SC Conversions single carb install

Classic Goldwings

Help Support Classic Goldwings:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

falconav8r

Member
Joined
Jun 28, 2015
Messages
10
Reaction score
0
Location
Fox River Grove Illinois
Just an update on a single carburetor conversion. I know there are some positive as well as negative reviews regarding these conversions , but just wanted to share my experience with a recent install. I just helped a friend install one last week. A VW 34 PICT3 on a SC Conversion manifold. He never got it running quite right, so I rewired all his connections, sealed all connections with a little silicon and re-adjusted the carb.These systems are really not plug and play, so to speak and while the 34 PICT3 is a carb that will work great, takes some fine tuning and as I found out, a little ingenuity. The engine started nice and had to adjust the idle on the air volume screw and achieved a 950 rpm idle when it warmed. There was a bit of bogging from 1500 - 2500 rpm and discovered that this carb was supplying way to much air. I taped the inside of the air cleaner with aluminum tape, starting with about 1/2 restriction and after a few test runs ended with a third more of the intake blocked. Unbelievable difference! The engine pulled hard, no hesitation, and ran smooth thru 6500 rpm! Also I adjusted the accelerator pump which helped alot when the throttle was cracked.This leads me to believe that it is a re jetting issue on this carb which isn't a big deal. IMHO this conversion would work a lot better with a 30 PICT carb which would eliminate those issues. All in all, very happy with the conversion on this bike.
 

Attachments

  • 20150625_085154.jpg
    20150625_085154.jpg
    134 KB · Views: 302
Welcome! You took a different path in adjusting the carb but. Like most you got it running good. Your in good company here.
 
Thanks for the responses. I realize that restricting the air intake into the 34PICT3 is a stop gap measure, and am I right assuming that it need to be jetted?
Would like to hear from someone who has resolved this problem with the lean running problem. It seems there has to be something else going on...all in all, the engine is running real strong at this point with this half ass mod!
 
half ass ...no way ..you just did an overall air jet move ... one air made the difference as in volume.... changing gas jets or adjust air scew will give that ... id ride it like this and make it prove itself .. somtimes it might not last ..testing is only way to know ... hink your move was great and broad spectrum ..ive done the same thing myself .. its like velosity stacks on carbs it changes air overall ..no one thinks that 1/2 ass ... :popcorn:
 
Success is a good thing no matter how you get there. I'd be a bit concerned about the tape being drawn in but if it works maybe the same width of sheet metal can be fitted to stay?
 
I think 2 things possible going on, the carb is jetted too lean, or there are vacuum leaks in the manifold or carb. Could be a combination of both too.

I have a solex on mine and had to go from a 1.15 main jet to a 1.40 to get it where I feel is a good mix. This is after making certain there are no vacuum leaks.
 
OK...Here is one thing that must be done to this carb. I'm sure some may be aware of this and others not, but on the bottom throttle plate, there is an 1/8" diameter hole that was added to meet EPA requirements. This hole must be sealed shut by either a small dab of JB weld or take the plate off and solder this hole closed. This hole amounts to a large vacuum leak in the carb itself and does not allow the throttle plate to respond fully. As the throttle butterfly (at the base of the carb) is opened, there are a series of progression ports which are supplied fuel by the idle circuit. Not enough vacuum down low, means no fuel at idle - a carb that won't idle. This also means not enough fuel in the progression ports at lower RPMs - hesitation off idle.The 4 small holes on the side of the bottom throttle body are part of the fuel circuit and with that 1/8" hole open, you may not get the full amount of fuel under certain conditions.
 

Attachments

  • Carb2.jpg
    Carb2.jpg
    79.7 KB · Views: 286
agree ive heard people say closed and people who leave it open ... im not sure myself ive never worked long with this carb at all ... to me its a huge hole ....

ive got a carb mod on the dft i have that actually dose bring air in below throttle plate as the dft runs rich at idle ... but the feed is much smaller ... i will be posting about it soon on my build ...its something i came up with while on my 2 month trip and bike testing.....
 
I run a 34-3 with no jetting changes or mods to carb., my manifold has 1" pvc runners, been running it for a year, no problems. Only thing I give up is about 100mph is top end, but I can get there with no flat spots during any type of acceleration. Cranks and idles perfect every time. It is on a GL1100 81. Maybe a fluke, but it works for me.
 
I don't think its a fluke. These carbs run well. They are just a bit temperamental until it get them dialed in. Maybe its the asian brand carburetors. I've never had a real German made Solex so nothing to compare it with
 
I'm not sure which hole you're referring to, if it's the big one in the barrel, on my Solex that is part of the idle enrichener circuit used at cold start.
There is a lever that opens and closes it.
 
Plugging this hole is a lot more critical on the GL1000 since that engine will not supply the required CFM on the 34PICT3. Seems the GL1100 and GL1200 are closer to what the 34/3 needs to operate properly. On the GL1000 a 30PICT would be better sized. Either way, plugging this hole would benefit those models also.
 
yes ive had the dft moded like that also ..and it helped ..just wasnt a cure all ...your right i did look at wrong hole as i been messing with hole below plate on dft as in the mix screw on dft
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=152231#p152231:19vm76k8 said:
falconav8r » 25 minutes ago[/url]":19vm76k8]
Her is the hole I'm referring to.
file.php
Yes I know, and I replied about it. No need to repost.

I don't see that hole as being required one way or the other or specifically for or not for any of the oldwing engine sizes but it can be a way to solve certain problems. I drilled one as a test in an effort to lean the rich condition the DFT idle circuit has. It did help some but it didn't solve the true problem.
 
Top