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Post by alanc on Sept 11, 2014 21:09:59 GMT
hi guys need your words of wisdom
finally got my 76 sprint veloce engine running but it's still popping/backfire think it's just the timing needing fine tuned?. however there is fuel spitting out of the top of the carb anyone know what is causing this.
big thanks in advance
Alan
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Post by vespasco on Sept 12, 2014 7:41:12 GMT
If your motor is totally standard then it could be your timing yes
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Post by alanc on Sept 12, 2014 21:03:58 GMT
yes it's totally standard
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Post by henri on Sept 12, 2014 22:43:15 GMT
as vespaco says timing could be a cause ,set it right n see, if its still happening we'll need more info ie carb,jetting,exhaust an a general engine age/condition, H
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Post by stevievespa on Sept 15, 2014 20:55:33 GMT
Henri could that be whats up with mine spitting as well the timing out didn't think of that .....
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Post by alanc on Sept 15, 2014 20:58:36 GMT
wayhay happy days
put on an extra condenser reset points checked for a good spark found the spark was arcing across the plug put new plug in second kick fired up and running sweet
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Post by stevievespa on Sept 15, 2014 21:09:03 GMT
Is it still spitting mate
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Post by alanc on Sept 15, 2014 21:36:11 GMT
dont know stevie i put the filter back on so cant see anymore. a mate told me at the weekend that spitting out off the carb is common with vespa's and whats spitting should drip back into the carb
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Post by alanc on Sept 15, 2014 21:38:37 GMT
keep going stevie trial and error you'll get there it's a great feeling when she fire's up and you've done the work yourself
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Post by henri on Sept 16, 2014 7:32:46 GMT
stevie i have been thinkin we shud check ya timing properley , when i set ya points it was just a rough/quick fix as we didnt have time for more , was concentrating more on gettin carb set up an scoot to tickover ,H
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mickymidas
High Number
2Ronnies sc , Nuneaton.....Promoting chuckleism to the masses
Posts: 232
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Post by mickymidas on Sept 16, 2014 7:58:35 GMT
You say you " cant see if spitting now you have put filter back on"....If you have carb top and filter off then you will see a small amount of fuel spit back when you rev up anyway?
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Post by alanc on Sept 16, 2014 13:05:53 GMT
have just run the engine for a while and yes it's still spitting fuel out of the top of the carb I can see it running down the caseing
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Post by partanen on Sept 16, 2014 15:24:26 GMT
I don't quite get it how timing could cause spitting? When there is ignition in combustion chamber rotary valve is closed. Or at least it should be closed.
I had some spitting when I had MMW high pressure cylinder head. When I went back to stock head spitting ended. I'm not quite getting it either. Might be something to do with induction timing though
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Post by vespasco on Sept 16, 2014 16:36:23 GMT
Yeh. If its spitting really bad then it its likely the port/inductions timings are not quite working together correctly and as a result the blow down timing is likely too little.
But unlikely on a stock motor?!
Wrong ignition timing could be the cause of the backfiring/popping experienced by the OP.
Spit back... I can normally see a little (without the air filter etc) if I rev it... Thats going to happen surely?! Pretty normal..?!
If its excessive then im sure the bottom of your air box would be flooded with fuel?!
Give your air filter and quick clean in petrol and blast it dry wirh compressed air (if you have those facilties)! Or shake it aggressively and leave in the sun to dry (if you have those facilities)!!!
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