Roadie Engine Compression Question? SVS?

[129drifter]

I will be using all of this great information and working to resolve the issue soon.

Having a complete bone stock Road Star carb sitting in a box in the closet should help. May start all over again using it since It has never been tampered with and still has the TPS, enricher choke cable etc attached. I am kind of a parts pack rat and also think I have everything made out of rubber that goes in (or on) the carb still in OEM packaging that I have accumulated in the last dozen years of owning Road Stars.

This time of year it might be a month before I accumulate enough miles to know the outcome but I will follow up on this message thread with the details

[Lug Nut]

You may also check that metal enricher cover and confirm it hasnt warped due to internal spring tension…

I would say this is about 99.999999% not possible lol. It's thick 6061 aluminum and that sping wouldn't affect the structural rigidity if that over 10,000 years of spring tension

[Tcontrol]

35 years in the maintenance and engineering field has taught me…
“Never say never!!! “
All it takes is a little contamination in the 6061 aluminum raw material or maybe an origination from a chinese metal forge… OP may have over torqued a screw or one may be loose… maybe the machine shop had a ‘bad ione’ slip through… it has been known to happen….

many things can compromise the integrity of what some consider a ‘Bullet Proof Design’…so i say

“Never say never”

[129drifter]

I said I would follow up on this message thread when more information was available.

I wound up replacing the whole carburetor with the other bone stock one I had.

In the process I did all the time honored Clinic procedures about removing the fuel inlet screen, Barons needle 4th groove and jetting, 2.5 PMS, Mikuni 40 pilot. I installed a new OEM enricher choke cable plunger unit, a new OEM coasting diaphragm under the aluminum cover I had, new OEM o ring and bowl o ring gasket. I trimmed the enricher knob a bit to ensure the plunger was seating properly. I bought a new OEM float and did not alter it along with installing a new Clinic recommended Grizzly needle and seat valve.

So far so good now that I have had the opportunity to accumulate enough miles to know if it made a difference. Seems to be running good and doing better overall.

[Shotround]

2.5 on pms is too much. I went through the same experience you did with the plugs. Got fed up went the other way to 1.5 turns and it ran and ran but was hot. So opened it up some. Don’t remember where it’s at now as I use the afr guage. Try 2 turns and see from there.

my setup is practically same as yours. 2006, pump less and grizzly, stock exhaust, ra-066v filter. 40 pilot. Barons needle 4clip with washer and spacer. Ais removed. Crankcase vent to atmosphere.

I’ve experimented with different main from 167.5 up to 175. Less than 2.5 on pms is what I’ve found.

I even tried the 37.5 pilot. But stuck with the 40 as recommended.

according to the innovate Motorsport afr. I thought barons needle on 4th clip with washer was rich. Without washer was a bit lean. Keep in mind I have stock exhaust and kn ra066v filter.

I even got 39mpg with the clip on 3 with washer. I don’t recommend that. It ran way too hot. Guess I have to slow down from 75mph to get that 40mpg.

I know many of you know what you’re doing but I don’t recall you all having the stock exhaust. The stock exhaust must really be restricted compared to aftermarket comparing the difference in findings.

saving my pennies for a replacement sensor as it died after I got this far.

edit: not sure I can find enough pennies to go full aftermarket exhaust

[Duke]

Stock pipes have more back pressure than aftermarket pipes and the headder pipes are smaller causing a little reduced exhaust flow, but a lot more back pressure. This has a big influence on the combustion chamber feeding the next air/fuel charge in the cylinder. Just as the air box can play a part in this process. It's all a balancing act in the fine tuning to get the most of what you have. The point being, is to get the most efficiency out of the set-up that you have.
Most aftermarket air filters, outside of a air box, are free flowing, and most aftermarket pipes are free flowing without the baffles being in place. Tuning the exhaust with different baffles helps bring out more efficiency in the combustion air charge, which helps increase horsepower and fuel mileage with the right carb jettings.
I have found that the 2 into 1 exhaust systems are easier to work with this tuning technique.
The 2 into 2 exhaust are different as the rear headder pipe is shorter and the back pressures, front and rear are a little different.
That being said, reading the spark plugs can help on figuring out the tune on each cylinder, although it can be frustrating trying to get it perfect. Sometimes it's good to use a colder, or hotter spark plug in a cylinder.
I find it a challenge, and rewarding when I get it close to coming together.