multi-carb tuning

[racerx]

hi guys
saan puwede magpatono ng carbs?
yung marunong sa side-draft na Mikuni pls? TIA

[racerx]

up

[racerx]

wala na bang gumagamit ng carbs ngayon?

[wildthing]

meron, kaso mahirap yata yung dual carbs...single carb lang ang kaya kong i-tune...btw what seems to be the specific problem with your mikunis?

[racerx]

thanks for the reply wildthing

it hiccups at low rpm but when above 2000 everything's fine another thing naman is when I downshift from 3500 to overtake there is hesitation like it runs out of gas or is nasasakal but when I rev it like the way the bus drivers do when they shift, it doesn't happen.

they are all equalized naman coz I have a flow meter and the timing is advanced maximum. I also have an electric fuel pump and regulator set at 5. thanks.

[ebbfolls]

I thought I had already replied to this post...I guess it didnt go thru. Anyway, bihira talaga sidedraft na multi-barrels dito sa atin. Usually kasi nasa mga 70's, early 80's high-end sports cars and multicylinder bikes, both of which are rare here. I must admit, mahirap i-diagnose ang mga side draft carbs lalo na kung multi-barrel. It takes time and patience to really figure them out. For one thing, they are more complex than downdraft (fixed venturi) carbs and they have 3 different jets for various modes of throttle openings. Compounding the problem is the fact that variable venture carbs(aka sidedrafts) are dependent on engine vacuum in metering the fuel to be mixed with the incoming air which makes them more prone to uneven Air-Fuel Ratios between the individual cylinders.

Here are a few options/suggestions:

1. Go to bike repair shops that specialize in multi-cylinder, chop-shop bikes. They should have better experience than most anybody else when it comes to multi-barrel sidedraft carbs.

2. Overhaul the carbs, make sure everything is matched between the 2 barrels (jet sizes, etc.). Replace old gaskets to make sure of no vacuum leaks.

3. Check out this website and see if you can figure out your problem.
http://www.factorypro.com/tech/carbt...m_engines.html

[racerx]

ebbfolls: thanks, that was a real informative
that website really explained what I had been trying to do before now I know what exactly to do. dati kasi puro guesswork and hit and miss rin.

problem is I'm kinda tamad na to do that all over again and want someone I can pay to do all that na lang. thanks again

[wildthing]

racerx,

it seems to me that you've opened up your carbs na...did you brush the gasket between the carbs and manifolds with shellac when you put it back?

I had a similar "sinok" and hesitation scenario and it was a vacuum leak scenario.

The manifold is a vacuum space, and small holes because hindi properly sealed ang in-between ng carb and manifold can show this symptoms.

Nasolve ng shellac (actually not my idea but rather the real mechanic who diagnosed my problem) being brushed on both sides of the gaskets....so when it dries up totally sealed.

The shellac (if you're not familiar) is the brown plastic bottle sold sa auto supply store. It's a standard for gaskets as pandikit nito.

[racerx]

hi wildthing,

yes, I've seen that before. If i'm not mistaken that's the real liquidy stuff na dark brown and looks really messy if it gets all over the place and you have to scrape it off. May caricature of a native american indian ba yun sa label?

i'll do that next week. Mukhang sasakit ulit lokod ko sa pakakatuwad over the engine bay. Thanks :D

[wildthing]

Yup i think thats the one that is the one (one of the brands). Nakasulat "shellac" ... tapos yung takip nito ay may kasamang round shape na brocha sa loob ng canister...good luck!!