Calling out Cactus... Spluttering around 1/4 throttle.

[Sidney]

hey

on my CT110, when you just give it a tiny bit of throttle, it splutters and doesn't fire 'in time' if you know what I mean. It will run fine after the 'spot'

I can't raise the idle any more than it is (i want to put it up a tiny bit more) but if I raise the idle it sits in the 'zone' of spluttering if you know what I mean.

What do I have to adjust to get rid of the spot. Oh and if it helps the bike doesn't have a baffle. (sounds beasty)

cheers

 

[Sidney]

Bump..........

 

[I_THUMP]

You have only asked the question to one member in the title so no one else wants to answer you

 

[Panda_ET]

pilot jet blocked?

 

[Sidney]

I thought of that, but I swear I remember hearing that the air fuel mixture screw is what causes problems around 1/4 throttle... am I right or...?

 

[twisties]

yeah that might be it too, i had a similar problem, fixed it today.

if you have the bike in nuetral (when its warm) and you give it a rev, does it just die?
if YES, flick on your choke a little bit and try it again, if it runs better then your running too lean.
for my carbi, (mikuni 24-26?mm) i turn the screw IN half a turn and it sorted it out.

if you can get to the screw with the idle on hte bike then adjust it until it sounds right, but for me i had to take the carby off to get to the screw so i just turned it in half a turn, and it fixed it (not perfect though) but i cant be bothered pulling the carb on and off all day so i just left it how it was.

if that doesnt fix it then im guessing it would be pilot jet

 

[Sidney]

It doesnt just die, it just has a spot where it splutters and missfires n shit like that.

My bike doesnt even run with the choke on I think, even when its freezing outside it starts first kick without the choke at all.

 

[Gawain]

It doesnt just die, it just has a spot where it splutters and missfires n shit like that.

My bike doesnt even run with the choke on I think, even when its freezing outside it starts first kick without the choke at all.

well thats a clue isnt it? What colour is ur plug, black smoke from exhaust when you rev slightly? Too much fuel will cause that type of splutter. Def try adjust mixture screw, located on head side of carb, turn in = lean etc.

 

[Sidney]

Ok I'll try turning it in to lean it out tomorrow.

It doesn't blow any smoke.

 

[Cactus Jack]

Howdy Sid , I've been offline with computer problems so I couldn't reply 'til now ...

So your engine is "eight stroking" and spluttering = too rich ... First of all check that your float bowl is clean as water or dirt can produce similar symptoms ... also check and redo the float level if it's too low or too high ... You can do that with the carb off the bike ... set the fuel level as high as you can without it leaking fuel out of the drain hose when you tilt it in all directions ... The float bowl fuel level affects the jetting right throughout the entire rev range ...

If your carb has a mixture screw on the side of it near the air intake like XR75/80/100 Keihin carbs have then it's an air screw so turning it in ENRICHENS the mixture and screwing it out leans it out ... To tune that carb , after making dead certain that the choke is OFF and the air filter is not restrictive ... Adjust the idle screw high enough until the engine will run without stalling ... Next , screw the screw in until the revs start to drop , then screw it out counting the turns until the revs start to drop again ... Screw back in by HALF the amount of turns you screwed out , lower the idle speed and repeat the procedure dropping the idle speed each time until you get a slow smooth plonking idle ... You eventually get to know the sound when the mixture is tuned right ... Once you've gotten the steadiest , slowest , constant idle speed without stalling you can turn the idle speed up to suit your needs ... A higher idle speed will give better off idle response when the throttle is blipped quickly ... Tuning by that method sets the combustion to a neutral flame , similar to how an oxy/acetylene torch is adjusted and the engine will hold the tune all day long as the weather gets hotter or colder ... After a while you'll get to be able to fine tune your engine quickly without even thinking about it ... like second nature ...

Mikuni carbs with the FUEL screw at the rear underneath enrichen the mixture when the screw is turned out and lean it out when it's turned in ... Those carbs are tuned using a different procedure as explained in the link below :

ThumperFaq: MXA Fuel Screw

ThumperFaq: MXA Thumper's Fuel Screw

IF your engine has a points ignition system then too small a points gap can also cause the symptoms you are describing ...

Let us know what you work the cause of the problems out to be ...

 

[rossetti]

^^^^^ Legend