125-200cc Should Carb Be Level? Photo

Hi Everyone

Poking around my bike today, it struck me how significantly the Keihin on my 2012 144 is tilted forward. If you look at the carb cap, you can see it's a long way from being level. Wiggling the carb in the boots helps a little, but not much. I can't remember if the original Mikuni suffered the same issue.

Anyway, I am wondering if the carb not being level is an issue? I have been chasing my tail with jetting on this carb for ever. Perhaps the carb not being level is making it tough to jet?

Would love to hear the input of the good people of this forum. Thank you.

If I recall, on the Mikuni, there was a tab on the top that fit into a slot on the rubber intake for alignment, and the carb did not really look level.

I think you are referring to leaning forwards . The mikuni does the same. You could try using the mikuni again . I had one of those keihins and wasnt a big fan . It would be worth trying a 36m keihin off a ktm I reckon . Whats your compression like? Jetting issues may be exaggerated by a need for freshen up ?

Thanks for the replies. I have been back to the Mikuni, but struggled with it. It was fine at WOT but at smaller throttle openings and in the mid-range I could never get it dialled in. It was either too rich or too lean.

Compression is currently 170 psi. Even when the piston and ring were brand new though, jetting was tough. I think a leakdown test would be helpful next.

Near my home in the UK there is a 2 stroke specialist called GT Engineering. They specialise in Honda's Grand Prix NSR500V & RS250 two strokes, the NSR250R series of road bikes, etc. but will work on any 2 stroke. They offer a carb set up service with access to a dyno. I plan to take my bike there and have them do a leakdown test and carb set-up. Will also be interesting to get their guidance on power valve adjustment.

170 psi wow thats high . I guess it depends on guage but mine were 120 and 125 psi and still ok . I have just fitted an as new 125 piston and cylinder on but I doubt it will be 175 . What settings on the Mikuni? I am running 470 or 480 main , 32.5 to 35 pilot , suzuki or stock needle . They like bigger main jets

On the power valve - I adjusted mine for the rhs bolt to be up near the top of the slot as some have recommended and it loses top end significantly . Not good on a 125 if you need any sort of power. It doesnt allow the the power valve to open fully and so it blocks the exhaust port.
Not sure why you would need a leak down test if you have that much compression and there are no valves to worry about

Thanks for the replies. On the Mikuni I ended up running 460 main, 35 pilot, 6CHY-16-62 needle, clip position 2, #5 slide. I agree the compression is healthy. But I would still like to run a leakdown test before dialling in the jetting on the Keihin to make sure the engine is in tip-top shape, i.e. no air leaks from the carb boots, case halves, cylinder base gasket etc.

Could be a jet block gasket failure.

Check up this thread:

http://www.cafehusky.com/threads/je...e-jet-block-gasket-failure.89613/#post-653014

jeanjean

Thank you, that's an interesting read. It would explain the way the Mikuni has been behaving. I will take a look at the gaskets in the carb when I get time.

Hi
Mikuni carbs suffer with the jet block gasket perishing and the float needle housing O-ring going hard
Before you consider setting up the jetting you need to change those two at least
StormWorks Garage in the midlands (there on instagram) usually have some JD kits for the mikuni there a bit of a 2 stroke husky specialist they seem to have quit a few hard to find parts they even sell OEM brake discs and talon clutch baskets for my 2002 bikes

That's really helpful info. Thanks very much.