power curve or carbs?

[NemisusDM]

Hello,
Well the engine is running well now. I have a steady idle and great acceleration through out but, I did discover that I have the infamous slipping gear issue. That will have to be in another post though.

[TopCatGr58]

Hey Nemisus,

Did you actually take the pilot JETS and the Main Jets and the Main Jet Nozzle's OUT and verify that the little aeration holes in the sides of the pilot and main nozzles were open and not clogged?! Just spraying carb cleaner into the 4 holes in the inlet bell won't cut it! Also, you didn't say whether you checked for vacuum leaks around the butterfly seals once you got it back running??

The pilot screws on the top front are actually fuel/air mixture controls, not just AIR screws, turning them out allows more fuel to flow thru the circuit, just an FYI! Also, your 79SF doesn't have any rubber O-rings under the pilot screws, those were on the later 80-81 carbs where the pilot screws are down inside the pilot screw holes.
T.C.

[NemisusDM]

Hello,
I tried the simple spraying to see if it would work and it did so I was satisfied. I never checked anything else once it started to idle steady.

I sprayed just the inlets useing the plastic straws on the can nozzles. It fit perfectly into the air jet so it overflowed out the breather on the left side of the carb and vice versa.
The needle valve side was spotless from the dip cleaning.

[skids]

You can't argue with success!

[corybakker]

Carb jets - Why 150 Main and 42.5 Pilot?

Thanks for all the help over the year. This site has allowed me to do just about everything to my bike. I want another one too. One for bad weather, one for the summer! Honestly, though, Victoria, BC is like spring year 'round.

So, I am cleaning up the bike, rebuilding this, fixing that. But I just noticed that the Main Jet is 150, and the Pilot is 42.5. Bike has Alphabet Headers 4-1, and everything else is stock. Bike ran great all year, no troubles other than electrical stuff. That must be why my pipes are always turning blue? According to elsewhere on the site, that is way wrong? Maybe 142.5 or 145 Main and 42.5 Pilot is acceptable, but 150?

I am getting about, if I recall, 108-111km to a tank before reserve? What's that, 65 to 70miles for 3.30 IMPgal tank? That's doesn't sound very good. I love the acceleration, but can't I jet down or is there a bigger problem? The bike runs great...but do I really need that much power?

Any thoughts? Carb jetting is new to me. The bike came from Halifax, Nova Scotia, and now being driven in Victoria, BC. I don't think the elevation is any different.

Pics are at corybakker.com

[HobbyMan]

are your floats set to the same level? I have found that it will make a big difference.

[TopCatGr58]

Hey Cory,

Yeah, for just 4-1 pipes the 150's do sound a bit too rich!? I ran 4-1 pipes on my stock 81SH for 8 years and didn't rejet at all, never burned a piston, etc. and had power all the way to redline!

Stock jets for your 79SF(helpful to put in your profile) are only 137.5's, and the jetting guide says about 2 sizes up, so like you said, 142.5 should be more than enough.

What do your plugs look like? Are they black sooty looking?? IF so, then you are probably running too rich. However, many other factors can also affect your mileage, from a proper tune, synch, float settings, ignition timing, vacuum leaks, brake drag, air filter clogged, airbox snorkel crimped/pinched, windshield presence, tendency to twist right wrist . Also, colder temps require a richer mixture to run.

Yes, you should be able to get 30+ mpg. So, check on these things and report back!
T.C.

[corybakker]

Rejetted, stock pipes, runs great now!

Thanks for any emails and replies on this subject, folks.

I love this bike. I love it so much that if I have to spend a few bucks on it here and there, I still smile.

I rejetted back to 137.5 mains, and changed the needle setting to stock with stock pipes (ebay).

I still have my sweet 4-1 exhaust, which had 150 mains. If and when I do go back to that setup, my mains won't be that high.

Doing a ride across Washington State in July with some new buds. My '79 is the oldest bike in this group. The next guy's bike is 1998, then 2001 and up. Thanks for helping keep up with the pack with all your advice folks!