LJ20 carb rebuild with LJ50 kit (ebay purchase)

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Simplesam
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LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 8:47 am

First I want to thank SuzukiTom for providing the link to an Ebay auction for a carb rebuild just when I needed it.

(disclaimer, I'm making a bunch of post with lots of photos incase others ever need some reference)

So my recently purchased LJ has a problem. Poor acceleration, however If I pump the crap out of the gas pedal it will accelerate up and maintain power once it gets there. So visual inspection shows very weak spray when activating the accelerator pump. Visually its very obvious that the carb is heavily lacquered as well, time for a rebuild.

here is a before pic
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 9:11 am

some quick detailed before photos, incase I get lost on the reassembly.
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 9:21 am

The banjo fitting needs to be removed in order to undue the screw holding the accelerator pump lever. Inside this banjo houses a cylindrical screen to filter large debris before entering the bowl. Also this will expose the top of the needle and seat assembly (new in kit). I took my time to pull this as all the fittings and screws were welded with age. I put the carb in the sun for an hour to loosen it up a little. It made a difference.
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 9:30 am

The needle assembly was the only significant difference from old to new. Just a few mm larger. I added an extra fiber washer to fix the difference. You can see it in completion photos later.
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 9:37 am

So the accelerator pump fit nicely and has a good feel to it when it operates. I noticed the old one moved with no resistance and inspection showed that it was pretty worn. There were no issues putting it back together but I would say be cautious with the metal screen in the banjo fitting, it acts as a spacer to center itself on the pedestal.
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Mon Sep 04, 2017 9:47 am

So recap.

During the disassembly I took careful measurements of the low idle air mix and idle set. All of these had to be completely readjusted afterwards. The LJ ran pretty rough before the rebuild and had no acceleration unless I pumped the hell out of the throttle. Once up to speed it fell flat on itself unless I periodically pumped it up and lost all power above third gear.

Now the acceleration is incredible. This thing spun the tires a little (ok it was in dirt and tires are over inflated). I can now drive at low speed in third and accelerate without issue. I haven't made it to fourth yet only because I cant drive it on the street until I fully fix all the brake issues.

Side note: before rebuild idle was perfect but everything else was terrible. Now idle is very hard to set, I think I may need to remake a base gasket (could be lean).

Any comments or questions? Post up.

thank you
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by SuzukiTom » Fri Sep 08, 2017 1:11 pm

I'm very glad it worked ok. I haven't used the one I received yet, but when it came in I checked the diameter and length of the accelerator pump, and the top carb gasket and they were the same. I just eyeballed the float needle valve, and at first glance it appeared to be the same too. So it's just the top length where the banjo fitting sits that is slightly too long?

Mine has a slight vacuum leak where the throttle shaft goes through the carb body. In the past (decades ago), you could have a competent carb shop re-bush the shaft to fix that. But I've found that no one does that kind of work anymore. It was an art, and the people who could do it have pretty much retired. I imagine a speciality machine shop could still do it, but I'm sure the cost would be :realshocked: .

On a side note, I found that the main jets used in the 150cc GY6 Scooter Keihin PD24J clone carb are the same size as the one found in the LJ's Hitachi carb (look up GY6 performance parts on Google, and you'll find many places that sell those carb jets. Usually about $5 each). The number on the jet is the orifice diameter in millimeters. For example, the 120 main jet has a orifice size of 1.20mm. My LJ20 engine runs significantly leaner on the number 2 cylinder for some reason. I replaced the stock 120 main jet with a 122 main jet and it doesn't run quite as scary lean on the number 2 cylinder as it did. I think this may be a problem with all LJ10 and LJ20 engines, since I have learned that they have a history of number 2 piston failures.
Still haven't found a source for different sized low-speed jets, though. Jegs and other sources sell precision drill bits (sizes 60-80) specifically for drilling out carb jets. You can mike them out to pick the correct mm size you want to go with, and just drill out your old jets. Obviously, you can only go larger, and if you go too far, you're SOL. But that's an option.

HTH,

Tom H.
Thomas Howlett

Resistance is Futile (if < 1 ohm)

SuzukiTom101@yahoo.com
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by Simplesam » Fri Sep 08, 2017 8:12 pm

Thanks for the notes Tom, I too noticed play between the shaft and bushing. I have a local shop that said they could replace the bushing, but when I brought it to them, they respectfully declined due to the unique/rarety of the carb. My cylinder #2 does show slightly more lean than 1 on the plug, however compression was 10lbs more than 1, so I'm not going to guess what's going on there. My next concern is expansion chamber/exhaust. I read all the post on it and have a local 2 stroke bike expert coming in for a second opinion but believe I will need to recreate a factory unit. I have the tools, but hate having to spend the time. I'd rather focus on 413 disc brake swap.
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by praiber » Tue Apr 24, 2018 11:49 am

Looking for one of these kits and cant seem to locate? Anyone have any ideas?

Praiber@hutchtel.net
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Re: LJ20 carb rebuild with LJ50 kit (ebay purchase)

Post by SuzukiTom » Sun May 06, 2018 5:51 pm

praiber wrote:Looking for one of these kits and cant seem to locate? Anyone have any ideas?

Praiber@hutchtel.net
The Ebay ones seem to have dried up, but this Australian shop still shows them in stock. Unfortunately, at over 3 times the cost!

https://www.4wdpartshop.com.au/suzuki/s ... etail.html

I've ordered from them before, so they're legit.

HTH,
Tom H.
Thomas Howlett

Resistance is Futile (if < 1 ohm)

SuzukiTom101@yahoo.com
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