hunting / surging / horse kicking on the overrun

adamgamsa · Post by **adamgamsa** » 11 May 2011, 23:44

Silly question answered elsewhere I'm sure, but Mk2 air screw default setting is 1 1/4 turns out. Does turning it in from there richen or lean the mixture? Thanks! I'm never sure if I'm dealing with a restriction in the air or the fuel, which have the opposite effects.

Post by **twistednuts** » 12 May 2011, 00:15

Clockwise, therefore less turns out, richens the mixture.

I hope im right else no wonder im runnin lean!!

Post by **knackeredMk1** » 12 May 2011, 10:21

Correct Twisted

.

adamgamsa · Post by **adamgamsa** » 13 May 2011, 23:00

I'm running premix for the time being with an opened up airbox, air filter which is currently unoiled (should I oil it?) and DEP pipe. I can richen the pilot mixture to my satisfaction (1 turn out seems rich enough without bogging badly), but I don't want to run lean in the powerband. Following the suggestion in the FAQ, I'm going to go for a main jet one size larger than stock. How about raising the needle one notch too? Do you think that's overkill? I know the answer's to run it and see, but what's your gut feeling? (I promise not to complain if the engine seizes etc) Cheers!

Post by **twistednuts** » 14 May 2011, 00:00

Well ive had running lean probs if youve seen my posts an ive done exactly what you propose - one size up on jet and moved one notch down (however you wanna word it) to raise the needle. Runs a lot better. Air screw is 1 1/8 out.

Oiled filter is good

adamgamsa · Post by **adamgamsa** » 14 May 2011, 08:07

That's really helpful to hear - cheers. I've found 1 1/8 good for the pilot screw good too.

garyd · Post by **garyd** » 15 May 2011, 14:29

Mine has EXACTLY the same problem ,i am running the same jets as you ,this only happened since changing to a DEP pipe!!!!!!!!!!!standard was fine no jerking ,it is the pipe that is the cause of it

Post by **knackeredMk1** » 17 May 2011, 21:07

The pipe may have caused sight rejetting. However since you are reboring etc you may that find rejetting is unneccessary .......... Or maybe it is

. We shall see.

Also jets wear with time so get bigger as the fluid flowing through them erodes the brass. So it's worth renewing the jets after long use.

garyd · Post by **garyd** » 26 May 2011, 16:15

Well after putting mine back together and running standard pipe........................................................................................................no hunting/surging etc so DEP front pipe for sale ,first £100 +p&p it is very good condition ,

Post by **back off road** » 29 May 2011, 03:40

after the cr conversion the bike that ran fine is now running CRAP probably due to the open airbox the main jet has gone from std 128 to 132 via 130 (no real difference)then with the pro-circuit silencer added a jump to 135 and the plug chop its giving decent results

trial and error but a quick plug chop and if its lean UPJET before any problems occur

garyd · Post by **garyd** » 05 Jun 2011, 14:14

If the bike is surging etc on a closed throttle ,ie,coming to a junction /bend etc is it running lean or rich and what part of the carb circuit is it therefore running on ??i think the idle circuit as in pilot jet ,am i correct or miles off here,got a 48/128 set up now

Post by **fallenmikethebike** » 05 Jun 2011, 15:51

garyd wrote:If the bike is surging etc on a closed throttle ,ie,coming to a junction /bend etc is it running lean or rich and what part of the carb circuit is it therefore running on ??i think the idle circuit as in pilot jet ,am i correct or miles off here,got a 48/128 set up now

It sounds as though you're engine is pulling in excess air through a leak somewhere.
There are many places that this could occur, here's a few.
Reed block, favourite.
Crank seals.
Crank cases.
Also check breather hoses are not blocked, ditto for the overflow hose.
Check the pilot jet is not partially blocked, clean it with some carb spray.
Richen up the needle jet by one notch, by, lowering the spring washer by one notch, middle is standard.
Clean the air filter, and re-oil it with a dedicated filter oil.
Can you hear the slide body clicking closed in the carb, body?
Mike

garyd · Post by **garyd** » 06 Jun 2011, 18:45

Didnt notice this before the piston /rebore,all ive done is clean carb,and adjust the mixture screw to standard ,think it was only 1 turn out before

Post by **fallenmikethebike** » 06 Jun 2011, 18:58

garyd wrote:Didnt notice this before the piston /rebore,all ive done is clean carb,and adjust the mixture screw to standard ,think it was only 1 turn out before

Their all slightly prone to requiring the personal setting, return the setting to one turn, if this does work, that would sort of confirm some air is getting into the system.
What's the story on the plug? is it showing signs of a weak mixture?
Mike

garyd · Post by **garyd** » 06 Jun 2011, 23:23

Im a bit shy of opening it up now ,dont want to go bang again

hunting / surging / horse kicking on the overrun

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