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post #16 of 56 Old 09-28-2012, 02:31 AM
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Re: The Mikuni to $14 Honda Carb Swap

Your main jet could be too rich as you said, but this symptom comes from the engine running too lean. I don't think it would act rich until the lean idle circuit is fixed. Let us know how it works tomorrow. If this is sucessful, it'd be interesting to see what mods are necessary for other engines.
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post #17 of 56 Old 09-28-2012, 07:04 AM
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Re: The Mikuni to $14 Honda Carb Swap

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Originally Posted by Y Block View Post
Your main jet could be too rich as you said, but this symptom comes from the engine running too lean. I don't think it would act rich until the lean idle circuit is fixed. Let us know how it works tomorrow. If this is sucessful, it'd be interesting to see what mods are necessary for other engines.
Yes that will effect main jet running also.

Carb tuning is something you have to work up to in steps. every change, changes something else. Its a give and take till you meet somewere in the middle and have a nice running engine.

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post #18 of 56 Old 09-29-2012, 09:02 PM Thread Starter
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Re: The Mikuni to $14 Honda Carb Swap

Preamble: I feel like I'm drawing out this thread, but I haven't had much run time on the Toro-Suzuki-Honda.

With that disclaimer, I have it running pretty well, seems rich overall.
Changes:
1. Cut notch in throttle arm to allow mower to throttle all the way down to a real idle. (more dremel fun).
2. 1/2 turn out on the idle screw
3. Loosened the airbox / carb mounting screws.

#3 was odd, running with no airbox, I'd often get no surging after richening up the idle. BUT as soon as I tightened up the airbox, I would have the surge back, as bad as before. I can see no place where the airbox interferes or hits a linkage. There's almost no way the studs could be exerting enough force on the huge rigid carb body to deflect anything, unless I'm somehow compressing the carb bowl.

I'm out of ideas on the cause, but I do have an easy to start, smooth running and easy idling Suzuki.

I'll see how reliable this ends up being, with all the quirks I've seen so far I can't recommend this as an "easy" swap. I should get some more run time on this before winter, but I'll be exercising other leaf-loving machines soon too.

Several LawnBoys, 1D, 1E, 2F's
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post #19 of 56 Old 09-29-2012, 10:56 PM
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Re: The Mikuni to $14 Honda Carb Swap

Atomix, great thread on this. I have lots of Mikuni experience as I have them on my wisconsin robins and kawasakis. Like was said in another post, surging, unless under a very heavy load, will always be something in the pilot and/or intermediate carb circuit. The Keihin carbs used on Honda engines seem to be much less sensitive to stale fuel issues. A thought for you: if you think the governor might be causing the surging, you could remove the carb and disconnect the linkage to the throttle and operate it manually to see if that smooths the engine out. If not, from what you said about tightening the airbox to the carb making it surge still sounds like a pilot circuit issue, either the jet or the passages. 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!

Lawn Equip
Snapper 214X2PR-2 with W/R WT1-125V
Snapper P216012 with Tecumseh TVXL-840
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McLane 801 series edger with Honda GX120
Echo SRM-225 trimmer
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Winco 3000 watt generator w/ Honda GX160
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post #20 of 56 Old 09-30-2012, 08:06 AM Thread Starter
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Re: The Mikuni to $14 Honda Carb Swap

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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.:
Ranger, glad you enjoyed it. Looks like you're the right audience- a Keihin and Mikuni expert!

You may be spot on about the airbox blocking the pilot inlet, that would make perfect sense.

As a somewhat related point, I bought my first WT1-125 ~10 days ago, fortunately it looks fairly lightly used besides showing signs of a leaking carb at one point. The important part the Mikuni looks quite a bit different if anyone is thinking about this swap. I think the jetting is similar, but the choke plate is enormous even though the throttle is about the same size. Linkages looked like they should work.

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post #21 of 56 Old 09-30-2012, 12:45 PM
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Re: The Mikuni to $14 Honda Carb Swap

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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post #22 of 56 Old 09-30-2012, 05:13 PM
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Re: The Mikuni to $14 Honda Carb Swap

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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!
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.

Branden
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post #23 of 56 Old 09-30-2012, 09:38 PM Thread Starter
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Re: The Mikuni to $14 Honda Carb Swap

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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Snapper Wisconsin Robin
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post #24 of 56 Old 09-30-2012, 09:51 PM Thread Starter
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Re: The Mikuni to $14 Honda Carb Swap

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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Snapper Wisconsin Robin
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post #25 of 56 Old 10-01-2012, 03:15 AM
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Re: The Mikuni to $14 Honda Carb Swap

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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post #26 of 56 Old 10-01-2012, 10:14 AM
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Re: The Mikuni to $14 Honda Carb Swap

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


Quote:
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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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post #27 of 56 Old 10-01-2012, 04:18 PM
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Re: The Mikuni to $14 Honda Carb Swap

Okay, thanks Mantas - that makes sense.
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post #28 of 56 Old 10-01-2012, 09:30 PM Thread Starter
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Re: The Mikuni to $14 Honda Carb Swap

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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Snapper Wisconsin Robin
A few others...
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post #29 of 56 Old 10-02-2012, 02:42 AM
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Re: The Mikuni to $14 Honda Carb Swap

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.

Lawn Equip
Snapper 214X2PR-2 with W/R WT1-125V
Snapper P216012 with Tecumseh TVXL-840
Snapper MRP216517B with Robin EH18V
McLane 801 series edger with Honda GX120
Echo SRM-225 trimmer
Echo PB-250 blower
Other Gas-powered Toys
Husky/Coleman 5000 watt generator w/ Robin EX30
Winco 3000 watt generator w/ Honda GX160
Dayton 750 watt baby generator w/ Kawasaki FA76
20 gal portable air compressor w/ Honda GX140
2600 psi pressure washer w/ Cat pump and Robin EX21
Plenty of spare engines!
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post #30 of 56 Old 10-02-2012, 11:36 PM
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Re: The Mikuni to $14 Honda Carb Swap

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.
https://www.mytractorforum.com/showth...ht=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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