17.5 dellorto

So, this morning got up early went to get some carb cleaner, dismantled my carb completely and gave it a good clean, even cleaned my malossi e13 filter with the carb cleaner, downjetted to an 85 main as my bike was spluttering at midrange rpm's (7000), then tested it, the spluttering had gone but a quarter way down the road full throttle the bike just died.. maybe not enough fuel getting in? so i put in a 98 main jet in, then all was fine again but still splutters at 7000 rpm mid throttle full throttle is fine.

reason i decided to clean the carb was because last week i had a malossi 70cc sport kit installed with a stage6 race clutch and a 9 roller weight polini super speed variator 3.0 gram rollers but its only hitting 45mph max... i dont get it, so i thought maybe it was my carb hence the clean..

my runner i had before, before it got stolen was standard 50cc just derestricted cut/welded orginal exhaust standard clutch/vari slightly lighter rollers and a upjet standard airbox and that was hitting 50mph with a 50cc cylinder..

whats going on? any suggestions? max speed on 50cc derestricted 50mph max speed on 70cc malossi sport 45mph?

 

standard jet on a dell 17.5mm is about 53 or 56 isnt it ?

and your running a 98 on a 49cc....thats like a 80% up jet

what you doing to the gallon ???

 

no no, standard jet was indeed a 53, the bike then got derestricted and an unrestricted polini manifold installed alongside a yasuni R exhaust, at this point we upjetted to 65 main, then i put on a malossi e13 open air filter and it stated i needed to upjet by 10 sizes, so i put a 77main in, and the bike just bog bog bog'd at full throttle...

i then put a malossi 70cc sport kit in and upjetted again to a 98main and now the bogging has gone but the speed is pish poor, sorry i didnt make myself clear, i have a 70cc malossi sport kit with a 98 main jet and malossi carbon fibre reeds/derestricted manifold and max speed is 45mph

 

what pipe n rollers?

 

yasuni R , 3gram rollers x9, i had 4gram rollers in but the bike would only rev to 7000 revs do lightened them to 3 gram

 

well.....have you done a plug chop to see how rich it is? i mean, you said you put an 85 in and it was fine till full throttle...then you put in a 98 and it was fine all the way except it sputtered. do you have a jet that is between an 85 and a 98? thats a HUGE jump!!

 

3 gram rollers in a 9 roller variator is the equivalent of 4.5 grams in a 6 roller variator,
which probably isnt too far wrong...

you do know that too large a jet will make your engine bog, as well as too small a jet!!
you really need a selection of jets (what we call a jet box) so you can jet up or down in small steps....

 

i have a jet pack ranging from 58 all the way up to 98.

when i down jetted to 85 today and took it for a test ride, i was full trottle for a while then the engine just stopped... dont know why... (ideas?) the 85 main jet didnt feel right though..

so i put the 98 back in and its fine.. no engine cut outs at full throttle but still splutters at mid rpm.

77 main just bogs out completely, 85 main makes the engine just cut out, so what do you suggest?

 

if youve got a jet box how come your going 98...85...77

these are massive differences in jet sizes, you should be going down from 98 in steps of 2, then when you get to the point it wont accept full throttle, up 2 and then plug chop

 

ya man, atleast find a 90 and put in there...that way you can see which way to go from there and you possibly cut half of the jets that you have out of the question. so throw the 90 in there...pay attention to what the throttle feels like and then plug chop. then repeat.

 

Why did my engine just turn off tho when I had a 85 main in at full throttle? Any ideas my bike literally just turned off?

Also can main jets affect top speeds? Sorry for the questions I'm a newbie

 

ok, i think ive got this figured out now...

the std jet is 53 with the gold plate on the carb mouth, i bet you havent got the gold plate fitted anymore, which means you need a much bigger jet.

if your bike cut out with an 85 jet but stutters with a 98 jet, your ideal jet is somewhere between the two :good:

would be worth buying a new spark plug as well, if you dont know how to clean and file a plug...

 

Gold plate? I didnt see any gold plate when I dismantled it today

 

no further questions your honour.... :grin:

 

hahaha it couldve died because the little jet couldnt supply enough fuel for those RPMs of that cylinder. yes, the main jet can affect the top speed.....thats the jet that is supplying the fuel to the motor at higher speeds. put in a new spark plug, put in a 90 main jet, take it for a spin and then do a plug chop (if you dont know what a plug chop is, search.....its here all over) and then report back with the color of the plug. if its white, its lean (go higher in a jet) if its black, its rich (go lower in a jet) if its chocolate, its good....leave it.

also, are you premixing or using the oil pump? if youre premixing then what ratio are you mixing at??

 

Oil pump

edit:

stuck in a 95 main jet, seems to be running slightly better, theres possibly the slightest little bogging still there when i pass the 7000 rpm range but i'm getting there! only thing is, 98 bogged, 95 is better, but my jet pack only has a 92 and a 90 left, and maximum of 98.

lower or higher? :O

 

It seems like your trying jets that you've already played with mate! As Dave continues to say you've done the hard bit - you know what ball park of a jet you need in it, if you've not tried the 90 & 92 try those & see how it feels. Remember not to neglect your plug.

 

I guess in the time it took to post this and wait for an answer, you could of tried the 92

have you bought a new plug yet, because if youve been running it rich for any amount of time, the plug will foul up and could well cause bogging or stuttering, even with the correct jet in.

at the very least, i would give the top of the centre electrode and bottom of the top electrode a clean up with wet n dry, and regap it

 

K mates thanks for the info, what plug should I get? I'm not sure which I have now, the it's an ngk but not 100%

 

it'll be an ngk br9es or alternatively look out for an ngk br9eix (iridium)