Carb Tuning

[Mastiff1776]

2007 Mastiff, S&S carb, ( i think super G is what came on them, right)?
Vance and hines big radius exhaust
I don't know what jets are in the bike.

At higher rpms the bike runs good, and also the slower you roll into the throttle the better it runs. If you are cruising along at say 50 mph and give the throttle a real quick twist, it sounds like it cuts out.

Any ideas what to look at for that?

Also, I notice there are different brands of jets that say they fit the S&S, does it matter what brand jets you get?

Thanks guys.

 

[mleach72]

2007 Mastiff, S&S carb, ( i think super G is what came on them, right)?
Vance and hines big radius exhaust
I don't know what jets are in the bike.

At higher rpms the bike runs good, and also the slower you roll into the throttle the better it runs. If you are cruising along at say 50 mph and give the throttle a real quick twist, it sounds like it cuts out.

Any ideas what to look at for that?

Also, I notice there are different brands of jets that say they fit the S&S, does it matter what brand jets you get?

Thanks guys.

Sounds like it could be the accelerator pump not set correctly. Follow the tuning guide. I would only buy genuine S&S jets.

 

[Mastiff1776]

. "If the engine has a flat spot, or is popping/sneezing in the air cleaner, it can indicate a lean condition. If you notice stumbling or sputtering, it can indicate a rich condition."

I don't really understand how to tell whether I have a flat spot or stumbling. But I think maybe stumbling.

The best way i can describe it is when i'm cruising around 50 and then do a real quick twist of the throttle it will stutter, and then kinda "kick in" and take on off and accelerate.

 

[Sven]

When you quickly snap the throttle open, nature is going to win. So say applying the throttle at 50 in a linear motion, in top gear, sure it is going to take awhile, if not in a lower gear, but linear in the opening, there is no lag, no pop, or sneezing, correct? Say it has no issues, normal riding at any throttle opening. Sounds like it runs OK.

Getting back to the quick snap, WOT is happening is someone is moving faster and the other can't keep up, so it lags a little due to who moves faster at the quick opening. This is why nature's vacuum is like the speed of E almost. The rush of more air entering is going to throw off the 'fuel to air ratio,' being air moved faster in at the close of the intake valve, thus not enough fuel to air.

Say fuel mileage is pretty good. Why go nuts to compensate for bog, and ruins the gas mileage, the change of plugs being too rich, just for those few times a WOTTING you will go.

Before dropping the bowl, what do the plugs look like?

 

[SCC007]

You should be able to tell what carb it has, the "G" is cast should be visible...also likely what you have.
My 06 Mastiff has a V&H big radius and the G carb, so I can tell you getting it exact is a bit of a chore...take the float bowl off and check to see what jets it has (they are also visible numbered and you should be able to see them without taking the carb off) to help with diagnosis. The air cleaner does make a big difference, she came to me with a foam type oiled filter (like you would find on a dirt bike or big chain saw). I couldn't tune out all the stumbles, flat spots or hesitation and neither could the carb wizard (old hot rod guy) I took it to. Replaced the air cleaner with a tuned induction and put baffles in the exhaust to help create a bit of back pressure and it is a world difference and a lot more rideable. My AIH had the same set up but with the spike filter and was the same problem...put baffles in and the s&s air filter back on it and it was a ton better. So lesson - motors don't care about how cool looking air filters or exhaust are or how loud the pipes are...they care about how well air can get in, mixed with the correct amount of fuel, how quickly it can respond to changes in that mix, and get that burnt stuff out.
Next stop is sending the carb to John Sachs to have him work his magic for more efficiency/power and he can put a thunder jet on it.

 

[Mikeinjersey]

2007 Mastiff, S&S carb, ( i think super G is what came on them, right)?
Vance and hines big radius exhaust
I don't know what jets are in the bike.

At higher rpms the bike runs good, and also the slower you roll into the throttle the better it runs. If you are cruising along at say 50 mph and give the throttle a real quick twist, it sounds like it cuts out.

Any ideas what to look at for that?

Also, I notice there are different brands of jets that say they fit the S&S, does it matter what brand jets you get?

Thanks guys.

If this is a new issue it will more than likely not require jetting unless you have changed something on the bike. Pull the air cleaner and look inside the carb as you twist the throttle. You should see a healthy squirt of fuel.
I would drop the bowl and clean everything up being careful not to damage anything. There is a small blue o-ring on top of the ejector nozzle to keep an eye out for because it is easily lost or overlooked when it comes time to put the carb back together. Remove the jets and make sure the orifices are clear but do not be aggressive. Take note of which jets you have in case you wish to replace them at a later time. Make sure your float valve is operating well. I would leave the accelerator pump alone for now unless you ultimately need to rebuild the carb .
Put the carb back together and go for a ride. Now if you still have the problem complete the carb tuning guide that mcleach72 gave you.

 

[Mastiff1776]

Thanks guys for the help.

 

[HMAN]

Ya might ck to see if the carb bowl vent plug is in place or been removed. If a/c and pipes are stock, leave bowl vent plug in. If aftermarket pipes or a/c have been installed, remove the plug.

 

[Mastiff1776]

Ya might ck to see if the carb bowl vent plug is in place or been removed. If a/c and pipes are stock, leave bowl vent plug in. If aftermarket pipes or a/c have been installed, remove the plug.

I recently installed this filter https://www.sscycle.com/products/hi...air-cleaners-for-super-e-and-g-carbs-and-efi/

and it has the vance and hines big radius, I think that is what came on them stock?

 

[bikeone]

sounds like Membran defect in accelerator pump.

 

[mleach72]

I recently installed this filter https://www.sscycle.com/products/hi...air-cleaners-for-super-e-and-g-carbs-and-efi/

and it has the vance and hines big radius, I think that is what came on them stock?

Did this start after you changed the filter?

 

[Mastiff1776]

Did this start after you changed the filter?

No it didn't

 

[mleach72]

No it didn't

You can try removing the auxiliary vent plug from the carb, but I doubt it will make any difference since you are still using the stock teardrop backing plate. The carb should be venting properly through the main vent. Try adjusting the accelerator pump per the tuning manual. Try moving both jets, one at a time, up and down a size and see if that makes any difference. The shorty carbs are known for their quirks, and sometimes it's really hard to get a glitch tuned out. That's why I switched to a mikuni a long time ago.

 

[mleach72]

Also check for any vacuum leaks. There should be a rubber cap where the carb bolts to manifold. Make sure it isn't missing or cracked. With the engine running, spray wd40 around the manifold where it bolts to the heads. If the idle changes, you have a vacuum leak.

 

[Nukeranger]

The only carb issues I have ever had were on my Triumphs and they were always rubber cap leaks or clogged jets which I just replace both items and they always run like new afterwards.

 

[SCC007]

Issue I had on my dog was actually the tank liner peeling/sluffing off and clogging up either the carb or as it got worse it actually just stopped flow from the tank (completely plugged petcock screen). When i had bought her she had sat for a long while, 5 years from what I was told. The previous owner had her looked through and had flushed everything but I guess the drying out and then having fuel sloshing around once ridden caused it to seperate.

Some of the similar symptoms and what I had noticed is that the shop that had gone through her had cranked the accelerator pump way up...lag on throttle sputtering unless you crept up acceleration.