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Author Topic: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke  (Read 8961 times)

Offline HerrDeacon

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Re: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #40 on: Oct 05, 2016, 08:23:50 »
If you still have the carb uncovered put your hand over the end while you kick it over to help suck in some gas.

Thats how I diagnosed a no-start after a rebuild on my MB5. Covering carb enabled it to catch so checked out carb and turns out I totally forgot to set the idle and air screws after cleaning the carb. I just screwed them back in after the cleaning and said I'd set them later. After setting them correctly it fired right up.
Perry

1972 Honda CB350 K4 / 1978 Honda XL250S /1982 Honda MB5 / 2014 Honda CB500X

Offline hillsy

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Re: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #41 on: Oct 05, 2016, 08:43:45 »
Thats how I diagnosed a no-start after a rebuild on my MB5. Covering carb enabled it to catch so checked out carb and turns out I totally forgot to set the idle and air screws after cleaning the carb. I just screwed them back in after the cleaning and said I'd set them later. After setting them correctly it fired right up.


I had to do that with an FZR250 after a carb rebuild. It had a fuel pump and everything but it still needed the carbs covered to suck the fuel in to get it to fire. Weird but true...

Offline advCo

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No luck with starter fluid through the carb or directly into the head, or covering the carb with my hand. It still sounds like it doesn't have spark, but the spark looks great when the plug is out resting on the head. I am going to swap out the coil from the XL tomorrow and see if I have any luck.


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74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
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74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Online teazer

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Re: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #43 on: Oct 11, 2016, 00:33:23 »
I'd stop at this point and check for bottom end leaks and rings to see if the problem is basic and mechanical.  I seem to recall a very low compression number but if that was on an HF compression tester, that reading might be inaccurate.  I have thrown 2 of them out.

Offline HerrDeacon

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Re: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #44 on: Oct 11, 2016, 04:32:09 »
Is the plug wet or dry after you've tried to start it?
Perry

1972 Honda CB350 K4 / 1978 Honda XL250S /1982 Honda MB5 / 2014 Honda CB500X

Offline advCo

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Plug has been slightly wet, but barely fuel - it usually seemed a bit oily.

Compression read in at 90psi before I replaced the crank seal and gaskets, then 60 afterwards. I am going to put a set of rings in and give the cylinder a light hone.

Where should I be looking for leaks in the bottom end? The mating surfaces all looked to be in decent shape, and the reed valve rubber was nice and pliable when I reinstalled. I installed a new base and head gasket.

The mating surface on the carb was not flat from the factory - the center was cupped about 1mm from the edges. I shaved it flat with a honing block before reinstalling.




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"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Offline hillsy

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The mating surface on the carb was not flat from the factory - the center was cupped about 1mm from the edges. I shaved it flat with a honing block before reinstalling.


Why did you do that? Are you using a gasket?

Offline advCo

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Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #47 on: Oct 11, 2016, 22:09:11 »
Why did you do that? Are you using a gasket?

Yeah. The gasket that was on there was fairly thick, maybe 1.5mm. The one in the kit/the gasket material I had was not as thin. It would not have sealed to the intake with the thin gaskets.

I figured it couldn't hurt. I wasn't getting fuel to the plugs before I did it, or after.
« Last Edit: Oct 11, 2016, 22:20:30 by adventurco »
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0

Online teazer

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Re: Suzuki FA50 Moped - "The Bumblebee," or, my first two stroke
« Reply #48 on: Oct 12, 2016, 02:23:51 »
You could do a leak down test with a fancy leak down test kit or get plugs for intake and exhaust to seal them and then make an adapter out of an old plug and pump in some air (6-8 psi and no more than 10psi) and listen for air hissing out of anywhere.  It's not as s subtle as a 250 buck MotionPro leakdown tester but it works.

More that 8-10 psi blows out the seals.

60 pis is really low and probably too low to actually fir and I wonder why it dropped by 30 PSI. could be new rings are not sealing. I have been known to run a piston up and down the bore with Brasso as the lubricant to get a recalcitrant set of rings to seal but It's a huge mess to clean up afterwards and just as likely to snap a ring getting it off to clean it.

Just out of interest, I wonder how far it can throw that spark.  I use a cheap spark tester from Autozone where I can adjust the gap to see how wide a gap it can jump.  It's a crude measurement of the HT lead output and if it struggles in fresh air to jump 3mm, it will probably fail to fire inside the cylinder. 

Offline advCo

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I will give that a go, teazer. I can make up a couple plates to seal the intake/exhaust and JB weld an old Schraeder valve to one of them.

I didn't put on new rings (yet), so It probably dropped 30 psi since the rings hadn't had time to reseat after I put the head back on.

My original thought was that the rings weren't creating enough compression to draw mix down. The PO mentioned it may have needed rings from the get go, maybe I should've started there


Sent from my iPhone using DO THE TON
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

74 CB360 - Luna - http://www.dotheton.com/forum/index.php?topic=63294.0
82 GS550L - Tracker-ish - http://www.dotheton.com/forum/index.php?topic=67229.0 - Sold
74 XL350 - The Turd - http://www.dotheton.com/forum/index.php?topic=70252.0
Suzuki FA50 "No-Ped" - http://www.dotheton.com/forum/index.php?topic=71189.0
73 Suzuki RV125 -http://www.dotheton.com/forum/index.php?topic=73875.0