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Honda SGX50 Scooter fuel problem
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Stoo63
GLASGOW
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May 20, 2020 - 10:06 pm
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Evening all, (Note to self: STOP buying "easy fix" non-runner projects)

Have started on this '97 Honda twist n go scooter that I bought coz my daughter loved the colour(why, else?) Blue and Orange. It's a very simple(sic) machine that was touted as the successor to the Honda cub. So......... it has a lovely spark, turns over fine, seems to have good compression, has plenty fuel in it. But, there is no bang! Not a whimper! Clearly, there can't be any fuel getting to the barrel. I fitted a new vacuum petcock - no difference. Cleaned the carb to within an inch of it's life - no difference. The petroil isn't premixed like our bantams, it has a separate fuel tank and oil tank and the mix appears to take place in the crankcases where the oil via a small pump controlled by a worm drive is delivered. The oil pump also has a (vacuum) pipe running to the inlet manifold. The petrol is supposed to enter the crankcases via the inlet manifold and then a reed valve. I tried an external fuel tank today, bypassing the vacuum to the carb and it just flooded, so petrol was getting to the float chamber but wasn't being sucked away to anywhere. Now my suspicions lie with the reed valve assembly, but this is a system that I'm unfamiliar with. Could that be why the fuel isn't getting sucked in? I think the bike had lain for a good while before I ended up taking it in. There is a chunk broken off the reed block itself but doesn't seem to interfere with the seal and/or air flow. So.... a reedy/vacuumy conundrum. And all the more frustrating for the fact that it'll probably turn out to be something ludicrously simple and it's a tidy wee bike that looks like it'll be a lot of fun - and my first ever Honda! 

Any tips would be most gratefully received

Ta , Stewart 

'52 D1 direct lighting plunger; '58 Square Four (project); '55 D3 Battery; '59 D1 direct lighting plunger;  '59 Tiger Cub; '60 5TA;  '76 FS1-E '97 Honda Sky SGX50.

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Blue Heeler
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May 20, 2020 - 11:55 pm
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Hi Stoo, All my many Yams had reed valves, standard stainless steel and the fibre ones I fitted during tuning mods, but instead of me trying to explain what to check...it`s getting late, here`s a good piece that may be worth following for your check on the reeds. ** Please log in to view ** .The airsports chaps tend to know their stuff, that`s why I went straight for that one...they can`t afford for things to go wrong.

Also I`ve had to replace crank seals on a low-mileage Puch before it would run. Can you get at the mains to test for slop...and therefore blown seals?

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cocorico
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May 21, 2020 - 7:47 am
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A Honda Step-through? What's not to like? Have you tried just wetting the plug to see if it will at least fire?

I recently had the head off a 100cc Peugeot to replace the piston, the cylinder / crankcase joint rotated on reassembly somehow, thereby blocking the transfer ports. Might be worth a check. If it's anything like the Pug (shrouded cylinder & head and ducted air cooling), it's best to check everything accessible before hiding it all again.

Just noticed - it's a big wheel one (like the Pug). So much better / safer IMO, and I found the Pug a real hoot, will even cruise at 80 (kph).

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine now running.

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Stoo63
GLASGOW
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May 21, 2020 - 9:02 am
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Thanks guys. Yes Bob, I've tried wetting it and still no pop. I've found an uprated replacement complete block for a tenner so just ordered that. Ticks one more box. The UK model apparently is limited to 30mph but unrestricted parts are availble from europe. I'm quite tempted, once it's running :-), to pep up the engine. And yes, it's all enclosed, so I'm keeping the cowlings off til I get the solution. Blue, interesting reading. That was how I thought things worked, just needed confirmation. I remember the system being very popular with the Yams in the 70's/80's. Certainly seemed to do the trick for the RDs 🙂 Haven't checked the seals yet but compression feels excellent. Last thing on my list to do. Had hoped to get it running without a full autopsy but apparently it seems you can replace the seals in situ 🙂 

Have a good day,

Stewart

'52 D1 direct lighting plunger; '58 Square Four (project); '55 D3 Battery; '59 D1 direct lighting plunger;  '59 Tiger Cub; '60 5TA;  '76 FS1-E '97 Honda Sky SGX50.

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rhi010
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May 29, 2020 - 12:46 pm
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Funny, I bought a sky as a cheap moped this year, an same problem, I would go for the seals, both mine were shot.

Remove the kick start cover a see if you can see/smell fuel, on mine you could see it on the bottom of the casing.

Do both sides, check there's only one in place, mine had two on one side an this got worn by the oil pump drive. 

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Stoo63
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May 29, 2020 - 1:32 pm
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Cheers , Robert

Flywheel puller arrived yesterday and seals today 🙂 When I get 5mins ......

It's the only option left as I've replaced everything else. "Cheap" wee project rofl

'52 D1 direct lighting plunger; '58 Square Four (project); '55 D3 Battery; '59 D1 direct lighting plunger;  '59 Tiger Cub; '60 5TA;  '76 FS1-E '97 Honda Sky SGX50.

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