think I'd try to put on a keihin for a 160cc or 120cc even. Well next time...
Hmm, if it's running fast something else is wrong....I'd say the carb is lean on the Zuki 2 stroke if anything.

You have an air leak (carb cleaner test?)? Idle screw way out?

Man I love the mower now... =D
 

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No air leak. I'll check the idle screw again tomorrow. I know I turned it out to enrich it thinking it was running fast because it was lean.
Did you have contact between the top of the heat guard plate and the shaft from the butterfly to the governor? I did.
I just split the cases and looked at the governor. It looked good.
 
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