Engine won't start after carb cleanout/rebuild

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markie76

Member
Messages
6
Location
UK
Hi Guys,

Wonder if I can ask for your expert advice/help.

I have a 1/5th Yama buggy which I got used 6 months ago but haven't started it up yet. It was stored in the loft with the fuel drained. Last week I topped it up with fresh fuel (oil mix 25:1), charged the batteries and went to start it. I primed the carb and fuel flowed into the bulb and out the return tube as expected. With the choke on I tried starting it and it spluttered a few times but would not start. I switched the choke off and tried again and same it spluttered a few times like it wanted to start but nothing.
I tried a few more times with the choke on and opening the throttle a little bit with my finger - it would start and run for 5-10 seconds then die. I tried again and when it started I would try revving it but when I opened the throttle the engine revs would die and if I closed the throttle quick enough the engine would continue to run roughly but would not rev.
After some more trial and error I could get it to 'idle' roughly by having the choke half open.

I decided to take the carb apart to inspect it and clean it out.
It has a Ruixing carb which looks very similar/clone of a Walbro 813.
Inside there was a few bits of dirt/debris on the wire mesh filter but the rest looked all good - the gaskets & diaphragm look good so I cleaned it with carb cleaner, checked the needle and reassembled.

Now it doesn't start at all - doesn't even make any spluttering like it is trying to start.

1. There are no leaks from carb or air filter/manifold gaskets.
2. The fuel lines are fitted same as before and fuel flows when the primer is pumped and returns to the tank.
3. The tank cap breather is clear.
4. The plug has been cleaned and gives a strong looking spark when tested.
5. There feels to be good compression with the plug out and finger pressed on the hole - finger comes off wet with petrol.
6. A quick spray of easy start down the carb throat and it will start, run at high revs for 3-5 seconds then dies.
7. The screws are set at H:1.5 & L:1.25 which I believe id the factory default.

Ideas and suggestions please.

Many Thanks.
 
Sounds like it has a bad air leak so it is drawing in un-metered air after the carb. Check the head bolts are tight and take the air filter off and check the bolts through the carb are tight. You may be as well taking the carb off to check the plastic insulator block between the carb and engine isnt cracked (common fault). You may find one of these to be the problem so try starting it up again at the stock setting you have and take it from there.
 
Try venting the gas tank.Also check the diphram breather its a small hole on the front of the carberator.Most guy`s don't even know it exists.Daves discount motors sells a filter for it part #av493 or you can make your own.Check that your klunk in the tank is clean and sitting in the sump.Chek that your intake manifold is not warped.Check your carbs throttle lever shaft for an air leak.Hope this helps.
 
Thanks for your replies.

1. The inlet block between the engine and carb is fine, no cracks or chips in the contact surfaces.
2. The diaphragm breather is nice and clean.
3. The gas tank klunk looks ok and I can suck up fuel through the supply pipe unrestricted.
4. The carb bolts & inlet bolts were all in good condition and nice and hand-tight.

When I had the carb off I cranked it a couple of time very slowly and noticed 2 things;

1. As the piston started on the compression stroke there was some 'bubbling' coming backwards - very slight and not on every stroke.
2. Shining a torch into the inlet hole I could see a puddle of liquid at the bottom swooshing around. I soaked it all up and it was petrol.

I reassembled it, took the plug out and put my thumb over the hole and cranked it and it was giving good pressure.
I tried the sparkplug out of the hole and touching the side of the engine and it was giving a good strong spark.

I put the spark plug back in and cranked it but nothing. After about 10 cranks I took the plug out and it smelt of petrol, I put my thumb over the hole and cranked it and my thumb smelt of petrol :(

How can I check the carb throttle lever shaft for an air leak?

What next?

Thanks.
 
Spray wd-40 on the throttle and see if there is any bubleing around the shaft.Are you shure your engine is not out of time.Check the coil bolts that thier not loose.To check the timeing,put a bussiness card between the flywheel and the coil and tighten the bolts.Check that your cylinder is tight,and check the pinch of your head gasket.set your needles to factory settings.1 1/4 and 1 1/2and check your idle screw.Hope this helps.Are you using a kill switch?Take the kill switch out and see if it will start,kill switches do go bad.
 
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Try a brand new plug. Even though it appears to give a good spark against the head it is maybe not strong enough to ignite the fuel mix.

Also check the operation of the choke with the filter off. The plastic levers can become worn inside so whilst the lever moves it is not actually turning the shaft to turn the choke off.
 
Update:

Got a new plug, installed it, cranked a few times and it started!!!!

I let it idle a bit then tried revving but it didn't want to rev but didn't die either.

It was splattering a bit out of the exhaust so I decided to shut it off while I got my screwdriver to adjust the jets/idle screw.

I tried starting it again... and ... nothing!!!!!

I took the carb off, checked the gaskets, drained the puddle of fuel inside the crankcase, reassembled, checked the jet screw settings, checked the plug - reassembled, recharged the battery and tried starting and nothing.

What now?
 
Update:

Got a new plug, installed it, cranked a few times and it started!!!!

I let it idle a bit then tried revving but it didn't want to rev but didn't die either.

It was splattering a bit out of the exhaust so I decided to shut it off while I got my screwdriver to adjust the jets/idle screw.

I tried starting it again... and ... nothing!!!!!

I took the carb off, checked the gaskets, drained the puddle of fuel inside the crankcase, reassembled, checked the jet screw settings, checked the plug - reassembled, recharged the battery and tried starting and nothing.

What now?

Sounds like its flooded. Did you remember to turn the choke off?? :lol::lol:
Take the plug out and turn it upside down & pull it over a couple of times to release the excess fuel. The yama carbs are made of cheese so could be faulty. Best off replacing with a Walbro 668 for approx £35.
If you get it started again adjust the L needle with it ticking over until you get a nice idle (try a few youtube videos for comparison if you are unsure - any 5th will do). From what you've said its too rich so try turning clockwise to start with. You may need to adjust the idle screw to get it right. Once you have the idle sorted then try to run it. It should set off okay as it runs on the L needle up to 1/3 throttle then the H needle kicks in. When its running tune the H needle to get it running sweet. don't forget to use small increments when adjusting the needles.
 
Sounds like its flooded. Did you remember to turn the choke off?? :lol::lol:.
Thanks for the reply.

I cleared out the excess fuel earlier this evening, firstly by soaking it up with a cloth through the inlet hole then cranked a number of times with the plug removed and holding the plug hole facing the ground.

When trying to start it I crank 1-2 times with the choke on - then turn the choke off.

Bad carb in what sense? Not mixing correctly? The ruixing carb isn't anything fancy but as a 'clone job' it looks ok and is in good condition. I have no problem replacing the carb if I knew for sure it would sort it.

With the carb connected I took the plug out and held a flame in front of the plug hole and cranked and got impressive puffs of flame :)
Holding a finger over the plug hole while cranking gives good pressure.

I'll leave the plug out to dry out and try again at weekend - but am getting increasingly frustratedand thats not good for me or the buggy!!! :hammer:
 
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As the previous person mentioned get a WT-668 and when fitting it
smear a light covering of silicone grease on the gaskets
Check the coil gap is set correctly and as you have a new plug it should fire up ok
The stock carb on these buggies is only useful as a paperweight
 
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