backfiring!!!!!!!

[deanjdk]

ok...iv sorted out the transmission problem i was having with the manston.
the other day i was driving and all of a sudden it started backfiring and spluttering like mad.i stoped and realised that there was a small split in the fuel inlet manifold and air was getting in so i parked the bike up and get a lift home to get a spare one that i had.i fit it on and the same thing stared happening......just a few minutes before this all started happening i had filled up the tank with normal pump gas (95 octane i think..i normaly use 98 or 100 octane with booster) and instead of mixing the octane booster with it properly i just squeezed a few squirts into the tank because i was a bit of a hurry.i think i might have put too much in there and the question i have is that when you put too much octane boost in there does it make it backfire.it also seems like it was running leaner than usual(sometimes when i pulled back the throttle it died like it was taking in too much air).please help...has anyone had experience with anything like this before....thanks for any replies

 

[deanjdk]

o yea sorry...my setup is basically....
gilera runner
manston 70cc
c20 exhaust
rms crank and race bearings
21mm dellorto carb with origional airbox and 72 main jet

 

[deanjdk]

anybody??????...........................please

 

[eLik]

Please do not bump the thread already! If someone know, they´ll answer, otherwise you´ve got to accept it..

 

[scootertrog]

You might try checking the exhaust gasket to see if everything is tight there.

 

[RickH]

Your mainjet is way too small!!!!!!! try 120 Or something like that big.

 

[roost]

Maybe your octane booster is tetraethyl lead (it is crap if it isn't). So lead maybe clogged your sensible thin-electrode sparkplug (guess you have it).

 

[deanjdk]

sorry for bumping the thread.

iv checked if the exhaust gasket and everythiong is fine there.

anything over a 74 main jet is running too rich for me rickh.i am using the origional air box.also my friend also has the exact same setup as me and he is not yet having any problems and he also runs a 74 jet.dont forget that a 74 jet in a 21mm isnt the same as a 74 jet in some other DO carbs ...eg 22mm/25mm/12mm/17.5mm.
i cant see any difference in the colout of the plug...its still a biscuity brown colour.ill try a different plug in it to see if lead has contaminated the plug like you said roost

i am still thinking(and hoping) that it has to do with the octane booster.btw...does anybody know if the manstons plug electrode gap and is it different from the standard size piaggio gap

 

[Browni]

sorry for bumping the thread.

iv checked if the exhaust gasket and everythiong is fine there.

anything over a 74 main jet is running too rich for me rickh.i am using the origional air box.also my friend also has the exact same setup as me and he is not yet having any problems and he also runs a 74 jet.dont forget that a 74 jet in a 21mm isnt the same as a 74 jet in some other DO carbs ...eg 22mm/25mm/12mm/17.5mm.
i cant see any difference in the colout of the plug...its still a biscuity brown colour.ill try a different plug in it to see if lead has contaminated the plug like you said roost

i am still thinking(and hoping) that it has to do with the octane booster.btw...does anybody know if the manstons plug electrode gap and is it different from the standard size piaggio gap

I don't think the octane booster caused the problem. Chech your ignition system (CDI). What type of ignition do you have?

On the other hand 95 octane gas + octane booster doesn't work with the Manston. The octane booster can't help too much!

 

[roost]

i am still thinking(and hoping) that it has to do with the octane booster.btw...does anybody know if the manstons plug electrode gap and is it different from the standard size piaggio gap

It most ashurely is. The Manston has higher compression, a high compression demands a strong spark, else it will shut the spark off. So we need an strong ignition system and an good sparkplug, but if we don't havem then reducing the sparkplug gap is the option.

 

[deanjdk]

thanks for all the replys people.i am running the origional ignition system with no advance or change to timings(i know i know i need one for a manston).i cant remember what plug i am using and what gap it has but what size gap would you recommend it to be roughly.i have a selectra ignition system that i could take off another gilera i have here but i think that i had problems with it before so im not sure its working properly.

this was the first time i used 95 gas with the manston but i had no other option and i was miles away from home and in a hurry.and not only that i was using crappy nitrox booster which only boosts octane by 2 which means that i was only running 97 octane.i usually use afterburn booster which has a 10 octane gain with 98 or 100 octane pump gas to give 108/110 octane gas.the manston is run on minimum 108 i think

 

[deanjdk]

anyway im gonna try changing the plug and draining out the tank for some freshly mixed gas with proper booster levels and see how it goes...after all the hassle iv had i dont want more trouble.so are any of you guys fairly sure its a problem with the plug and/or octane level

 

[Cruz_e_Silva]

It's a fuel problem I think. Change to your original fuel.

 

[Eoin70]

i think its a spark plug problem
on my Malossi Aerox i was first using a basic technigas pipe on my team cylinder and it never gave any spark related problems

but when i fitted the Yasuni c20 onto my cylinder it would not spark
properly i presume because there was more compression and back pressure due to the better pipe.which created more pressure on the spark plug and wouldnt allow it to spark.

id say the soluyion is to get a better Bobine a coil for my igniton system
reducing spark plug gap will help
but it will restrict your power output as your getting a very weak spark

 

[deanjdk]

it ahs been running the c20 now for a couple of weeks with no problems .i think its a combination of both spark and fuel

 

[tiba_karotsu]

adjust your spark plug gap closer to around .40 to .50mm, your problems might be caused by misfiring & no amount of plug change or high octane fuel you use will make it better. also you did mention you're still using the stock ignition so i'm positive that the source of your problems is due to a weak spark so close up that gap!

 

[deanjdk]

yes i will do that today tiba.i will also change the fuel aswell anyway back to what i was using.it just seems odd that my friend is using the "exact" same setup and he is having no problems at all with the exact same spark plug ! lol.thanks for your help everybody.ill let you know how i get on!

 

[deanjdk]

ok iv changed the fuel back and fitted a new plug with a .40 gap and still i have the same problem....i dont know what to do.money is running a bit low lately so buying a new ignition system is out of the question for now.

any suggestions???????

 

[E.Stuntin_Sebas]

ik sluit me aan bij deanjdk

 

[deanjdk]

sorry bmxtreem i can only speak english....please translate